Suppose a trolley is hurtling down a track, on which are placed five innocent people with no chance to escape in time. You are standing beside a switch that will redirect the trolley onto a track where stands one innocent person, who also has no chance to escape. Should you flip the switch, and thereby kill one to save five?

Now suppose there is no track onto which the trolley can be redirected; the five innocents will be in its path no matter what happens. Instead of being beside a switch, you are standing on a bridge over the tracks, beside a very fat man looking down over the action. You can push the man over the bridge, knowing his enormous girth will stop the trolley’s movement before it hits the innocents. Should you push the man, and thereby kill one to save five?

Michael Sandel begins his famous course on Justice with this action scene, and it’s a great way to start such a course. This trolley problem, ingeniously introduced by Judith Jarvis Thomson and the late Philippa Foot, is a wonderful way to shock beginning students out of their ethical complacency. For nearly all people faced with this problem agree they would kill one to save five in the first situation but not the second. After hearing one case they think there’s an easy principle by which to decide the right action; after hearing the second, they are forced to admit that there isn’t. Continue reading →