2. Why does Quinn think that it is morally IMPERMISSIBLE to intend to harm someone even when the action can cause a greater good in society? 

Quinn has argued that double effect does not rest on the distinction between intended and merely foreseen harm, but instead is best formulated using a distinction between direct and indirect agency. 
- in harmful direct agency, “harm comes to some victims, at least in part, from the agent’s deliberately involving them in something in order to further his purpose precisely by way of their being so involved”; whereas

- in harmful indirect agency, “either nothing is in that way intended for the victims or what is so intended does not contribute to their harm.” 

 

He claimed that harmful direct agency involves a stronger form of disrespect for its victims than harmful indirect agency.  
Quinn is not saying that all harmful direct agency is wrong, and all harmful indirect agency is permissible.
He said that the distinction between harmful direct agency and harmful indirect agency is morally significant.

3. Does the DDE provide a good explanation about the Trolley Problem? (The Trolley Problem: it is permissible to proceed in Trolley, but not in Transplant, though the costs and benefits are the same in both cases.)

We think that DDE does provide a good explanation about the Trolley problem. In Trolley, it is permissible to kill the one because one’s primary intention is to save the five. The death of the one on the side track is a double-effect.Trolley Problem provides three distinct arguments in favor of the Doctrine of Double Effect: summarizing, the Doctrine of Double Effect offers a solution to the Trolley Problem; the two scenarios which constitute the Trolley Problem illustrate the distinction between ‘means’ and ‘side-effects’ .