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One of the most famous scientist in history. He went to University of Cambridge. He theorized the laws of planetary motion, and later invented the three laws of motion and gravity. He also invented optical instruments such as the telescope. He was a humble man and didn't care about the fame that came with his inventions and discoveries.

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William Harvey was an english physician and he was the first to "discover" that the heart pumped blood throughout the body. He also created a theory that an egg is fertilized by sperm. He was respected in England but many people were sceptic.

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Robert Boyle was born in Lismore Castle on 25th January, 1627. He has 6 other siblings. He was a writer on theology, philosophy and new science. Robert Hooke and him built the air-pump and used it in experiments in the necessity for air combustion, for animal breathing and the transmission of sound. He also described air in respiration, combustion and sound transmission. Boyle made a discovery that the volume of a gas is proportional to the pressure (principle known as Boyle's Law). He died in 1630.

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Read a biography about Willam Harvey, the 17th century physician who discovered circulation.

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informal website about Sir Isaac Newton

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Isaac Newton was born on Christmas Day 1642, but according to the corrected Gregorian calendar, this would be January 4, 1643. Early in his schooling, Newton showed little promise in academic work, so was removed from school to manage his mother's estate. He soon showed he had no talent for this either, so he was allowed to return to the Free Grammar School in Grantham in 1660 to complete his school education under Stokes.

Newton entered Trinity College in Cambridge in 1661 to study law. He studied the philosophy of Descartes, Gassendi, Hobbes, and in particular Boyle. He read works of Galileo, Kepler, Descartes, Viète, and Wallis. Despite some evidence that his progress had not been particularly good, Newton was elected a scholar on 28 April 1664 and received his bachelor's degree in April 1665.

When the plague closed the University in the summer of 1665, he had to return to Lincolnshire. There, in a period of less than two years, he began revolutionary advances in mathematics, optics, physics, and astronomy. While Newton remained at home he laid the foundations for differential and integral calculus, several years before its independent discovery by Leibniz. The 'method of fluxions', as he termed it, was based on his crucial insight that the integration of a function is merely the inverse procedure to differentiating it. Taking differentiation as the basic operation, Newton produced simple analytical methods that unified many separate techniques previously developed to solve apparently unrelated problems such as finding areas, tangents, the lengths of curves and the maxima and minima of functions. Newton's De Methodis Serierum et Fluxionum was written in 1671, but it did not appear in print until 1736.

When the University reopened in 1667, Newton was awarded his Master's Degree and was elected to a major fellowship in 1668. The following year, he was awarded the Lucasian chair. Newton's first work as Lucasian Professor was on optics. He had reached the conclusion that white light is not a simple entity. When he passed a thin beam of sunlight through a glass prism Newton noted the spectrum of colours that was formed.

In 1672 Newton was elected a fellow of the Royal Society after donating a reflecting telescope. Also in 1672, Newton published his first scientific paper on light and colour in the Philosophical Transactions of the Royal Society. The paper was generally well received but Hooke and Huygens objected to Newton's attempt to prove, by experiment alone, that light consists of the motion of small particles rather than waves. Newton's relations with Hooke deteriorated further when Hooke claimed that Newton had stolen some of his optical results. Consequently, he delayed the publication of a full account of his optical researches until after the death of Hooke in 1703. Newton's Opticks appeared in 1704, dealing with investigations of the colours of thin sheets, "Newton's rings", and the diffraction of light.

Newton's greatest achievement was his work in physics and celestial mechanics, which culminated in the theory of universal gravitation. By 1666, Newton had early versions of his three laws of motion. He had also discovered the law giving the centrifugal force on a body moving uniformly in a circular path. Newton's novel idea was to imagine that the Earth's gravity influenced the Moon, counter-balancing its centrifugal force. From his law of centrifugal force and Kepler's third law of planetary motion, Newton deduced the inverse-square law.

Halley persuaded Newton to write a full treatment of his new physics and its application to astronomy. In 1687, Newton published the Philosophiae naturalis principia mathematica, or Principia as it is always known. The Principia is recognised as the greatest scientific book ever written. Newton analysed the motion of bodies in resisting and non-resisting media under the action of centripetal forces. The results were applied to orbiting bodies, projectiles, pendulums, and free-fall near the Earth. He further demonstrated that the planets were attracted toward the Sun by a force varying as the inverse square of the distance and generalised that all heavenly bodies mutually attract one another.

Newton explained a wide range of previously unrelated phenomena: the eccentric orbits of comets, the tides and their variations, the precession of the Earth's axis, and motion of the Moon as perturbed by the gravity of the Sun. This work made Newton an international leader in scientific research.

After suffering a nervous breakdown in 1693, Newton retired from research. Newton decided to leave Cambridge to take up a government position in London becoming Warden of the Royal Mint in 1696 and Masterof the Mint in 1699. He became very rich. In 1703 he was elected president of the Royal Society and was re-elected each year until his death. He was knighted in 1705 by Queen Anne, the first scientist to be so honoured for his work.

The last portion of his life was dominated in many ways with the controversy with Leibniz over which had invented the calculus. Newton used his position as President of the Royal Society to appoint an "impartial" committee to decide whether he or Leibniz was the inventor of the calculus. He even wrote the official report of the committee.

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Isaac Newton was born on Christmas Day 1642, but according to the corrected Gregorian calendar, this would be January 4, 1643. Early in his schooling, Newton showed little promise in academic work, so was removed from school to manage his mother's estate.

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Blood Flow Path Body Systemic Circulation Anatomy Physiology Nursing

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Which Foods Can Increase Your Blood Flow & Circulation

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Known for: Bacon is known for his ideas circulated around Natural Philosohy, or the way we think     (deductive and inductive reasoning). Bacon struggled to come to terms with the so called facts of science early humanists and greek thinkers had produced. So in turn he turned to his own way of thinking, a way that put fact and truth before a excepted answer.

Adult life: Francis Bacon worked in high society, manovering through jobs such as being a lawyer, Queen Elizabeth's council man, and holding a position in parliament.

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Who is Rene Descartes and why is he remembered?

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Who is Rene Descartes and why is he remembered?

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Descartes was a mathematician, natural scientist, a metaphysician, and a scientific thinker. He has also been named the first modern philosopher. People remember Descartes for developing techniques to make algebraic (analytic) geometry possible. He also offered a new perspective for the natural world. Descartes most famous line is, "I think therefore I am."

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Joseph Priestly discovered oxygen, though it was named 'oxygen' by Antoine- Laurent Lavoisier. It wasn't until the 1770s that he started working on his research of natural properties and gases, before that he had been a minister. Joseph Priestly talked about oxygen as “dephlogisticated air.”

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He was a Polish astronomer and mathematician who discovered certain theories. Such as the heliocentric theory that planets revolve around the sun. Along with that the Earth rotates on its axis daily and affects what people see. He didn't have what was necessary to prove his theories but later scientists took his ideas and proved them.

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Sir Isaac Newton

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Isaac Newton - English Physicist & Formulated the Laws of Gravity |Mini Bio | BIO

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Molecular Expressions: Science, Optics and You - Timeline - Zacharias Janssen

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Zacharias Janssen is generally believed to be the first investigator to invent the compound microscope.

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Galileo Galilei was an Italian physicist and astronomer. He went to school to study medicine, but later became a professor of mathematics. He improved upon the spyglass and later turned it into a telescope. Later in Life, he was convicted of being a heretic and later was cleared of all charges. Once again, he believed something other than the Church's beliefs and was convicted as a heretic. This time, he was sentenced to life in prison but served it under house arrest until he died on January 8, 1642

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Wow!

Galileo discovered four of Jupiter's moons almost four hundred years ago.

Galileo Galilei was an Italian physicist and astronomer. He was born in Pisa on February 15, 1564. Galileo's father, Vincenzo Galilei, was a well-known musician. Vincenzo decided that his son should become a doctor.

In 1581, Galileo was sent to the University of Pisa to study medicine. While a student at the university, Galileo discovered that he had a talent for mathematics. He was able to persuade his father to allow him to leave the university to become a tutor in mathematics. He later became a professor of mathematics.

In 1609, Galileo heard about the invention of the spyglass, a device which made distant objects appear closer. Galileo used his mathematics knowledge and technical skills to improve upon the spyglass and build a telescope. Later that same year, he became the first person to look at the Moon through a telescope and make his first astronomy discovery. He found that the Moon was not smooth, but mountainous and pitted - just like the Earth! He subsequently used his newly invented telescope to discover four of the moons circling Jupiter, to study Saturn, to observe the phases of Venus, and to study sunspots on the Sun.

Galileo's observations strengthened his belief in Copernicus' theory that Earth and all other planets revolve around the Sun. Most people in Galileo's time believed that the Earth was the center of the universe and that the Sun and planets revolved around it.

The Catholic Church, which was very powerful and influential in Galileo's day, strongly supported the theory of a geocentric, or Earth-centered, universe. After Galileo began publishing papers about his astronomy discoveries and his belief in a heliocentric, or Sun-centered, Universe, he was called to Rome to answer charges brought against him by the Inquisition (the legal body of the Catholic Church). Early in 1616, Galileo was accused of being a heretic, a person who opposed Church teachings. Heresy was a crime for which people were sometimes sentenced to death. Galileo was cleared of charges of heresy, but was told that he should no longer publicly state his belief that Earth moved around the Sun. Galileo continued his study of astronomy and became more and more convinced that all planets revolved around the Sun. In 1632, he published a book that stated, among other things, that the heliocentric theory of Copernicus was correct. Galileo was once again called before the Inquisition and this time was found guilty of heresy. Galileo was sentenced to life imprisonment in 1633. Because of his age and poor health, he was allowed to serve his imprisonment under house arrest. Galileo died on January 8, 1642.

A Question

Why did the Inquisition sentence Galileo to life imprisonment?

The StarChild site is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC.

StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Curator:J.D. Myers
Responsible NASA Official: Phil Newman

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Wow! Galileo discovered four of Jupiter's moons almost four hundred years ago. Galileo Galilei was an Italian physicist and astronomer. He was born in Pisa on February 15, 1564. Galileo's father, Vincenzo Galilei, was a well-known musician. Vincenzo decided that his son should become a doctor.

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Who was Evangelista Torricelli? (description)

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Who was Evangelista Torricelli? (description)

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Born 1604, Evangelista Torricelli was an italian Physicist and mathematician. He admired Galileo's astronomical work, but also did not want to clash with the RCC, so he instead chose to work on mathematics. We remember Torricelli for his improvement upon the "theory of indivisibles", and his founding of the "torricelli theorum", which states that "the flow of liquid through an opening is proportional to the square root of the height of the liquid.". He also studied a geometric figure, now called "torricelli's trumpet". He also studied the parabolic motion of projectiles, and invented the mercury barome

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First published Wed Dec 3, 2008; substantive revision Mon Oct 23, 2023
René Descartes (1596-1650) was a creative mathematician of the first order, an important scientific thinker, and an original metaphysician. During the course of his life, he was a mathematician first, a natural scientist or "natural philosopher" second, and a metaphysician third. In mathematics, he developed the techniques that made possible algebraic (or "analytic") geometry. In natural philosophy, he can be credited with several achievements: the first to publish the sine law of refraction; developer of an important empirical account of the rainbow; and proposer of a naturalistic account of the formation of the earth and planets (a precursor to the nebular hypothesis, that the planets formed from loose matter orbiting the sun). More importantly, he offered a new vision of the natural world, which shaped modern physics: a world of matter possessing a few fundamental properties and interacting according to a few universal laws. This natural world included an immaterial mind that, in human beings, was directly related to the brain, a position that led to the modern mind-body problem. In metaphysics (the search for the basic principles of everything there is), Descartes provided arguments for the existence of God and to show that the essence of matter is to be spatially extended, and that the essence of mind is thought (where "thought" includes sensory images as well as rational discourse). Descartes claimed early on to possess a special method, which was variously exhibited in mathematics, natural philosophy, and metaphysics, and which came to include, or to be supplemented by, a method of doubt.

Descartes presented his results in major works published during his lifetime: the Discourse on the Method (in French, 1637), with its essays, the Dioptrics, Meteorology, and Geometry; the Meditations on First Philosophy (i.e., on metaphysics), with its Objections and Replies (in Latin, 1641, 2nd edn. 1642); the Principles of Philosophy, covering his metaphysics and much of his natural philosophy (in Latin, 1644); and the Passions of the Soul, on the emotions (in French, 1649). Works published posthumously included his Compendium of Music (in Latin, 1650), Letters (in Latin and French, 1657-67); World, or Treatise on Light, containing the core of his natural philosophy (in French, 1664); Treatise on Man (in French, 1664), containing his physiology and mechanistic psychology; and the Rules for the Direction of the Mind (in Latin, 1701), an early, unfinished work attempting to set out his method.

Descartes' works have been variously received and valued. Among the learned of his day he was considered to be a top mathematician, the developer of a new and comprehensive physics or theory of nature (including living things), and the proposer of a new metaphysics. In the years following his death, his natural philosophy was especially valued and discussed. His works were invoked in debates over the equality of women. In the eighteenth century, aspects of his science remained influential, as did his project of investigating the cognitive capacities of the knower in assessing the possibility and extent of human knowledge. He was also remembered for his skeptical arguments and for failing to provide a successful response to them in his metaphysics. In the nineteenth century, he was revered for his mechanistic physiology and theory that animal bodies are machines (are constituted by material mechanisms, governed by the laws of matter alone). The twentieth century variously celebrated his famous "cogito" starting point, reviled the sense data that some alleged to be the legacy of his skeptical starting point, and looked to him as a model of the culturally engaged philosopher. He has been variously seen as a hero and a villain; as a brilliant theorist forging new directions in thought and as harbinger of a cold, rationalistic, and calculative conception of human beings. Those new to the study of Descartes should engage his own works in some detail prior to developing a view of his legacy.

1. Intellectual Biography

1.1 Early life and education

Descartes was born on 31 March 1596 in his maternal grandmother's house in La Haye, in the Touraine region of France. His father Joachim, a lawyer who lived in Châtellerault (22 kilometers southwest of La Haye, across the Creuse River in the Poitou region), was away at the Parliament of Brittany in Rennes. The town of La Haye, which lies 47 kilometers south of Tours, has subsequently been renamed Descartes.

When Descartes was thirteen and one-half months old, his mother, Jeanne Brochard, died in childbirth. The young René spent his early years with his grandmother, Jeanne Sain Brochard, in La Haye, together with his older brother Pierre and older sister Jeanne. It is likely that he then moved to the house of his great uncle, Michel Ferrand, who, like many of René's male relatives, was a lawyer; he was a Counselor to the King and held the royal office of provincial Lieutenant General in Châtellerault. When Descartes met Isaac Beeckman in 1618, he introduced himself as "Poitevin," or from Poitou ( 10:46, 51-4; Rodis-Lewis 1998, 3, 26; see also 2:642). At this time (and now and again later on), he also signed letters as "du Perron" and called himself "sieur du Perron" (Lord of Perron), after a small farm in Poitou he inherited from his mother's family (Watson 2007, 81, 230). But he did not neglect his birthplace in La Haye: in a letter of 1649, he described himself as "a man who was born in the gardens of Touraine" (5:349).

In 1606 or 1607, Descartes, a Roman Catholic, entered the newly founded Jesuit College of La Flèche, where he remained until 1614 or 1615. He followed the usual course of studies, which included five or six years of grammar school, including Latin and Greek grammar, classical poets, and Cicero, followed by three years of philosophy curriculum. By rule, the Jesuit philosophy curriculum followed Aristotle; it was divided into the then-standard topics of logic, morals, physics, and metaphysics. The Jesuits also included mathematics in the final three years of study.

Aristotle's philosophy was taught through textbooks and printed commentaries on his works. Aristotle himself frequently discussed the positions of his ancient predecessors. The most extensive commentaries also elaborated in some detail on positions other than Aristotle's. Within this framework, and taking into account the reading of Cicero, Descartes would have been exposed in school to the doctrines of the ancient atomists, Plato, and the Stoics, and he would have heard of the skeptics. Further, important intellectual events were celebrated at La Flèche, including Galileo's discovery of the moons of Jupiter in 1610. Although scholastic Aristotelian philosophy was dominant in Descartes' school years, it was not the only philosophy that he knew.

Famously, Descartes wrote in the autobiographical portion of the Discourse (1637) that, when he left school, "I found myself beset by so many doubts and errors that I came to think I had gained nothing from my attempts to become educated but increasing recognition of my ignorance" (6:4). And yet, he continued, he did not "cease to value the exercises done in the schools" (6:5), for languages, fables, oratory, poetry, mathematics, morals, theology, and philosophy all had their value, as did jurisprudence, medicine, and other sciences (including engineering) that serve as professions and which one might study after attending a school such as La Flèche. He noted the contradiction and disagreement that beset philosophy and so infected the higher sciences (including medicine) "insofar as they borrow their principles from philosophy" (6:8). A year later, in 1638, he told an inquiring father that "nowhere on earth is philosophy taught better than at La Flèche," where he advised his correspondent to send his son even if he wanted him subsequently to transcend the learning of the schools-while also suggesting that the son might study at Utrecht with Henry le Roy, a disciple of Descartes (2:378-9). According to the Discourse, it was not surprising that philosophy as taught at La Flèche was uncertain: it had to be, since he (Descartes) was now offering a first glimpse of the one true philosophy, only recently discovered. Until it could be promulgated, La Flèche, or another good school, would do.

His family wanted Descartes to be a lawyer, like his father and other relatives. To this end, he obtained a law degree from Poitiers in 1616. But he never practiced law or entered into the governmental service that such practice would have made possible (Rodis-Lewis 1998, 18-22). Instead, he became a gentleman soldier, moving in 1618 to Breda, to support the Protestant Prince Maurice against the Catholic parts of the Netherlands (which later constituted Belgium), which were controlled by Spain-a Catholic land, like France, but at this point an enemy.

1.2 First results, a new mission, and method

Perhaps at this time, though certainly by 1628, Descartes had the fundamental insight that makes analytic geometry possible: the technique for describing lines of various sorts by using mathematical equations involving ratios between lengths in relation to coordinate lines. (Descartes did not require that the lines be perpendicular to one another.) Descartes himself did not foresee replacing geometrical constructions with algebraic formulas; rather, he viewed geometry as the basic mathematical science and he considered his algebraic techniques to provide an extension beyond compass-and-ruler constructions. When the right-angled coordinate system of algebraic geometry was subsequently developed, the name "Cartesian coordinates" honored Descartes' discovery. (See Boyer 1968, Ch. 17, Shea 1991, Ch. 3, and, more generally, Domski 2022.)

Descartes left Breda in 1619 to join the Catholic army of Maximilian I (Duke of Bavaria and ally of France). The war concerned the authority of Ferdinand II, a Catholic, who in September had been crowned emperor of the Holy Roman Empire (located in Central Europe and including Austria and parts of northern Italy). Descartes attended the coronation and was returning to the army when winter caught him in the small town of Ulm (or perhaps Neuburg), not far from Munich. On the night of 10 November 1619, he had three dreams that seemed to provide him with a mission in life. The dreams themselves are interesting and complex (see Sebba 1987). Descartes took from them the message that he should set out to reform all knowledge. He decided to begin with philosophy, since the principles of the other sciences must be derived from it ( Disc. II, 6:21-2).

Descartes' activities during the early 1620s are not well-documented. He was in France part of the time, visiting Poitou to sell some inherited properties in 1622 and visiting Paris. He also went to Italy (1623-25). Upon his return he lived in Paris, where he was in touch with mathematicians and natural philosophers in the circle of his long-time friend and correspondent Marin Mersenne (1588-1648). While in Paris, he worked on some mathematical problems and derived the sine law of refraction, which facilitated his work on formulating mathematically the shapes of lenses (later published in the Dioptrics). His major philosophical effort during these years was on the Rules.

In the Rules, he sought to generalize the methods of mathematics so as to provide a route to clear knowledge of everything that human beings can know. His methodological advice included a suggestion that is familiar to students of elementary geometry: break your work up into small steps that you can understand completely and about which you have utter certainty, and check your work often. But he also had advice for the ambitious seeker of truth, concerning where to start and how to work up to greater things. Thus, Rule 10 reads: "In order to acquire discernment we should exercise our intelligence by investigating what others have already discovered, and methodically survey even the most insignificant products of human skill, especially those which display order" (10:403). As examples of "simple" arts "in which order prevails" (10:404), he offered carpet-making and embroidery, and also number-games and arithmetic games. He went on to discuss the roles of the "cognitive faculties" in acquiring knowledge, which include the intellect, imagination, sense perception, and memory. These faculties allow the seeker of knowledge to combine simple truths in order to solve complex problems as found in optics (10:394) or to discover how a magnet works (10:427).

By the end of 1628, Descartes abandoned work on the Rules, having completed about half of the projected treatise. He moved to the Dutch Netherlands, returning to France only infrequently prior to moving to Sweden in 1649. While in the Netherlands, he tried to keep his address secret and changed locations often, according to his motto, "who lives well hidden, lives well" (1:286*).

Descartes spent his first year in the Netherlands in Franeker, where he registered at the University in April, 1629. Initially, he worked on two topics: mathematical science and metaphysics. In Summer, 1629, an impressive set of parhelia, or false suns, were observed near Rome. When Descartes heard of them, he set out to find an explanation. (He ultimately hypothesized that a large, solid ice-ring in the sky acts as a lens to form multiple images of the sun [ Met. 6:355].)

While working on the parhelia, Descartes conceived the idea for a very ambitious treatise, about which he wrote Mersenne on 16 November 1629 from his new residence in Amsterdam. He now intended to explain not "just one phenomenon" (the parhelia), but "all the phenomena of nature, that is to say, the whole of physics" (1:70). This work eventually became The World, which was to have three parts: on light (a general treatise on visible, or material, nature), on man (a treatise on physiology), and on the soul. Only the first two survive (and perhaps only they were ever written), as the Treatise on Light and Treatise on Man. In these works, which Descartes decided to suppress upon learning of the condemnation of Galileo (1:270, 305), he offered a comprehensive vision of the universe as constituted from bare matter possessing the properties length, breadth, and depth (three-dimensional volume) and carved up into particles with size and shape, which may be in motion or at rest, and which interact through quantitative laws of motion that are formulated and sustained by God ( Light, 11:33-4). These works described the visible universe as a single physical system in which all operations, from the formation of planets and the transmission of light from the sun to the physiological processes of human and nonhuman animal bodies, can be explained through the mechanism of matter arranged into shapes and structures and moving according to three laws of motion. In fact, his explanations in the World and the subsequent Principles made little use of the three laws of motion in other than a qualitative manner. The laws sustained the notion that matter moves regularly (in a straight line) and that upon impact bits of matter alter their motions in regular ways-something that happens constantly in the full universe (the "plenum") conceived by Descartes. (At this time, Descartes received an offer of appointment to the medical faculty in Bologna-even though he had not yet made public any of his results-which he declined; see Manning 2014.)

After suppressing his World, Descartes decided to put forward, anonymously, a limited sample of his new philosophy, in the Discourse with its attached essays. The Discourse recounted Descartes' own life journey, explaining how he had come to the position of doubting his previous knowledge and seeking to begin afresh. It offered some initial results of his metaphysical investigations, including mind-body dualism. It did not, however, engage in the deep skepticism of the later Meditations, nor did it claim to establish, metaphysically, that the essence of matter is extension. This last conclusion was presented merely as a hypothesis whose fruitfulness could be tested and "proven," or perhaps merely confirmed (see McMullin 2008), by the results contained in the attached essays on Dioptrics and Meteorology (the latter covering "atmospheric" phenomena).

In his Meteorology, Descartes described his general hypothesis (or supposition) about the nature of matter, before offering accounts of vapors, salt, winds, clouds, snow, rain, hail, lightning, the rainbow, coronas, and parhelia. His hypothesis was as follows:

that the water, earth, air, and all other such bodies that surround us are composed of many small parts of various shapes and sizes, which are never so properly disposed nor so exactly joined together that there do not remain many intervals around them; and that these intervals are not empty but are filled with that extremely subtle matter through the mediation of which, I have said above, the action of light is communicated. (6:233)

He presented a corpuscularian basis for his physics that denied the atoms-and-void theory of ancient atomism and affirmed that all bodies are composed from one type of matter, which is infinitely divisible into particles or corpuscles (6:239). He here also proclaimed that his natural philosophy had no need for the "substantial forms" and "real qualities" that other philosophers (i.e., Aristotelians) "imagine to be in bodies" (6:239). He had taken the same position in the Treatise on Light, where he said that in conceiving his new "world" (i.e., his conception of the universe), "I do not use the qualities called heat, cold, moistness, and dryness, as the Philosophers do" (11:25).

In effect, he was denying the then-dominant scholastic Aristotelian ontology, which explained all natural bodies as comprised of a "prime matter" informed by a "substantial form," and which explained qualities such as hot and cold as really inhering in bodies in a way that is "similar" to the qualities of hot and cold as we experience them tactually. According to the Aristotelian explanation, the qualities that are proper to each sense-color, sound, odor, tastes, and tactual qualities-are really inherent in things, and our experienced sensations resemble these qualities in things. As regards prime matter, many scholastic Aristotelians held that it cannot exist on its own; to form a substance, or something that can exist by itself, prime matter must be "informed" by a substantial form (a form or active principle that gives a substance its essential properties). The four Aristotelian elements, earth, air, fire, and water, had substantial forms that combined the basic qualities of hot, cold, wet, and dry: earth is cold and dry; air is hot and wet; fire is hot and dry; and water is cold and wet. These elements can themselves then serve as "matter" to higher substantial forms, such as the form of a mineral, or a magnet, or a living thing. Whether in the case of earth or of a living thing, such as a rabbit, the "form" of a thing directs its characteristic activity. For earth, that activity is to approach the center of the universe; water has the same tendency, but not as strongly. Accordingly, Aristotelians explained, the planet earth exists at the center, with water on its surface. A new rabbit is formed when a male rabbit contributes, through its seed-matter, the "form" of rabbithood to the seed-matter of the female rabbit. This form then organizes that matter into the shape of a rabbit, including its various organs and physiological processes. The newborn rabbit's behavior is guided by its "sensitive soul," a rabbit-specific instance of the type of substantial form possessed by all animals. Other properties of the rabbit, such as the whiteness of its fur, are explained by the "real quality" of white inhering in each strand of hair.

Although in the World and Meteorology Descartes avoided outright denial of substantial forms and real qualities, it is clear that he intended to deny them ( Corr. 1:324; 2:200; 3:420, 500, 648). Indeed, he claimed that he could explain these qualities themselves through matter in motion ( Light 11:26, Met. 6:235-6). As an example, he explained color in things as a property of surfaces that puts a spin on particles of light, which in turn affect the nerves in the retina, which then affect the brain, causing a sensation in the mind (via matter's effect on the immaterial mind). The sensation of a color (such as red) does not resemble the surface property that causes the effect on the nerve that produces the sensation. The experienced red is an apparently arbitrary sign or signal for a surface property in objects ( Light I; see also Dioptrics VI, 6:130, and Princ. I.68-70).

Two considerations help explain Descartes' tentative language with respect to substantial forms and real qualities. First, when he wrote these works in the 1630s, he was not yet prepared to release his metaphysics, which would support his hypothesis about matter and so rule out substantial forms (1:563). Second, he was sensitive to the prudential value of not directly attacking the scholastic Aristotelian position (3:298), since it was the accepted position in university education (3:577) and was strongly supported by orthodox theologians, both Catholic and Protestant (1:85-6; 3:349).

In 1635, Descartes fathered a daughter named Francine. Her mother was Descartes' housekeeper, Helena Jans. They lived with Descartes part of the time in the latter 1630s. He was arranging for the daughter to live with a female relative of his for the sake of her education when he learned of her death in September 1640, which saddened him greatly (Rodis-Lewis 1998, 140). Subsequently, in 1644, he contributed a dowry for Helena's marriage (Watson 2007, 188).

Recall that Descartes considered the Meditations to contain the principles of his physics. But there is no Meditation labeled "principles of physics." The principles in question, which are spread through the work, concern the nature of matter, the activity of God in creating and conserving the world, the nature of mind (that it is an unextended, thinking substance), mind-body union and interaction, and the ontology of sensory qualities.

The Principles appeared in Latin in 1644, with a French translation in 1647. Descartes added to the translation an "Author's Letter" as a preface. The letter explained important aspects of his attitude toward philosophy, including the view that, in matters philosophical, one must reason through the arguments and evaluate them for one's self (9B:3). He also presented an image of the relations among the various parts of philosophy, in the form of a tree:

Thus the whole of philosophy is like a tree. The roots are metaphysics, the trunk is physics, and the branches emerging from the trunk are all the other sciences, which may be reduced to three principal ones, namely medicine, mechanics and morals. By "morals" I understand the highest and most perfect moral system, which presupposes a complete knowledge of the other sciences and is the ultimate level of wisdom. (9B:14)

The extant Principles offers metaphysics in Part I; the general principles of physics, in the form of his matter theory and laws of motion, as following from the metaphysics, in Part II; Part III concerns astronomical phenomena; and Part IV covers the formation of the earth and seeks to explain the properties of minerals, metals, magnets, fire, and the like, to which are appended discussions of how the senses operate and a final discussion of methodological issues in natural philosophy. His intent had been also to explain in depth the origins of plants and animals, human physiology, mind-body union and interaction, and the function of the senses. (Descartes and his followers variously included topics concerning the nature of the mind and mind-body interaction within physics or natural philosophy, on which, see Hatfield 2000.) In the end, he had to abandon the discussion of plants and animals ( Princ. IV.188), but he included some discussion of mind-body union in his abbreviated account of the senses.

1.5 Theological controversy, Passions, and death

From early in his correspondence with Mersenne, Descartes expressed concern to avoid becoming embroiled in theological controversy or earning the enmity of church authorities (1:85-6, 150, 271). Aside from such prudential concerns, he strictly separated theological doctrines based in faith (e.g., the trinity) from his claims about God based solely in reason ( Corr. 1:44, 150, 153; 4:117). Descartes was a Roman Catholic, but it is clear that the God of his metaphysics is nondenominational, tending toward the deistic. If Descartes were fully consistent, he would make no claims about God's plans or his Providential acts and there would be no miracles in his world ( Light VII, 11:48; Princ. III.2-3; see also Corr. 2:558, 3:214).

In the mid-1640s, Descartes continued work on his physiological system, which he had pursued throughout the 1630s. He allowed the unpublished manuscript of the Treatise on Man to be copied (4:566-7) and he began a new work (5:112), Description of the Human Body, in which he sought to explain the embryonic development of animal bodies. During this period he corresponded with Princess Elisabeth of Bohemia (daughter of Frederick V, a Protestant, and briefly King of Bohemia), now living in the Netherlands, at first on metaphysical topics from the Meditations and then on the passions and emotions. Eventually, he wrote the Passions of the Soul (1649), a comprehensive and original theory of the passions and emotions that presented the most extensive account of his behavioral physiology published during his lifetime.

In 1649, Descartes accepted the invitation of Queen Christina of Sweden to join her court. At her request, he composed the Statutes of the Swedish Royal Academy. On the day he gave them to her, he became ill. He never recovered, and died on 11 February 1650. (On Descartes' intellectual biography, see Clarke 2006, Gaukroger 1995, and Rodis-Lewis 1998.)

2. Philosophical Development

In general, it is rare for a philosopher's positions and arguments to remain the same across an entire life. This means that, in reading philosophers' works and reconstructing their arguments, one must pay attention to the place of each work in the philosophical development of the author. Readers of Immanuel Kant are aware of the basic distinction between his critical and precritical periods. Readers of G. W. Leibniz are also aware of his philosophical development, although in his case there is less agreement on a developmental scheme.

Scholars have proposed various schemes for dividing Descartes' life into periods. This entry adopts a relatively simple division between the era when mathematics provided the model for his method (in the Rules) and the period after the "metaphysical turn" of 1629, when his conception of the role of the intellect in acquiring knowledge changed to privilege purely intellectual intuitions. At this time, he also recognized that the truth of his special or particular hypotheses in natural philosophy was less than certain and so was subject to confirmation through consequences (as mentioned in Sec. 1.3, above). In effect, he adopted what is now called a hypothetico-deductive scheme of confirmation, but with this difference: the range of hypotheses was limited by his metaphysical conclusions concerning the essences of mind and matter, their union, and the role of God in creating and conserving the universe. Consequently, some hypotheses, such as the "substantial forms" of the scholastics, were ruled out. Argumentative differences among the World, Discourse, and Meditations and Principles may then be ascribed to the fact that, in the 1630s, Descartes had not yet presented his full metaphysics and so adopted an empirical mode of justification for even the first principles of his physics, whereas, after 1641, he appealed to his published metaphysics in securing those principles.

Other scholars see things differently. John Schuster (1980) finds that the epistemology of the Rules lasted into the 1630s and was superseded (unhappily, in his view) only by the metaphysical quest for certainty of the Meditations. Daniel Garber (1992, 48) also holds that Descartes abandoned his early method only after the Discourse. In contrast, Peter Machamer and J. E. McGuire (2006) believe that Descartes held natural philosophy to the standard of absolute certainty through the Meditations but admitted defeat on that score at the end of Principles IV, adopting a lower standard of certainty for his particular hypotheses (such as the explanation of magnetism by corkscrew-shaped particles). They see the Principles as marking Descartes' "epistemic turn" away from the methodological stance of realism about intuitive knowledge of substances that they find in the Rules, Discourse, and Meditations.

