Here are three moral dilemmas, you have to read them and think about them in order:
1. A train is running at high speed when its brakes fail. The conductor sees five hikers ahead of him on the tracks who will surely be killed by the train if it reaches them. The conductor notices that the track is about the fork, and there is a single hiker on the side track. The conductor can either do nothing, in which case the train will continue on its path and kill the five hikers, or he can throw a switch that will send the train along the side track, killing the one hiker there. Is it morally permissible for the conductor to throw the switch and send the train onto the side track?
2. A train is running at high speed when its brakes fail. A man who is standing on bridge notices five hikers on the tracks ahead who will surely be killed by the train if it reaches them. However, there is a woman standing next to him on the bridge. If he pushes the woman off the bridge onto the tracks, the train will kill her, but the force of the impact will stop the train's progress and the five hikers will be spared (pretend there is no uncertainty as to the outcome). Is it morally permissible for the man to push the woman onto the tracks?
3. Five accident victims arrive at a hospital emergency room, all of them needing transplants of different organs to survive the night. There are no organs available at the hospital. Meanwhile, a healthy young man walks into the emergency room to ask for directions. Is it morally permissible for the doctor to kidnap the young man, kill him, and harvest his organs so that the other five patients can be saved (again, pretend there is no uncertainty as to the outcome)?
Apparently, the most common reaction is to say yes, unambiguously to #1, then to say no, but be slightly uncomfortable with that for #2, and then to say no unambiguously to #3.
However, some people say yes, unambiguously to #1, and then yes, unambiguously to #2, since they figure that the reasoning is the same in both cases: clearly, the action that should be taken is the one saves the most people. But then when they get to #3, they hem and haw and get flustered- obviously, it's not OK to kidnap people and harvest their organs, even though that would save the most people. So they give #3 a very uncomfortable no.
I confess to being in the second group. It seems like #1 and #2 absolutely have to be yes, and #3 has to be no. But I can't think of a good reason why #2 is has to be a yes and #3 has to be a no (can you?) In fact, I think it would be easier to convince me that #3 is a yes than it would of the more widely held view that #2 is a no.
One thing I take away from this exercise is that the more and more you sit down and think about it, the less and less it makes sense to try to tell anyone else what they "should" think is right or wrong.
This is all from Marc Hauser's book Moral Minds.