Most people say yes. Now consider a slightly different dilemma. Once again, a trolley is heading down a set of tracks toward five people. You are on a footbridge over the tracks next to a large man. The only way you can save these five people is to push this man off the bridge and into the path of the trolley.
Most people say no.
One hypothesis is that we have an implicit understanding of a complex set of shared moral principles from which we deduce our answers. A different hypothesis appeals to common emotional response rather than shared principles. The thought of pushing someone to his death with one's bare hands is, we'll suppose, more emotionally salient than the thought of hitting a switch that will have similar consequences. According to this theory, our shared dispositions to respond emotionally to some things and not others explains the consistency found in people's reactions to these two cases.