Some scholars who emphasize epistemology find that the main change in Descartes' intellectual development is the introduction of skeptical arguments in the Discourse and Meditations. Some interpreters, perhaps inspired by Richard Popkin (1979), believe that Descartes took the skeptical threat to knowledge quite seriously and sought to overcome it in the Meditations (e.g., Curley 1978). By contrast, in the interpretive thread followed here, skeptical arguments were a cognitive tool used to guide the reader of the Meditations into the correct cognitive frame of mind for grasping the first truths of metaphysics. An answer to skepticism was a side-effect of this fundamental aim.

Descartes presented his metaphysics first in the Meditations and then, in textbook-format, in Principles I. His metaphysics sought to answer such questions as: How does the human mind acquire knowledge? What is the mark of truth? What is the actual nature of reality? How are our mental experiences related to our bodies and brains? Is there a benevolent God, and if so, how can we reconcile his existence with the facts of illness, error, and immoral actions?

3.1 How do our minds know?

Descartes had no doubt that human beings know some things and are capable of discovering others, including (at least since his metaphysical insights of 1629) fundamental truths about the basic structure of reality. Yet he also believed that the philosophical methods taught in the schools and used by most of his contemporaries were deeply flawed. Accordingly, the doctrines of scholastic Aristotelian philosophy contained a basic error about how fundamental truths, such as those in metaphysics, are obtained. He articulated this error in the First Meditation, by saying (not in his own voice, but in that of the reader): "Whatever I have up till now accepted as most true I have acquired either from the senses or through the senses" (7:18). He then challenged the veridicality of the senses with the skeptical arguments of the First Meditation, including the dream argument (that we might experience sensory images while dreaming that are indistinguishable from waking experience) and the argument that a deceptive God or an evil deceiver is causing our sensory experience or causes us to err even when reasoning.

In the Aristotelian scheme against which Descartes was moving, all knowledge arises through the senses, in accordance with the slogan "There is nothing in the intellect that was not previously in the senses" (7:75, 267). Similarly, orthodox scholastic Aristotelians agreed that there is "no thought without a phantasm," or an image. Descartes explained these convictions as the results of childhood prejudice (7:2, 17, 69, 107; Princ. I.71-3). As children, we are naturally led by our senses in seeking benefits and avoiding bodily harms. As a result, when we grow into adults we are "immersed" in the body and the senses, and so we accept the philosophical view that the senses reveal the nature of reality (7:38, 75, 82-3).

Descartes unfolds a sequence of clear and distinct perception in Meditations III-VI and again in Principles I-II. We consider these results in Secs. 3.3-3.5. For now, let us examine Descartes' thoughts about the senses as a source of knowledge, different from pure intellect.

Descartes assigned two roles to the senses in the acquisition of human knowledge. First, he acknowledged that the senses are usually adequate for detecting benefits and harms for the body. Their natural function is "to inform the mind of what is beneficial or harmful for the composite of which the mind is a part" (7:83), that is, for the composite of mind and body. Here, he adopted a widely held conception of sensory function within natural philosophy, also found in the Aristotelian and medical literatures.

Second, he acknowledged an essential role for the senses in natural philosophy. Older interpretive literature sometimes has Descartes claiming to derive all natural philosophical or scientific knowledge from the pure intellect, independent of the senses. But Descartes knew full well that he could not do that. He distinguished between the general principles of his physics and the more particular mechanisms by which he explained natural phenomena such as magnetism or the properties of oil and water. He claimed to derive the general principles "from certain seeds of truth" that are innate in the mind ( Disc. 6:64). These include the fundamental doctrine that the essence of matter is extension ( Princ. II.3-4, IV.203). For particular phenomena, he relied on observations to determine their properties (such as the properties of the magnet), and he acknowledged that multiple hypotheses about subvisible mechanisms could be constructed to account for those phenomena. The natural philosopher must, therefore, test the various hypotheses by their consequences, and consider empirical virtues such as simplicity and scope ( Disc. VI; Princ. IV.201-6). Further, Descartes knew that some problems require measurements that rely on the senses, including determining the size of the sun ( Med. 7:80, Princ. III.5-6) or the refractive indexes of various materials ( Met. VIII).

Although Descartes recognized an important role for the senses in natural philosophy, he limited that role by comparison with Aristotelian epistemology. Many scholastic Aristotelians held that all intellectual content arises through a process of intellectual abstraction that starts from sensory images found in the faculty of imagination. Mathematical objects are formed by abstraction from such images. Even metaphysics rests on knowledge derived by abstraction from images. Of course, they held that the intellect plays a crucial role in abstracting mathematical objects or the essences of natural things. By contrast, Descartes affirmed that the truths of mathematics and metaphysics are grasped by the pure intellect operating independently of the senses and without assistance from the imagination.

As regards knowledge, Descartes accepted that in order to know something you must not only represent it as true (e.g., "the essence of matter is extension"), but you must also affirm its truth and do so with some justification. In his scheme of mental capacities, the intellect, as the faculty of representation, offers content for judgment. A second mental faculty, the will ( Med. IV, Princ. I.32-4), affirms or denies the truth of that content (e.g., asserts that the essence of matter is extension).

Not all content deriving from the intellectual faculty is "pure." Purely intellectual content arises from innate ideas without any accompanying brain processes. Other intellectual acts require the presence of the body: sense perception, imagination, and corporeal (body-involving) memory. The content of these acts is less clear and distinct than that of pure intellect, and may indeed be obscure and confused (as in the case of color sensations). Nonetheless, the will can affirm or deny such intellectual content. With clear and distinct purely intellectual perceptions, the will is justified in affirming their truth. (As discussed in the next subsection, no error can arise in these judgments.) For lesser degrees of clarity and distinctness, care must be taken in what the will affirms ( Med. IV, Princ. I.66-70, IV.205-6). (See Newman 2019.)

In sum, in considering Descartes' answer to how we know, classes of knowledge differ in the degree of expected certainty. Metaphysical first principles as known by the intellect acting alone should attain absolute certainty. Practical knowledge concerning immediate benefits and harms is known by the senses. Such knowledge needn't attain absolute certainty; even so, it is usually accurate enough. Objects of natural science are known by a combination of pure intellect and sensory observation: the pure intellect tells us what properties bodies can have, and we use the senses to determine which particular instances of those properties bodies do have. For submicroscopic particles, we must reason from observed effects to potential cause. In these cases, our measurements and our inferences may be subject to error, but with care we may hope to arrive at the truth.

3.2 The mark of truth and the circle

At the beginning of the Third Meditation, Descartes declares "I now seem to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true" (7:35). Clarity and distinctness of intellectual perception is the mark of truth.

In the fifth set of Objections to the Meditations, Gassendi suggests that there is difficulty concerning

what possible skill or method will permit us to discover that our understanding is so clear and distinct as to be true and to make it impossible that we should be mistaken. As I objected at the beginning, we are often deceived even though we think we know something as clearly and distinctly as anything can possibly be known. (7:318)

Gassendi has in effect asked how it is that we should recognize clear and distinct perceptions. If clarity and distinctness is the mark of truth, what is the method for recognizing clarity and distinctness?

In reply, Descartes claims that he has already supplied such a method (7:379). What could he have in mind? It cannot be the simple belief that one has attained clarity and distinctness, for Descartes acknowledges that individuals can be wrong in that belief (7:35, 361). He offers this criterion: we have a clear and distinct perception of something if, when we consider it, we cannot doubt it (7:145). That is, in the face of genuine clear and distinct perception, our affirmation of it is so firm that it cannot be shaken, even by a concerted effort to call the things thus affirmed into doubt.

As mentioned in Section 3.1, Descartes held that any act of judgment, such as the affirmation "I think, therefore I am," involves both the intellect and will. The intellect perceives or represents the content of the judgment; the will affirms or denies that content. In the face of genuine clarity and distinctness, "a great light in the intellect" is followed by "a great inclination of the will" (7:59). The inclination of the will is so strong that it amounts to compulsion; we cannot help but so affirm. Descartes maintains that unshakable conviction provides the criterion of genuinely clear and distinct perception. Can't someone be unshakable in their conviction merely because they are stubborn? Assuredly. But Descartes is talking about a conviction that remains unshakable in face of serious and well-thought out challenges (7:22). To be immune from doubt does not mean simply that you do not doubt a proposition, or even that it resists a momentary attempt to doubt; the real criterion for truth is that the content of a proposition is so clearly perceived that the will is drawn to it in such a way that the will's affirmation cannot be shaken even by the systematic and sustained doubts of the Meditations. Perhaps because the process for achieving knowledge of fundamental truths requires sustained, systematic doubt, Descartes indicates that such doubt should be undertaken only once in the course of a life (7:18; 3:695).

Even so, problems remain. Having extracted clarity and distinctness as the criterion of truth at the beginning of the Third Meditation, Descartes immediately calls it into question. He re-introduces an element of the radical doubt from the First Meditation: that a powerful God might have created him with "a nature such that I was deceived even in matters which seemed most evident" (7:36). Descartes therefore launches an investigation of "whether there is a God, and, if there is, whether he can be a deceiver" (7:36).

In the course of the Third Meditation, Descartes constructs an argument for the existence of God that starts from the idea of an infinite being. The argument is intricate. It invokes the metaphysical principle that "there must be at least as much reality in the efficient and total cause as in the effect of that cause" (7:40). This principle is put forward as something that is "manifest by the natural light" (7:40), which itself is described as a cognitive power whose results are indubitable (7:38), like clear and distinct perception (7:144). Descartes then applies that principle not to the mere existence of the idea of God as a state of mind, but to the content of that idea. Descartes characterizes that content as infinite, and he then argues that a content that represents infinity requires an infinite being as its cause. He concludes, therefore, that an infinite being, or God, must exist. He then equates an infinite being with a perfect being and asks whether a perfect being could be a deceiver. He concludes: "It is clear enough from this that he cannot be a deceiver, since it is manifest by the natural light that all fraud and deception depend on some defect" (7:52). (If you are concerned by the move from infinity to perfection, consider that in Descartes' philosophical landscape perfect meant complete, and infinitude is the highest degree of completeness.)

The second and fourth sets of objections drew attention to a problematic characteristic of this argument. In the words of Arnauld:

I have one further worry, namely how the author avoids reasoning in a circle when he says that we are sure that what we clearly and distinctly perceive is true only because God exists. But we can be sure that God exists only because we clearly and distinctly perceive this. Hence, before we can be sure that God exists, we ought to be able to be sure that whatever we perceive clearly and evidently is true. (7:214).

Arnauld here raises the well-known problem of the Cartesian circle, much discussed in recent years.

In reply to Arnauld, Descartes claims that he avoided this problem by distinguishing between present clear and distinct perceptions and those that are merely remembered (7:246). He is not here challenging the reliability of memory (Frankfurt 1962). Rather, his strategy is to suggest that the hypothesis of a deceiving God can only present itself when we are not clearly and distinctly perceiving the infinity and perfection of God, because when we are doing that we cannot help but believe that God is no deceiver. It is as if this very evident perception is to be balanced against the uncertain opinion that God might be a deceiver (7:144). The evident perception wins out and the doubt is removed.

Scholars have debated whether the above response is adequate. Some have constructed other responses on Descartes' behalf or have found them embedded in his writings. One type of response appeals to a distinction between the natural light and clear and distinct perception, and seeks to vindicate the natural light without appeal to God (Jacquette 1996). Another response suggests that, in the end, Descartes was not aiming at metaphysical certainty concerning a mind-independent world but was merely seeking an internally coherent set of beliefs (Frankfurt 1965). A related response suggests that Descartes was after mere psychological certainty (Loeb 1992). The interested reader can follow up this question by turning to the literature just cited (as also to Carriero 2008, Doney 1987, Hatfield 2006, and Newman 2019).

Building on his claim that clear and distinct perceptions are true, Descartes seeks to establish various results concerning the nature of reality, including the existence of a perfect God as well as the natures of mind and matter (discussed more fully in Sec. 3.3). Here we must ask: What is the human mind that it can perceive the nature of reality? Descartes has a specific answer to this question: the human mind comes supplied with innate ideas that allow it to perceive the main properties of God (infinity and perfection), the essence of matter, and the essence of mind. For readers in Descartes' day, this claim would naturally raise a further question: assuming that these innate ideas concern "eternal truths" about God, matter, and mind, do these truths hold independently of God, or do they instead derive from the original contents of God's own intellect?

Descartes rejected both alternatives. He denied, along with many of his contemporaries, that there are eternal truths independent of the existence of God. But he departed from many of his contemporaries in also denying that the eternal truths are fixed in God's intellect. Some Neoplatonist philosophers held that the eternal truths in the human mind are copies, or ectypes, of the archetypes in the mind of God. Some Aristotelian philosophers just prior to Descartes, including Francisco Suárez (1548-1617), held that the eternal truths reflect God's own understanding of his creative power; God's power includes that, if he creates a rabbit, it must be an animal. Eternal truths are latent in God's creative power, and he understands this, so that if human beings understand the eternal truths as eternal, they do so by understanding the creative power of God, which may be something beyond human capacity (Hatfield 1993).

Descartes had a different account. He held that the eternal truths are the free creations of God ( Corr. 1:145, 149, 151; Med. 7:380, 432), originating from him in a way that does not distinguish among his power, will, and intellect. God decides what the essence of a circle is, or to make 2 + 3 = 5. He might have created other essences, but we can't conceive what they might have been. Our conceptual capacity is limited to the innate ideas that God has implanted in us, and these reflect the actual truths that he created. God creates the eternal truths (concerning logic, mathematics, the nature of the good, the essences of mind and matter), and he creates the human mind and provisions it with innate ideas that correspond to those truths. Even in this scheme there must be some eternal truths not created by God: those that pertain to the essence of God himself, including his existence and perfection (see Wells 1982).

3.3 The nature of reality

Descartes' arguments to establish the essences of these substances appeal directly to his clear and distinct perception of those essences. God is an infinite substance and the idea of God includes necessary existence ( Med. III, V, Princ. I.14, 19). Descartes used this idea of God to fashion an argument for the existence of God, now called the Ontological Argument (see Nolan 2021).

The essence of matter is extension in length, breadth, and depth. One might speak here of "spatial extension," but with this proviso: that Descartes denied the existence of space separate from matter. Cartesian matter does not fill a distinct spatial container; rather, spatial extension is constituted by extended matter (there is no void, or unfilled space). This extended substance possesses the further "modes" of size, shape, position, and motion. Modes are properties that exist only as modifications of the essential or principal attributes of a substance. In addition to its essence, extension, matter also has the general attributes of existence and temporal duration (these are shared with mind).

The essence of mind is thought. Minds have the principal attribute of thinking, divided into the two chief powers or faculties previously mentioned: intellect and will. The intellectual, or perceiving power is further divided into the modes of pure intellect, imagination, and sense perception. As mentioned in Section 3.3, pure intellect operates independently of the brain or body, while imagination and sense perception require the body for their operation. The will is also divided into various modes, including desire, aversion, assertion, denial, and doubt. These always require some intellectual content (whether pure, imagined, or sensory) upon which to operate. Perhaps for that reason, Descartes describes the mind as an "intellectual substance" ( Med. VI, 7:78; also, 7:12). The mind essentially has a will, but the intellectual (or perceptive, or representational) power is more basic, as the operations of the will depend on it.

What role does consciousness play in Descartes' theory of mind? Many scholars believe that, for Descartes, consciousness is the defining property of mind (e.g., Rozemond 2006). There is some support for this position in the Meditations (Second Replies). Descartes defines mind as "the substance in which thought immediately resides" (7:161), and he says that the term "thought" extends to "everything that is within us in such a way that we are immediately conscious of it" (7:160*). If mind is thinking substance and thoughts are essentially conscious, perhaps consciousness is the essence of thought?

Perhaps not. Descartes did hold that all thoughts are, in some way, conscious (7:226), but this did not mean that we have reflective awareness of, or notice, every thought that we have ( Corr. 5:220). In the Second Meditation, he describes himself as a thinking thing by enumerating all the modes of thoughts of which he is conscious: understanding (or intellection), willing, imagining, and (at this point, at least seeming to have) sense perceptions (7:28). He thus sets up consciousness as a mark of thought. But is it the essence? Not necessarily. If perception (intellection, representation) is the essence of thought, then all thoughts might have basic consciousness because the character of the intellectual substance is to represent, and any representation present in an intellectual substance is, thereby, present in mind. An intellectual substance (a mind) is a perceiving substance, which intrinsically perceives its own states. Further, he held that any act of will present in an intellectual substance is thereby available to consciousness ( Pass. I.19). (On consciousness and the essence of mind, see Jorgensen 2020, 2.1).

In distinguishing between conscious thoughts and thoughts of which we are reflectively aware, Descartes allowed for conscious thoughts that we don't notice or remember. Indeed, his theory of the senses (Sec. 5) allows for unnoticed sensations and mental operations.

3.4 Mind-body relation

In the Discourse, Descartes presented the following argument to establish that mind and body are distinct substances:

Next I examined attentively what I was. I saw that while I could pretend that I had no body and that there was no world and no place for me to be in, I could not for all that pretend that I did not exist. I saw on the contrary that from the mere fact that I thought of doubting the truth of other things, it followed quite evidently and certainly that I existed; whereas if I had merely ceased thinking, even if everything else I had ever imagined had been true, I should have had no reason to believe that I existed. From this I knew I was a substance whose whole essence or nature is simply to think, and which does not require any place, or depend on any material thing, in order to exist. (6:32-3)

This argument moves from the fact that he can doubt the existence of the material world, but cannot doubt the existence of himself as a thinking thing, to the conclusion that his thoughts belong to a nonspatial substance that is distinct from matter.

While this argument might secure the existence of a thinker, it does not show that the thinker is not a material thing. That conclusion fallaciously rests on conceivability based in ignorance. There is nothing to preclude that the thinking thing is in fact a complex material system. Descartes has merely relied on the fact that he can doubt the existence of matter to conclude that matter is distinct from mind. That argument doesn't work. From the fact that the Joker cannot, at a certain moment, doubt the existence of Batman (because he is with him), but he can doubt the existence of Bruce Wayne (who might, for all the Joker knows, have been killed by the Joker's henchmen), it does not follow that Bruce Wayne is not Batman. In fact, he is Batman. The Joker is merely ignorant of that fact.

In the Meditations, Descartes altered the argument. In the Second Meditation, he again asserted that he could doubt the existence of matter but not the existence of himself as a thinking thing. But he explicitly refrained from concluding that his mind was distinct from body, on the grounds that he remained ignorant of his nature (7:27). Then, in the Sixth Meditation, having established, to his satisfaction, the mark of truth, he used it to support a positive argument that the essence of mind is thought and that a thinking thing is unextended; and that the essence of matter is extension and that extended things cannot think (7:78). He based this argument on clear and distinct intellectual perceptions of the essences of mind and matter, not on the fact that he could doubt the existence of one or the other.

This conclusion asserts the well-known substance dualism of Descartes. That dualism has problems. As Princess Elisabeth of Bohemia, among others, asked: if mind is unextended and matter is extended, how do they interact? This problem vexed not only Descartes, who admitted to Elisabeth that he didn't have a good answer (3:694), but it also vexed Descartes' followers and other metaphysicians. It seems that, somehow, mind and body must be brought into relation, because when we decide (a mental act) to pick up a pencil, our arm (a physical thing) actually moves, and when light hits our eyes, we mentally experience the visible world. But how do mind and body relate? Some of Descartes' followers adopted the position of occasionalism, according to which God mediates the causal relations between mind and body; mind does not affect body and body does not affect mind, but God gives the mind appropriate sensations given the state of the body, and he makes the body move by putting it into the correct brain state when we decide (mentally) to pick up the pencil (see Lee 2020). Other philosophers adopted other solutions, including the monism of Spinoza and the pre-established harmony of Leibniz.

In the Meditations and Principles, Descartes did not focus on the metaphysical question of how mind and body interact. Rather, he discussed the functional role of mind-body union in the economy of life. Our sensations serve us well in avoiding harms and pursuing benefits. Pain-sensations induce us toward behaviors that usually protect our bodily integrity. Pleasure leads us toward things that are usually good for us. Our sense perceptions are reliable enough for distinguishing objects that need distinguishing and for navigating as we move about. As Descartes saw it, "God or nature" set up these relations for our benefit. They are not perfect. Sometimes our senses present things differently than they are, and sometimes we make judgments about sensory things that extend beyond the appropriate use of the senses.

3.5 God and sensory error

In discussing the mark of truth, Descartes maintained that the human intellect is generally reliable because God created it. In discussing the functioning of the senses to preserve the body, he explained that God has arranged mind-body interaction so that our sensations generally are conducive to the good of the body. Nonetheless, errors occur. Our judgments about sensory things may be false, just as, more broadly, human beings may make poor moral choices even though God has given them a will that is intrinsically drawn to the good ( Corr. 1:366, 5:159, Princ. I.42). For example, we may form the childhood habit of judging, with respect to our color sensations, that the color we experience "resembles" something in objects (the Aristotelian theory). Subsequent philosophical reflection (perhaps instigated by reading Descartes) may lead us to conclude that these judgments are unwarranted, because color sensations are not clear and distinct but obscure and confused ( Princ. I.66-70). In other cases, our sense perceptions may represent things as being a certain way when they are not. Sometimes we feel pain because a nerve has been damaged somewhere along its length, and yet there is no tissue damage at the place the pain is felt. Amputees may feel pain as located in their fingers when they have no fingers ( Princ. IV.196).

Descartes responded to these errors differently. He explained cognitive (judgmental) and moral errors as resulting from human freedom ( Med. IV). God provides human beings with a will, and wills are intrinsically free. But we have finite intellects. Because we are free, we can choose to judge in cognitive or moral situations in which we do not have clear and distinct perceptions of the true or the good. If human beings restricted their acts of will to cases of maximum clear and distinct perception, they would never err. If we go wrong, Descartes contends, we are responsible, because we might have restricted our judgments to matters about which we have the certainty of clear and distinct perception. The applicability of this solution to the case of color sensations and resemblance is, however, not apparent, as we may not have made a reflective choice when, as children, we accepted the resemblance account of color experience. In that case, we might become culpable only after reading and accepting Descartes' arguments that color sensations are obscure and confused and applying this finding to our habitual assertion of resemblance.

Matters are different for specific errors of sensory representation, such as the mislocation of pain. The senses depend on media and sense organs and on nerves that must run from the exterior of the body into the brain. God sets up the mind-body relation so that our sensations are good guides in most circumstances. But the media may be poor (the light may not be good), circumstances may be unusual (as when a partially submerged stick appears bent), or the nerves may be damaged (as with the amputee). In these cases, the reports of the senses are misleading. Since God has set up the system of mind-body union, shouldn't God be held accountable for the fact that the senses can misrepresent how things are? Here Descartes does not appeal to our freedom of judgment, for in fact we must often use the senses in suboptimal cognitive circumstances when navigating through life, with no opportunity for reflection and reasoned choice. Rather, he points out that God was working with the finite mechanisms of the human body (7:88), and he suggests that God did the best that could be done given the type of parts needed to constitute such a machine (extended parts that might break or be unusually perturbed). It's not God's fault that a well-made bodily machine can occasionally create sensations that misrepresent.

Some cases of sensory misrepresentation are clear-cut cases of error. With the amputee, the pain seems to be in fingers that are not there. The representational content (that the fingers are damaged) does not match the world. Similarly, a partially submerged stick may look bent. Even if we use our intellects to interpret the illusions or sensory misrepresentations so as to avoid error by withholding judgment or even by judging correctly (7:438), it remains clear that sensory misrepresentation has occurred.

In other cases, Descartes describes the senses as providing material for error, but it remains uncertain whether such error arises from making unwarranted judgments on obscure and confused sensations or is due to straightforward sensory misrepresentation. In the Third Meditation, he describes sensations that were later called "secondary qualities" (e.g., colors, sounds, hot and cold) as "materially false." Scholars have difficulty interpreting this notion. Descartes initially defines material falsity as something that "occurs in ideas, when they represent non-things as things" (7:43). He offers the idea of cold as an example: our senses represent cold as a positive quality of objects, but Descartes considers that cold may instead simply be the absence of heat and so isn't a quality of its own. Accordingly, this case should be assimilated to sensory misrepresentation: representing things as they are not (representing cold as a quality when it is the absence of a quality).

Descartes also offers a different gloss on the obscurity of sensory ideas. He allows that such ideas may be "true" in the sense of representing something positive in things, but that they may do so in such a way that "the reality which they represent is so extremely slight that I cannot even distinguish it from a non-thing" (7:44). Accordingly, sensory ideas are not misrepresentations, they are simply so obscure and confused that we cannot tell what their representational content might be by considering their experienced character, such as the phenomenal character of cold or of color. We then precipitately make an erroneous judgment that color sensations resemble their causes in objects. (Metaphysics and natural philosophy are needed to tell us what our color sensations obscurely represent: properties of object-surfaces that reflect light a certain way-see Sec. 5.) "Material falsity" arises from representations so obscure that they allow room for mistaken judgments (e.g., about resemblance).

The issues surrounding the notion of material falsity in Descartes are intricate but telling of his theory of mind and sensory representation. Entrance to the literature can be gained through Wee (2006), Brown (2006, Ch. 4), and Hatfield (2013).

4. The New Science

During Descartes' school days, there were signs that the scientific conception of the universe was changing. Recall that Galileo's discovery of the four moons of Jupiter was celebrated at La Flèche in 1610 (see Galileo 1610). More generally, Copernicus had, in the previous century, argued forcefully that the sun, not the earth, is at (or near) the center of the solar system (Copernicus 1543). Early in the seventeenth century, Johannes Kepler (1604) announced new results in optics, concerning the formation of images, the theory of lenses, and the fact that the retinal image plays a central role in vision. By the early 1630s, Descartes was aware of William Harvey's claim that the blood circulates in the body ( Corr. 1:263).

Descartes contributed new results to the mathematical description of nature, as developer of an accurate model of the rainbow ( Met. VIII) and as a discoverer of the sine law of refraction. (Descartes was the first to publish the sine law, in Diop. II. Previously, the law had been discovered by the Islamic investigator Ibn Saul [10th c.], the English astronomer Thomas Harriot [ca. 1600], and the Dutch mathematician and astronomer Willebrord Snell [ca. 1620]. See Sabra 1967, 99-103, and Rashed 1990.) As significant as these results are, his primary contribution to the "new science," or the "new mechanical philosophy," lay in his general vision of a mechanistic approach to nature, together with many details of that vision for specific natural phenomena (such as magnetism, the formation of the solar system, and sensory physiology), so as to provide a comprehensive alternative to the dominant Aristotelian physics. The process of forming a new science continued after Descartes, reaching a high point in Newton's mechanics, including a consolidation of the Copernican hypothesis.

In the textbooks of Aristotelian physics of Descartes' day, it was common to divide physics into "general" and "special." General physics pertained to the basic Aristotelian principles for analyzing natural substances: form, matter, privation, cause, place, time, motion. Special physics concerned actually existing natural entities, divided into inanimate and animate. Inanimate physics further divided into terrestrial and celestial, in accordance with the Aristotelian belief that the earth is at the center of the universe and differs in nature from the heavens (including the moon, and everything beyond it). Inanimate terrestrial physics first covered the four elements (earth, air, fire, and water), then the "mixed" bodies composed from them, including the various mineral kinds. Animate terrestrial physics concerned the various powers that Aristotelians ascribed to ensouled beings, where the soul is considered as a principle of life (possessing vital as well as mental or cognitive powers). In the simplest textbooks, the powers of the soul were divided into three groups: vegetative (including nutrition, growth, and reproduction), which pertained to both plants and animals; sensitive (including external senses, internal senses such as memory and imagination, appetite, and motion), which pertains only to animals, both nonhuman and human; and rational powers, pertaining to human beings alone. All the bodies in both inanimate and animate terrestrial physics were governed by a "form" or active principle, as described in Section 1.3.

Descartes' ambition was to provide replacements for all the main parts of Aristotelian physics. In his physics, there is only one matter and it has no active forms. He dissolved the boundary that made celestial and terrestrial differ in kind. His one matter possesses the properties of size, shape, position, and motion; it is infinitely divisible and constitutes space (see Sec. 3.3). This matter is governed by three laws of motion, including a precursor to Newton's law of inertia (but without the notion of vector forces) and a law of impact. Descartes' matter possessed no "force" or active agency; the laws of motion as decreed by God were sustained by his activity. Earth, air, fire, and water were simply four among many natural kinds, all distinguished simply by the characteristic sizes, shapes, positions, and motions of their parts.

Descartes also wanted to provide an account of the formation of plants and animals by mechanical causes ( Disc. V, 6:44-45), but he did not succeed in framing an account that he was willing to publish (so that only portions of his physiology were revealed in the Discourse, Dioptrics, Meditations, Principles, and Passions). In writings that were published only posthumously (in 1664), including the Treatise on Man, he developed an extensive physiological description of animal bodies, in which he explained the functions of life in a purely mechanical manner, without appeal to a soul or vital principle. (The Treatise on Man was circulated in manuscript form during Descartes' lifetime [5:112].) The Description of the Human Body (1664) included his speculations on embryogenesis.

In mechanizing the concept of living thing, Descartes did not deny the distinction between living and nonliving, but he redrew the line between ensouled and unensouled beings. In his view, among earthly beings, only humans have souls. He thus equated soul with mind: souls account for intellection and volition, including conscious sensory experiences, conscious experience of images, and consciously experienced memories. He regarded nonhuman animals as machines, devoid of mind and consciousness, and hence lacking in sentience. (Although Descartes' followers understood him to have denied all feeling to animals, some recent scholars question this interpretation; on this controversy, see Cottingham 1998 and Hatfield 2008.) Consequently, Descartes was required to explain all of the powers that Aristotelians had ascribed to the vegetative and sensitive soul by means of purely material and mechanistic processes ( Man 11:202). These mechanistic explanations extended not merely to nutrition, growth, and reproduction, but also to the functions of the external and internal senses, including the ability of nonhuman animals to respond via their sense organs in a situationally appropriate manner: to approach things that are beneficial to their body (including food) and to avoid danger (as the sheep avoids the wolf).

In the Treatise on Man and Passions, Descartes described purely mechanical processes in the sense organs, brain, and muscles, that were to account for the functions of the sensitive soul. These processes involved "animal spirits," or fine fluid matter as distilled from the blood at the base of the brain and distributed down the nerves to cause muscle motions in accordance with current sensory stimulation. The brain structures that mediate behavior may be innate or acquired. Descartes ascribed some things that animals do to instinct; he explained other aspects of their behavior through a kind of mechanistic associative memory. He regarded human physiology as similar to nonhuman animal physiology, anent both vegetative and (some) sensitive functions-those sensitive functions that do not involve consciousness or intelligence:

Now a very large number of the motions occurring inside us do not depend in any way on the mind. These include heartbeat, digestion, nutrition, respiration when we are asleep, and also such waking actions as walking, singing, and the like, when these occur without the mind attending to them. When people take a fall, and stick out their hands so as to protect their head, it is not reason that instructs them to do this; it is simply that the sight of the impending fall reaches the brain and sends the animal spirits into the nerves in the manner necessary to produce this movement even without any mental volition, just as it would be produced in a machine. (Fourth Replies to Objections, Med. 7:229-30)

Much human behavior occurs without intervention from the mind.

The fact that Descartes offered mechanistic explanations for many features of nature does not mean that his explanations were successful. His followers and detractors debated the success of his proposals for nearly a century after his death. His accounts of magnetism and gravity were challenged. Leibniz questioned the coherence of Descartes' laws of motion and impact. Newton offered his own laws of motion and an inverse square law of gravitational attraction. His force-based account of orbital planetary motions replaced Descartes' vortexes. Others struggled to make Descartes' physiology work. There were also deeper challenges. Some wondered whether Descartes could explain how his infinitely divisible matter coalesces into solid bodies. Why shouldn't collections of particles act like puffs of smoke, that separate upon contact with larger particles? Indeed, how do particles themselves cohere?

Such problems were real, and Descartes' physics was abandoned over the course of the eighteenth century. Nonetheless, it provided a conception for a comprehensive replacement of Aristotelian physics that persisted in the Newtonian vision of a unified physics of the celestial and terrestrial realms, and that continued in the mechanistic vision of life as revived in the nineteenth century. (On the rise of the new science, or what is sometimes called the "scientific revolution," see Henry 2008 and Shapin 1996; for a survey of Descartes' natural philosophy, see Gaukroger 2002.)

5. Theory of Sense Perception

As the "mechanical philosophy" of Descartes and others replaced the Aristotelian physics, the theory of sensory qualities required revision. This was especially true for what came to be known as the "secondary qualities" (in the terminology of Robert Boyle and John Locke). The secondary qualities include colors, sounds, odors, tastes, and tactile qualities such as hot and cold. The Aristotelians maintained that these qualities exist in objects as "real qualities" that are like instances or samples of the quality as experienced. A red thing possesses the quality red in just the same way it possesses a shape: it simply is red, and we experience that very redness when we see a red object (the "resemblance thesis" from Sec. 3.5).

Descartes sought to replace "real qualities" with a mechanistic account of qualities in objects. The sensory qualities of objects would be explained by what were later called "primary qualities" (such as size, shape, position, and motion). Accordingly, Descartes rendered light as a property of particles and their motions: it is a "tendency to move" as found in a continuous medium and radiating out from a luminous body. When light strikes an object, the particles that constitute light alter their rotation about their axis. "Spin" is what makes light have one color rather than another. When particles with one or another degree of spin interact with retinal nerves, those nerves jiggle in a certain way. In the brain, this jiggling affects the animal spirits, which in turn affect the mind, causing it to experience one or another color. Color in objects is thus that property of their surface that causes light particles to spin in one way or another, and hence to cause one sensation or another ( Diop. I, 6:85, 91-2). Sound arises from vibrations in sounding things, and odor from shaped particles that differentially affect the olfactory nerves.

