Imagine the following scenario:
A trolley has lost control of its brakes, and the driver has no way of
stopping the train as it hurtles down the tracks on a very steep hill. A bit farther down the hill, you are standing and watching the episode unfold. You notice that a little farther down from where you are standing, five workmen stand on the tracks. The trolley is headed right for them. If something is not done, these five men will surely die.
Right next to you, you notice there is a lever that will make the trolley move onto another track. However, upon looking at this second track, you see that there is one person on it. If you switch the direction of the trolley, the five workers from the first track will survive; however, the one person on the second track will die. What do you do?
Now imagine this scenario:
You are standing on a bridge and watch as a trolley loses control and hurtles down the hill. At the end of the tracks are the five workmen who are bound to die. This time, there is no lever to move the trolley to another track. The trolley will be passing under the bridge that you are standing on, though, and you know that dropping a heavy weight in front of the trolley will make it stop. You happen to be standing next to a very fat man and realize that the only way to stop the trolley from killing the five workmen is by pushing the fat man over the bridge and onto the track, which, as a result, will kill the fat man. What do you do?
The trolley problem, which continues to be a source of debate to this day, was first introduced in 1967 by British philosopher Philippa Foot and was later expanded upon by American philosopher Judith Jarvis Thomson.