“Would You Kill the Fat Man?” is the title of a recent book about a set of moral problems that philosophers like to ponder, and psychologists to put to their experimental subjects.
In the canonical form, you are on a footbridge watching a trolley speeding down a track that will kill five unsuspecting people. You can push a fat man over the bridge onto the tracks to save the five. (You cannot stop the trolley by jumping yourself, only the fat man is heavy enough.) Would you do it?