Descartes introduced this new theory of sensory qualities in the first six chapters of Light. He defended it by arguing that his explanation of qualities in bodies in terms of size, shape, and motion are clearly understood by comparison with the Aristotelian qualities (11:33). Subsequently, in the Meditations and Principles, he supported this account by appeal to the metaphysical result that bodies possess only geometrical modes of extension ( Med. V, Princ. I.69, II.4-5, IV.199). Real qualities are ruled out because they are not themselves instances of size, shape, or motion (even if patches of color have a size and a shape, and can be moved about).

In addition to a new theory of sensory qualities, Descartes offered theories of the way in which the spatial properties-size, shape, distance, and position-are perceived in vision. In Descartes' day and before, "optics" was defined as the theory of vision, including physical, physiological, and psychological aspects. In antiquity, Euclid and Ptolemy wrote on optical problems. During the Middle Ages, the Arabic natural philosopher Ibn al-Haytham produced an important new theoretical work on vision that included an extensive account of the perception of spatial properties.

The theoretical terrain in optics changed with Kepler's doctrine that vision is mediated by the retinal image and that the retina is the sensitive body in the eye. Previous theorists generally believed that the "crystalline humor," now known as the lens, was the sensitive body. Descartes accepted Kepler's result and framed a new theory of spatial perception. Some of his theorizing simply adapted Ibn al-Haytham's theories to the newly discovered retinal image. Ibn al-Haytham held that size is perceived by combining the visual angle that a body subtends with perception of its distance, to arrive at a perception of the true size of the object. (Visual angle is formed by the directions from a vantage point to a seen-object for a given fixation, e.g., the angle formed by the direction to the feet and to the crown of the head of a person standing at moderate distance to us.) In Ibn al-Haytham's scheme, visual angle is registered at the surface of the crystalline humor. Descartes held that size is perceived by combining visual angle with perceived distance, but he now treated visual angle as the extent of an object's projection onto the retina. (On spatial perception from Euclid to Descartes, see Hatfield 2020.)

In Ibn al-Haytham's account, if the size of an object is known, distance may be perceived through an inference; for a given size, an object's distance is inversely proportional to its visual angle. Descartes recognized this traditional account ( Diop. VI, 6:138-40), depending as it does on past experience of an object's size and on an inference or rapid judgment that combines perceived visual angle with this known or remembered size. Descartes held that these judgments are habitual and happen so quickly that they go unnoticed, as do the sensations that present visual angle, being rapidly replaced by visual experiences of objects at a distance (Sixth Replies, Med. 7:437-38).

Ibn al-Haytham further maintained that distance can be perceived by an observer's being sensitive to the number of equal portions of ground space that lie between the observer and a distant object. Descartes did not adopt this explanation. However, Descartes used his mechanistic physiology to frame a new account of how distance might be perceived that drew on Kepler's results.

In the Keplerian theory of how the eye works, an image is formed on the retina as a result of refraction by the cornea and lens. For objects at different distances, the focal properties of the system must be changed, just as the focal length of a camera is changed (Kepler 1611, prop. 64). There were several theories of how this might occur, and Descartes sometimes said merely that the shape of the eye changes to accommodate for near and far vision ( Diop. VI, 6:137), sometimes that specifically the shape of the lens changes ( Man 11:155-56, 159). He then theorized that this change in the shape of the lens must be controlled by muscles, which themselves are controlled by nerve processes in the brain.

When we correctly perceive the distance and combine it with visual angle (by an unnoticed mental act), the result is a veridical perception of a size-at-a-distance. Descartes described the resulting perception as possessing the attributes that were labelled "size constancy" in the twentieth century:

Concerning the manner in which we see the size and shape of objects, I need not say anything in particular since it is included in the way we see the distance and position of their parts. That is, we judge their size by the knowledge or opinion that we have of their distance, compared with the size of the images they imprint on the back of the eye-and not simply by the size of these images. This is sufficiently obvious from the fact that the images imprinted by objects very close to us are a hundred times bigger than those imprinted by objects ten times farther away, and yet they do not make us see the objects a hundred times larger; instead they make the objects look almost the same size, at least if their distance does not deceive us. (Diop. VI, 6:140)

When Descartes speaks of taking into account the "size of the images" on the retina, he need only be speaking of visual angle, which is equivalent to retinal-image size. In saying that a nearby object is a hundred times larger on the retina than one ten times farther away, he is speaking of area; the nearby object would be ten times larger in linear height. If visual angle and object distance are correctly perceived and combined, the object's constant true size is perceived. If we get the distance wrong, as in underperceiving the distance to the sun and moon, we misperceive the size, in this case, as too small ( Diop. VI, 6:144-45).

Descartes' work on visual perception is but one instance of his adopting a naturalistic stance toward conscious mental experience. The Passions constitute another (Sec. 6). It is sometimes said that Descartes' dualism placed the mind outside nature by rendering it as an immaterial substance. That is a retrospective judgment from a perspective in which immaterial substances are automatically deemed "unnatural." For Descartes and his followers, mind-body interaction and its laws were included within the domain of natural philosophy or physics (in the general meaning of the latter term, as the theory of nature). Descartes spoke of regular relations between brain states and the resulting sensory experiences, which his followers, such as Regis, subsequently deemed "laws" of mind-body relation (see Hatfield 2000). In this way, Descartes and his followers posited the existence of psychophysical or psychophysiological laws, long before Gustav Fechner (1801-1887) formulated a science of psychophysics in the nineteenth century.

6. Passions and Emotions

The passions and emotions had been a topic of philosophical interest since antiquity and were much discussed in Descartes' day (James 1997). His own interest intensified during the 1640s, as a result of his correspondence with Princess Elisabeth (trans. Shapiro, 2007). Descartes recognized two separate types of mental states that can be classified as emotions (excitations) of the soul: purely intellectual feelings, such as the intellectual joy of loving God, and body-dependent affects on the mind, called "passions" (in the etymological sense of the mind being passive in receiving them). We will focus on the latter, which are the subject of Descartes' final publication, the Passions of the Soul (1649). In the preferatory letters to this work, Descartes acknowledged that he approaches the passions "as a physicist" or natural philosopher (11:326); but he in fact engaged to some extent all the main genres of writings on the passions: medical, natural philosophical, and moral.

Recall that Descartes attributed only two powers to the mind: intellect and will. The intellect is the seat of ideas or perceptions, which are representations. The will is an active power that responds to the represented content, by affirming its truth, denying its truth, doubting it, or desiring it to be the case. The will performs acts such as choosing to think about mathematics or to raise one's arm ( Princ. I.32, Pass. I.17-19).

In the Passions (I.22-29), Descartes divided the perceptions of the intellect that are caused by the body into three kinds: perceptions of external objects (such as a candle or a bell); perceptions of internal bodily states (such as hunger or thirst); and perceptions that we refer to the soul itself, such as bodily love, hate, and desire. These passions are "bodily" because it is part of their definition that they have a bodily cause (as opposed to purely intellectual emotions, which have the soul as cause, Pass. I.91, 147). This third type of bodily passions can be called the "passions proper."

Descartes defined the passions proper as "perceptions or sensations or emotions of the soul that we refer particularly to it and that are caused, maintained, and strengthened by some movements of the spirits" ( Pass. I.27). Like external sensations, the passions are immediately caused by brain activity (animal spirits). But they are referred to the soul, not to an external object, even if they are in many cases triggered by an external object. Suppose that we see a ferocious animal. The sense of vision gives us a perception of the shape, size, and color of the animal, according to the ways in which the nerves are affected and cause animal spirits to flow (see Sec. 5). But the flow of animal spirits also causes us to experience the passion of fear. Interestingly, Descartes did not hold that we then run from the animal because we experience the fear. Rather, the same flow of spirits that causes us to feel fear also, at the same time, by purely mechanical processes (see Sec. 4), affects the muscles of the legs so as to make us run. This occurs "witout any contribution from the soul" ( Pass. I.38). The function of the experienced passion (the feeling of fear) is to "move and dispose the soul to want the things for which they prepare the body" (I.40; see also II.52), in this case, to make us want to continue running.

The passions do not respond to all the properties that affect the external senses. That is, "the objects which stimulate the senses do not excite different passions in us because of all the differences in them, but only because of the various ways in which they may harm or benefit us, or in general have importance for us" ( Pass. II.52). Felt fear responds to the ferocious animal under the aspect of potential harm. Descartes recognized six simple or primitive passions: wonder, love, hatred, desire, joy, and sadness (II.69), from which all the other passions are generated. Wonder arises when we perceive something that is novel. Rare objects affect the brain differently than objects we have seen before. The resulting brain state causes the body to stay physically focused on the novel object. The experienced passion of wonder then causes us to focus mentally on the same object (II.70-78). The inclusion of wonder as a primitive type of passion was new (or newly made prominent) in the Passions.

The other five passions present objects as good or bad for us. The passion of love makes us want to join ourselves willingly with its object; hatred makes us want to separate ourselves. Desire is a future-oriented feeling of wanting something it represents as good to be the case. Joy arises from the present possession of a good thing; sadness arises when an evil is represented as pertaining to us (II.78-93). Again, these passions are caused by brain states that arise in the machine of the body. States arise in the brain which then prepare the body for behaviors and cause the felt passion. Here, Descartes speaks of brain states as "representations"; joy, for example, "is a pleasant emotion that the soul has when it enjoys a good that impressions in the brain represent to it as its own" (II.91). The Passions relies heavily on the mechanistic physiology in Descartes' earlier works.

Descartes' theory of the passions is complex and covers many aspects, including the role of the brain, the role of judgment in triggering passions, and the passions in morality. Entrance to the literature can be found in Brown (2006), Rutherford (2021), Shapiro (2003), and Hatfield (2007).

7. Reception and Legacy

The things that readers find valuable in Descartes' work have changed across the centuries. His natural philosophy had an immediate impact that lasted into the eighteenth century. His theory of vision was part of that heritage, as were his results in mathematics. His mechanistic account of the psychology of the sensitive soul and his view that animals are like machines were revived in the nineteenth century.

Descartes was strongly invoked in some works on the equality of the sexes and the education of women. The seventeenth-century French Cartesian François Poulain de la Barre used substance dualism in arguing to the conclusion that "the mind has no sex" (trans. Clarke, 157), although he was not above suggesting that female physiology yields cognitive advantages (Schmitter 2018, 5). The early eighteenth-century English philosopher Mary Astell used Cartesian philosophy in her advocacy of education for women (Atherton 2001). In contrast, Nicolas Malebranche was less favorable toward attributing cognitive equality to women, showing that there was no single position shared among the Cartesians concerning equality (Hamerton 2008). (For entry into recent work on feminism and Descartes, including historical studies, see Bordo 1999 and Schmitter 2018.)

The fortune of Descartes' metaphysics and epistemology is complex. In his own time, he inspired a raft of followers, who sought to develop his metaphysics, epistemology, and natural philosophy, and to add a worked-out ethics. These authors included Géraud de Cordemoy, Arnold Geulincx, Poulin de la Barre, Antoine Le Grand, Malebranche, Regis, and Rohault. The British philosopher Henry More had a long history of engaging with Descartes' mechanical philosophy and metaphysics, toward which he at first expressed qualified admiration, which later turned to deep hostility (More 1662, 1671; see Leech 2013). Pierre-Daniel Huet (1689) offered a scathing critique of Descartes' philosophy. Other major philosophers, including Benedict de Spinoza and G. W. Leibniz, were influenced by Descartes' thought but developed their own, distinct systems.

Descartes' project to examine the knower as a means to determine the scope and possibilities of human knowledge had a profound effect on early modern epistemology and metaphysics. Among his immediate followers, Malebranche most fully developed this aspect of Descartes' philosophy. Subsequent philosophers who were not followers of Descartes also adopted the strategy of investigating the knower. The epistemological works of Locke, George Berkeley, David Hume, Thomas Reid, and Immanuel Kant pursued this investigation. These authors came to different conclusions than had Descartes concerning the ability of the human mind to know things as they are in themselves. Hume and Kant especially-and each in his own way-rejected the very notion of a metaphysics that reveals reality as it is in itself. They did not merely deny Descartes' particular metaphysical theories; they rejected his sort of metaphysical project altogether. But they did so through the type of investigation that Descartes himself had made prominent: the investigation of the cognitive capacities of the knower.

During the twentieth century and into the twenty-first, various aspects of Descartes' philosophy were widely invoked and perhaps just as widely misinterpreted. The first is Descartes' skepticism. In the early twentieth century, one response to the threat of skepticism about our knowledge of the external world was to retreat to the position that we can only know our own sense data, where "sense data" are equated with the supposed contents of immediate sensory experience: for vision, color patches having a shape (e.g., Russell 1914). Some authors then treated Descartes' project in the Meditations as that of reducing human knowledge to immediate sense data, from which knowledge of the external world was to be constructed. (A version of this reading is Williams 1986.)

As a reading of Descartes, this position has little to offer. As we have seen, in the Second and Third Meditations Descartes argues from the indubitability of the cogito reasoning to the trustworthiness of intellectual perception to the existence of a perfect being (God). This argument does indeed seek to infer the reality of a being external to the mind. But the inference does not invoke sensory experience. It proceeds from a non-sensory and innate idea of God to the existence of that God. Whatever one may think of the quality of this argument, it has nothing to do with sense data. Descartes used skeptical arguments as a tool to temporarily disengage the reader from the sensory world in order to undertake metaphysical investigations that rely on the pure intellect. But again, sense data are not in the mix. The use of skepticism to "withdraw the mind from the senses" ( Med. pref., 7:9) may be read as an instance of Descartes re-purposing, for his own philosophical ends, a type of writing from his time: the spiritual exercise, now reconfigured as cognitive exercises. Accordingly, Descartes' meditator is guided by the text of Meditations in purging our everyday reliance on the senses in order to uncover the pure intellect (see Sec. 3.1). Recall that the metaphysical doubt is to be used once in one's life in order to find the true metaphysics. The search for absolute certainty supports this project and does not extend to ordinary life ( Med. I, VI, 7:22, 89-90). (On Descartes and meditative writing, see Underkuffler 2019.)

Another line of twentieth- and twenty-first century interpretation also focused on the isolation of the subject in the Second Meditation. In the course of that Meditation, Descartes accepts that he knows the contents of his mind, including putative sensory experiences, even though he doubts the existence of his body. Some philosophers have concluded from this that Descartes believed that human beings actually can, in their natural state, have sensory experiences while lacking a body. But Descartes rejected that possibility. In his metaphysics, sense perception and imagination depend for their existence on mind-body union. Purely intellectual perceptions do not depend on the brain. But acts of imagination and sense perception require the brain ( Pass. I.19-20, 43). Descartes did allow that God conceivably could produce sense experiences in us independent of the brain; but because God's perfection is inconsistent with deceit, he would never do this. In any event, in the natural case, human sensations require a brain.

A third conception is little more than the use (or abuse) of Descartes as a straw-man representative of a kind of over-arching "Western rationality" that over-rationalized the human being and denied the body and emotions. One recent version of this caricature suggests that Descartes affirmed a "sense-represent-plan-move" cycle in all explanations of human behavior (Wheeler 2005, Chap. 3). As mentioned above, Descartes explained many human behaviors through the machine of the body, without mental involvement. As he said in the Fourth Replies, "When people take a fall, and stick out their hands so as to protect their head, it is not reason that instructs them to do this" (7:230); rather, the machine of the body (material processes in the sense organs, brain, and muscles) produces this behavior. Descartes envisioned similar purely mechanistic explanations for many of the behaviors that arise with the passions or emotions, in which the body acts first and the felt experience of the passion serves to get the mind to want to do what the body is already doing ( Pass. I.37-40). Descartes by no means held that all human behavior does or should arise from rational deliberation. Which is not to say that he devalued rational deliberation when there is time and need to undertake it. But he was under no illusion that all effective human behavior stems from reason.

How could interpreters get Descartes so wrong? One recent explanation suggests that many post-modern theorists have absorbed their Descartes at second hand, and the same explanation might be extended to others who invoke Descartes after only cursory engagement with his writings. As the literary historian Michael Moriarty explains, leading French theorists such as Jacques Lacan and Michel Foucault would have, in the course of their French educations, "received a solid grounding in philosophy, and in Descartes' works in particular" (Moriarty 2003, 52). They then use Descartes as a stalking horse. Moriarty suggests that many readers of Lacan and Foucault have not received the same education in philosophy or in Descartes. Such individuals, "who read Lacan or Foucault without, or before, reading Descartes, thus imbibe a certain perception of Descartes, more negative, perhaps, than the authors themselves, writing against the grain of their own culture, may have intended to convey" (2003, 53). The implication is that Lacan and Foucault engaged Descartes from a knowledge of his writings, whereas others who lack such knowledge misunderstand the value of such genuine engagement and take away misunderstood implications.

What is Descartes' legacy now? His influence on the seventeenth century is historically permanent, including his specific contributions in mathematics and optics, his vision for a mechanistic physiology, and the model he offered to Newton of a unified celestial and terrestrial physics that assigns a few basic properties to a ubiquitous matter the motions of which are governed by a few simple laws. In this regard, Descartes' work offers an example of culturally engaged philosophy. Descartes had a sense for the fundamental philosophical issues of his time, many of which concerned the theory of nature and the attempt to found a new natural science. He not only offered a systematic reformulation of the extant natural philosophy, but he did so in a way that could be heard and understood.

Beyond past historical influences, Descartes' philosophy continues to speak to us now and to offer new insights to new generations of philosophers who are in position to hear what he said. This can be seen in the revival of body-first theories of the emotions. (Ironically, some of Descartes' most vocal detractors among scientists who study the emotions, including Damasio 1994, espouse theories similar in many respects to Descartes' own, on which, see Hatfield 2007.) Further, his theories of sensory qualities have inspired new reflections (Simmons 2003), as has his account of distance perception (see Wolf-Devine 1993 and the entries on optics and perception in Nolan 2014). More generally, his Meditations is one of the most finely crafted examples of philosophical prose ever written. That in itself ensures its ongoing value.

In the end, Descartes' legacy partly consists of problems he raised, or brought into prominence, but did not solve. The mind-body problem is a case in point. Descartes himself argued from his ability clearly and distinctly to conceive mind and body as distinct beings to the conclusion that they really are separate substances. Most philosophers today accept neither the methodological basis for his claim nor the claim itself. All the same, the mind-body problem persists. In distinguishing the domain of the mental from that of the physical, Descartes struck a chord. Many philosophers accept the conceptual distinction, but remain uncertain of the underlying metaphysics: whether mind is identical with brain; or the mental emerges from complex processes in the brain; or constitutes a property that is different from any purely physical property, even while being instantiated by the brain. In this case, a problem that Descartes made prominent has lived far beyond his proposed solution.

Bibliography

Note on references and abbreviations: References to Descartes' works as found herein use the pagination of the Adam and Tannery volumes (AT), Oeuvres de Descartes, 11 vols. The citations give volume and page numbers only (dropping the abbreviation "AT"). Where possible, the Cottingham, Stoothoff, Murdoch, and Kenny translation, The Philosophical Writings of Descartes, 3 vols., has been used; it shows the AT pagination in the margins. The AT volume numbers provide a guide to which work is being cited in translation: vols. 1-5, 10, correspondence; vol. 6, Discourse and essays (including the Dioptrics and Meteorology); vol. 7, Meditations; vol. 10, Rules; vol. 11:1-118, World, or Treatise on Light; vol. 11:119-222, Treatise on Man; vol. 11:301-488, Passions. Where there is no accessible translation for a citation from AT, the citation is shown in italics. Works that are broken into parts and/or articles are cited by abbreviated title, part, and article: Diop. for Dioptrics, Disc. for Discourse on the Method, Med. for the Meditations, Met. for the Meteorology, Pass. for the Passions, and Princ. for the Principles. When context doesn't show that Descartes' letters are being referred to, Correspondence, abbreviated as Corr., is added.

Primary Literature: Works by Descartes

Original editions and early translations

See Otegem 2002 for a full bibliography.

1637, Discours de la methode pour bien conduire sa raison, & chercher la verité dans les sciences. Plus La dioptrique, Les meteores, et La geometrie. Qui sont des essais de cete Methode, Leiden: Jan Maire. Digitized photographic reproduction (DPR)online (pdf).

1641, Meditationes de prima philosophia, in qua Dei existentia et animae immortalitas demonstrantur, Paris: Michel Soly. DPRonline (pdf).

1642, Meditationes de prima philosophia, in quibus Dei existentia & animae humanae à corpore distinctio demonstrantur: his adjunctae sunt variae objectiones doctorum virorum in istas de Deo & anima demonstrationes, cum responsionibus authoris, Amsterdam: Elzevir, 2nd edn. The main title was changed from the first edition, which had promised to demonstrate "the immortality of the soul"; this edition promises to demonstrate "the distinction of the human soul from the body." The seventh set of Objections and Replies, by Pierre Bourdin, first appeared in the second edition, along with Descartes' letter to Father Dinet, Bourdin's superior in the Jesuit order.

1643, Epistola ad celeberrimum virum D. Gisbertum Voetium, Amsterdam: Elzivir. DPRonline (pdf). Published in Dutch the same year. A related polemical work appeared posthumously (1656; see Verbeek 1988).

1644, Principia philosophiae, Amsterdam: Elzevir. DPRonline (pdf and tiff).

1644, Specimina philosophiae, seu Dissertatio de methodo recte regendae rationis & veritatis in scientiis investigandae: Dioptrice et Meteora, trans. Etienne de Courcelles, Amsterdam: Elzevir. DPRonline (pdf).

1647, Les meditations metaphysiques, touchant la premiere philosophie, dans lesquelles l'existence de Dieu, & la distinction réele entre l'ame & le corps de l'homme, sont demonstrées: et les Objections faites contre ces Meditations par diverses personnes tres-doctes, avec les réponses de l'Auteur, trans. Louis-Charles d'Albert, duc de Luynes (Meds.) and Claude Clerselier (Objections and Replies). Paris: Jean Camusat and Pierre Le Petit. DPRonline (pdf). The Seventh Objections and Replies appeared first in the 2nd French edn. (1661).

1647, Les principes de la philosophie, trans. Claude Picot, Paris: Henry Le Gras. DPRonline (pdf). Descartes added an "Author's letter" to the translation, as a preface.

1649, A discourse of a method for the well guiding of reason, and the discovery of truth in the sciences, London: Thomas Newcombe. Available through Early Modern Books (EMB), accessible through many College and University libraries.

1649, Geometria, trans. Frans van Schooten, Leiden: Jan Maire. DPRonline (pdf).

1649, Les passions de l'ame, Paris: Henry Le Gras. DPRonline (pdf).

1650, Compendium musicae, Utrecht: Gijsbert van Zijll and Dirck van Ackersdijck. DPRonline (pdf).

1650, Meditationes de prima philosophia, in quibus Dei existentia, & animæ humanæ à corpore distinctio, demonstrantur: his adjunctæ sunt variæ objectiones doctorum virorum in istas de Deo & anima demonstrationes; cum responsionibus authoris, Amsterdam: Elzevir, 3rd edn. DPRonline (pdf).

1650, Passiones animae, Henry Desmarets (trans.), Amsterdam: Elzevir. DPRonline (pdf).

1650, The passions of the soule, London: John Martin and John Ridley. Available through EMB.

1653, Compendium of musick: With necessary and judicious animadversions thereupon, William Brouncker (trans.), London: Thomas Harper. DPRonline (pdf).

1656, Querela apologetica, Groningen: Misopodem. A response to Voetius, written in 1648 in French and translated into Dutch and Latin (Otegem 2:472-75).

1657-67, Lettres, où sont traittées les plus belles questions de la morale, physique, medecine, et des mathematiques, 3 vols., Claude Clerseliers (ed.), Paris: Charles Angot. DPRs online,Vol. 1,Vol. 2,Vol. 3 (pdf).

1662, De homine figuris, trans. Florent Schuyl, Leiden: Leffen and Moyardum. DPRonline (pdf). A Latin translation of the original French, which was published asL'Homme in 1664.

1664, Le monde, ou, Le traite de la lumiere, et des autres principaux objects des sens, Paris: Girard. DPRonline (pdf).

1664, L'homme, et un Traitté de la formation du foetus, Claude Clerselier (ed.), Paris: Charles Angot. DPRonline (pdf). This is the first edition of Descartes' original French. It includes Remarks by Louis de la Forge and a translation of Florentius Schuyl's Preface to the Latin translation.

1668, Abbregé de la musique, Nicolas Poisson (trans.), Paris: Charles Angot. DPRonline (pdf).

1677, L' Homme, et La formation du foetus, avec Les remarques de Louis de La Forge; à quoy l'on a ajouté Le monde ou Traité de la lumière, Claude Clerselier (ed.), Paris: Theodore Girard, 2nd edition.L'Homme and Le Monde are brought together in this second edition. Clerselier had the firgures forLe Monde redrawn, and used a putatively more accurate manuscript for that work. DPRonline (pdf).

1680, Six metaphysical meditations wherein it is proved that there is a God and that mans mind is really distinct from his body: hereunto are added the objections made against these meditations by Thomas Hobbes, with the authors answers, William Molyneux (trans.), London: Benjamin Tooke. This translation of the six Meditations is reprinted in Gaukroger (2006). The entire book (including the Third Objections and Replies) is available through EMB.

1701, Opuscula posthuma, physica et mathematica, Amsterdam: Blaeu. DPRonline (pdf). The first publication of theRules in Latin (a Dutch translation had appeared in 1684), together with other writings.

Modern editions of Descartes' works: French and Latin

1936-1963, Correspondance, Charles Adam and Gaston Milhaud (eds.), 8 vols., Paris: Presses Universitaires de France. A complete edition of the known correspondence at date, with French translations accompanying letters in Latin.

1996, Oeuvres de Descartes,Charles Adam and Paul Tannery (eds.), 11 vols., Paris: Vrin/CNRS, new edition. Remains the standard edition, presenting works in the original French or Latin along with early translations of major works from Latin into French (Meditations, Principles) or from French into Latin (Discourse, Dioptrics, Meteorology), and also presenting manuscript material and posthumously published works. Cited by volume and page number.

2010, Oeuvres philosophiques, Fernand Alquié, Denis Moreau (eds.), 3 vols., Paris: Garnier, new edition. Contains major works in French, including correspondence (Latin letters are translated into French), with extensive notes.

2009-, Oeuvres complètes, Jean-Marie Beyssade and Denis Kambouchner (eds.), 8 vols. Paris: Gallimard. A new edition in French, including correspondence, with Latin facing page for theRules, Meditations, and Principles. Extensive notes and bibliography, with an overview of both French and English scholarship and some notice of material in German and Italian. (4 volumes have appeared to date.)

Recent English translations (selected)

1965, Discourse on Method, Optics, Geometry, and Meteorology, Paul J. Olscamp (trans.), Indianapolis: Bobbs-Merrill.

1972, Treatise of Man, Thomas S. Hall (trans.), Cambridge: Harvard University Press. With an introduction and many explanatory notes.

1979, Le Monde, ou Traité de la lumiere = The World, or Treatise on Light, Michael S. Mahoney (trans.), New York: Abaris Books. Facing page translation, with an introduction and explanatory notes.

1983, Principles of Philosophy, V. R. Miller and R. P. Miller (trans.), Dordrecht: Reidel.

1984-91, Philosophical Writings of Descartes, 3 vols., John Cottingham, Robert Stoothoff, Dugald Murdoch, and Anthony Kenny (ed. and trans.), Cambridge: Cambridge University Press.

1989, Passions of the Soul, Stephen H. Voss (trans.), Indianapolis: Hackett.

1990, Meditations on First Philosophy = Meditationes de prima philosophia, George Heffernan (trans.), Notre Dame: University of Notre Dame Press. A literal translation of the six Meditations proper, with facing-page Latin.

1994, Discours de la méthode: pour bein conduire sa raison et chercher la verité dans les sciences = Discourse on the Method: of Conducting One's Reason Well and of Seeking the Truth in the Sciences, George Heffernan (trans.), Notre Dame: University of Notre Dame Press. A bilingual edition with an interpretive essay.

1998, Meditations and Other Metaphysical Writings, Desmond M. Clarke (trans.), London: Penguin.

1998, Regulae ad directionem ingenii = Rules for the Direction of the Natural Intelligence: A Bilingual Edition of the Cartesian Treatise on Method, George Heffernan (trans.), Amsterdam: Editions Rodopi.

1998, The World and Other Writings, Stephen Gaukroger (trans.), Cambridge: Cambridge University Press.

1999, Discourse on Method and Related Writings, Desmond M. Clarke (trans.), London: Penguin.

2007, The Correspondence between Princess Elisabeth of Bohemia and René Descartes, Lisa Shapiro (trans.), Chicago: University of Chicago Press.

2006, A Discourse on the Method of Correctly Conducting One's Reason and Seeking Truth in the Sciences, Ian Maclean (trans.), Oxford: Oxford University Press.

2008, Meditations on First Philosophy: With Selections from the Objections and Replies, Michael Moriarty (trans.), Oxford: Oxford University Press. A fresh translation with detailed explanatory notes.

2015, The Passions of the Soul and Other Late Philosophical Writings, Michael Moriarty (trans.), Oxford: Oxford University Press. Also includes the correspondence with Elisabeth and other letters.

Other Primary Literature

Some works known to Descartes (selected)

Ordered alphabetically, translations shown where available.

Alhazen, or Ibn al-Haytham, and Witelo. Opticae thesaurus: Alhazeni Arabis libri septem nunc primum editi; ejusdem Liber de crepusculis et nubium ascensionibus. Item Vitellonis, libri X, Friedrich Risner (ed.), Basel: Episcopius. DPRonline (pdf). Translation of Alhazen's theory of vision:Alhacen's Theory of Visual Perception: A Critical Edition, with English Translation and Commentary, of the first three books of Alhacen's De aspectibus, the medieval Latin version of Ibn al-Haytham's Kitab al-Manazir, A. Mark Smith (trans.), 2 vols., Philadelphia: American Philosophical Society, 2001. Descartes cites Witelo (10:8).

Coimbran Commentators, 1598, Commentarium in tres libros De anima Aristotelis, Coimbra: Antonio de Maris.

Copernicus, Nicholas, 1543, De revolutionibus orbium caelestium, Nuremberg: Johannes Petreius; On the Revolutions of the Heavenly Spheres, Edward Rosen (trans.), Baltimore: Johns Hopkins University Press, 1978.

Eustachius a Sancto Paulo, 1638, Summa philosophiae quadripartita: de rebus dialecticis, ethicis, physicis, & metaphysicis, rev. ed., Cologne: Philip Albert. Available through EMB. Translation (selections):A Compendium of Philosophy in Four Parts, in Descartes' Meditations: Background Source Materials, Roger Ariew, John Cottingham, and Tom Sorell (eds.), Cambridge: Cambridge University Press,1998, 68-96.

Galilei, Galileo, 1610, Siderius nuncius, Venice: Tommaso Baglioni;Starry Messenger, Albert van Helden (trans.), Chicago: University of Chicago Press, 1989.

---, 1632, Dialogo sopra i due massimi sistemi del mondo, Tolemaico e Copernicano, Florence: Batista Landini;Dialogue Concerning the Two Chief World Systems, Ptolemaic & Copernican, Stillman Drake (trans.), Berkeley: University of California Press, 2nd edition, 1967.

---, 1638, Discorsi e dimostrazioni matematiche: intorno à due nuoue scienze, attenenti alla mecanica & i movimenti locali, Leiden: Elzevir; Two New Sciences, Including Centers of Gravity & Force of Percussion, Stillman Drake (ed. and trans.), Madison: University of Wisconsin Press.

Kepler, Johannes, 1604, Ad Vitellionem paralipomena, quibus astronomiae pars optica traditur, Frankfurt: Claudius Marnius and Ioannes Aubrius. Available through EMB. Translation:Optics: Paralipomena to Witelo and Optical Part of Astronomy,William H. Donahue (ed. and trans.), Santa Fe, N.M.: Green Lion Press, 2000.

---, 1611, Dioptrice, Augsburg: David Franke; reprint, Cambridge, UK: Heffer, 1962.

Rubio, Antonio, 1611, Commentarium in libros Aristotelis De anima, Alcalá de Henares: Andre Sanchez.

Toledo, Francisco de, 1575, Commentaria una cum quaestionibus in tres libros Aristotelis De anima, Venice: Iuntas.

For additional background sources, see Descartes' Meditations: Background Source Materials, Roger Ariew, John Cottingham, and Tom Sorell (eds.), Cambridge: Cambridge University Press, 1998.

Early reactions to Descartes' philosophy, favorable and unfavorable.

Ordered chronologically. Not exhaustive.

Heereboord, Adrianus, 1643, Parallelismus Aristotelicae et Cartesianae philosophiae naturalis, Leiden. Reported to have been read at Harvard College in the seventeenth century (Morison 1936, 1:233).

Schoock, Martin, 1643, Admiranda methodvs novae philosophiae Renati Des Cartes, Utrecht: Joannis van VVaesberge. An attack on Descartes; according to Schoock, Gisbertus Voetius also contributed. See Verbeek (1988, 1992).

Hogelande, Cornelius van, 1646, Cogitationes, quibus Dei existentia: item animae spiritalitas, et possibilis cum corpore unio, demonstrantur: nec non, brevis historia oeconomiae corporis animalis, proponitur, atque mechanice explicator, Amsterdam: Elzevir. Book dedicated to Descartes. Available online tlhrough Early Modern Books (EMB) in many university libraries.

Regius, Henricus, 1646, Fundamenta physices, Amsterdam: Elzevir. DPRonline (pdf). Influenced by Descartes' physics and physiology.

