Interesting thought experiment from the philosophers Judith Jarvis Thompson and Philippa Foot:

1) Imagine you’re at the wheel of a trolley and the brakes have failed. You’re approaching a fork in the track at top speed. On the left side, five rail workers are fixing the track. On the right side, there is a single worker. If you do nothing, the trolley will bear left and kill the five workers. The only way to save five lives is to take the responsibility for changing the trolley’s path by hitting a switch. Then you will kill one worker. What would you do?

2) Now imagine that you are watching the runaway trolley from a footbridge. This time there is no fork in the track. Instead, five workers are on it, facing certain death. But you happen to be standing next to a big man. If you sneak up on him and push him off the footbridge, he will fall to his death. Because he is so big, he will stop the trolley. Do you willfully kill one man, or do you allow five people to die?

If you are like me, your answer on senario one is to flip the switch and save 5 lives at the expense of 1, and is the opposite on senario two. Despite the fact that logically, the answer should be the same for the second.