---, 1648, Brevis explicatio mentis humanae, sive animae rationalis: ubi explicatur, quid sit et quid esse possit, Utrecht: Dirck van Ackersdijck. Descartes replied with hisComments on a Certain Broadsheet.

Raei, Johannes de, 1654, Clavis philosophiae naturalis, seu Introductio ad naturae contemplationem Aristotelico-Cartesiana, Leiden: Elzevir. DPRonline (pdf). A student of Regius, favorable toward Descartes (see Verbeek 1992).

More, Henry, 1662, A Collection of Several Philosophical Writings, 2 vols., London: Flesher, 2nd edition; reprint, New York, Garland, 1978.

Heereboord, Adrianus, 1663, Philosophia naturalis: cum commentariis peripateticis antehac edita, Leiden: Cornelius Driehuysen. Discusses Descartes' mechanization of the vegetative and sensitive souls. Later editions available through EMB.

Spinoza, Benedictus de, 1663, Renati Des Cartes Principiorum philosophiae pars I et II, more geometrico demonstratae, Amsterdam: Joannes Riewerts. DPRonline (pdf). Spinoza's reconstruction of the arguments of the first two parts of Descartes'Principles of Philosophy.

La Forge, Louis de, 1666, Traitté de l'esprit de l'homme, de ses facultez et fonctions, et de son union avec le corps, suivant les Principes de René Descartes, Paris: Michel Bobin and Nicolas Le Gras. DPRonline (pdf). A treatise on the human mind following Descartes' principles.

More, Henry, 1671, Enchiridion metaphysicum, London: Flesher;Manual of Metaphysics, Alexander Jacob (trans.), 2 vols., Hildesheim: Georg Olms, 1995.

Rohault, Jacques, 1671, Traité de physique, Paris: Charles Savreux. DPRonline (pdf).

Poulain de la Barre, François, 1673, De l'égalité des deux sexes, discours physique et moral où l'on voit l'importance de se défaire des préjugez, Paris: Jean du Puis. DPRonline (pdf). Translation:A Physical and Moral Descourse concerning the Equality of Both Sexes, Desmond M. Clarke (trans.), in The Equality of the Sexes: Three Feminist Texts of the Seventeenth Century, Desmond M. Clarke (ed.), Oxford: Oxford University Press, 2013.

Huet, Pierre-Daniel, 1689, Censura philosophiae cartesianae, Paris: D. Horthemels; Against Cartesian Philosophy, Thomas M. Lennon (ed. and trans.), New York: Humanity Books, 2003.

Regis, Pierre Sylvain, 1690, Système de philosophie, contenant la logique, la métaphysique, la physique et la morale, Paris: Denys Thierry. DPR:Tome 1,Tome 2,Tome 3.

Le Grande, Antoine, 1694, An Entire Body of Philosophy, According to the Principles of the Famous Renate des Cartes, Richard Blome (trans.), 2 vols., London: Samuel Roycroft. Available through EMB (under EEBO). Originally published in Latin, 1672-1675.

Secondary Literature

References

Atherton, Margaret, 2001, "Cartesian Reason and Gendered Reason", in A Mind of One's Own: Feminist Essays on Reason and Objectivity, Louise M. Antony and Charlotte E. Witt (eds.), Boulder, CO: Westview Press, 2nd edition, 21-37.

Ben-Yami, Hanoch, 2015, Descartes' Philosophical Revolution: A Reassessment, Houndmills: Palgrave Macmillan.

Bordo, Susan (ed.), 1999, Feminist Interpretations of René Descartes, University Park, PA: Pennsylvania State University Press.

Boyer, Carl B., 1885, A History of Mathematics, Princeton: Princeton University Press, Ch. 17.

Brown, Deborah J., 2006, Descartes and the Passionate Mind, Cambridge: Cambridge University Press.

Brown, Deborah J., and Calvin G. Normore, 2019, Descartes and the Ontology of Everyday Life, Oxford: Oxford University Press.

Carriero, John, 2008, "Cartesian Circle and the Foundations of Knowledge", in Janet Broughton and John Carriero (eds.), A Companion to Descartes, Malden, MA: Blackwell, 302-18.

Clark, Desmond M., 2006, Descartes: A Biography. Cambridge: Cambridge University Press.

Cottingham, John, 1998, "Descartes' Treatment of Animals", in Descartes, ed. John Cottingham. Oxford: Oxford University Press, 225-33.

Curley, Edwin, 1978, Descartes against the Skeptics, Cambridge, MA: Harvard University Press.

Damasio, Antonio, 1994, Descartes' Error: Emotion, Reason, and the Human Brain, New York: Putnam.

Des Chene, Dennis, 2001, Spirits and Clocks: Machine and Organism in Descartes, Ithaca, NY: Cornell University Press.

Domski, Mary, 2022, "Descartes' Mathematics", The Stanford Encyclopedia of Philosophy (Fall 2022 Edition), Edward N. Zalta & Uri Nodelman (eds.), URL = <https://plato.stanford.edu/archives/fall2022/entries/descartes-mathematics/>.

Doney, Willis (ed.), 1987, Eternal Truth and the Cartesian Circle, New York: Garland Publishing.

Frankfurt, Harry G., 1962, "Memory and the Cartesian Circle", Philosophical Review, 71: 504-11.

---, 1965. "Descartes' Validation of Reason", American Philosophical Quarterly, 2: 149-56.

Garber, Daniel, 1992, Descartes' Metaphysical Physics, Chicago: University of Chicago Press.

Gaukroger, Stephen, 1995, Descartes: An Intellectual Biography, Oxford: Oxford University Press.

---, 2002, Descartes' System of Natural Philosophy, Cambridge: Cambridge University Press.

Hamerton, Katharine J., 2008, "Malebranche, Taste, and Sensibility: The Origins of Sensitive Taste and a Reconsideration of Cartesianism's Feminist Potential", Journal of the History of Ideas, 69(4): 533-58.

Hatfield, Gary, 1993, "Reason, Nature, and God in Descartes", in Stephen Voss (ed.), Essays on the Philosophy and Science of Rene Descartes, New York: Oxford University Press, 259-87.

---, 2000, "Descartes' Naturalism about the Mental," in Stephen Gaukroger, John Schuster, and John Sutton (eds.), Descartes' Natural Philosophy, London: Routledge, 630-58.

---, 2006, "Cartesian Circle," in Stephen Gaukroger (ed.), Blackwell Guide to Descartes' Meditations, Oxford: Blackwell, 122-41.

---, 2007, "The Passions of the Soul and Descartes's Machine Psychology", Studies in History and Philosophy of Science, 38: 1-35.

---, 2008, "Animals," in John Carriero and Janet Broughton (eds.), Companion to Descartes, Oxford: Blackwell, 404-25.

---, 2013, "Descartes on Sensory Representation, Objective Reality, and Material Falsity", in Karen Detlefsen (ed.), Descartes' Meditations: A Critical Guide, Cambridge: Cambridge University Press, 127-50.

---, 2020, "Geometry and Visual Space from Antiquity to the Early Moderns", in Andrew Janiak (ed.), Space, New York: Oxford University Press, 184-222.

Henry, John, 2008, The Scientific Revolution and the Origins of Modern Science, New York: Palgrave Macmillan.

Jacquette, Dale, 1996, "Descartes' Lumen Naturale and the Cartesian Circle", Philosophy and Theology: Marquette University Quarterly, 9: 273-320.

James, Susan, 1997, Passion and Action: The Emotions in Seventheetnth-Century Philosophy, Oxford: Clarendon Press.

Jorgensen, Larry M., 2020, "Seventeenth-Century Theories of Consciousness", The Stanford Encyclopedia of Philosophy (Spring 2020 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2020/entries/consciousness-17th/>.

Lee, Sukjae, 2020, "Occasionalism", The Stanford Encyclopedia of Philosophy (Fall 2020 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/fall2020/entries/occasionalism/>.

Leech, David, 2013, The Hammer of the Cartesians: Henry More's Philosophy of Spirit and the Origins of Modern Atheism, Leuven: Peeters.

Loeb, Louis, 1992, "Cartesian Circle", in John Cottingham (ed.), Cambridge Companion to Descartes, Cambridge: Cambridge University Press, 200-35.

Machamer, Peter, and J. E. McGuire, 2006, "Descartes's Changing Mind", Studies in History and Philosophy of Science, 37: 398-419.

Manning, Gideon, 2014, "Descartes and the Bologna Affair", British Journal for the History of Science, 47: 1-13.

Mantovani, Mattia, 2022, "The Institution of Nature: Descartes on Human and Animal Perception", in Donald Rutherford (ed.), Oxford Studies in Early Modern Philosophy Volume 11, Oxford: Oxford University Press, 1-30.

McMullin, Ernan, 2008, "Explanation as Confirmation in Descartes's Natural Philosophy," in Janet Broughton and John Carriero (eds.), A Companion to Descartes, Malden, Mass.: Blackwell, 84-102.

Moriarty, Michael, 2003, Early Modern French Thought: The Age of Suspicion, Oxford: Oxford University Press.

Morison, Samuel Eliot, 1936, Harvard College in the Seventeenth Century, 2 vols., Cambridge, Mass.: Harvard University Press.

Newman, Lex, 2019, "Descartes' Epistemology", The Stanford Encyclopedia of Philosophy (Spring 2019 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2019/entries/descartes-epistemology/>.

Nolan, Lawrence (ed.), 2014, The Cambridge Descartes Lexicon, Cambridge: Cambridge University Press.

---, 2021, "Descartes' Ontological Argument", The Stanford Encyclopedia of Philosophy (Spring 2021 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2021/entries/descartes-ontological/>.

Otegem, Matthijs van, 2002, A Bibliography of the Works of Descartes (1637-1704) = Een bibliografie van de werken van Descartes (1637-1704), 2 vols., Utrecht: Zeno.

Popkin, Richard H., 1979, History of Scepticism from Erasmus to Spinoza, Berkeley: University of California Press.

Rashed, Roshdi, 1990, "A Pioneer in Anaclastics: Ibn Sahl on Burning Mirrors and Lenses", Isis, 81(3): 464-91.

Rodis-Lewis, Geneviève, 1998, Descartes: His Life and Thought, J. M. Todd (trans.), Ithaca: Cornell University Press.

Rozemond, Marleen, 2006, "The Nature of the Mind", in Stephen Gaukroger (ed.), Blackwell Guide to Descartes' Meditations, Oxford: Blackwell, 48-66.

Russell, Bertrand, 1914, Our Knowledge of the External World as a Field for Scientific Method in Philosophy, Chicago: Open Court.

Rutherford, Donald, 2021, "Descartes' Ethics", The Stanford Encyclopedia of Philosophy (Winter 2021 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/win2021/entries/descartes-ethics/>.

Sabra, A. I., 1967, Theories of Light from Descartes to Newton, London: Oldbourne Press.

Schmitter, Amy M., 2018, "Cartesian Prejudice: Gender, Education, and Authority in Poulain de la Barre", Philosophy Compass, 13(12): 1-12.

Schuster, John, 1980, "Descartes' Mathesis Universalis, 1619-28", in Stephen Gaukroger (ed.),Descartes: Philosophy, Mathematics and Physics, New Jersey: Barnes and Noble, 41-96.

Sebba, Gregor, 1987, The Dream of Descartes, Carbondale, IL: Southern Illinois University Press.

Shapin, Steven, 1996, The Scientific Revolution, Chicago: University of Chicago Press.

Shapiro, Lisa, 2003, "Descartes' Passions of the Soul and the Union of Mind and Body", Archiv für Geschichte der Philosophie, 85: 211-48.

Shea, William R., 1991, The Magic of Numbers and Motion: The Scientific Career of René Descartes, Canton, MA: Science History Publications.

Simmons, Alison, 2003, "Descartes on the Cognitive Structure of Sensory Experience", Philosophy and Phenomenological Research, 67: 549-79.

Slowik, Edward, 2021, "Descartes' Physics", The Stanford Encyclopedia of Philosophy (Winter 2021 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/win2021/entries/descartes-physics/>.

Underkuffler, Wilson, 2019, "Teresa, Descartes, and de Sales: The Art of Augustinian Meditation", Intellectual History Review, 30(4): 561-84.

Verbeek, Theo (ed.), 1988, La querelle d'Utrecht, Paris: Les impressions nouvelles. Includes writings by Martin Schoock and Descartes.

---, 1992, Descartes and the Dutch: Early Reactions to Cartesian Philosophy, 1637-1650, Carbondale, IL: Southern Illinois University Press.

Watson, Richard, 2007, Cogito, Ergo Sum, Boston: Godine, rev. edition.

Wee, Cecilia, 2006, Material Falsity and Error in Descartes' Meditations, London: Routledge.

Wells, Norman J., 1982, "Descartes' Uncreated Eternal Truths", The New Scholasticism, 56: 185-99.

Wheeler, Michael, 2005, Reconstructing the Cognitive World: The Next Step, Cambridge, MA: MIT Press.

Williams, Michael, 1986, "Descartes and the Metaphysics of Doubt", in Amélie Rorty (ed.), Essays on Descartes' Meditations, Berkeley: University of California Press, 117-139.

Wolf-Devine, Celia, 1993, Descartes on Seeing: Epistemology and Visual Perception, Carbondale, IL: Southern Illinois University Press.

Other Readings

Alanen, Lilli, 1994, "Sensory Ideas, Objective Reality, and Material Falsity", in John Cottingham (ed.), Reason, Will, and Sensation: Studies in Descartes's Metaphysics, Oxford: Clarendon Press, 229-50.

Ariew, Roger, 2011, Descartes among the Scholastics, Leiden: Brill.

Broughton, Janet, 2002, Descartes's Method of Doubt, Princeton: Princeton University Press.

Broughton, Janet, and John Carriero (eds.), 2008, Companion to Descartes, Malden, Mass.: Blackwell.

Brown, Deborah J., 2012, "Cartesian Functional Analysis", Australasian Journal of Philosophy, 90(1): 75-92.

Carriero, John, 2009, Between Two Worlds: A Reading of Descartes's Meditations, Princeton: Princeton University Press.

Clarke, Desmond M., 1982, Descartes' Philosophy of Science, University Park: Pennsylvania State University Press.

Cottingham, John (ed.), 1992, Cambridge Companion to Descartes, Cambridge: Cambridge University Press.

--- (ed.), 1994, Reason, Will and Sensation: Studies in Descartes's Metaphysics, Oxford: Clarendon Press.

--- (ed.), 1998, Descartes, Oxford: Oxford University Press.

Cunning, David, 2010, Argument and Persuasion in Descartes' Meditations, Oxford: Oxford University Press.

Des Chene, Dennis, 1996, Physiologia: Natural Philosophy in Late Aristotelian and Cartesian Thought, Ithaca: Cornell University Press.

Detlefsen, Karen (ed.), 2013, Descartes' Meditations: A Critical Guide, Cambridge: Cambridge University Press.

Dicker, Georges, 2013, Descartes: An Analytical and Historical Introduction, 2nd edn., New York: Oxford University Press.

Dobre, Mihnea, and Tammy Nyden (eds.), 2013, Cartesian Empiricisms, Dordrecht: Springer.

Flage, Daniel E., and Clarence A. Bonnen, 1999, Descartes and Method: A Search for a Method in Meditations, London: Routledge.

Frankfurt, Harry G., 1970, Demons, Dreamers, and Madmen, Indianapolis: Bobbs-Merrill.

Gaukroger, Stephen (ed.), 2006, The Blackwell Guide to Descartes' Meditations, Malden, Mass.: Blackwell.

Gaukroger, Stephen, John Schuster, and John Sutton (eds.), 2000, Descartes' Natural Philosophy, London: Routledge.

Gaukroger, Stephen, and Catherine Wilson (eds.), 2017, Descartes and Cartesianism: Essays in Honour of Desmond Clarke, Oxford: Oxford University Press.

Grene, Marjorie, 1985, Descartes, Minneapolis: University of Minnesota Press.

Guèroult, Martial, 1984-85, Descartes' Philosophy Interpreted According to the Order of Reasons, trans. R. Ariew, 2 vols., Minneapolis: University of Minnesota Press.

Hatfield, Gary, 1986, "The Senses and the Fleshless Eye: The Meditations as Cognitive Exercises", in Amèlie Rorty (ed.),Essays on Descartes' Meditations, Berkeley: University of California Press, 45-79.

---, 2014. Descartes' Meditations, London: Routledge.

Kenny, Anthony, 1968, Descartes: A Study of His Philosophy, New York: Random House.

Laudens, Laurens, 1966, "The Clock Metaphor and Probabilism: The Impact of Descartes on English Methodological Thought, 1650-65", Annals of Science, 22: 74-104.

Manning, Gideon, 2012, "Descartes' Healthy Machines and the Human Exception", in Sophie Roux and Dan Garber (eds.), The Mechanization of Natural Philosophy, New York: Kluwer, 237-62.

Menn, Stephen, 1998, Descartes and Augustine, Cambridge: Cambridge University Press.

Nelson, Alan (ed.), 2005, Blackwell Companion to Rationalism, Oxford: Blackwell.

Rorty, Amélie (ed.), 1986, Essays on Descartes' Meditations, Berkeley: University of California Press.

Rozemond, Marleen, 1998, Descartes's Dualism, Cambridge: Harvard University Press.

Secada, Jorge, 2000, Cartesian Metaphysics: The Late Scholastic Origins of Modern Philosophy, Cambridge: Cambridge University Press.

Shapiro, Lisa, 2003, "The Health of the Body-Machine? 17th Century Mechanism and the Concept of Health", Perspectives on Science, 11: 421-42.

Shea, William R., 1991, Magic of Numbers and Motion, Canton, Mass.: Science History Publications.

Simmons, Alison, 1999, "Are Cartesian Sensations Representational?" Noûs, 33: 347-69.

---, 2001, "Sensible Ends: Latent Teleology in Descartes' Account of Sensation", Journal of the History of Philosophy, 39: 49-75.

Smith, Norman Kemp, 1953, New Studies in the Philosophy of Descartes: Descartes as Pioneer, London: Macmillan.

Voss, Stephen (ed.), 1993, Essays on the Philosophy and Science of René Descartes, New York: Oxford University Press.

Williams, Bernard, 1978, Descartes, The Project of Pure Inquiry, London: Penguin.

Wilson, Margaret D., 1978, Descartes, London: Routledge & Kegan Paul.

Other Internet Resources

Links to digitized photographic reproductions of early editions of Descartes' works may be found under Original editions and early translations of major works. The following links are to other online editions:

French Meditations and Discourse, online French text of the six Meditations and theDiscourse (from the Association de Bibliophiles Universels,http://abu.cnam.fr/)

French Dioptrics, online French text ofLa dioptrique (from Les classiques des sciences sociales, University of Quebec at Chicoutimi)

French Discourse and Meditations, online French text of theDiscourse and six Meditations plus the first three Objections and Replies, from the edition of Descartes' works by Victor Cousin (Project Gutenburg)

Latin Meditations, online Latin text of the six Meditations (from The Latin Library, Classics Page, Neo-Latin, Descartes)

Latin Meditations, online Latin text of the six Meditations, ed. Artur Buchenau. Leipzig: Felix Meiner, 1913 (from Project Gutenburg)

Latin, French, and English Meditations, Latin text of the six Meditations, plus the 1647 French translation and the 1901 John Veitch translation into English (Wright State University)

French and English Passions (1649/1650), side by side (Descartes Web Project, Claremont Graduate University)

The following provide access to digital photographic reproductions of many additional texts:

Acknowledgments

The author thanks Elle Kirsch, who served as research assistant and offered many useful suggestions, and Tiina Rosenqvist, who provided many helpful comments.

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First published Wed Dec 3, 2008; substantive revision Mon Oct 23, 2023 René Descartes (1596-1650) was a creative mathematician of the first order, an important scientific thinker, and an original metaphysician. During the course of his life, he was a mathematician first, a natural scientist or "natural philosopher" second, and a metaphysician third.

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Robert Hooke studied physics, astronomy, geology, biology, and chemistry. He was born in 1635 and died in 1703. He discovered cells and cell tissue.

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German scientist and mathematician that discovered laws of planetary motion, such as that the planets revolve in an elliptical motion (oval), rather than a circular one.

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Paracelsus was an alchemist and physician, who established chemistry in medicine. In 1530 Paracelsus wrote a clinical description about syphilis and how he contained it and treated the disease with mercury taken internally. He also stated that scoliosis was a disease was caused by metal vapors.

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John G. Hargrave Author of The Life and Soul of Paracelsus and others.

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Paracelsus | Biography & Facts | Britannica

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Paracelsus, German-Swiss physician and alchemist who established the role of chemistry in medicine. His chemical remedies, including those containing mercury, sulfur, iron, and copper sulfate, united medicine with chemistry and contributed substantially to the rise of modern medicine.

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Zacharias Janssen was believed to create the first telescope and first compact microscope.

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Daniel Gabriel Fahrenheit | Encyclopedia.com

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Fahrenheit, Daniel Gabriel(b. Danzig [Gdansk], Poland, 24 May 1686; d. The Hague, Natherlands, 16 September 1736)experimental physics.Fahrenheit was the scion of a wealthy merchant family that had come to Danzig from Königsberg in the middle of the serventeenth century.

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Francis Bacon was born January, 22, 1561, the second child of Sir Nicholas Bacon (Lord Keeper of the Seal) and his second wife Lady Anne Cooke Bacon, daughter of Sir Anthony Cooke, tutor to Edward VI and one of the leading humanists of the age. Lady Anne was highly erudite: she not only had a perfect command of Greek and Latin, but was also competent in Italian and French. Together with his older brother Anthony, Francis grew up in a context determined by political power, humanist learning, and Calvinist zeal. His father had built a new house in Gorhambury in the 1560s, and Bacon was educated there for some seven years; later, along with Anthony, he went to Trinity College, Cambridge (1573-5), where he sharply criticized the scholastic methods of academic training. Their tutor was John Whitgift, in later life Archbishop of Canterbury. Whitgift provided the brothers with classical texts for their studies: Cicero, Demosthenes, Hermogenes, Livy, Sallust, and Xenophon (Peltonen 2007). Bacon began his studies at Gray's Inn in London in 1576; but from 1577 to 1578 he accompanied Sir Amias Paulet, the English ambassador, on his mission in Paris. According to Peltonen (2007):

During his stay in France, perhaps in autumn 1577, Bacon once visited England as the bearer of diplomatic post, delivering letters to Walsingham, Burghley, Leicester, and to the Queen herself.

When his father died in 1579, he returned to England. Bacon's small inheritance brought him into financial difficulties and since his maternal uncle, Lord Burghley, did not help him to get a lucrative post as a government official, he embarked on a political career in the House of Commons, after resuming his studies in Gray's Inn. In 1581 he entered the Commons as a member for Cornwall, and he remained a Member of Parliament for thirty-seven years. He was admitted to the bar in 1582 and in 1587 was elected as a reader at Gray's Inn. His involvement in high politics started in 1584, when he wrote his first political memorandum, A Letter of Advice to Queen Elizabeth. Right from the beginning of his adult life, Bacon aimed at a revision of natural philosophy and-following his father's example-also tried to secure high political office. Very early on he tried to formulate outlines for a new system of the sciences, emphasizing empirical methods and laying the foundation for an applied science ( scientia operativa). This twofold task, however, proved to be too ambitious to be realized in practice. Bacon's ideas concerning a reform of the sciences did not meet with much sympathy from Queen Elizabeth or from Lord Burghley. Small expectations on this front led him to become a successful lawyer and Parliamentarian. From 1584 to 1617 (the year he entered the House of Lords) he was an active member in the Commons. Supported by Walsingham's patronage, Bacon played a role in the investigation of English Catholics and argued for stern action against Mary Queen of Scots. He served on many committees, including one in 1588 which examined recusants; later he was a member of a committee to revise the laws of England. He was involved in the political aspects of religious questions, especially concerning the conflict between the Church of England and nonconformists. In a tract of 1591, he tried to steer a middle course in religious politics; but one year later he was commissioned to write against the Jesuit Robert Parson (Jardine and Stewart 1999, p. 125), who had attacked English sovereignty.

From the late 1580s onwards, Bacon turned to the Earl of Essex as his patron. During this phase of his life, he particularly devoted himself to natural philosophy. He clearly expressed his position in a famous letter of 1592 to his uncle, Lord Burghley:

I confess that I have as vast contemplative ends, as I have moderate civil ends: for I have taken all knowledge to be my province; and if I could purge it of two sorts of rovers, whereof the one with frivolous disputations, confutations, and verbosities, the other with blind experiments and auricular traditions and impostures, hath committed so many spoils, I hope I should bring in industrious observations, grounded conclusions, and profitable inventions and discoveries; the best state of that province. This, whether it be curiosity, or vain glory, or nature, or (if one take it favourably) philanthropia, is so fixed in my mind as it cannot be removed. And I do easily see, that place of any reasonable countenance doth bring commandment of more wits than of a man's own; which is the thing I greatly affect. (Bacon 1857-74, VIII, 109)

In 1593 Bacon fell out favor with the queen on account of his refusal to comply with her request for funds from Parliament. Although he did not vote against granting three subsidies to the government, he demanded that these should be paid over a period six, rather than three, years. This led Sir Robert Cecil and Sir Walter Raleigh to argue against him in Parliament. Bacon's patron, the Earl of Essex, for whom he had already served as a close political advisor and informer, was not able to mollify the queen's anger over the subsidies; and all Essex's attempts to secure a high post for Bacon (attorney-general or solicitor-general) came to nothing. Nevertheless, the queen valued Bacon's competence as a man of law. He was involved in the treason trial of Roderigo Lopez and later on in the proceedings against the Earl of Essex. In his contribution to the Gesta Grayorum (the traditional Christmas revels held in Gray's Inn) of 1594-5, Bacon had emphasized the necessity of scientific improvement and progress. Since he failed to secure for himself a position in the government, he considered the possibility of giving up politics and concentrating on natural philosophy. It is no wonder, then, that Bacon engaged in many scholarly and literary pursuits in the 1590s. His letters of advice to the Earl of Rutland and to the Earl of Essex should be mentioned in this context. The advice given to Essex is of particular importance because Bacon recommended that he should behave in a careful and intelligent manner in public, above all abstaining from aspiring to military commands. Bacon also worked in this phase of his career for the reform of English law. In 1597 his first book was published, the seminal version of his Essays, which contained only ten pieces (Klein 2004b). His financial situation was still insecure; but his plan to marry the rich widow Lady Hatton failed because she was successfully courted by Sir Edward Coke. In 1598 Bacon was unable to sell his reversion of the Star Chamber clerkship, so that he was imprisoned for a short time on account of his debts. His parliamentary activities in 1597-98, mainly involving committee work, were impressive; but when the Earl of Essex in 1599 took command of the attempt to pacify the Irish rebels, Bacon's hopes sank. Essex did not solve the Irish question, returned to court and fell from grace, as Bacon had anticipated he would. He therefore lost a valuable patron and spokesman for his projects. Bacon tried to reconcile the queen and Essex; but when the earl rebelled against the crown in 1601, he could do nothing to help him. The queen ordered Bacon to participate in the treason trial against Essex. In 1601 Bacon sat in Elizabeth's last parliament, playing an extremely active role.

Bacon's struggle to overcome intellectual blockades and the dogmatic slumber of his age and of earlier periods had to be fought on many fronts. Very early on he criticized not only Plato, Aristotle and the Aristotelians, but also humanists and Renaissance scholars such as Paracelsus and Bernardino Telesio.

Although Aristotle provided specific axioms for every scientific discipline, what Bacon found lacking in the Greek philosopher's work was a master principle or general theory of science, which could be applied to all branches of natural history and philosophy (Klein 2003a). For Bacon, Aristotle's cosmology, as well as his theory of science, had become obsolete and consequently so too had many of the medieval thinkers who followed his lead. He does not repudiate Aristotle completely, but he opposes the humanistic interpretation of him, with its emphasis on syllogism and dialectics ( scientia operativa versus textual hermeneutics) and the metaphysical treatment of natural philosophy in favor of natural forms (or nature's effects as structured modes of action, not artifacts), the stages of which correspond-in the shape of a pyramid of knowledge-to the structural order of nature itself.

Bacon's doctrine of the idols not only represents a stage in the history of theories of error (Brandt 1979) but also functions as an important theoretical element within the rise of modern empiricism. According to Bacon, the human mind is not a tabula rasa. Instead of an ideal plane for receiving an image of the world in toto, it is a crooked mirror, on account of implicit distortions (Bacon IV [1901], 428-34). He does not sketch a basic epistemology but underlines that the images in our mind right from the beginning do not render an objective picture of the true objects. Consequently, we have to improve our mind, i.e., free it from the idols, before we start any knowledge acquisition.

As early as Temporis partus masculus, Bacon warns the student of empirical science not to tackle the complexities of his subject without purging the mind of its idols:

On waxen tablets you cannot write anything new until you rub out the old. With the mind it is not so; there you cannot rub out the old till you have written in the new. (Farrington 1964, 72)

In Redargutio Philosophiarum Bacon reflects on his method, but he also criticizes prejudices and false opinions, especially the system of speculation established by theologians, as an obstacle to the progress of science (Farrington 1964, 107), together with any authoritarian stance in scholarly matters.

Bacon deals with the idols in the Second Book of The Advancement of Learning, where he discusses Arts intellectual (Invention, Judgment, Memory, Tradition). In his paragraph on judgment he refers to proofs and demonstrations, especially to induction and invention. When he comes to Aristotle's treatment of the syllogism, he reflects on the relation between sophistical fallacies (Aristotle, De Sophisticis Elenchis) and the idols (Bacon III [1887], 392-6). Whereas induction, invention, and judgment presuppose "the same action of the mind", this is not true for proof in the syllogism. Bacon, therefore, prefers his own interpretatio naturae, repudiating elenches as modes of sophistical 'juggling' in order to persuade others in redargutions ("degenerate and corrupt use ... for caption and contradiction"). There is no finding without proof and no proof without finding. But this is not true for the syllogism, in which proof (syllogism: judgment of the consequent) and invention (of the 'mean' or middle term) are distinct. The caution he suggests in relation to the ambiguities in elenches is also recommended in face of the idols:

there is yet a much more important and profound kind of fallacies in the mind of man, which I find not observed or enquired at all, and think good to place here, as that which of all others appertaineth most to rectify judgment: the force whereof is such, as it doth not dazzle or snare the understanding in some particulars, but doth more generally and inwardly infect and corrupt the state thereof. For the mind of man is far from the nature of a clear and equal glass, wherein the beams of things should reflect according to their true incidence, nay, it is rather like an enchanted glass, full of superstition and imposture, if it be not delivered and reduced. For this purpose, let us consider the false appearances that are imposed upon us by the general nature of the mind .... (Bacon III [1887], 394-5)

Bacon still presents a similar line of argument to his reader in 1623, namely in De Augmentis (Book V, Chap. 4; see Bacon IV [1901], 428-34). Judgment by syllogism presupposes-in a mode agreeable to the human mind-mediated proof, which, unlike in induction, does not start from sense in primary objects. In order to control the workings of the mind, syllogistic judgment refers to a fixed frame of reference or principle of knowledge as the basis for "all the variety of disputations" (Bacon IV [1901], 491). The reduction of propositions to principles leads to the middle term. Bacon deals here with the art of judgment in order to assign a systematic position to the idols. Within this art he distinguishes the 'Analytic' from the detection of fallacies (sophistical syllogisms). Analytic works with "true forms of consequences in argument" (Bacon IV [1901], 429), which become faulty by variation and deflection. The complete doctrine of detection of fallacies, according to Bacon, contains three segments:

1. Sophistical fallacies,

2. Fallacies of interpretation, and

3. False appearances or Idols.

Concerning (1) Bacon praises Aristotle for his excellent handling of the matter, but he also mentions Plato honorably. Fallacies of interpretation (2) refer to "Adventitious Conditions or Adjuncts of Essences", similar to the predicaments, open to physical or logical inquiry. He focuses his attention on the logical handling when he relates the detection of fallacies of interpretation to the wrong use of common and general notions, which leads to sophisms. In the last section (3) Bacon finds a place for his idols, when he refers to the detection of false appearances as

the deepest fallacies of the human mind: For they do not deceive in particulars, as the others do, by clouding and snaring the judgment; but by a corrupt and ill-ordered predisposition of mind, which as it were perverts and infects all the anticipations of the intellect. (IV, 431)

Idols are productions of the human imagination (caused by the crooked mirror of the human mind) and thus are nothing more than "untested generalities" (Malherbe 1996, 80).

In his Preface to the Novum Organum Bacon promises the introduction of a new method, which will restore the senses to their former rank (Bacon IV [1901], 17f.), begin the whole labor of the mind again, and open two sources and two distributions of learning, consisting of a method of cultivating the sciences and another of discovering them. This new beginning presupposes the discovery of the natural obstacles to efficient scientific analysis, namely seeing through the idols, so that the mind's function as the subject of knowledge acquisition comes into focus (Brandt 1979, 19).

According to Aphorism XXIII of the First Book, Bacon makes a distinction between the Idols of the human mind and the Ideas of the divine mind: whereas the former are for him nothing more than "certain empty dogmas", the latter show "the true signatures and marks set upon the works of creation as they are found in nature" (Bacon IV [1901], 51).

3.1.1 Idols of the Tribe

The Idols of the Tribe have their origin in the production of false concepts due to human nature, because the structure of human understanding is like a crooked mirror, which causes distorted reflections (of things in the external world).

3.1.2 Idols of the Cave

The Idols of the Cave consist of conceptions or doctrines which are dear to the individual who cherishes them, without possessing any evidence of their truth. These idols are due to the preconditioned system of every individual, comprising education, custom, or accidental or contingent experiences.

3.1.3 Idols of the Market Place

These idols are based on false conceptions which are derived from public human communication. They enter our minds quietly by a combination of words and names, so that it comes to pass that not only does reason govern words, but words react on our understanding.

3.1.4 Idols of the Theatre

According to the insight that the world is a stage, the Idols of the Theatre are prejudices stemming from received or traditional philosophical systems. These systems resemble plays in so far as they render fictional worlds, which were never exposed to an experimental check or to a test by experience. The idols of the theatre thus have their origin in dogmatic philosophy or in wrong laws of demonstration.

Bacon ends his presentation of the idols in Novum Organum, Book I, Aphorism LXVIII, with the remark that men should abjure and renounce the qualities of idols, "and the understanding [must be] thoroughly freed and cleansed" (Bacon IV [1901], 69). He discusses the idols together with the problem of information gained through the senses, which must be corrected by the use of experiments (Bacon IV [1901], 27).

the force implanted by God in these first particles, form the multiplication thereof of all the variety of things proceeds and is made up. (Bacon V [1889], 463)

Similarly, in De Sapientia Veterum he attributes to this force an

appetite or instinct of primal matter; or to speak more plainly, the natural motion of the atom; which is indeed the original and unique force that constitutes and fashions all things out of matter. (Bacon VI [1890], 729)

Suffice it to say here that Bacon, who did not reject mathematics in science, was influenced by the early mathematical version of chemistry developed in the 16 th century, so that the term 'instinct' must be seen as a keyword for his theory of nature. The natural philosopher is urged to inquire into the

appetites and inclination of things by which all that variety of effects and changes which we see in the works of nature and art is brought about. (Bacon III [1887], 17-22; V [1889], 422-6 and 510ff.: Descriptio Globi Intellectualis; cf. IV [1901], 349)

Bacon's theory of active or even vivid force in matter accounts for what he calls Cupid in De Principiis atque Originibus (Bacon V [1889], 463-5). Since his theory of matter aims at an explanation of the reality which is the substratum of appearances, he digs deeper than did the mechanistic physics of the 17 th century (Gaukroger 2001, 132-7). Bacon's ideas concerning the quid facti of reality presuppose the distinction

between understanding how things are made up and of what they consist, ... and by what force and in what manner they come together, and how they are transformed. (Gaukroger 2001, 137)

This is the point in his work where it becomes obvious that he tries to develop an explanatory pattern in which his theory of matter, and thus his atomism, are related to his cosmology, magic, and alchemy.

In De Augmentis, Bacon not only refers to Pan and his nymphs in order to illustrate the permanent atomic movement in matter but in addition revives the idea of magic in a 'honourable meaning' as

the knowledge of the universal consents of things .... I ... understand [magic] as the science which applies the knowledge of hidden forms to the production of wonderful operations; and by uniting (as they say) actives with passives, displays the wonderful works of nature. (Bacon IV [1901], 366-7: De Augmentis III.5)

Bacon's notion of form is made possible by integration into his matter theory, which (ideally) reduces the world of appearances to some minimal parts accessible and open to manipulation by the knower/maker. In contrast to Aristotle, Bacon's knowing-why type of definition points towards the formulation of an efficient knowing-how type (Pérez-Ramos 1988, 119). In this sense a convergence between the scope of definition and that of causation takes place according to a 'constructivist epistemology'. The fundamental research of Graham Rees has shown that Bacon's special mode of cosmology is deeply influenced by magic and semi-Paracelsian doctrine. For Bacon, matter theory is the basic doctrine, not classical mechanics as it is with Galileo. Consequently, Bacon's purified and modified versions of chemistry, alchemy, and physiology remain primary disciplines for his explanation of the world.

According to Rees, the Instauratio Magna comprises two branches: (1) Bacon's famous scientific method, and (2) his semi-Paracelsian world system as "a vast, comprehensive system of speculative physics" (Rees 1986, 418). For (2) Bacon conjoins his specific version of Paracelsian cosmic chemistry to Islamic celestial kinematics (especially in Alpetragius [al-Bitruji]; see Zinner 1988, 71). The chemical world system is used to support Bacon's explanation of celestial motion in the face of contemporary astronomical problems (Rees 1975b, 161f.). There are thus two sections in Bacon's Instauratio, which imply the modes of their own explanation.

Bacon's speculative cosmology and matter theory had been planned to constitute Part 5 of Instauratio Magna. The theory put forward refers in an eclectic vein to atomism, criticizes Aristotelians and Copernicans, but also touches on Galileo, Paracelsus, William Gilbert, Telesio, and Arabic astronomy.

For Bacon, 'magic' is classified as applied science, while he generally subsumes under 'science' pure science and technology. It is never identified with black magic, since it represents the "ultimate legitimate power over nature" (Rees 2000, 66). Whereas magia was connected to crafts in the 16 th and 17 th centuries, Bacon's science remains the knowledge of forms in order to transform them into operations. Knowledge in this context, however, is no longer exclusively based on formal proof.

Terrestrial fire is presented as the weak variant of sidereal fire; it joins with oily substances and sulphur, for all of which Bacon introduces the Sulphur Quaternion. These quaternions comprise antithetical qualities: air and ether versus fire and sidereal fire. The struggle between these qualities is determined by the distance from the earth as the absolute center of the world system. Air and ether become progressively weaker as the terrestrial and sidereal fire grow stronger. The quaternion theory functions in Bacon's thought as a constructive element for constituting his own theory of planetary movement and a general theory of physics. This theory differs from all other contemporary approaches, even though Bacon states that "many theories of the heavens may be supposed which agree well enough with the phenomena and yet differ with each other" (Bacon IV [1901], 104). The diurnal motion of the world system (9 th sphere) is driven by sympathy; it carries the heavens westward around the earth. The sidereal fire is powerful and, accordingly, sidereal motion is swift (the stars complete their revolution in 24 hours). Since the sidereal fire becomes weaker if it burns nearer to the earth, the lower planets move more slowly and unevenly than the higher ones (in this way Bacon, like Alpetragius, accounts for irregular planetary movement without reference to Ptolemy's epicycle theory). He applies his theory of consensual motion to physics generally (e.g., wind and tides) and thus comes into conflict with Gilbert's doctrine of the interstellar vacuum and Galileo's theory of the tides (for Bacon, the cycle of tides depends on the diurnal motion of the heavens but, for Galileo, on the earth's motion).

With quaternion theory we see that, in the final analysis, Bacon was not a mechanist philosopher. His theory of matter underwent an important transformation, moving in the direction of 'forms', which we would nowadays subsume under biology or the life sciences rather than under physics. Bacon distinguishes between non-spiritual matter and spiritual matter. The latter, also called 'subtle matter' or 'spirit', is more reminiscent of Leibniz' 'monads' than of mechanically defined and materially, as well as spatially, determined atoms. The spirits are seen as active agents of phenomena; they are endowed with 'appetition' and 'perception' (Bacon I [1889], 320-21: Historia Vitae et Mortis; see also V, 63: Sylva Sylvarum, Century IX: "It is certain that all bodies whatsoever, though they have no sense, yet they have perception: for when one body is applied to another, there is a kind of election to embrace that which is agreeable, and to exclude or expel that which is ingrate").

There are and can be only two ways of searching into and discovering truth. The one flies from the senses and particulars to the most general axioms, and from these principles, the truth of which it takes for settled and immoveable, proceeds to judgment and to the discovery of middle axioms. And this way is now in fashion. The other derives axioms from the senses and particulars, rising by gradual and unbroken ascent, so that it arrives at the most general axioms last of all. This is the true way, but as yet untried. (Bacon IV [1901], 50)

The laws of nature, which Bacon intended to discover by means of his new method, were expressed in the 'forms', in which the 'unbroken ascent' culminates. Through these forms the natural philosopher understands the general causes of phenomena (Kargon 1966, 48). In his endeavor to learn more about the secret workings of nature, Bacon came to the conclusion that the atomist theory could not provide sufficient explanations for the "real particles, such as really exist" (Bacon IV [1901], 126: Novum Organum, II.viii), because he thought that the immutability of matter and the void (both necessary assumptions for atomism) were untenable. His language turned from that of Greek physics to the usage of contemporary chemists. This is due to his insight that "subtlety of investigation" is needed, since our senses are too gross for the complexity and fineness of nature, so that method has to compensate for the shortcomings of our direct comprehension. Only method leads to the knowledge of nature: in Sylva Sylvarum, Century I.98 Bacon deals explicitly with the question of the asymmetrical relationship between man's natural instrument (i.e., the senses) and the intricacy of nature's structures and workings.

Bacon distinguishes 'animate' or vital spirits, which are continuous and composed of a substance similar to fire, from lifeless or inanimate spirits, which are cut off and resemble air: the spirits interact with gross matter through chemical processes (Bacon IV, 195-6 ( Novum Organum, II.xl)). These spirits have two different desires: self-multiplication and attraction of like spirits. According to Kargon (1966, 51):

Bacon's later theory of matter is one of the interaction of gross, visible parts of matter and invisible material spirits, both of which are physically mixed.

Spirits interact with matter by means of concoction, colliquation and other non-mechanical chemical processes, so that Bacon's scientific paradigm differs from Descartes' mechanist theory of matter in his Principia Philosophiae (1644), which presupposes res extensa moving in space. Bacon's theory of matter is thus closely related to his speculative philosophy:

The distinction between tangible and pneumatic matter is the hinge on which the entire speculative system turns. (Rees 1996, 125; Paracelsus had already stated that knowledge inheres in the object: see Shell 2004, 32)

Bacon's theory of matter in its final version was more corpuscular than atomist (Clericuzio 2000, 78). Bacon's particles are semina rerum: they are endowed with powers, which make a variety of motions possible and allow the production of all possible forms. These spirits are constitutive for Bacon's theory of matter. As material, fine substances, composed of particles, combined from air and fire, they can, as we have seen, be either inanimate or animate. Bacon thus suggests a corpuscular and chemical chain of being:

Small wonder, then, that Bacon's spirits are indispensable for his conception of physiology:

the vital spirits regulate all vegetative functions of plants and animals. Organs responsible for these functions, for digestion, assimilation, etc., seem to act by perception, mere reaction to local stimuli, but these reactions are coordinated by the vital spirit. These functions flow from the spirit's airy-flamy constitution. The spirit has the softness of air to receive impressions and the vigour of fire to propagate its actions. (Rees in OFB VI, 202-3)

This physiological stratum of Bacon's natural philosophy was influenced by his semi-Paracelsian cosmology (on Paracelsus see Müller-Jahncke 1985, 67-88), which Graham Rees (Rees and Upton 1984, 20-1) has reconstructed from the extant parts of the Instauratio Magna. Detailed consideration therefore has to be given to Bacon's theory of the 'quaternions'.

Bacon's speculative system is a hybrid based on different sources which provided him with seminal ideas: e.g., atomism, Aristotelianism, Arabic astronomy, Copernican theory, Galileo's discoveries, the works of Paracelsus, and Gilbert. In his theory he combines astronomy, referring to Alpetragius (see Dijksterhuis 1956, 237-43; Rees and Upton 1984, 26; Gaukroger, 2001, 172-5; and see Grant 1994, 533-66, for discussion of the cosmology of Alpetragius), and chemistry (Rees 1975a, 84-5):

[i]t was partly designed to fit a kinematic skeleton and explain, in general terms, the irregularities of planetary motion as consequences of the chemical constitution of the universe. (Rees 1975b, 94)

Bacon had no explanation for the planetary retrogressions and saw the universe as a finite and geocentric plenum, in which the earth consists of the two forms of matter (tangible and pneumatic). The earth has a tangible inside and is in touch with the surrounding universe, but through an intermediate zone. This zone exists between the earth's crust and the pure pneumatic heavens; it reaches some miles into the crust and some miles into air. In this zone, pneumatic matter mixes with tangible matter, thus producing 'attached spirits', which must be distinguished from 'free spirits' outside tangible bodies. Bacon's four kinds of free spirits are relevant for his 'quaternion theory':

The planets move around the earth in the ether (a tenuous kind of air), which belongs to the 'mercury quaternion': it includes watery bodies and mercury. Terrestrial fire is a weakened form of sidereal fire. It is related to oily substances and sulphur, and constitutes the 'sulphur quaternion'. The two quaternions oppose each other: air/ether vs. fire/sidereal fire. Air and ether loose power when terrestrial and sidereal fires grow more energetic-Bacon's sulphur and mercury are not principles in the sense of Paracelsus, but simply natural substances. The Paracelsian principle of salt is excluded by Bacon and the substance, which plays a role only in the sublunary realm, is for him a compound of natural sulphur and mercury (Rees and Upton 1984, 25).

Bacon used his quaternion theory for his cosmology, which differs greatly from other contemporary systems (Rees 2000, 68):

the diurnal motion turns the heavens about the earth towards the west;

under powerful sidereal fire (i.e., principle of celestial motion) the motion is swift: the revolution of the stars takes place in twenty-four hours;

under weaker sidereal fire-nearer to the earth-planets move more slowly and more erratic.

Bacon, who tried to conceive of a unified physics, rejected different modes of motion in the superlunary and in the sublunary world (Bacon I [1889], 329). He did not believe in the existence of the (crystalline) spheres nor in the macrocosm-microcosm analogy. He revised Paracelsian ideas thoroughly. He rejected the grounding of his theories in Scripture and paid no attention at all to Cabbalistic and Hermetic tendencies (Rees 1975b, 90-1). But he extended the explanatory powers of the quaternions to earthly phenomena such as wind and tides.

Bacon's two systems were closely connected:

System 1: (The Two Quaternions)

explained and comprised the cosmological aspect of his natural philosophy.

System 2: (Theory of Matter)

explained terrestrial nature, that is, it "dealt with the manifold changes in the animal, vegetable, and mineral kingdoms of the frontier zone between the celestial heavens and the Earth's interior" (Rees 1996, 130; the two tables are taken from Rees).

System 2 depends on System 1, since explanations for terrestrial things were subordinated to explanations of the cosmological level. The table of System 2 shows Bacon's matter theory. His quaternion theory is relevant for System 1. System 2 is explained in terms of 'intermediates', which combine the qualities of the items in one quaternion with their opposites in the other.

Bacon's system is built in a clear symmetrical way: each quaternion has four segments, together eight and there are four types of intermediates. Thus, the system distinguishes twelve segments in all. He wanted to explain all natural phenomena by means of this apparatus:

Sulphur Quaternion

Mercury Quaternion

Tangible Substances (With Attached Spirits)

Sulphur (subterranean)

Mercury (subterranean)

Oil and oily inflammable substances (terrestrial)

Water and 'crude' non-inflammable substances (terrestrial)

Pneumatic Substances

Terrestrial fire (sublunary)

Air (sublunary)

Sidereal fire (planets)

Ether (medium of the planets)

Sulphur Quaternion

Intermediates

Mercury Quaternion

Tangible Substances (with attached spirits)

Sulphur (subterranean)

Salts (subterranean and in organic beings)

Mercury (subterranean)

Oil and oily inflammable substances (terrestrial)

Juices of animals and plants

Water and 'crude' non-inflammable substances (terrestrial)

Pneumatic substances

Terrestrial fire (sublunary)

Attached animate and inanimate spirits (in tangible bodies)

Air (sublunary)

Sidereal fire (planets)

Heaven of the fixed stars

Ether (medium of planets)

There are two principal intermediates:

it has not been ill observed by the chemists in their triad of first principles, that sulphur and mercury run through the whole universe ... in these two one of the most general consents in nature does seem to be observable. For there is consent between sulphur, oil and greasy exhalation, flame, and perhaps the body of a star. So is there between mercury, water and watery vapors, air, and perhaps the pure and intersiderial ether. Yet these two quaternions or great tribes of things (each within its own limits) differ immensely in quantity of matter and density, but agree very well in configuration. (Bacon IV [1901], 242-3; see also V [1889], 205-6; for tables of the two quaternions and Bacon's theory of matter see Rees 1996, 126, 137; Rees 2000, 68-9)

Bacon regarded his cosmological worldview as a system of anticipations, which was open to revision in light of further scientific results based on the inductive method (Rees 1975b, 171). It was primarily a qualitative system, standing aside from both mathematical astronomers and Paracelsian chemists. It thus emphasized the priority which he gave to physics over mathematics in his general system of the sciences.

Bacon's two quaternions and his matter theory provide a speculative framework for his thought, which was open to the future acquisition of knowledge and its technical application. His Nova Atlantis can be understood as a text which occupies an intermediate position between his theory of induction and his speculative philosophy (Klein 2003c; Price 2002).

It is important to bear in mind that Bacon's speculative system was his way out of a dilemma which had made it impossible for him to finish his Instauratio Magna. His turn towards speculation can only be interpreted as an intellectual anticipation during an intermediate phase of the history of science, when a gigantic amount of research work was still to be accomplished, so that empirical theories could neither be established nor sufficiently guaranteed. Speculation in Bacon's sense can therefore be seen as a preliminary means of explaining the secrets of nature until methodical research has caught up with our speculations. The speculative stance remains a relative and intermediate procedure for the 'man of science'.

The Great Instauration, Bacon's main work, was published in 1620 under the title: Franciscus de Verulamio Summi Angliae Cancellaris Instauratio magna. This great work remained a fragment, since Bacon was only able to finish parts of the planned outline. The volume was introduced by a Prooemium, which gives a general statement of the purpose, followed by a Dedication to the King (James I) and a Preface, which is a summary of all "directions, motifs, and significance of his life-work" (Sessions 1996, 71). After that, Bacon printed the plan of the Instauratio, before he turned to the strategy of his research program, which is known as Novum Organum Scientiarum. Altogether the 1620 book constitutes the second part of Part II of the Instauratio, the first part of which is represented by De Augmentis and Book I of The Advancement of Learning. When Bacon organized his Instauratio, he divided it into six parts, which reminded contemporary readers of God's work of the six days (the creation), already used by writers like Guillaume Du Bartas ( La Sepmaine, ou Création du Monde, 1579, transl. by Joshua Sylvester, Bartas His Devine Weekes & Workes, 1605) and Giovanni Pico della Mirandola ( Heptaplus, 1489).

Bacon sees nature as a labyrinth, whose workings cannot be exclusively explained by reference to "excellence of wit" and "repetition of chance experiments":

Our steps must be guided by a clue, and see what way from the first perception of the sense must be laid out upon a sure plan. (Bacon IV [1901], 18)

Bacon's Plan of the Work runs as follows (Bacon IV [1901], 22):

1. The Divisions of the Sciences.

2. The New Organon; or Directions concerning the Interpretation of Nature.

3. The Phenomena of the Universe; or a Natural and Experimental History for the foundation of Philosophy.

4. The Ladder of Intellect.

5. The Forerunners; or Anticipations of the New Philosophy.

6. The New Philosophy; or Active Science.

Part 1 contains the general description of the sciences including their divisions as they presented themselves in Bacon's time. Here he aimed at a distinction between what was already invented and known in contrast to "things omitted which ought be there" (Bacon IV [1901], 23). This part could be taken from The Advancement of Learning (1605) and from the revised and enlarged version De Dignitate et Augmentis Scientiarum (1623).

Part 3 was going to contain natural and experimental history or the record of the phenomena of the universe. According to De Augmentis Scientarum (Bacon IV [1901], 275), natural history is split up into narrative and inductive, the latter of which is supposed "to minister and be in order to the building up of Philosophy". These functional histories support human memory and provide the material for research, or the factual knowledge of nature, which must be certain and reliable. Natural history starts from and emphasizes the subtlety of nature or her structural intricacy, but not the complexity of philosophical systems, since they have been produced by the human mind. Bacon sees this part of Instauratio Magna as a foundation for the reconstruction of the sciences in order to produce physical and metaphysical knowledge. Nature in this context is studied under experimental conditions, not only in the sense of the history of bodies, but also as a history of virtues or original passions, which refer to the desires of matter (Rees 1975a). This knowledge was regarded by Bacon as a preparation for Part 6, the Second Philosophy or Active Science, for which he gave only the one example of Historia Ventorum (1622); but-following his plan to compose six prototypical natural histories-he also wrote Historia vitae et mortis(1623) and the Historia densi, which was left in manuscript. The text, which develops the idea of Part 3, is called Parasceve ad Historiam Naturalem et Experimentalem.

Part 4, which Bacon called The Ladder of Intellect or Scala Intellectus, was intended to function as a link between the method of natural history and that of Second Philosophy/Active Science. It consists not only of the fragment Filum labyrinthi (Bacon III [1887], 493-504), but also includes the Abecedarium nouum naturae (OFB XIII, xxi), which was planned as a preface to all of section 4 "[to] demonstrate the whole process of the mind" (OFB XIII, xxii). Filum labyrinthi is similar to, but not identical with, Cogitata et Visa. Speaking of himself in an authorial voice, Bacon reflects on the state of science and derives his construction of a research program from the gaps and deficiencies within the system of disciplines: sciences of the future should be examined and further ones should be discovered. Emphasis must be laid on new matter (not on controversies). It is necessary to repudiate superstition, zealous religion, and false authorities. Just as the Fall was not caused by knowledge of nature, but rather by moral knowledge of good and evil, so knowledge of natural philosophy is for Bacon a contribution to the magnifying of God's glory, and, in this way, his plea for the growth of scientific knowledge becomes evident.

Part 6 was scheduled to contain Bacon's description of the new philosophy, as the last part of his Great Instauration; but nothing came of this plan, so that there is no extant text at all from this part of the project.

[of] induction the logicians seem hardly to have taken any serious thought, but they pass it by with a slight notice, and hasten to the formulae of disputation. I on the contrary reject demonstration by syllogism .... (Bacon IV [1901], 24)

Bacon's method appears as his conceptual plot,

applied to all stages of knowledge, and at every phase the whole process has to be kept in mind. (Malherbe 1996, 76)

Induction implies ascending to axioms, as well as a descending to works, so that from axioms new particulars are gained and from these new axioms. The inductive method starts from sensible experience and moves via natural history (providing sense-data as guarantees) to lower axioms or propositions, which are derived from the tables of presentation or from the abstraction of notions. Bacon does not identify experience with everyday experience, but presupposes that method corrects and extends sense-data into facts, which go together with his setting up of tables (tables of presence and of absence and tables of comparison or of degrees, i.e., degrees of absence or presence). "Bacon's antipathy to simple enumeration as the universal method of science derived, first of all, from his preference for theories that deal with interior physical causes, which are not immediately observable" (Urbach 1987, 30; see: sect. 2). The last type can be supplemented by tables of counter-instances, which may suggest experiments:

To move from the sensible to the real requires the correction of the senses, the tables of natural history, the abstraction of propositions and the induction of notions. In other words, the full carrying out of the inductive method is needed. (Malherbe 1996, 85)

The sequence of methodical steps does not, however, end here, because Bacon assumes that from lower axioms more general ones can be derived (by induction). The complete process must be understood as the joining of the parts into a systematic chain. From the more general axioms Bacon strives to reach more fundamental laws of nature (knowledge of forms), which lead to practical deductions as new experiments or works (IV, 24-5). The decisive instruments in this process are the middle or 'living axioms,' which mediate between particulars and general axioms. For Bacon, induction can only be efficient if it is eliminative by exclusion, which goes beyond the remit of induction by simple enumeration. The inductive method helps the human mind to find a way to ascertain truthful knowledge.

Novum Organum, I, Aphorism CXV (Bacon IV [1901], 103) ends the "pulling down" of "the signs and causes of the errors" within the sciences, achieved by means of three refutations, which constituted the condition for a rational introduction of method: refutation of 'natural human reason' (idols); refutation of 'demonstrations' (syllogisms) and refutation of 'theories' (traditional philosophical systems).

Bacon's method presupposes a double starting-point: empirical and rational. True knowledge is acquired if we want to proceed from a lower certainty to a higher liberty and from a lower liberty to a higher certainty. The rule of certainty and liberty in Bacon converges with his repudiation of the old logic of Aristotle, which determined true propositions by the criteria of generality, essentiality, and universality. Bacon rejects anticipatio naturae ("anticipation of nature") in favor of interpretatio naturae ("interpretation of nature"), which starts with the collecting of facts and their methodical (inductive) investigation, shunning entanglement in pure taxonomy (as in Ramism), which establishes the order of things (Urbach 1987, 26; see also Foucault 1966 [1970]), but does not produce knowledge. For Bacon, making is knowing and knowing is making (Bacon IV [1901], 109-10). In accordance with the maxim "command nature ... by obeying her" (Sessions 1996, 136; Gaukroger 2001, 139ff.), the exclusion of superstition, imposture, error, and confusion are obligatory. Bacon introduces variations into "the maker's knowledge tradition" as the discovery of the forms of a given nature lead him to develop his method for acquiring factual and proven knowledge.

Bacon argues against "anticipation of nature", which he regards as a conservative method, leading to theories that recapitulate the data without producing new ones conducive to the growth of knowledge. Moreover, such theories are considered to be final, so that they are never replaced.

"Anticipation of nature" resembles "conventionalism" (Urbach 1987, 30-41), according to which theories refer to unobservable entities (e.g., atoms, epicycles). The theories are "computation rules" or "inference licences" within this given framework, which give explanations and predictions of particular kinds of observable events. The conventionalist acceptance of making predictions concerning future events cannot be separated from the question of probability. Bacon's procedure of knowledge acquisition goes against "conventionalism", because "anticipation of nature" does not reject authoritative and final speculations concerning "unobservables" and because it permits "ad hoc adjustments". Nowadays, however,

philosophers would not accept the idea that just because we can't observe something directly ... it follows that there is no such thing. (Huggett 2010, 82. See also Von Weizsäcker and Juilfs 1958, pp.67-70; Rae 1986 [2000], 1-27 and passim)

Conventionalist deep-level theories of the world are chosen from among alternative ways of observing phenomena. Although theories revealing the world structure are not directly provable or disprovable by means of observation or experiment, conventionalists might maintain their chosen theory even in the face of counter-evidence. They therefore avoid changes of theory. Any move to a new theory is not taken on the basis of new evidence, but because a new theory seems to be simpler, more applicable or more beautiful. Laws of nature are generally understood as being unrevisable (O'Hear 1995, 165). The famous debate, sparked by Thomas Kuhn, on paradigmatic and non-paradigmatic science and theory is relevant here. Bacon's position-open to scientific progress-is nearer to Kuhn than to Duhem or Poincaré. For Bacon, "anticipation of nature" (as a mode of "conventionalism") produces obstacles to the progress of knowledge. Traditional methods shun speculation concerning things which are not immediately visible; Bacon's speculation, however, is an element of "interpretation of nature". He presupposes hypothetical theories, but these do not go beyond the collected data. His acceptance of hypotheses is connected with his rejection of " anticipation of nature". Thus, hypotheses are related to the axioms of "interpretation of nature", which go beyond the original data. The amount of established facts is not identical with that of possible data (Gillies 1998, 307). Anticipation is rejected, only if it "flies from the senses and particulars to the most general axioms" (OFB XI, xxv). Because of the dangers of premature generalization, Bacon is careful about speculations and rigorously rejects any dogmatic defense of them and the tendency to declare them infallible.

...the philosophy that we now possess clutches to its breast certain tenets with which (if we look into it carefully) they want wholly to conceive men that nothing difficult, nothing with real power and influence over nature, should be expected from art or human effort; [...] These things, if we examine them minutely, tend wholly towards a wicked circumscription of human power and an intentional and unnatural despair which not only confounds the presages of hope but breaks every nerve and spur of industry, and throws away the chances afforded by experience itself-while all they care about is that their art be considered perfect, expending their effort to achieve the most foolish and bankrupt glory of having it believed that whatever has not been found out or understood so far cannot be found out or understood in the future. (OFB XI, 141)

Bacon sees nature as an extremely subtle complexity, which affords all the energy of the natural philosopher to disclose her secrets.

For him, new axioms must be larger and wider than the material from which they are taken. At the same time, "interpretation of nature" must not leap to remote axioms. In terms of his method, he rejects general ideas as simple abstractions from very few sense perceptions. Such abstract words may function as conventions for organizing "new observations", but only in the sense of means for taxonomical order. Such a sterile procedure is irrelevant for "interpretation of nature", which is not final or infallible and is based on the insight that confirming hypotheses do not provide strict proofs. Bacon's method is therefore characterized by openness:

Nevertheless, I do not affirm that nothing can be added to what I prescribe; on the contrary, as one who observes the mind not only in its innate capacity but also insofar as it gets to grips with things, it is my conviction that the art of discovering will grow as the number of things discovered will grow. (OFB, XI, 197)

Peter Urbach's commentary exactly underlines Bacon's openness:

He believed that theories should be advanced to explain whatever data were available in a particular domain. These theories should preferably concern the underlying physical, causal mechanisms and ought, in any case, to go beyond the data which generated them. They are then tested by drawing out new predictions, which, if verified in experience, may confirm the theory and may eventually render it certain, at least in the sense that it becomes very difficult to deny. (Urbach 1987, 49)

Bacon was no seventeenth-century Popperian. Rather, on account of his theory of induction, he was:

the first great theorist of experimentalism": "the function of experiment was both to test theories and to establish facts" (Rees, in OFB XI, xli).

Encyclopaedic repetition with an Aristotelian slant is being displaced by original compilation in which deference to authority plays no part whatever. Individual erudition is being dumped in favour of collective research. Conservation of traditional knowledge is being discarded in the interest of a new, functional realization of natural history, which demands that legenda -things worth reading-be supplanted by materials which will form the basis of a thoroughgoing attempt to improve the material conditions of the human race. (Rees, in OFB XI, xlii)

Form is for Bacon a structural constituent of a natural entity or a key to its truth and operation, so that it comes near to natural law, without being reducible to causality. This appears all the more important, since Bacon-who seeks out exclusively causes which are necessary and sufficient for their effects-rejects Aristotle's four causes (his four types of explanation for a complete understanding of a phenomenon) on the grounds that the distribution into material, formal, efficient, and final causes does not work well and that they fail to advance the sciences (especially the final, efficient, and material causes). Consider again the passage quoted in Section 3.3:

There are and can be only two ways of searching into and discovering truth. The one flies from the senses and particulars to the most general axioms, and from these principles, the truth of which it takes for settled and immovable, proceeds to judgment and to the discovery of middle axioms. And this way is now in fashion. The other derives axioms from the senses and particulars, rising by a gradual and unbroken ascent, so that it arrives at the most general axioms at last. This is the true way, but as yet untried. (Bacon IV [1901], 50: Novum Organum, I, Aphorism XIX).

Since for Bacon the formal necessity of the syllogism does not suffice to set up first principles, his method comprises two basic tasks: (1) the discovery of forms, and (2) the transformation of concrete bodies. The discovery from every case of generation and motion refers to a latent process according to which efficient and material causes lead to forms; but there is also the discovery of latent configurations of bodies at rest and not in motion (Bacon IV [1901], 119-20).

Bacon's new mode of using human understanding implies a parallelism between striving towards human power and constituting human knowledge. Technical know-how leads to successful operations, which converge with the discovery of forms (Pérez-Ramos 1988, 108; Bacon IV [1901], 121). To understand the workings of nature presupposes an arrangement of facts which makes the investigative analysis of cause and effect possible, especially by means of new experiments. At this point the idea of scientia operativa comes in again, since the direction for a true and perfect rule of operation is parallel to the discovery of a true form. Bacon's specific non-Aristotelian Aristotelianism (Pérez-Ramos 1988, 113, 115) is one of the main features of his theory. Other indispensable influences on Bacon, apart from a modified version of Aristotle, are critically assessed Hermeticism, rhetoric (Vickers) and alchemy (Rees).

Nowadays the view that Bacon "made little first-hand contribution to science" (Hesse 1964, 152) no longer coincides with the opinion that we have to assume an underestimation of the "place of hypothesis and mathematics" in his work (Urban 1987; Sessions 1999, 139; Rees 1986). But there were few doubts in the past that Bacon "encouraged detailed and methodical experimentation" (Hesse 1964, 152); and he did this on account of his new inductive method, which implied the need for negative instances and refuting experiments. Bacon saw that confirming instances could not suffice to analyze the structure of scientific laws, since this task presupposed a hypothetical-deductive system, which, according to Lisa Jardine, is closely connected to "the logical and linguistic backgrounds from which Bacon's New Logic proceeds ..." (Sessions 1999, 140; Jardine 1974, 69ff.).

In his "[m]ethod of analysis by exclusion" (Sessions 1999, 141), negation proved to be "one of Bacon's strongest contributions to modern scientific method" (Wright 1951, 152). Most important were his tables of degrees and of exclusion. They were needed for the discovery of causes, especially for supreme causes, which were called forms. The method of induction works in two stages:

1. Learned experience from the known to the unknown has to be acquired, and the tables (of presence, absence, degrees) have to be set up before their interpretation can take place according to the principle of exclusion. After the three tables of the first presentation have been judged and analyzed, Bacon declares the First Vintage or the first version of the interpretation of nature to be concluded.

2. The second phase of the method concentrates on the process of exclusion. The aim of this procedure is the reduction of the empirical character of experience, so that the analysis converges with an anatomy of things. Here, too, tables of presence and of absence are set up. The research work proper consists of finding the relationship of the two natures of qualities. Here exclusion functions as the process of determination. Bacon's method starts from material determination in order to establish the formal determination of real causes, but does not stop there, because it aims at the progressive generalization of causes. Here, again, the central element of the inductive method is the procedure of exclusion.

Forms, as the final result of the methodical procedure, are:

nothing more than those laws and determinations of absolute actuality which govern and constitute any simple nature, as heat, light, weight, in every kind of matter and subject that is susceptible of them (Bacon IV [1901], 145-6);

They are not identical with natural law, but with definitions of simple natures (elements) or ultimate ingredients of things from which the basic material structure has been built (Gaukroger 2001, 140). Forms are the structures constituted by the elements in nature (microphysics). This evokes a cross-reference to Bacon's atomism, which has been called the "constructivist component" (Pérez-Ramos 1988, 116) of his system, including an alchemical theory about basic kinds of matter. He aims at "understanding the basic structures of things ... as a means to transforming nature for human purposes" (Gaukroger 2001, 140; Clericuzio 2000, 78ff.); and thus he "ends" the unfinished Novum Organum with a list of things which still have to be achieved or with a catalogue of phenomena which are important and indispensable for a future natural history.

Historians of science, with their predilection for mathematical physics, used to criticize Bacon's approach, stating that "the Baconian concept of science, as an inductive science, has nothing to do with and even contradicts today's form of science" (Malherbe 1996, 75). In reaching this verdict, however, they overlooked the fact that a natural philosophy based on a theory of matter cannot be assessed on the grounds of a natural philosophy or science based on mechanics as the fundamental discipline. One can account for this chronic mode of misunderstanding as a specimen of the paradigmatic fallacy (Gaukroger 2001, 134ff.; see Rees 1986).

In Bacon's thought we encounter a relation between science and social philosophy, since his ideas concerning a utopian transformation of society presuppose an integration into the social framework of his program concerning natural philosophy and technology as the two forms of the maker's knowledge. From his point of view, which was influenced by Puritan conceptions, early modern society has to make sure that losses caused by the Fall are compensated for, primarily by man's enlargement of knowledge, providing the preconditions for a new form of society which combines scientia nova and the millennium, according to the prophecy of Daniel 12:4 (Hill 1971, 85-130). Science as a social endeavor is seen as a collective project for the improvement of social structures. On the other hand, a strong collective spirit in society may function as a conditio sine qua non for reforming natural philosophy. Bacon's famous argument that it is wise not to confound the Book of Nature with the Book of God comes into focus, since the latter deals with God's will (inscrutable for man) and the former with God's work, the scientific explanation or appreciation of which is a form of Christian divine service. Successful operations in natural philosophy and technology help to improve the human lot in a way which makes the hardships of life after the Fall obsolete. It is important to note that Bacon's idea of a-to a certain extent-Christian society by no means conveys Christian pessimism in the vein of patristic thinkers but rather displays a clear optimism as the result of compounding the problem of truth with the scope of human freedom and sovereignty (Brandt 1979, 21).

With regard to Bacon's Two Books-the Book of God and the Book of Nature-one has to keep in mind that man, when given free access to the Book of Nature, should not content himself with merely reading it. He also has to find out the names by which things are called. If man does so, not only will he be restored to his status a noble and powerful being, but the Book of God will also lose importance, from a traditional point of view, in comparison to the Book of Nature. This is what Blumenberg referred to as the "asymmetry of readability" (Blumenberg 1981, 86-107). But the process of reading is an open-ended activity, so that new knowledge and the expansion of the system of disciplines can no longer be restricted by concepts such as the completeness and eternity of knowledge (Klein 2004a, 73).

The glory of God is to conceal a thing, but the glory of the king is to find it out; as if, according to the innocent play of children, the Divine Majesty took delight to hide his works, to the end to have them found out; and as if kings could not obtain a greater honour than to be God's playfellows in that game, considering the great commandment of wits and means, whereby nothing needeth to be hidden from them. (Bacon III [1887], 299; Blumenberg, 1973, 196-200)

From this perspective, the punishment of mankind on account of the very first disobedience by Adam and Eve can be seen in a different light from that of theological interpretations. In Bacon's view, this disobedience and its consequences can be remedied in two ways: (1) by religion and moral imperatives, and (2) by advancement in the arts and sciences: "the purpose in advancing arts and sciences is the glory of God and the relief of man's estate" (Wormald 1993, 82).

The two remedies, which are interconnected with the moral dimension, refer to the advancement of learning and religion. All three together (the advancement of learning, religion, and morality) are combined in such a way that they promote each other mutually; consequently, limited outlooks on coping with life and knowledge are ruled out completely in these three fields.

The ethical dimension of Bacon's thought has been underrated by generations of scholars. Time and again a crude utilitarianism has been derived from Book I, Aphorism 1 of the Novum Organum; this cannot, however, withstand a closer analysis of his thought. Since Bacon's philosophy of science tries to answer the question of how man can overcome the deficiencies of earthly life resulting from the Fall, he enters the realm of ethical reflection. The improvement of mankind's lot by means of philosophy and science does not start from a narrow utilitarian point of view, involving sheer striving for profit and supporting the power or influence of select groups of men, but instead emphasizes the construction of a better world for mankind, which might come into existence through the ascertaining of truths about nature's workings (Bacon III [1887], 242). Thus, the perspective of the universal in Bacon's ethical thought is given predominance. The range of science and technology in their ethical meaning transcends the realm of the application of tools and/or instruments, in so far as the aim is the transformation of whole systems. Since causality and finality can interact on the basis of human will and knowledge, a plurality of worlds becomes feasible (Bacon V [1889], 506-7). Moral philosophy is closely connected to ethical reflections on the relationship between the nature of virtues-habitual or innate?-and their use in life, privately and collectively. Any application of the principles of virtue presupposes for Bacon the education of the mind, so that we learn what is good and what should be attained (Gaukroger 2006, 204-5 and passim):

The main and primitive division of moral knowledge seemeth to be into the Exemplar or Platform of Good, and the Regimen of Culture of the Mind; the one describing the nature of good, the other prescribing rules how to subdue, apply, and accommodate the will of man thereunto (Bacon III [1887], 419).

So, already in his Advancement of Learning Bacon studied the nature of good and distinguished various kinds of good. He insisted on the individual's duty to the public. Private moral self-control and the concomitant obligations are relevant for behavior and action in society. One's ethical persona is connected to morality by reference to acceptable behaviour. Though what we can do may be limited, we have to muster our psychological powers and control our passions when dealing with ourselves and with others. We need to apply self-discipline and rational assessment, as well as restraining our passions, in order to lead an active moral life in society.

Thus, for Bacon, the acquisition of knowledge does not simply coincide with the possibility of exerting power. Scientific knowledge is a condition for the expansion and development of civilization. Therefore, knowledge and charity cannot be kept separate:

I humbly pray ... that knowledge being now discharged of that venom which the serpent infused into it, and which makes the mind of man to swell, we may not be wise above measure and sobriety, but cultivate truth in charity.... Lastly, I would address one general admonition to all; that they consider what are the true ends of knowledge, and that they seek it not either for pleasure of the mind, or for contention, or for superiority to others, or for profit, or fame, or power, or any of these inferior things; but for the benefit and use of life; and that they perfect and govern it in charity. For it was from the lust of power that the angels fell, from lust of knowledge that man fell; but of charity there can be no excess, neither did angel or man ever come in danger by it (Bacon IV [1901], 20f.: Instauratio Magna, Preface).

Finally, the view that Bacon's Nova Atlantis "concerns a utopian society that is carefully organized for the purposes of scientific research and virtuous living" (Urbach 1988, 10) holds true for his entire life's work. In Nova Atlantis, social, political, and scholarly life are all organized according to the maxim of efficiency; but the House of Solomon is a separate and highly esteemed institution for research, which nevertheless is closely connected to the overall system of Bensalem. In his utopian state, Bacon presents a thoroughgoing collective life in society and science, both of which are based on revealed religion. Religion-Christian in essence-is not dogmatic, but it instills into the people of Bensalem veneration for the wise and morally exemplary members of society, and-which is of the utmost importance-the strictest sense of discipline (Gaukroger 2001, 128-30). Discipline is indispensable for those involved in the religious life as well as for the researchers, since both must proceed methodically. The isomorphic structures of nature and science, on the one hand, society and religion, on the other, prescribe patterns of political procedure, social processes, and religious attitudes, which overcome any craving for individuality. If religion and scientific research are both shown as truthful in Bensalem, then, according to Bacon, the imagination functions as a means of illustrating scientific revelation: "Bacon's purpose is ... to show that scientific research properly pursued is not inconsonant with religious propriety and social stability..." (Bierman 1963, 497). The scientists in Bensalem are sacred searchers for truth: ethics, religion, and science merge. Bacon's parabolic strategy, which we should not separate from the power of the idols, enables him to make much of his trick of introducing new ideas like a smuggler: his colored wares are smuggled into the minds of his readers by being visualized in terms of sacred and highly symbolic rituals (Peltonen 1996, 175). Science and religion are separated in Nova Atlantis, but they are also interrelated through the offices of the society of Bensalem. What Bacon obviously wants to make clear to his readers is that the example of Bensalem should free them from any fear that scientific progress will lead to chaos and upheaval. This crucial point has made by Jürgen Mittelstrass, who understands Bacon's Nova Atlantis as a utopia and regards utopias as

blueprints of practical reason, not of theoretical, that is: they set in exactly there, where the early modern idea of progress appears meagre with regards to the contents: within ethics and political theory. (Mittelstrass 1960, 369)

1857-74, The Works, edited by J. Spedding, R. L. Ellis, and D. D. Heath, 14 vols. London.

1861, The Works, edited by J. Spedding, R. L. Ellis, and D. D. Heath, 15 vols. Boston: Taggard and Thompson.

1861-74, The Letters and the Life of Francis Bacon, edited by J. Spedding, 7 vols. London: Longman, Green, Longman, and Roberts.

1889-1901, The Works, edited by J. Spedding, R. L. Ellis, and D. D. Heath. Volumes I (1889), II (1887), III (1887), IV (1901), V (1889), VI (1890), VII (1892).

1898, Novum Organum or True Suggestions for the Interpretation of Nature, London and New York.

1958, Essays, intr. by O. Smeaton. London and New York.

1962, The Advancement of Learning, edited by G. W. Kitchin, London and New York: Dent.

1982, Neu Atlantis, transl. by G. Bugge, edited by Jürgen Klein, Stuttgart.

1996-, The Oxford Francis Bacon [OFB], General Editors: Graham Rees and Lisa Jardine; Brian Vickers; Oxford University Press. In order of publication: Volume VI (1996),Philosophical Studies c. 1611-c. 1619, edited by G. Rees; Volume IV (2000),The Advancement of Learning, edited by M. Kiernan; Volume XIII (2000),The Instauratio Magna: Last Writings, edited by G. Rees; Volume XV (2000), The Essayes or Counsels, Civill and Moralledited by M. Kiernan; Volume XI (2004),The Instauratio Magna: Part II. Novum Organum, edited by G. Rees and M. Wakely; Volume XII (2007),The Instauratio Magna. Part 3, Historia naturalis et experimentalis, Historia ventorum and Historia vitæ & mortis, edited by G. Rees and M. Wakely; Volume VIII (2011),The Historie of the Raigne of King Henry the Seuenth and Other Works of the 1620s, edited by M. Kiernan.

2000, A Critical Edition of the Major Works, edited by Brian Vickers. Oxford and New York: Oxford University Press.

Anderson, F. H., 1948, The Philosophy of Francis Bacon, Chicago: University of Chicago Press.

Bierman, J., 1963, "Science and Society in the New Atlantis and other Renaissance Utopias", PMLA, 78(5): 492-500.

Blumenberg, H., 1973, Der Prozess der theoretischen Neugierde, Frankfurt am Main.

Bowen, C. D., 1963 [1993], Francis Bacon. The Temper of a Man, New York: Fordham University Press. First edition 1963, Boston: Little, Brown.

Brandt, R., 1979, "Francis Bacon, Die Idolenlehre", in Grundprobleme der großen Philosophen. Philosophie der Neuzeit I, edited by Josef Speck. Göttingen, pp. 9-34.

Burtt, E. A., 1924 [1932], The Metaphysical Foundations of Modern Physical Science, London. First Edition, April 1924; Second Edition (revised) January 1932; reprinted 1972.

Cassirer, E., 1922 [reprint 1994], Das Erkenntnisproblem in der Philosophie und Wissenschaft der Neueren Zeit, Darmstadt.

Clericuzio, A., 2000, Elements, Principles, and Corpuscles, Dordrecht: Kluwer Academic Publishers.

Dampier, W. C., 1929 [1948], A History of Science and its relations with Philosophy and Religion, Cambridge: Cambridge University Press. Fourth edition, 1948; reprinted with postscript by I. Bernard Cohen 1966.

Dijksterhuis, E. J., 1969, The Mechanization of the World Picture, Oxford.

Farrington, B., 1964, The Philosophy of Francis Bacon, Liverpool: Liverpool University Press.

Fischer, K., 1923, Francis Bacon und seine Schule,Entwicklungsgeschichte der Erfahrungsphilosophie, Heidelberg.

Gaukroger, S., 2001, Francis Bacon and the Transformation of Early-Modern Philosophy, Cambridge: Cambridge University Press.

---, 2006, The Emergence of a Scientific Culture. Science and the Shaping of Modernity 1210-1685, Oxford: Clarendon Press.

Giglioni, G., 2011, Francesco Bacone, Rome.

Henry, J., 2002, Knowledge is Power. Francis Bacon and the Method of Science, Cambridge: Icon Books.

Hesse, M. B., 1964, "Francis Bacon's Philosophy of Science", in A Critical History of Western Philosophy, edited by D. J. O'Connor, New York: Free Press, pp. 141-52.

Hill, C., 1965, Intellectual Origins of the English Revolution, Oxford: Clarendon Press.

Jardine, L., 1974, Francis Bacon. Discovery and the Art of Discourse, Cambridge: Cambridge University Press.

Jardine, L. and A. Stewart, 1999, Hostage to Fortune. The Troubled Life of Francis Bacon 1561-1626, London: Victor Gollancz.

Kargon, R. H., 1966, Atomism in England, Oxford: Oxford University Press.

Klein, J., 1984, Radikales Denken in England: Neuzeit, Frankfurt, Berne and New York.

---, 1987, Francis Bacon oder die Modernisierung Englands, Hildesheim, Zurich and New York.

---, 2003a "Bacon's Quarrel with the Aristotelians", Zeitsprünge, 7: 19-31.

---, 2003b, "Francis Bacon (1561-1626)", in Metzler Philosophen Lexikon, B. Lutz (ed.), Stuttgart.

---, 2003c, "Nachwort", in Francis Bacon, Neu-Atlantis, Stuttgart, 64-9.

---, 2004a, "Francis Bacon's The Advancement of Learning. An Early Modern Programme for the Revision of the Systems of Disciplines", inScholarly Environments. Centres of Learning and Institutional Contexts 1560-1960, edited by Alasdair A. MacDonald and Arend H. Huusen. Leuven, Paris, and Dudley, MA, pp. 65-73.

---, 2004b, "Francis Bacons Essays von 1597: Der politische Subtext", in Against the Grain/Gegenden Strich gelesen. Studies in English and American Literature and Literary Theory. Festschrift für Wolfgang Wicht, Peter Drexler and Rainer Schnoor (eds.), Berlin, pp.201-223.

---, 2008, "Francis Bacon's Scientia Operativa, The Tradition of the Workshops, and the Secrets of Nature", inPhilosophies of Technology. Francis Bacon and His Contemporaries, Claus Zittel, Gisela Engel, Romano Nanni, and Nicole C. Karafyllis (eds.), Leiden and Boston, pp.21-49.

---, 2010, Elisabeth I und ihre Zeit, 2nd ed., Munich.

Krohn, W., 1987, Francis Bacon, Munich.

Lange, F. A., 1898, Geschichte des Materialismus, Bd 1. Leipzig.

Losee, J., 1972, A Historical Introduction to the Philosophy of Science, Oxford: Oxford University Press.

Malherbe, M., 1996, "Bacon's Method of Science", in Peltonen (ed.) 1996, pp. 75-98.

Martin, J., 1992, Francis Bacon, the State, and the Reform of Natural Philosophy, Cambridge: Cambridge University Press.

Mathews, N., 1996, Francis Bacon. The History of a Character Assassination, New Haven and London: Yale University Press.

Matthews, S., 2008, Theology and Science in the Thought of Francis Bacon, Aldershot: Ashgate.

Mittelstrass, J., 1960, Neuzeit und Aufklärung. Studien zur Entstehung der neuzeitlichen Wissenschaft und Philosophie, Berlin and New York.

Peltonen, M. (ed.), 1996, The Cambridge Companion to Bacon, Cambridge: Cambridge University Press.

Peltonen, M., 2007, "Bacon; Francis, Viscount St Alban (1561-1626)", Oxford Dictionary of National Biography, Oxford: Oxford University Press, 2004.

Pérez-Ramos, A., 1988, Francis Bacon's Idea of Science and the Maker's Knowledge Tradition, Oxford: Clarendon Press.

Price, B. (ed.), 2002, Francis Bacon's New Atlantis. New Interdisciplinary Essays, Manchester and New York: Manchester University Press.

Quinton, A., 1980, Francis Bacon, Oxford, Toronto, and Melbourne: Hill and Wang.

Rees, G., 1975a,b, "Francis Bacon's Semi-Paracelsian Cosmology", Ambix, XXII: 82-101; 165-73.

---, 1977, "Matter Theory: A Unifying factor in Bacon's Natural Philosophy?", Ambix, XXIV: 110-25.

---, 1980, "Atomism and 'Subtlety' in Francis Bacon's Philosophy", Annals of Science, XXXVII: 549-71.

---, 1985, "Quantitative Reasoning in Francis Bacon's Natural Philosophy", Nouvelle de la republique des lettres: 27-48.

---, 1986, "Mathematics in Francis Bacon's Natural Philosophy", Revue internationale de philosophie, 159(4): 399-426.

---, 1996, "Bacon's Speculative Philosophy", in Peltonen (ed.) 1996, pp.121-45.

---, 2000, "Francis Bacon (1561-1626)", in W. Applebaum (ed.), Encyclopedia of the Scientific Revolution From Copernicus to Newton, New York and London, pp. 65- 69.

---, 2004, "On Francis Bacon's Originality", ISIH: Intellectual News, 14: 69-73.

Rees, G. and C. Upton, 1984, Francis Bacon's Natural Philosophy: A New Source. A transcription of manuscript Hardwick 72A with Translation and Commentary (The British Society for the History of Science Monographs, 5), Chalfont St Giles.

Rossi, P., 1968, Francis Bacon: From Magic to Science, translated by S. Rabinovitch, London: University of Chicago Press.

Schäfer, L., 1993, Das Bacon-Programm. Von der Erkenntnis, Nutzung und Schonung der Natur, Frankfurt am Main.

Schmidt-Biggemann, W., 1983, Topica Universalis. Eine Modellgeschichte humanistischer und barocker Wissenschaft, Hamburg.

Sessions, W. A. (ed.), 1990, Francis Bacon's Legacy of Texts, New York: AMS Press.

---, 1996, Francis Bacon Revisited, New York and London: Twayne Publishers.

Urbach, P., 1987, Francis Bacon's Philosophy of Science: An Account and a Reappraisal, La Salle, IL: Open Court.

Vickers, B., 1968a, Francis Bacon and Renaissance Prose, Cambridge: Cambridge University Press.

--- (ed.), 1968b, Essential Articles for the Study of Francis Bacon, Hamden, Conn.: Archon Books.

---, 1978, Francis Bacon, Harlow: Longman Group.

Webster, C., 1975, The Great Instauration. Science, Medicine, and Reform 1626-1660, London: Duckworth.

Zaller, R., 1971, The Parliament of 1621: A Study in Constitutional Conflict, Berkeley CA: University of California Press.

Zagorin, P., 1999, Francis Bacon, Princeton: Princeton University Press.

Ayer, A. J., 1973, The Central Questions of Philosophy, London: Weidenfeld and Nicolson.

Blumenberg, H., 1981, Die Lesbarkeit der Welt, Frankfurt am Main.

Carnap, R. and W. Stegmüller, 1959, Induktive Logik und Wahrscheinlichkeit, Vienna.

Cohen, I. B., 1985, Revolution in Science, Cambridge, MA: Belknap Press.

Cohen, J. L., 1970, The Implications of Induction, London: Methuen.

Curd, M. and J. A. Cover (eds.), 1998, Philosophy of Science. The Central Issues, London and New York: W.W. Norton.

Dijksterhuis, E. J., 1956, Die Mechanisierung des Weltbildes, Berlin etc.

Duhem, P., 1904-5, The Aims and Structure of Physical Theory, English translation by Philip P. Wiener, New York, 1954.

---, 1998, Ziel und Struktur der physikalischen Theorien, übersetzt von Friedrich Adler, mit einem Vorwort von Ernst Mach, herausgegeben mit einer Einleitung von Lothar Schäfer, Hamburg.

Foucault, M., 1966 [1970], The Order of Things: The Archaeology of the Human Sciences, London: Tavistock; English translation 1970.

Gillies, D., 1998, "The Duhem Thesis and the Quine Thesis", in Curd and Cover 1998, pp. 302-319.

Godfrey-Smith, P., 2003, Theory and Reality. An Introduction to the Philosophy of Science, Chicago/London: University of Chicago Press.

Grant, E., 1994, Planets, Stars, & Orbs. The Medieval Cosmos 1200-1687, Cambridge: Cambridge University Press.

Haack, S., 1993, Evidence and Inquiry. Towards Reconstruction in Epistemology, Oxford, UK: Blackwell.

Hacking, I. (ed.), 1981, Scientific Revolutions, Oxford: Oxford Univerity Press.

Hempel, C. G., 1966, Philosophy of Natural Science, Englewood Cliffs: Prentice-Hall.

Huggett, N., 2010, Everywhere and Everywhen. Adventures in Physics and Philosophy, Oxford: Oxford University Press.

Hylton, P., 2010, "Willard Van Orman Quine", in: Stanford Encyclopedia of Philosophy (Fall 2010 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/fall2010/entries/quine/>.

Kocher, P. H., 1953, Science and Religion in Elizabethan England, San Marino, CA: Huntington Library.

Kuhn, Th. S., 1962, The Structure of Scientific Revolutions, Chicago: University of Chicago Press.

Lakatos, I., 1970, "Falsificationism and the Methodology of Scientific Research Programmes", in Criticism and the Growth of Knowledge, edited by I. Lakatos and A. Musgrave. Cambridge: Cambridge University Press, pp. 91-196.

---, 1981, "History of Science and Its Rational reconstructions", in Hacking (ed.) 1981, pp. 107-27.

Lambert, K. and G. C. Brittan, 1979 [1987], An Introduction to the Philosophy of Science, Atascadero, CA: Ridgeview. Third edition 1987.

Müller-Jahncke, W. D., 1985, Astrologisch-Magische Theorie in der Heilkunde der Frühen Neuzeit, Stuttgart.

O'Hear, A., 1995, "Conventionalism", in Oxford Companion to Philosophy, T. Honderich (ed.), Oxford: Oxford University Press, p. 165.

Poincaré, H., 1905 [reprint 1952], Science and Hypothesis, translated by W. J. Greenstreet, New York: Dover Publications.

Popper, K. R., 1969, Logik der Forschung, Tübingen, 3rd edition.

Quine, W. V. Q., 1951, "Two Dogmas of Empiricism", The Philosophical Review 60: 20-43. Reprinted in Quine, 1963,From a Logical Point of View, New York: Harper Torchbook, pp. 20-46.

Rae, A. I. M., 1986 [2000], Quantum physics: Illusion or Reality? Cambridge: Cambridge University Press. Fourth Canto edition, 2000.

Russell, B., 1948, Human Knowledge. Its Scope and its Limits, London: Allen & Unwin.

Schäfer, L., 1998, "Duhems Bedeutung für die Entwicklung der Wissenschaftstheorie", in: Duhem (1998), pp. X-XXXIII.

Shell, H. R., 2004, "Casting Life, Recasting Experience: Bernard Palissy's Occupation between Maker and Nature", Configurations, 12(1): 1-40.

Stegmüller, W., 1973, Probleme und Resultate der Wissenschaftstheorie und Analytischen Philosophie, Band II: Theorie und Erfahrung. Zweiter Halbband. Theorienstruktur und Theoriendynamik, Berlin, Heidelberg, New York.

Swinburne, R. (ed.), 1974, The Justification of Induction, Oxford: Oxford University Press.

Von Weizsäcker, C. F. and J. Juilfs, 1958, Physik der Gegenwart, Göttingen.

Wright, G. H. von, 1951, A Treatise of Induction and Probability, London: Routledge and K. Pau.

Zinner, E., 1988, Entstehung und Ausbreitung der copernicanischen Lehre, Munich.

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Francis Bacon was born January, 22, 1561, the second child of Sir Nicholas Bacon (Lord Keeper of the Seal) and his second wife Lady Anne Cooke Bacon, daughter of Sir Anthony Cooke, tutor to Edward VI and one of the leading humanists of the age.

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And now a page from our "Sunday Morning" Almanac: May 24, 1686, 329 years ago today ... a day for temperate celebration.

For that was the birthday of Daniel Gabriel Fahrenheit, the European physicist who used purified mercury to create the first modern thermometer.

Fahrenheit also invented his namesake temperature scale, where water freezes at 32 degrees, and boils at 212.

For centuries, Fahrenheit's mercury thermometer was the standard in countless fields, including medicine.

A somewhat overheated British industrial film from 1953 followed the thermometer-making process step-by-step:

"The tubing must be perfectly straight, so she's gauging it for possible twists, but few of these thermometer strips fail to measure up to the highest degree of accuracy! ... A high standard of manufacture, great care taken to pack them up, and the result is, we hope, to save many of us from 'packing up.'"

Today, modern digital thermometers have largely replaced mercury devices in doctors' offices and hospitals.

And in most of the world outside the United States, Fahrenheit's temperature scale has largely been replaced by Centigrade, where water freezes at zero degrees, and boils at 100.

Still, there remains good reason to salute Daniel Fahrenheit's contributions:

How hot is hot?
How cold is cold?
A vexing problem in days of old.
Back then it was almost cause for derision,
To claim to take temperatures with precision.
The first to do it,
And do it right,
Was Daniel Gabriel Fahrenheit.

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And now a page from our "Sunday Morning" Almanac: May 24, 1686, 329 years ago today ... a day for temperate celebration. For that was the birthday of Daniel Gabriel Fahrenheit, the European physicist who used purified mercury to create the first modern thermometer.

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Gabriel Fahrenheit was a Dutch Physicist. He is most known for creating the temperature unit that we use in the US. Fahrenheit

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Tycho Brahe was a  Danish astronomer born on December 14 1546 and died October 24 1601. His work was developing astronomical instruments and meusuring and fixing the positions of the stars which paved the way for the future. He was also known for his accurate and comprehensive astronomical observations.

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Lived 1608 - 1647.
The 1600s were marked by ferocious conflicts between old superstitions and new sciences. A small number of people began using observations and experiments to reveal how Nature worked and in doing so changed the way we understand our world.

Evangelista Torricelli was one of these people. He invented the mercury barometer and deduced from experiments that his device revealed the height of our planet's atmosphere. In 1644, he concluded that we live at the bottom of a sea of air.

Torricelli's hectic few years of scientific activity began when Galileo was an old man and ended when Isaac Newton was a young boy.

Torricelli was the first person to explain correctly why the wind blows, and he discovered an extraordinary and controversial geometrical figure, Gabriel's horn, which has a finite volume but infinite surface area.

Beginnings

Evangelista Torricelli was born on October 15, 1608 in the great Italian city of Rome.

His mother was Giacoma Ruberti (born Torricelli). His father was Gaspare Ruberti, a weaver. Evangelista was the eldest of their three sons; he took his mother's surname - it was not exceptionally rare in Rome for children to do this. Two of the family's three sons took their mother's surname, while one took the surname Ruberti.

Sometimes biographers incorrectly state that Evangelista was born in the small northern Italian city of Faenza. This is actually where he was educated and where his mother was born - he regarded Faenza as his spiritual birthplace.

Education

Evangelista's parents grasped that their son was unusually intelligent, but they were too poor to pay for school.

Enter Evangelista's uncle, Gian Francesco Torricelli, priest of the Abbey of Saint Ippolito in Faenza, Evangelista mother's birthplace. Gian Francesco was a graduate of the famous University of Padua and was ideally placed to help with Evangelista's education.

Evangelista moved north to live with his Gian Francesco, who began his education by teaching him the basics.

In 1619, age 11, Evangelista began attending Faenza's Jesuit school. In 1623, he began studying mathematics.

Gian Francesco soon learned from Evangelista's teachers that his nephew was an extraordinarily talented mathematician. Gian Francesco got in touch with a friend, Professor Benedetto Castelli of Sapienza College in Rome - both men were in the same Catholic Camaldolese order.

Mathematics and Physical Sciences

In 1626, age 18, Evangelista Torricelli moved to Rome to be taught mathematics and physical sciences by Professor Castelli. This was a fantastic break for the young Torricelli: Castelli had been taught these subjects by Galileo.

Torricelli could not afford fees, so he worked as Castelli's secretary for six years, until 1632. Near the end of this period, he took over Castelli's lecturing duties whenever Castelli was sick or traveling.

Galileo: First Contact

At the beginning of 1632, Galileo Galilei changed the course of scientific and religious history by publishing Dialogue Concerning the Two Chief World Systems. Within a year, this book and everything else he had ever written were suppressed by the Catholic Church.

Galileo was declared "vehemently suspect of heresy." The trigger for the Church's outrage was that part of Galileo's book discussed the Copernican view that the solar system is centered on the sun rather than the earth, a view Galileo said he agreed with.

Soon after the book was published and before it was banned, Torricelli, age 23, read it hungrily, working through all its implications for himself. He soon found himself in a position to write to the great man. In his professor's absence, Torricelli replied to a letter Galileo had sent to Professor Castelli.

In the letter, Torricelli explains that Professor Castelli is absent and so he, as Castelli's secretary, must reply. He introduces himself and tells Galileo that he has read his new book "with delight." Torricelli's letter is a gift for future biographers, because so little of his early life is recorded. Torricelli informs Galileo (and us) that he has studied the works of the great Ancient Greek mathematicians, such as Archimedes', and has studied the works of Ptolemy, Tycho Brahe, and Kepler. He says that he agrees with the Copernican view of the solar system.

This was the only time Torricelli ever openly supported the Copernican view. Soon enough, to do so would risk death.

Torricelli's Lifetime in Context

Evangelista Torricelli's Contributions to Science

The Barometer and Earth's Sea of Air

Torricelli is best known for his invention and, even more importantly, his explanation of the mercury barometer. He did this in in 1643.

Torricelli's device measures atmospheric pressure, which is related to the weight of the miles of air in the atmosphere pressing down on us.

Torricelli's Barometer

Looking at the results of his experiment, Torricelli rather brilliantly concluded that the barometer acts as a balance. On one side of the balance is the downward push of a column of mercury about 76 cm high. On the other is the downward push of Earth's atmosphere.

Torricelli was right. In modern terms we can measure at sea level that the average weight of Earth's atmosphere is 1.03 kg on every square centimeter of surface (14.7 lb on every square inch.)

Torricelli's explanation contradicted Galileo's theory that the mercury column was held in the tube by the suction power of the vacuum above it. Galileo had also been contradicted by Giovanni Baliani of Genoa in 1630, who advanced similar ideas to Torricelli, albeit less developed, about the effects of air pressure. Whether Torricelli had heard of Baliani's ideas is unknown.

In a series of experiments Torricelli and his friend Vincenzo Viviani proved that the vacuum at the top of the tube was not the cause of the mercury column's height.

"We live immersed at the bottom of a sea of air, which by experiment undoubtedly has weight, and so much weight that the densest air in the neighborhood of the surface of the earth weighs about one four-hundredth part of the weight of water... On the surface of the liquid which is in the bowl there rests the weight of a height of fifty miles of air."

Air Exerts a
Surprisingly Powerful Pressure

Otto von Guericke, who lived in the same era as Torricelli, demonstrated just how forceful air pressure can be when he performed a famous experiment. He placed two metal hemispheres together and created a vacuum between them with a pump. Two teams each containing eight horses could not overcome the pressure from our planet's atmosphere holding the hemispheres together.

Air Pressure Extremes

Atmospheric pressure changes as weather systems come and go, which means the height of the mercury column in barometers changes with it.

The world record high pressure (at sea level) is 813 mm of mercury, recorded in Russia in 2001.

In the center of tornados, very low pressures exist. The world record low pressure (at sea level) outside a tornado is 652 mm of mercury, recorded in the Pacific Ocean during a hurricane in 1979.

Since the height of a barometer's mercury column is a measure of the weight of the air above us, it's not surprising that if you climb a mountain the mercury column's height will fall. At the summit of Mount Everest, at a height of 8,848 m, you would expect a barometer's mercury column to be just 250 mm high.

Air pressure is used in weather forecasting. Rising pressure tends to mean the weather will be fair. Falling pressure is more likely to point to wetter conditions.

Why does the Wind Blow?

In Torricelli's day people believed that the wind was caused by vapors released by the damp earth.

Torricelli gave the correct explanation as part of a series of lectures. These were published in 1823, long after his death, as Lezioni accademiche di Evangelista Torricelli.

Torricelli observed prevailing wind directions for some time in the city of Florence and gathered reports from around Europe.

Moreover, he took into account his observation that when the doors of large buildings are opened on hot days, cold air rushes outward through the doorway.

He said that winds are caused by what today we call convection currents, whose circulation he described. Put simply, he said that hot air is less dense than cold air, so hot air rises from the earth's surface - he said it could rise to heights of three or four miles - and is replaced by cooler air. The result is that air moves from regions where its density is high to regions where it is low and this moving air is the wind.

Archimedes and Torricelli's Principle

Torricelli made a number of startling discoveries in mathematics and mechanics, publishing many in his Opera geometrica (Geometry Work).

As a mathematician, his greatest influence was Archimedes, whose work by then was almost two millennia old. Torricelli believed Archimedes had worked " ad occultandum artis arcanum" - in other words using some hidden or secret art. Torricelli was right - Archimedes' work The Method, in which he revealed his remarkable techniques, was only rediscovered in 1906 in the renowned Archimedes Palimpsest.

The concept of center of gravity was discovered by Archimedes. Torricelli, following in his footsteps, discovered a new principle, Torricelli's principle, which says:

A system of bodies in equilibrium can only move spontaneously on the earth's surface if its center of gravity descends.

How Fast Should Water Flow Through an Opening?

Torricelli observed water flowing through openings in water tanks and figured out that the water should move through the opening with the same velocity as if it had fallen under gravity from the height of the water above the opening.

This allowed him to prove in Opera geometrica that the rate a liquid flows through an opening is proportional to the square root of the depth of the liquid. This proportionality is called Torricelli's law.

As a result of his law, Torricelli has a good claim to be recognized as the founder of modern fluid dynamics.

An Infinity Paradox

Gabriel's horn (or Torricelli's trumpet) starts wide and diminishes forever without reaching an end. Torricelli revealed this object to the world in 1644, provoking awe, bewilderment, jeers and acrimony.

The horn has finite volume, infinite length and infinite surface area.

In the 1600s, mathematicians were distinctly uncomfortable with infinity - Torricelli described his discovery as a paradox.

Some philosophers refused to believe Gabriel's horn could exist at all. Thomas Hobbes, of the empiricist school, believed knowledge can only come from experience. Since we cannot experience infinity, Hobbes argued we cannot make any trustworthy statement about it in general or accept Torricelli's discovery in particular. Attempting to defeat mathematics with mockery, Hobbes said of Gabriel's Horn:

"For to understand this for sense, it is not required that a man should be a geometrician or a logician, but that he should be mad."

Modern mathematicians see infinity as an everyday aspect of their work.

Gabriel's horn is made by taking the function y = ¹⁄ x and rotating it around the x-axis for x=1 to ∞.

Parabolas and Projectiles

The study of parabolas began with the Ancient Greeks. In renaissance Italy, parabolas once again fascinated mathematicians. Galileo, building on the work of Niccolo Tartaglia, showed that projectiles, such as cannon balls, follow a parabola-shaped path.

Torricelli made a number of advances in the study of parabolas and projectiles. He recorded these in De motu gravium, published as part of Opera geometrica. The gunnery tables he produced were not improved upon until the 1700s.

Below you can see his 'safety parabola' in blue. Torricelli imagined a cannon ball shot many times, always emerging from the cannon at the same speed, but at different angles to the ground. He deduced that you can draw a 'safety parabola' which will form an envelope around all the possible parabolic trajectories. Anyone outside the envelope is safe from the cannonball, whatever angle the cannon is fired at. The safety parabola is of mathematical interest because it was the first envelope discovered. Torricelli also showed that all possible parabolic trajectories of the cannonball are tangent to the safety parabola.

Honors

The torr unit of pressure is named after Torricelli.

Originally it was defined as the pressure equal to one millimeter of mercury at 0 °C. It is now defined as ¹⁄ ₇₆₀ of a standard atmosphere (101325 Pa).

In 1958, Italy issued a new stamp, shown here, to commemorate the 350th anniversary of Torricelli's birth.

Some Personal Details and the End

Torricelli never married and had no children.

He loved old literature - many of the books he owned were Latin and Ancient Greek classics. His book collection also revealed his enthusiasm for architecture and military technology.

In 1641, three months before Galileo's death, Torricelli traveled to live at his home in the city of Florence to act as his eyes and writer in his final days - Galileo had been completely blind for three years and under house arrest for eight years.

Despite his house arrest, Galileo was the mathematician and philosopher to the Grand Duke Ferdinando II of Tuscany. After Galileo's death, Torricelli was appointed to the post, with an ample salary and an apartment in the Medici Palace in Florence. He was also appointed Chair of Mathematics at the University of Pisa. He remained in these posts until his untimely death.

Torricelli was acclaimed among his friends as a scintillating conversationalist. Before his death, he was working on comedies for performance. Sadly, they no longer exist.

Evangelista Torricelli died in Florence 10 days after his 39th birthday on October 25, 1647. He was feverish for about 20 days before his death, probably resulting from typhoid or pneumonia. During the fever he was sometimes rational, sometimes delirious.

Fearing he would not recover, he wrote his will 11 days before the end came. He left almost all he had to his two brothers, Carlo and Francesco, a sum to his great friend Doctor Buonaiuti, who had treated him during his illness, a sum to his servant Dianora, and his old shoes, socks and similar items to Ceccotto the sweeper.

To his friend Lodovico Serenai, who was responsible for executing his will, he left a ring and his books. He told Serenai to erase any and all the notes he had made in book margins criticizing the Jesuit scholars Niccolò Cabeo and Athanasius Kircher - Torricelli did not want future generations to learn of his profound contempt for them.

Evangelista Torricelli was buried in the Basilica of San Lorenzo in Florence. He died at the peak of his intellectual powers.

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Further Reading
Charles Coulston Gillispie, Editor in Chief
Dictionary of Scientific Biography, Vol. 13
Scribner, 1981

Franco Gabici, Fabio Toscano
Scienziati di Romagna
Alpha Test, 2006

Fabio Toscano
L'erede di Galileo: vita breve e mirabile di Evangelista Torricelli
Sironi Editore, 2008

Raffaele Pisano, Paolo Bussotti
Notes on Mechanics and Mathematics in Torricelli as Physics Mathematics Relationships in the History of Science
Problems of education in the 21st Century, Vol. 61, pp 88-97, 2014

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Lived 1608 - 1647. The 1600s were marked by ferocious conflicts between old superstitions and new sciences. A small number of people began using observations and experiments to reveal how Nature worked and in doing so changed the way we understand our world. Evangelista Torricelli was one of these people.

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Vesalius was a Flemish physician, anatomist, and author of one of the most famous and influential book on anatomy.

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Anton Van Leeuwenhoek was the dutch scientist who discovered bacteria, blood cells, microscopic nematodes, rotifers, and much more. His research opened up an entire world of microscopic life to the awareness of scientists. Van Leeuwenhoek, in his time,  built microscopes that magnified over 200 times with clearer and brighter images than any of his colleagues could achieve. What further distinguished him was his curiosity to observe nearly anything that could be placed under a lense, and the care he invested in describing what he saw.

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Nicolaus Copernicus was born in Thorn, Poland on February 19, 1473. He was the son of a wealthy merchant. After his father's death, he was raised by his mother's brother, a bishop in the Catholic Church. Copernicus studied mathematics and astronomy at the University of Krakow.

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Johannes Kepler: His Life, His Laws and Times

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NASA.gov brings you the latest images, videos and news from America's space agency. Get the latest updates on NASA missions, watch NASA TV live, and learn about our quest to reveal the unknown and benefit all humankind.

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Copernicus - Astronomer | Mini Bio | BIO

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R obert H ooke (1635-1703)

No portrait survives of Robert Hooke. His name is somewhat obscure today, due in part to the enmity of his famous, influential, and extremely vindictive colleague, Sir Isaac Newton. Yet Hooke was perhaps the single greatest experimental scientist of the seventeenth century. His interests knew no bounds, ranging from physics and astronomy, to chemistry, biology, and geology, to architecture and naval technology; he collaborated or corresponded with scientists as diverse as Christian Huygens, Antony van Leeuwenhoek, Christopher Wren, Robert Boyle, and Isaac Newton. Among other accomplishments, he invented the universal joint, the iris diaphragm, and an early prototype of the respirator; invented the anchor escapement and the balance spring, which made more accurate clocks possible; served as Chief Surveyor and helped rebuild London after the Great Fire of 1666; worked out the correct theory of combustion; devised an equation describing elasticity that is still used today ("Hooke's Law"); assisted Robert Boyle in studying the physics of gases; invented or improved meteorological instruments such as the barometer, anemometer, and hygrometer; and so on. He was the type of scientist that was then called a virtuoso -- able to contribute findings of major importance in any field of science. It is not surprising that he made important contributions to biology and to paleontology.

Relatively little is known about Robert Hooke's life. He was born on July 18, 1635, at Freshwater, on the Isle of Wight, the son of a churchman. He was apparently largely educated at home by his father, although he also served an apprenticeship to an artist. He was able to enter Westminster School at the age of thirteen, and from there went to Oxford, where some of the best scientists in England were working at the time. Hooke impressed them with his skills at designing experiments and building equipment, and soon became an assistant to the chemist Robert Boyle. In 1662 Hooke was named Curator of Experiments of the newly formed Royal Society of London -- meaning that he was responsible for demonstrating new experiments at the Society's weekly meetings. He later became Gresham Professor of Geometry at Gresham College, London, where he had a set of rooms and where he lived for the rest of his life. His health deteriorated over the last decade of his life, although one of his biographers wrote that "He was of an active, restless, indefatigable Genius even almost to the last." He died in London on March 3, 1703.

Hooke's reputation in the history of biology largely rests on his book Micrographia, published in 1665. Hooke devised the compound microscope and illumination system shown above, one of the best such microscopes of his time, and used it in his demonstrations at the Royal Society's meetings. With it he observed organisms as diverse as insects, sponges, bryozoans, foraminifera, and bird feathers. Micrographia was an accurate and detailed record of his observations, illustrated with magnificent drawings, such as the flea shown below, which Hooke described as "adorn'd with a curiously polish'd suite of sable Armour, neatly jointed. . ." It was a best-seller of its day. Some readers ridiculed Hooke for paying attention to such trifling pursuits: a satirist of the time poked fun at him as "a Sot, that has spent 2000 £ in Microscopes, to find out the nature of Eels in Vinegar, Mites in Cheese, and the Blue of Plums which he has subtly found out to be living creatures." More complimentary was the reaction of the diarist and government official Samuel Pepys, who stayed up till 2:00 AM one night reading Micrographia, which he called "the most ingenious book that I ever read in my life."

Perhaps his most famous microscopical observation was his study of thin slices of cork, depicted above right. In "Observation XVIII" of the Micrographia, he wrote:

. . . I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular. . . . these pores, or cells, . . . were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this. . .

Hooke had discovered plant cells -- more precisely, what Hooke saw were the cell walls in cork tissue. In fact, it was Hooke who coined the term "cells": the boxlike cells of cork reminded him of the cells of a monastery. Hooke also reported seeing similar structures in wood and in other plants. In 1678, after Leeuwenhoek had written to the Royal Society with a report of discovering "little animals" -- bacteria and protozoa -- Hooke was asked by the Society to confirm Leeuwenhoek's findings. He successfully did so, thus paving the way for the wide acceptance of Leeuwenhoek's discoveries. Hooke noted that Leeuwenhoek's simple microscopes gave clearer images than his compound microscope, but found simple microscopes difficult to use: he called them "offensive to my eye" and complained that they "much strained and weakened the sight."

Hooke was also a keen observer of fossils and geology. While some fossils closely resemble living animals or plants, others do not -- because of their mode of preservation, because they are extinct, or because they represent living taxa which are undiscovered or poorly known. In the seventeenth century, a number of hypotheses had been proposed for the origin of fossils. One widely accepted theory, going back to Aristotle, stated that fossils were formed and grew within the Earth. A shaping force, or "extraordinary Plastick virtue," could thus create to stones that looked like living beings but were not. Hooke's contemporary, the naturalist and shell collector Martin Lister wrote in 1678 that "our English Quarry-shells were not cast in any Animal mold, whose species or race is yet to be found in being at this day." We would now interpret these fossils as belonging to extinct taxa, but extinction was not widely accepted at the time, and Lister concluded: "I am apt to think, there is no such matter, as Petrifying of Shells in the business. . . but that these Cockle-like shells ever were, as they are at present, lapides sui generis [stones of their own kind], and never any part of an Animal."

Hooke examined fossils with a microscope -- the first person to do so -- and noted close similarities between the structures of petrified wood and fossil shells on the one hand, and living wood and living mollusc shells on the other. In Micrographia he compared a piece of petrified wood with a piece of rotten oak wood, and concluded that

this petrify'd Wood having lain in some place where it was well soak'd with petrifying water (that is, such water as is well impregnated with stony and earthy particles) did by degrees separate abundance of stony particles from the permeating water, which stony particles, being by means of the fluid vehicle convey'd, not onely into the Microscopical pores. . . but also into the pores or Interstitia. . . of that part of the Wood, which through the Microscope, appears most solid. . .
Hooke's language may be archaic, but his meaning is quite modern: Dead wood could be turned to stone by the action of water rich in dissolved minerals, which would deposit minerals throughout the wood. Hooke also concluded in Micrographiathat the shell-like fossils that he examined really were "the Shells of certain Shel-fishes, which, either by some Deluge, Inundation, earthquake, or some such other means, came to be thrown to that place, and there to be fill'd with some kind of Mud or Clay, or petrifying Water, or some other substance. . . "

Hooke's Discourse of Earthquakes, published two years after his death, shows that his geological reasoning had gone even further. Following in the footsteps of Leonardo da Vinci, Hooke explained the presence of fossil shells on mountains and in inland regions: "Most of those Inland Places. . . are, or have been heretofore under the Water. . . the Waters have been forc'd away from the Parts formerly cover'd, and many of those surfaces are now raised above the level of the Water's Surface many scores of Fathoms. It seems not improbable, that the tops of the highest and most considerable Mountains in the World have been under Water, and that they themselves most probably seem to have been the Effects of some very great Earthquake." Hooke continued to study fossils and compare them with living organisms -- the illustration above shows the coiled shells of three living cephalopods, Nautilus, Argonauta, and Spirula, compared with a fossil ammonite (upper right). He concluded that many fossils represented organisms that no longer existed on Earth: "There have been many other Species of Creatures in former Ages, of which we can find none at present; and that 'tis not unlikely also but that there may be divers new kinds now, which have not been from the beginning."

Hooke had grasped the cardinal principle of paleontology -- that fossils are not "sports of Nature," but remains of once-living organisms that can be used to help us understand the history of life. Hooke realized, two and a half centuries before Darwin, that the fossil record documents changes among the organisms on the planet, and that species have both appeared and gone extinct throughout the history of life on Earth. These questions of the nature of fossils and the possibility of extinction would continue to challenge natural scientists, from Edward Lhwyd and John Ray down to Jean-Baptiste Lamarck and Georges Cuvier.
roberthooke.org.uk is an excellent, well-illustrated site on Hooke's life and work, including a number of images from Micrographia.
A brief biography of Hooke, with a listing of his contributions to mathematics, is part of the resources in the history of mathematics maintained at the School of Mathematics of Trinity College, Dublin. A listing of Hooke's biographical data is available from the Galileo Project website. Somewhat more extensive information on Hooke's life and accomplishments is available in this biography, part of the History of Mathematics archive; and in the online essay "Seeing Further: The Legacy of Robert Hooke". There is also information about Hooke's contributions to microscopy in the thorough History of the Light Microscope pages.

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R obert H ooke (1635-1703) No portrait survives of Robert Hooke. His name is somewhat obscure today, due in part to the enmity of his famous, influential, and extremely vindictive colleague, Sir Isaac Newton. Yet Hooke was perhaps the single greatest experimental scientist of the seventeenth century.

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Youth and education

Tycho's father was a privy councillor and later governor of the castle of Helsingborg, which controls the main waterway to the Baltic Sea. His wealthy and childless uncle abducted Tycho at a very early age and, after the initial parental shock was overcome, raised him at his castle in Tostrup, Scania, also financing the youth's education, which began with the study of law at the University of Copenhagen in 1559-62.

Several important natural events turned Tycho from law to astronomy. The first was the total eclipse of the Sun predicted for August 21, 1560. Such a prediction seemed audacious and marvelous to a 14-year-old student, but when Tycho witnessed its realization he saw and believed-the spark was lit-and, as his many later references testify, he never forgot the event. His subsequent student life was divided between his daytime lectures on jurisprudence, in response to the wishes of his uncle, and his nighttime vigil of the stars. The professor of mathematics helped him with the only printed astronomical book available, the Almagest of Ptolemy, the astronomer of antiquity who described the geocentric conception of the cosmos. Other teachers helped him to construct small globes, on which star positions could be plotted, and compasses and cross-staffs, with which he could estimate the angular separation of stars.

In 1562 Tycho's uncle sent him to the University of Leipzig, where he studied until 1565. Another significant event in Tycho's life occurred in August 1563, when he made his first recorded observation, a conjunction, or overlapping, of Jupiter and Saturn. Almost immediately he found that the existing almanacs and ephemerides, which record stellar and planetary positions, were grossly inaccurate. The Copernican tables were several days off in predicting this event. In his youthful enthusiasm Tycho decided to devote his life to the accumulation of accurate observations of the heavens, in order to correct the existing tables.

Between 1565 and 1570 (or 1572?) he traveled widely throughout Europe, studying at Wittenberg, Rostock, Basel, and Augsburg and acquiring mathematical and astronomical instruments, including a huge quadrant. In 1566 he lost his nose in a duel with Manderup Parsberg, his third cousin who was also a fellow student at Rostock. He and Parsberg became good friends afterward, but Tycho wore a prosthetic nose for the rest of his life. (His nose was long believed to be silver, but an exhumation of Tycho's corpse in 2010 revealed that it was brass.)

Inheriting the estates of his father and of his uncle Jørgen, Tycho then settled in Scania in 1571(?) and constructed a small observatory on property owned by a relative. Here occurred the third and most important astronomical event in Tycho's life. On November 11, 1572, he suddenly saw a " new star," brighter than Venus and where no star was supposed to be, in the constellation Cassiopeia. He carefully observed the new star, and showed that it lay beyond the Moon and therefore was in the realm of the fixed stars. To the world at the time, this phenomenon-a supernova (which could be seen by the unaided eye until March 1574)-was a disquieting discovery because the intellectual community protected itself against the uncertainties of the future by confidence in the Aristotelian doctrine of inner and continuous harmony of the whole world. This harmony was ruled by the stars, which were regarded as perfect and unchanging. The news that a star could change as dramatically as that described by Tycho, together with the reports of the Copernican theory that the Sun, not Earth, was the centre of the universe, shook confidence in the immutable laws of antiquity and suggested that the chaos and imperfections of Earth were reflected in the heavens. Tycho's discovery of the new star in Cassiopeia in 1572 and his publication of his observations of it in De nova stella in 1573 marked his transformation from a Danish dilettante to an astronomer with a European reputation.

By marrying a peasant's daughter, named Kirstine, in 1573, Tycho-as a nobleman's son-scandalized most of his contemporaries. He seldom mentioned her in his extensive correspondence (which still exists), and it is probable that he was interested mainly in a companion who would superintend his household without being involved in court functions and intrigues. Tycho and Kirstine had eight children, six of whom survived him.

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Tycho Brahe | Accomplishments, Biography, & Facts

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Tycho Brahe, (born December 14, 1546, Knudstrup, Scania, Denmark-died October 24, 1601, Prague), Danish astronomer whose work in developing astronomical instruments and in measuring and fixing the positions of stars paved the way for future discoveries. His observations-the most accurate possible before the invention of the telescope-included a comprehensive study of the solar system and accurate positions of more than 777 fixed stars.

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And now a page from our "Sunday Morning" Almanac: November 27th, 1701, 315 years ago today ... the birthday of the Swedish scientist Anders Celsius.

Celsius is best-known for the temperature scale that bears his name.

Unlike his predecessor, Daniel Gabriel Fahrenheit -- whose scale had water freezing at 32 degrees and boiling at 212 -- Anders Celsius separated boiling and freezing by exactly 100 degrees.

However, for some reason, he marked the degrees on his original thermometer upside down -- with ZERO as the boiling point, and ONE HUNDRED as the freezing point! Go figure.

The Celsius scale was soon flipped right-side up, with zero for freezing and 100 for boiling.

And generations of American schoolkids have been figuring out how to convert Fahrenheit to Celsius and vice versa ever since.

Today the United States stands alone among the major industrial nations in still using Fahrenheit.

And based on the apparent degree of resistance across the land to a switch to Celsius, it seems unlikely we'll be warming to the idea any time soon.

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And now a page from our "Sunday Morning" Almanac: November 27th, 1701, 315 years ago today ... the birthday of the Swedish scientist Anders Celsius. Celsius is best-known for the temperature scale that bears his name.

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Marie Lavoisier is a French scientific collaborator. She is married to Antoine. Also, she was the founder of modern chemistry. She would often work alongside Antoine in whatever he was doing. Antoine Lavoisier revolutionized chemistry. He named oxygen, hydrogen, and carbon, discovered the role oxygen plays in respiration and combustion, discovered sulfur, and he also helped move science from a qualitative to a quantitative science.

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Anders Celsius was a Swedish astronomer and mathematician who worked in theometry. Celsius disagreed with Newton's temperature scale, and decided to make his own. In this he changed the scale, making it 100 degrees between the freezing point and boiling point of water. He published his ideas in a paper called "Observations on two persistent degrees on a thermometer". This scale was called the Celsius scale, named after him.

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Tycho Brahe, the scandalous astronomer - Dan Wenkel

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When Joseph Priestley (1733-1804) wasn't in his laboratory investigating gases-he isolated and characterized eight of them, including oxygen-this 18th-century British scientist was often defending himself and his home against angry mobs.

Priestley, who discovered the gas that would later be named "oxygen" by Antoine-Laurent Lavoisier, was ceremoniously welcomed to the United States in 1794 as a leading contemporary thinker and friend of the new republic. Then 61, this Englishman was known to Americans at least as well for his prodigious political and theological writings as for his scientific contributions.

Religion and Politics

Priestley was educated to be a minister in the churches that dissented from the Church of England, and he spent most of his life employed as a preacher or teacher. He gradually came to question the divinity of Jesus, while accepting much else of Christianity-in the process becoming an early Unitarian.

Priestley was a supporter of both the American and French Revolutions. He saw the latter as the beginning of the destruction of all earthly regimes that would precede the Kingdom of God, as foretold in the Bible. These freely expressed views were considered seditious by English authorities and many citizens. In 1791 a mob destroyed his house and laboratory in Birmingham. This episode and subsequent troubles made him decide to emigrate to the United States. With his sons he planned to set up a model community on undeveloped land in Pennsylvania, but like many such dreams, this one did not materialize. He and his wife did, however, build a beautiful home equipped with a laboratory far up the Susquehanna River in Northumberland, Pennsylvania.

Oxygen and Other "Airs"

Priestley's first scientific work, The History of Electricity (1767), was encouraged by Benjamin Franklin, whom he had met in London. In preparing the publication Priestley began to perform experiments, at first merely to reproduce those reported in the literature but later to answer questions of his own. In the 1770s he began his most famous scientific research on the nature and properties of gases. At that time he was living next to a brewery, which provided him an ample supply of carbon dioxide. His first chemical publication was a description of how to carbonate water, in imitation of some naturally occurring bubbly mineral waters. Inspired by Stephen Hales's Vegetable Staticks (first edition, 1727), which described the pneumatic trough for gathering gases over water, Priestley began examining all the "airs" that might be released from different substances. Many, following Aristotle's teachings, still believed there was only one "air." By clever design of apparatus and careful manipulation, Priestley isolated and characterized eight gases, including oxygen-a record not equaled before or since. In addition, he contributed to the understanding of photosynthesis and respiration.

Priestley fought a long-running battle with Lavoisier and his followers over how to interpret the results of experiments with gases. Priestley interpreted them in terms of phlogiston-the hypothetical principle of flammability that was thought to give metals their luster and ductility and was widely used in the early 18th century to explain combustion, calcination, smelting, respiration, and other chemical processes. Proponents of phlogiston did not consider it to be a material substance, and so it was therefore unweighable. Priestley gave qualitative explanations of these phenomena, talking, for example, about oxygen as "dephlogisticated air."
The information contained in this biography was last updated on December 14, 2017.

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When Joseph Priestley (1733-1804) wasn't in his laboratory investigating gases-he isolated and characterized eight of them, including oxygen-this 18th-century British scientist was often defending himself and his home against angry mobs. Priestley, who discovered the gas that would later be named "oxygen" by Antoine-Laurent Lavoisier, was ceremoniously welcomed to the United States in 1794 as a leading contemporary thinker and friend of the new republic.

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French scientific collaborator of her husband Antoine Lavoisier, the founder of modern chemistry. Name variations: Marie Anne Pierrette Paulze; comtesse de Rumford; countess of Rumford; Madame de Rumford. Born Marie Anne Pierrette (also seen as Pierette) Paulze in 1758; died on February 10, 1836; daughter of Jacques Paulze and Claudine (Thoynet) Paulze; had three brothers; married Antoine Laurent Lavoisier (1743-1794), the founder of modern chemistry, in 1771; married Benjamin Thomson, count of Rumford, in October 1805.
In an arranged marriage, Marie Lavoisier and Antoine Lavoisier enjoyed a relationship which developed into a successful scientific collaboration, but they were caught up in one of the most dramatic events in modern European history. Marie survived the French Revolution, which cost her husband his life, but was imprisoned for several months at the height of the Terror.

The 1788 dual portrait of the Lavoisiers by the great French painter Jacques Louis David, now in New York's Metropolitan Museum of Art, enlivens a moment in time of historic importance to modern civilization. The painting was completed only months before Antoine published his crowning scientific achievement in February 1789, Traité élémentaire de chimie ( Elementary Treatise on Chemistry), the volume which laid the foundations of modern chemistry. The portrait gives every sign of presenting not Antoine Lavoisier as its leading figure, but rather his wife, who occupies the foreground of the canvas and is shown as small, somewhat plump, with a long, straight nose and lips that are tightly closed. In contrast to Marie, whose pose has been called protective and maternal toward her husband, Antoine, a wealthy and powerful member of the new nobility, is depicted as diffident and even docile. Some see the portrait as an indicator of the painter David's growing anti-establishment attitudes; others ask if it hints at tensions beneath the surface of a couple known to be close. Regardless, the portrait reveals two major figures in the intellectual life of France as they wished to be seen, at a time when their nation was poised on the brink of revolution.

Both Marie and Antoine Lavoisier were born into the highest reaches of the French bourgeoisie. Marie's father Jacques Paulze was director of the royal tobacco commission. After her mother Claudine Thoynet Paulze 's death, Marie was brought back to Paris from the convent where she had been sent for her education and served as hostess of her father's lavish entertainments. With her striking blue eyes, brown hair, and perfect complexion, she was both feminine and charming by age 13.

Antoine Laurent Lavoisier was born in Paris in 1743, more than a decade before Marie. He was a handsome man whose papers were brilliant analyses of various scientific problems, including the nature of thunder, the aurora, and the then still-prevalent belief, which he refuted, that by means of repeated distillation water was converted into earth. Where science was concerned, he was the man to watch in French intellectual life. By the time of his marriage to Marie, he would also be a wealthy man, having become a full titular member of the Ferme Générale (General Farm), the lucrative system of taxation carried on by a few privileged families on behalf of the French crown. Antoine's scientific interests left him little time to mix with fashionable women but through Jacques Paulze, who was also a member of the General Farm, Antoine met his daughter Marie. Antoine (15 years her senior) felt at ease in the company of the 13-year-old, who despite her age listened with interest as he talked about his scientific projects and displayed her musical talents on the harp and harpsichord while they spent many evenings in each other's company.

There was, however, another with interest in marrying Marie. The count of Amerval, a relatively impoverished 50-year-old aristocrat, hoped that by marrying her he would enter into a union that would be to his financial advantage. Marie's mother's uncle, the Abbé Terray, who was controller general of finance and the individual in charge of the General Farm tax system that provided the Paulze family's wealth, attempted to pressure Jacques to approve the marriage. Revealing the independent spirit that would characterize her long life, Marie called Amerval "a fool, an unfeeling rustic and an ogre." Jacques refused to grant permission for his daughter's marriage to a much older (and financially pinched) suitor, despite the fact that by doing so he risked losing his lucrative post as tobacco commission director. Jacques kept his job and, to forestall more meddling by his powerful uncle-in-law, he made clear his approval of Marie's marriage to Antoine.

The marriage contract, which was signed on December 4, 1771, stipulated that Marie would bring a dowry of 80,000 livres ($3,200,000). The groom brought much greater wealth into the marriage, which guaranteed that the couple's annual income would be about 20,000 livres ($800,000), providing for a life of considerable luxury. After their marriage ceremony (which took place on December 16, 1771, in the chapel of the Hôtel des Finances on the rue Neuve des Petits Champs), the couple moved into a house bought for them by Antoine's father on the fashionable rue Neuve des Bons Enfants, near the gardens of the Royal Palace. Antoine's father then bought him a title of nobility in 1772.

Although Marie was very likely pregnant in 1774, the couple remained childless. This allowed Marie, who was interested in her husband's scientific work, both the time and energy to assist him in his research. By 1775, when Marie was 17, she was already being referred to in correspondence as Antoine Lavoisier's "philosophical wife." By 1777, she was being tutored in chemistry by her husband's disciple and collaborator Jean Baptiste Bucquet. She learned English, a language her husband would never master, and translated many chemical works for him not only from English but also from other languages. Of her published translations, the most important is Richard Kirwan's 1787 Essay on Phlogiston, which appeared in Paris during 1788 and includes a few notes by Marie as well as commentaries by her husband and other French chemists who effectively refuted Kirwan's erroneous theories. She also studied drawing with the painter Jacques Louis David and made sketches of the Lavoisier laboratory.

One of her most important achievements was her assistance to Antoine in the preparation of the plates for his epoch-making book, Elementary Treatise on Chemistry (1789). She was often in his laboratory, assisting him by recording his scientific observations in large registers that served as raw data for his articles and books. An enthusiastic conversationalist and correspondent as well as a competent editor, Marie Lavoisier played a major role as an effective disseminator for the doctrines of the new chemistry that grew out of her husband's experiments.

After the couple moved to an apartment in the Arsenal where Antoine held the post of Régisseur des Poudres that placed him in charge of the French monarchy's production of gunpowder, Marie often presided over intellectual soireés, to which were invited many of Paris'

most brilliant scientists and artists. A testament to the intensity with which the couple carried out their scientific pursuits, their laboratory was immediately adjacent to their apartment. Often working together with Marie, Antoine arose at six in the morning and worked until eight; they returned to the laboratory in the evenings, working there from seven until ten. At least one full day of the week-"the day of happiness"-was devoted entirely to scientific experiments.

In addition to the hours spent investigating the basic mysteries of chemistry in their laboratory, much of Antoine's time went to his job as director of the state gunpowder administration. When he took over the newly established agency in 1775, France was producing less than half of its annual requirements of gunpowder. Antoine's thorough reforms of the organization brought rapid improvements, and, by the time the American Revolution began in 1776, the French found it possible to supply the American rebels with sufficient powder to continue their resistance against the British crown. As quantities increased, prices dropped, and the quality of the gunpowder also improved markedly. Antoine wrote with pride in April 1789: "One can truly say that North America owes its independence to French gunpowder." He was often assisted and encouraged by Marie while carrying out this work, which at times proved life-threatening. In October 1788, while both of them were in a mill observing the grinding of a new type of gunpowder, the mill exploded, killing one of the organization's directors and a young woman standing nearby. Both Lavoisiers had been positioned behind a barrier at the time and consequently were not injured.

The Lavoisiers were in no immediate danger at the start of the French Revolution in the spring of 1789. In fact, Antoine's public record, as a highly respected government administrator and scientist as well as an advocate of economic and social reform, was exemplary. He had started a model farm to demonstrate the advantages of the latest techniques of scientific agriculture as early as 1778, was a member of the provincial assembly of Orleans, and participated in various schemes of local improvements, and during the famine of 1788 advanced money without interest to several towns for the purchase of barley to alleviate suffering. Once the revolution began, he was called on to participate in various reform efforts, including the creation of a new system of taxation, and served on committees overseeing changes in public education, public hygiene, coinage, and the casting of cannon. He was also a leading member of the commission appointed to create a system of uniform weights and measures, a reform effort that resulted in the establishment of the metric system.

At first optimistic in his assessment of the revolution, in a letter dated February 5, 1790, Antoine Lavoisier informed his American friend and fellow scientist Benjamin Franklin that as far as he could judge, he regarded "our Revolution ... as completed." From the very start of the revolution, however, the situation in Paris was precarious for members of the privileged elite classes like the Lavoisiers. In early August 1789, after a boat loaded with gunpowder was seen being prepared to leave the quay on the Seine near the Arsenal, suspicious local residents became convinced that this was evidence that the Régisseurs des Poudres were trying to deny the Paris populace access to gunpowder, thus threatening their ability to defend their newly acquired freedoms. A mob formed at the Arsenal demanding the arrest of Antoine and one of his colleagues, both of whom were taken to the Hôtel de Ville (City Hall). Fortunately for Antoine, he secured his release with a sufficiently convincing explanation of the situation, which was that the boat contained low-grade gunpowder for export, and another vessel, loaded with high-grade powder, was soon expected to arrive on the Seine from the factory at Essonnes. This began to calm frayed tempers, and after another tense day, when both Antoine and Marie found themselves to be virtual prisoners at the Arsenal, the mob dispersed.

During these increasingly troubled years, Antoine, assisted by Marie, continued to carry out his scientific investigations. Two sketches made by her (1790 and 1791) show experiments on human respiration and are of both artistic and scientific interest. No doubt because she had studied with Jacques Louis David, Marie Lavoisier's sketches depict her husband in bold Davidian poses that celebrate political republicanism as much as they depict prosaic scientific reality. Her sketches illustrate the ways in which politically inspired modes of representation could also be utilized when depicting other, quite different, forms of human activity.

By 1792, with the rapidly increasing radicalization of the French Revolution, Antoine Lavoisier had become an object of suspicion. As a Tax Farmer and prominent member of the Ferme Générale, he was linked to one of the most hated aspects of the Old Regime's discredited system of privilege and exploitation. Even his many years of work at the Arsenal as head of the government gunpowder monopoly were now open to criticism. The politician Jean Paul Marat accused Antoine of putting the city of Paris in prison as well as impeding the city's air circulation by means of the mur d'octroi (toll-house wall) erected at his suggestion in 1787. In August 1792, the Lavoisiers had to leave their apartment and laboratory at the Arsenal because mob violence made living there unsafe. In November of that year, the revolutionary government of the Convention ordered the arrest of the former Farmers General. Antoine was tried by the revolutionary tribunal at the height of the Terror in May 1794, and the perfunctory proceedings against him and 31 others took only a few hours to conclude. Of the 32 tried, 28 were found guilty and sentenced to death. In the afternoon of the same day, May 8, 1794, Antoine and the others who had been convicted, including Marie's father Jacques Paulze, were guillotined at the Place de la Revolution, now the Place de la Concorde. Without ceremony, the victims were buried in anonymous graves in the cemetery of the Parc Monceaux. The following day, Joseph Lagrange remarked: "It required only a moment to sever that head, and perhaps a century will not be sufficient to produce another like it."

Soon after the execution of her husband and father, Marie Lavoisier was arrested and jailed along with other heirs of dead Tax Farmers. Two months later, she wrote abjectly to her local revolutionary committee to declare her belief in the ideals and principles of the revolution and the French Republic. By this time, the dictator Maximillien Robespierre had been guillotined, and the Reign of Terror was over. In August 1794, she was released from prison. Now destitute, she had to be supported by a former servant who took pity on her plight. Although traces of the trauma she had endured would mark her personality for the rest of her life, over the next few years Madame Lavoisier slowly put the pieces of her shattered existence back together. With the end of the terrorist phase of the revolution, she inherited the bulk of her husband's wealth and began once more to entertain Parisian society. During this difficult period of adjustment, she carried on an intense love affair with an old family friend who was 20 years her senior, Pierre Samuel Dupont, a relationship that appears to have begun in the final, chaotic months before her husband's trial and execution. Although their strong personalities made a permanent stable relationship virtually impossible to achieve, even after their liaison had ended Dupont remained emotionally attached to Marie. In 1799, at the time of his departure for America, he addressed her in a letter which he never sent: "my dear lady, your name will always be linked with mine." (In the New World, Dupont had an immensely successful business career as founder of the chemical company that still bears his family name.)

In October 1805, Marie Lavoisier married Count Rumford, whose title was Bavarian but who was in fact a colorful Massachusetts-born scientist named Benjamin Thomson. His accomplishments included service as a colonel in the British Army during the Revolutionary War. One of the most highly regarded scientific investigators of the day, Count Rumford studied the nature of light, demonstrated the mechanical nature of heat, and made practical discoveries in the area of the rational use of foods and fuels, resulting in more nourishing soups for feeding the poor and greatly improved fireplace designs. In a letter describing Lavoisier soon after he met her in 1801, Rumford praised "this amiable lady ... [who is] ... very sociable ... [and who] ... lives in elegant style, and is hostess to the greatest philosophers and the most eminent scientists and writers in Paris. And above all, she is kindness itself."

It soon became obvious to all of Paris that this union-of two highly intelligent and strong-willed individuals, both of whom were middle-aged and set in their ways-was very much a mismatch. Lavoisier lived to entertain friends in her charming house, surrounded by an English garden, in one of the most elegant districts of Paris. Rumford, on the other hand, desired the peace and quiet of his laboratory and his beloved rose garden. Both were stubborn and unwilling to compromise on even the most trivial matters, and they argued much of the time, sometimes in public. After he forbade the porter to let his wife's friends enter the house (forcing them to speak with their hostess through the mansion gate), she got her revenge by pouring boiling water over his exquisite rose bushes. After four years characterized by little wedded bliss, the marriage ended in 1809 with an amicable separation that left the oft-poor but famous scientist Rumford with a handsome financial settlement of between 300,000 and 400,000 francs.

For the next 27 years, Madame de Rumford, as she continued to be known, devoted herself entirely to entertaining her friends in grand style. In the words of historian François Guizot, she chose to entertain her distinguished guests-scientists, artists, and high society-with "a rather singular mixture of rudeness and courtesy." Most of her visitors were flattered to receive her invitations and usually ignored the fact that "her language could be brusque and she was subject to authoritarian whims." For a number of years before he was forced to return to America, one of her most favored party guests was her old lover Pierre Samuel Dupont. Several years after his return to the States, Dupont died in Wilmington, Delaware, of a chill caught while helping to put out a fire at his son's gunpowder works.

As Lavoisier's friends of the past began to die, she lived more and more alone. A relic from the Old Regime, she became ever more eccentric, a nature often commented on by the younger generation of French writers and intellectuals. The Delahante brothers, descended like Antoine Lavoisier from a family of pre-revolutionary Tax Farmers, wrote about their visits to her home on the rue d'Anjou. They began by noting the striking David portrait of Antoine and Marie Lavoisier, going on to describe Marie:

This old Turk [who] was all that remained of the beautiful young woman depicted by David: it was Madame de Rumford, with her aged, masculine face, coiffed and rigged out in the most bizarre way. She greeted us in her abrupt manner, which was not unkind, asked us to sit down, and began asking us questions about our studies and pastimes.... After a few minutes she would suddenly get up from the love seat and go and stand with her back to the fireplace ... pull up her skirts from behind as high as her garters and leisurely warm her enormous calves.... She often gave elegant balls that we enjoyed more than the visits, in spite of her active surveillance and the severity with which she chased us away from the buffet to have us dance the quadrille.

Marie Lavoisier died on February 10, 1836, having played an important role in the birth of modern chemistry. She had lived under and survived the various political and other vicissitudes of seven constitutions and eight forms of government in a turbulent era of French history.

sources:

Alic, Margaret. Hypatia's Heritage. Boston, MA: Beacon Press, 1986.

Donovan, Arthur. Antoine Lavoisier: Science, Administration, and Revolution. Oxford, U.K. and Cambridge, MA: Blackwell, 1993.

Duveen, Denis I. "Madame Lavoisier, 1758-1836," in Chymia. Vol. 4, 1953, pp. 13-29.

Holmes, Frederic Lawrence. Lavoisier and the Chemistry of Life: An Exploration of Scientific Creativity. Madison, WI: University of Wisconsin Press, 1985.

Miller, Jane A. "Women in Chemistry," in G. Kass-Simon and Patricia Farnes, eds., Women of Science: Righting the Record. Bloomington: Indiana University Press, 1990, pp. 300-334.

Ogilvie, Marilyn Bailey. Women in Science: Antiquity through the Nineteenth Century. Cambridge, MA: MIT Press, 1986.

Perrin, C.E. "The Lavoisier-Bucquet Collaboration: A Conjecture," in Ambix: The Journal of the History of Alchemy and Chemistry. Vol. 36, no. 1. March 1989, pp. 5-13.

Poirier, Jean-Pierre. Lavoisier: Chemist, Biologist, Economist. Translated by Rebecca Balinski. Philadelphia, PA: University of Pennsylvania Press, 1996.

Schofield, Maurice. "Women in the History of Science," in Contemporary Review. Vol. 21, no. 1215, 1967, pp. 204-206.

Smeaton, W.A. "The Chemical Work of Horace Bénédict de Saussure (1740-1799), With the Text of a Letter Written to Him by Madame Lavoisier," in Annals of Science. Vol. 35, no. 1. January 1978, pp. 1-16.

--. "Monsieur and Madame Lavoisier in 1789: The Chemical Revolution and the French Revolution," in Ambix: The Journal of the Society for the History of Alchemy and Chemistry. Vol. 36, no. 1. March 1989, pp. 1-4.

Umesh, Nila. "The Woman Behind Antoine Lavoisier," in Link [ New Delhi]. Vol. 31, no. 14-15. November 13-20, 1988, pp. 42-43.

John Haag , Associate Professor of History, University of Georgia, Athens, Georgia

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marie (1758–1836)french scientific collaborator of her husband antoine lavoisier

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the founder of modern chemistry. name variations: marie anne pierrette paulze; comtesse de rumford; countess of rumford; madame de rumford.

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Lavoisier, Marie (1758-1836)French scientific collaborator of her husband Antoine Lavoisier, the founder of modern chemistry. Name variations: Marie Anne Pierrette Paulze; comtesse de Rumford; countess of Rumford; Madame de Rumford. Source for information on Lavoisier, Marie (1758-1836): Women in World History: A Biographical Encyclopedia dictionary.

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Antoine Lavoisier - Biography, Facts and Pictures

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Lived 1743 - 1794. Antoine Lavoisier revolutionized chemistry. He named the elements carbon, hydrogen and oxygen; discovered oxygen’s role in combustion and respiration; established that water is a compound of hydrogen and oxygen; discovered that sulfur is an element, and helped continue the transformation of chemistry from a qualitative science into a quantitative one. Advertisements

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Andreas Vesalius | Anatomy in the Age of Enlightenment

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Born in Brussels and trained in anatomy at the University of Padua (where he would return to teach), Vesalius became the leading figure in the renewed practice of human dissection. He produced two seminal texts, Tabulae sex (Six Plates, 1538) and De humani corporis fabrica ( The Fabric of the Human Body, 1543).

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Vesalius went to school in a time where the writings og a man named Galen were taken and fully accepted as true in terms of anatomical science. When Vesalius graduated, he became a teacher at his university and was he first person to ever question Galen's theories. It turned out that Galen was totally wrong, and shad actually based his findings off of dissecting pigs and apes. So, Vesalius published a book with all of his findings, called The Fabric of the Human Body, something that is accurate and still referred to today.

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by Andreas Vesalius

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Born in Brussels in 1514, descending from a family of physicians, studied in Leuven, Paris & Padua and became professor of surgery and anatomy in Padua at the age of 23. This so-called" greatest of anatomists" produced the first detailed anatomical textbook, called the "Humani Corporis Fabrica."

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Tut2Learn - GK, Exam Tips, Job Tips, Biography

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Famous Scientist Robert Boyle Interesting Facts

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http://knarf.english.upenn.edu/People/boyle.html

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Robert Boyle Life and Legacy - Robert Boyle

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In 1655 Boyle moved to Oxford where he joined the Invisible College - a group of natural philosophers that foreshadowed the Royal Society that was founded in 1660. About this time Boyle employed Robert Hooke to help him with his experiments.

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. . . my work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men. And therewithal, whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof.
Antony van Leeuwenhoek. Letter of June 12, 1716

Antony van Leeuwenhoek was an unlikely scientist. A tradesman of Delft, Holland, he came from a family of tradesmen, had no fortune, received no higher education or university degrees, and knew no languages other than his native Dutch. This would have been enough to exclude him from the scientific community of his time completely. Yet with skill, diligence, an endless curiosity, and an open mind free of the scientific dogma of his day, Leeuwenhoek succeeded in making some of the most important discoveries in the history of biology. It was he who discovered bacteria, free-living and parasitic microscopic protists, sperm cells, blood cells, microscopic nematodes and rotifers, and much more. His researches, which were widely circulated, opened up an entire world of microscopic life to the awareness of scientists.

Leeuwenhoek was born in Delft on October 24, 1632. (His last name, incidentally, often is quite troublesome to non-Dutch speakers: "layu-wen-hook" is a passable English approximation.) His father was a basket-maker, while his mother's family were brewers. Antony was educated as a child in a school in the town of Warmond, then lived with his uncle at Benthuizen; in 1648 he was apprenticed in a linen-draper's shop. Around 1654 he returned to Delft, where he spent the rest of his life. He set himself up in business as a draper (a fabric merchant); he is also known to have worked as a surveyor, a wine assayer, and as a minor city official. In 1676 he served as the trustee of the estate of the deceased and bankrupt Jan Vermeer, the famous painter, who had had been born in the same year as Leeuwenhoek and is thought to have been a friend of his. And at some time before 1668, Antony van Leeuwenhoek learned to grind lenses, made simple microscopes, and began observing with them. He seems to have been inspired to take up microscopy by having seen a copy of Robert Hooke's illustrated book Micrographia, which depicted Hooke's own observations with the microscope and was very popular.

Leeuwenhoek is known to have made over 500 "microscopes," of which fewer than ten have survived to the present day. In basic design, probably all of Leeuwenhoek's instruments -- certainly all the ones that are known -- were simply powerful magnifying glasses, not compound microscopes of the type used today. A drawing of one of Leeuwenhoek's "microscopes" is shown at the left. Compared to modern microscopes, it is an extremely simple device, using only one lens, mounted in a tiny hole in the brass plate that makes up the body of the instrument. The specimen was mounted on the sharp point that sticks up in front of the lens, and its position and focus could be adjusted by turning the two screws. The entire instrument was only 3-4 inches long, and had to be held up close to the eye; it required good lighting and great patience to use.

Compound microscopes (that is, microscopes using more than one lens) had been invented around 1595, nearly forty years before Leeuwenhoek was born. Several of Leeuwenhoek's predecessors and contemporaries, notably Robert Hooke in England and Jan Swammerdam in the Netherlands, had built compound microscopes and were making important discoveries with them. These were much more similar to the microscopes in use today. Thus, although Leeuwenhoek is sometimes called "the inventor of the microscope," he was no such thing.

However, because of various technical difficulties in building them, early compound microscopes were not practical for magnifying objects more than about twenty or thirty times natural size. Leeuwenhoek's skill at grinding lenses, together with his naturally acute eyesight and great care in adjusting the lighting where he worked, enabled him to build microscopes that magnified over 200 times, with clearer and brighter images than any of his colleagues could achieve. What further distinguished him was his curiosity to observe almost anything that could be placed under his lenses, and his care in describing what he saw. Although he himself could not draw well, he hired an illustrator to prepare drawings of the things he saw, to accompany his written descriptions. Most of his descriptions of microorganisms are instantly recognizable.

In 1673, Leeuwenhoek began writing letters to the newly-formed Royal Society of London, describing what he had seen with his microscopes -- his first letter contained some observations on the stings of bees. For the next fifty years he corresponded with the Royal Society; his letters, written in Dutch, were translated into English or Latin and printed in the Philosophical Transactions of the Royal Society, and often reprinted separately. To give some of the flavor of his discoveries, we present extracts from his observations, together with modern pictures of the organisms that Leeuwenhoek saw.

In a letter of September 7, 1674, Leeuwenhoek described observations on lake water, including an excellent description of the green charophyte alga Spirogyra: "Passing just lately over this lake, . . . and examining this water next day, I found floating therein divers earthy particles, and some green streaks, spirally wound serpent-wise, and orderly arranged, after the manner of the copper or tin worms, which distillers use to cool their liquors as they distil over. The whole circumference of each of these streaks was about the thickness of a hair of one's head. . . all consisted of very small green globules joined together: and there were very many small green globules as well."

A letter dated December 25, 1702, gives descriptions of many protists, including this ciliate, Vorticella: "In structure these little animals were fashioned like a bell, and at the round opening they made such a stir, that the particles in the water thereabout were set in motion thereby. . . And though I must have seen quite 20 of these little animals on their long tails alongside one another very gently moving, with outstretched bodies and straightened-out tails; yet in an instant, as it were, they pulled their bodies and their tails together, and no sooner had they contracted their bodies and tails, than they began to stick their tails out again very leisurely, and stayed thus some time continuing their gentle motion: which sight I found mightily diverting."

On September 17, 1683, Leeuwenhoek wrote to the Royal Society about his observations on the plaque between his own teeth, "a little white matter, which is as thick as if 'twere batter." He repeated these observations on two ladies (probably his own wife and daughter), and on two old men who had never cleaned their teeth in their lives. Looking at these samples with his microscope, Leeuwenhoek reported how in his own mouth: "I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort. . . had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort. . . oft-times spun round like a top. . . and these were far more in number." In the mouth of one of the old men, Leeuwenhoek found "an unbelievably great company of living animalcules, a-swimming more nimbly than any I had ever seen up to this time. The biggest sort. . . bent their body into curves in going forwards. . . Moreover, the other animalcules were in such enormous numbers, that all the water. . . seemed to be alive." These were among the first observations on living bacteria ever recorded.

Leeuwenhoek looked at animal and plant tissues, at mineral crystals and at fossils. He was the first to see microscopic foraminifera, which he described as "little cockles. . . no bigger than a coarse sand-grain." He discovered blood cells, and was the first to see living sperm cells of animals. He discovered microscopic animals such as nematodes and rotifers. The list of his discoveries goes on and on. Leeuwenhoek soon became famous as his letters were published and translated. In 1680 he was elected a full member of the Royal Society, joining Robert Hooke, Henry Oldenburg, Robert Boyle, Christopher Wren, and other scientific luminaries of his day -- although he never attended a meeting. In 1698 he demonstrated circulation in the capillaries of an eel to Tsar Peter the Great of Russia, and he continued to receive visitors curious to see the strange things he was describing. He continued his observations until the last days of his life. After his death on August 30, 1723, the pastor of the New Church at Delft wrote to the Royal Society:

. . . Antony van Leeuwenhoek considered that what is true in natural philosophy can be most fruitfully investigated by the experimental method, supported by the evidence of the senses; for which reason, by diligence and tireless labour he made with his own hand certain most excellent lenses, with the aid of which he discovered many secrets of Nature, now famous throughout the whole philosophical World.
British scientist Brian J. Ford has rediscovered some of Leeuwenhoek's original specimens in the archives of the Royal Society of London. His study of these historic specimens and other material, using Leeuwenhoek's own microscopes and other single-lens microscopes, has shown how remarkably good a scientist and craftsman Leeuwenhoek really was. Here's the full story of Dr. Ford's research.
Berkeley, California resident Al Shinn manufactures replicas of Leeuwenhoek microscopes. He has also made plans and instructions available, for those who would like to make their own Leeuwenhoek-type microscopes.

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. my work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men.

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Edward Jenner was a physician known for discovering that people who had come down with cowpox developed an immunity to smallpox. In the late eighteenth century, smallpox was treated with matter from the smallpox pustules so that the patient would develop an immunity to the disease. This came with risks of severe disease and the spread of smallpox. Jenner discovered that by using matter from a lesser disease called cowpox, people could develop an immunity to smallpox. At first his discoveries were shot down and made fun of, but with some help of his friend, Frederick Augustus, His ideas were able to spread and eventually smallpox disappeared thanks to Edward Jenner.

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Edward Jenner: Biography of a Great Thinker

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Edward Jenner (1749-1823) is known as the "Father of Immunology. " He pioneered the use of vaccination against smallpox, a deadly scourge. After initial resistance, vaccination became compulsory in England, and across the world there was a mass vaccination effort. In 1980, smallpox was declared eradicated.

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Somewhere in my immunological training I learned that Edward Jenner, a simple country doctor from Gloucestershire, discovered that it was possible to protect against the dread disease Small Pox by injecting material taken from a similar pox disease of cows. Then, as the story goes, soon after his publication (Jenner, 1798), the Queen had her children vaccinated, which led to an immediate acceptance of the practice, and Parliament voted to recognize Jenner by granting him a life-time pension. Then to top it all, King George III Knighted Jenner, and he lived happily ever after.

Essentially the only true part of this story relates to Jenner's discovery of vaccination against Small Pox using Cow Pox. The rest is all far from what really happened.

In the eighteenth century, Small Pox was a dread disease, accounting for about 10% of all deaths. It was especially virulent in infants and children, and when it swept through a village, from 20 to 50% of those infected died as a consequence. Moreover, those who survived were often disfigured from pockmarks, and smallpox led to blindness when it spread to the eyes.

Around 1720, Lady Mary Wortley Montegue, the wife of the British Ambassador to Turkey, returned to England enthusiastic about Small Pox inoculation, a practice she had learned of in Constantinople (Saunders, 1982). At the time, it was well known that survivors of Small Pox were exempt from the disease during subsequent epidemics. As a consequence, in Asia, protection from Small Pox was commonly attempted by intranasal inhalation of pox material. During a Small Pox epidemic in London in 1721, Lady Montegue had her 4-year-old daughter inoculated with pox material. Subsequently, throughout the eighteenth century, the practice, known as variolation, or simply inoculation, became commonplace throughout the United Kingdom (Saunders, 1982).

Variolation held that it was possible to protect against the very high mortality resulting from a natural infection, which usually occurred by the inhalation of a large dose of virus, by the well-controlled inoculation of a smaller dose of the virus into the skin. Physicians became expert in the practice, and set up special inoculation infirmaries to support and care for those who became ill after inoculation. Although it was common for the inoculated to become symptomatic, and some actually succumbed, the mortality rates advertised by the most expert physicians were as low as 1%. As such, variolation became a very lucrative practice for British doctors, especially during epidemics, when the populace was terribly frightened. However, variolation also ensured that the disease would be endemic and never disappear from the communities.

Edward Jenner was born in 1749 in the UK western county of Gloucestershire. Unfortunately he lost both his mother and father as a young child, and was raised by his older brother (Saunders, 1982). As a consequence of the family's reduced financial circumstances, he did not attend university at Oxford to be trained for the clergy as was customary for his family, but instead he was apprenticed to a local physician at the age of 13. He proved to be an excellent student, and after 6 years, he was sent to St. Georges Hospital in London, where he was taken in by John Hunter, who was to become one of the world's most famous surgeons. While he was with Hunter he met and became friends with Joseph Banks, who in 1771 had just returned as the naturalist on Captain Cook's first around the world voyage. On the recommendation of Hunter, Jenner helped Banks in the arrangement and cataloging of the specimens from the voyage. Banks went on to an illustrious career, and became the President of the Royal Society for more than 40 years. Thus, early in his career, Jenner entered into an exceptional community of scientists and physicians of his generation.

Toward the end of his training at St. Georges, Hunter offered Jenner a post as his assistant for his teaching and dissecting efforts at the Hospital. However, Jenner declined and returned to his hometown, Berkley, a small village west of Oxford in dairy country and set up a general practice. There, Jenner spent the next 20 years, administering to the people from the surrounding farmlands. He did find time to pursue his studies in natural history (i.e., science), and submitted his studies on the reproductive habits of the cuckoo to the Royal Society, encouraged by the now Sir Joseph Banks, with whom Jenner was in steady correspondence throughout his life (Jenner, 1788). As a consequence, Jenner was elected as a Fellow of the Royal Society at the age of 39, quite an accomplishment for a "simple country doctor."

Like the other physicians of his day, Jenner became expert at variolation. In this regard, it is important to appreciate that variolation had become established and practiced for 50 years when Jenner commenced his practice (Saunders, 1982). While administering to his country clientele, Jenner described in his "The Origin of the Vaccine Inoculation":

I was first excited by observing, that among those whom in the country I was frequently called upon to inoculate, many resisted every effort to give them the Small Pox. These patients I found had undergone a disease they called the Cow Pox, contracted by milking cows affected with a peculiar eruption on their teats. On inquiry, it appeared that this had been known among the dairies immemorial, and a vague opinion prevailed that the Cow Pox was preventative of the Small Pox.......This led me to inquire among medical practitioners in the country around me, who all agreed in the sentiment that the Cow pox was not relied upon as a preventative of the Small Pox.(Jenner, 1801)

Although these considerations from the medical establishment temporarily dissuaded Jenner from following his intuition, he persisted in his thoughts, and collected over the years a wealth of experience from variolating people who had previously contracted the Cow Pox.

After 20 years of general practice, in 1792 Jenner was awarded the MD degree from St. Andrews University, Scotland, upon the recommendation of two of his longtime friends, as well as the payment of a fee, evidently a common practice at the time (Saunders, 1982). Accordingly, now able to advertise himself as a physician and surgeon, MD, FRS, he gave up general practice and became a private consultant. Soon thereafter, Jenner contracted typhus, which led to a long convalescence, and eventually in 1795 his move to Cheltenham, a "spa town" between Berkley and Oxford, where mineral springs had been discovered. Here, Jenner began to mix with the aristocracy, which migrated there from London to "take the waters" during the summer months ("The Season"). Also, he now had time to organize and write-up his experiences with variolation of individuals who had a history of a prior illness due to the Cow Pox.

In Cheltenham, Jenner evidently underwent a "midlife crisis," or at least a metamorphosis. Removed from the small village of Berkley, and surrounded by "London society," Jenner was described as a gregarious gentleman who thrived in his new environment (Saunders, 1982). He played the violin, drew well, and fancied himself as a poet. He kept a good table, was an interesting host, conversant in a variety of subjects, and was well regarded both professionally and socially by a wide range of colleagues and friends, many of whom were very influential, politically, and socially.

In 1796, Jenner submitted a manuscript to the Royal Society, which described the case histories of 13 people who had resisted either variolation or natural Small Pox after having a history of Cow Pox. This manuscript also described Jenner's first vaccination, which will be discussed in detail later. Sir Joseph Banks evidently was not too impressed by the manuscript, as he sent it on to Lord Somerville, President of the Board of Agriculture. Eventually, the manuscript was simply returned without being read to the Royal Society. Such was the appreciation of medicine by the "real scientists" of the time.

Rebuffed by the Royal Society, Jenner extended the manuscript with additional case histories, eventually comprising 25 individuals with a history of having had Cow Pox: he tested 24 and found them to resist variolation. Some of these individuals who appeared immune to Small Pox had had a Cow Pox infection several decades previously, thereby suggesting that the Cow Pox "immunity" was very long lasting. Most important, Jenner added a description of at least nine individuals who were injected with Cow Pox, of whom four he variolated and found to resist Small Pox. With this enhanced manuscript, Jenner arranged to have it published in London at his own expense, thereby circumventing the Royal Society (Jenner, 1798). This represents the first "open access" report published in immunology!

Reading through Jenner's descriptions of his cases, the meticulous detail and the thought and analysis that he employed are quite impressive, even two centuries later. Several points made by Jenner via these case histories are noteworthy. For example, in case number four, he describes a woman who had Cow Pox 31 years prior to variolation in 1791.

Upon inoculation of Small Pox,

an effervescence of a palish red color soon appeared about the parts where the (variolous) matter was inserted, and spread itself rather extensively, but died away in a few days without producing any variolous symptoms. It is remarkable that variolous matter, when the system is disposed to reject it, should excite inflammation on the part to which it is applied more speedily than when it produces the Small Pox.

Thus, this is perhaps the first description of an anamnestic immune response!

In case six, Jenner states

It is so well known among our Dairy Farmers, that those who have had the Small Pox either escape the Cow Pox, or are disposed to have it slightly. Thus, as soon as the complaint shews itself among the cattle, assistants are procured who have had the Small Pox, and are thus rendered less susceptible of the Cow Pox. Otherwise, the farm could scarcely go forward.

Accordingly, Jenner describes the reciprocal protection afforded by Small Pox and Cow Pox infections.

Jenner's description of his first successful vaccination (Cases 16 and 17) is especially interesting.

Sarah Nelmes, a dairymaid at a farmer's near this place, was infected with the Cow Pox from her master's cows in May, 1796. She received the infection on a part of the hand, which had previously in a slight degree been injured by a scratch from a thorn. A large pustulous sore and the usual symptoms accompanying the disease were produced in consequence. The pustule was so expressive of the true character of the Cow Pox, as it commonly appears on the hand, that I have given a representation of it in the annexed plate. (Figure ​(Figure1 1 )

The more accurately to observe the progress of the infection, I selected a healthy boy, about eight years old, for the purpose of inoculation for the Cow Pox. The matter was taken from a sore on the hand of a dairymaid (Sarah Nelmes), and it was inserted on the 14 th of May, 1796, into the arm of the boy by means of two superficial incisions, barely penetrating the cutis, each about half an inch long.

On the seventh day he complained of uneasiness in the axilla, and on the ninth he became a little chilly, lost his appetite, and had a slight head-ache. During the whole of this day he was perceptively indisposed, and spent the night with some degree of restlessness, but on the day following he was perfectly well.

In order to ascertain whether the boy, after feeling so slight an affection of the system from the Cow-pox virus, was secure from the contagion of the Small Pox, he was inoculated the 1 st of July following with variolous matter, immediately taken from a pustule. Several slight punctures and incisions were made on both arms, and the matter was carefully inserted, but no disease followed....... Several months afterwards, he was again inoculated with variolous matter, but no sensible effect was produced on the constitution.

Jenner published his An Inquiry into The Causes and Effects of Variolae Vaccinae, a Disease Discovered in some of the Western Counties of England, Particularly Gloucestershire, and Known by the Name of Cow Pox, on June 21st 1798.

Subsequently, Jenner followed-up his original publication with a 1799 "Further Observations on the Variolae Vaccinae," in which he detailed how to recognize typical Cow Pox lesions and to discriminate them from other similar pustular lesions that were not Cow Pox (Jenner, 1799). In this regard, it is important to point out that the causes of all microbial infections, particularly pyogenic bacterial infections that could be confused with Cow Pox pustules, were completely unrecognized in 1798, and did not become known until Robert Koch's description of the bacilli that causes anthrax in 1876, almost 100 years later (Koch, 1876).

In 1800 Jenner continued to educate physicians about vaccination with "A Continuation of Facts and Observations Relative to the Variolae Vaccinae or Cow Pox," in which he chronicled the successes from his physician friends who he had sent Cow Pox material to propagate and to vaccinate individuals in their own communities (Jenner, 1800). Thus, within the early years after his first publication, word of the innocuous nature of vaccination spread fairly rapidly, also making its way to the European continent and to the US. During these years Jenner focused his practice almost entirely on vaccinating all who came to Cheltenham. Consequently, he slowly depleted his savings as the word spread, because he did not charge for the vaccination, especially of the poor.

Not everyone immediately embraced the idea, especially the physicians who had lucrative Small Pox inoculation infirmaries and practices. Thus, as time progressed, the UK became divided into those who ascribed to vaccination and those who were skeptical and thought that only Small Pox inoculation would confer true protection against Small Pox.

Thus, when several of Jenner's Cheltenham acquaintances, who were Members of Parliament, petitioned Parliament to award him a prize for his discovery, there were both supporters as well as dissenters. In 1802 Parliament awarded him £10,000, which in today's currencies is ∼$700,000. However, an award of £20,000 was defeated by only three votes. This award was crucial for Jenner, in that it allowed him to establish himself in Cheltenham society, and to devote himself to furthering the spread of vaccination all over the world. Then in 1807, after he had been recognized by many foreign governments, Parliament awarded him a second prize, this time of £20,000.

However, despite the fact that vaccination was recognized as a miracle by most of the world, one that saved many lives, the practice of variolation continued in the UK. This practice ensured that Small Pox circulated continuously and intermittently caused epidemics, leading to death, and disfigurement. Moreover, the one thing that would have made a difference in his homeland, i.e., recognition by the Crown, proved elusive. Evidently, those physicians who made their living from variolation held more sway with the King than those who supported Jenner and vaccination. Not until King George III died in 1820, did the new King George IV appoint Edward Jenner Physician Extraordinary to the King on March 16, 1821. However, he was never made a Knight.

Jenner continued to press his case for 25 years after the publication of the Inquiry, facilitating worldwide vaccination by sending seed samples of Cow Pox material to anyone who asked. He died in 1823, at the age of 74. It was not until 1840 that Parliament outlawed the practice of variolation, making Cow Pox vaccination the official UK policy.

As one can imagine, during the entire nineteenth century and the first half of the twentieth century methods were not available to characterize viruses at the molecular and genetic levels. Therefore, the vaccines used all over the world became diverse. Initially, most Cow Pox vaccines were derived via Jenner and his colleagues and passaged arm-to-arm from vaccinees (Baxby, 1981). However, these sources gradually became mixed with other isolates, derived from cows as well as most probably Small Pox isolates passed through animals as well as humans. Toward the end of the nineteenth century, vaccines became produced from calf skin after escarification. In the US, several isolates circulated, some of which were obtained from the UK in the first half of the nineteenth century, which were assumed to be derived from Jenner's source material. Obviously there was no way to determine the pedigree of the viruses used. Eventually, the vaccine used in the US as part of the worldwide Small Pox eradication program was called Vaccinia and was manufactured from infected calf skin in the US by Wyeth under the name Dryvax ®.

Given this state of the art of virology, or rather lack thereof, it is remarkable that vaccination with Vaccinia Virus was as efficacious as it proved to be, ultimately leading to the total eradication of Small Pox from the face of the earth by 1980! The success of this first vaccine led the scientific as well as the lay communities to the erroneous conclusion that producing vaccines was a simple affair and that knowledge of the immune response was unnecessary. This attitude was reinforced by Pasteur ( 1880) about 100 years after Jenner, and then during the 1950s and 1960s when virologists successfully attenuated many of the viruses responsible for the childhood viral exanthems to produce a new catalog of viral vaccines.

It is only now, in the aftermath of the 9/11 tragedies and the anthrax scare in the US, with the specter of bioterrorism threatening to reintroduce Small Pox to the world, that efforts have been undertaken to produce a new vaccine by modern methods. Thus, the Dryvax ® vaccine, which is a mixture of viruses, has been grown in tissue culture, and individual viruses have been cloned and characterized genetically and biologically after injection in humans (Nalca and Zumbrun, 2010). A phylogenetic tree of the orthopox viruses is shown in Figure (Guiyun et al., 2006). This tree was generated using an 82 kb DNA sequence conserved among all fully sequenced orthopox viruses. It's of interest that the Vaccinia Virus strains (VACV) are clustered and distinct from the Cow Pox strains (CPXV), and both are distinct from the Small Pox isolates (VARV). Thus, the vaccine used to eradicate Small Pox is probably not actually the Cow Pox virus discovered by Jenner to protect against the dread disease Small Pox.

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