“Suppose that there is a trolley that is headed toward five people tied to the tracks ahead. There is no switch, but there is a bridge with you and someone else on it. But in this case, this is no wimpy trolley; a mere man in its way will not significantly affect its movement; it will easily crush flesh and bone. However, in this case, both you and the other person are in cars on the bridge. You know that a car is enough to stop the trolley, and you would like to drive yours off the bridge and stop the trolley, but the other car is in the way of you doing that, so you cannot simply drive off the bridge. You can, however, use your car to ram the other car, which will knock it off the bridge and onto the tracks, and thus stop the trolley from running over the five people. For stopping the trolley, it makes no difference whether someone is in the car or not; it is the car, and the car by itself, that will stop the trolley. But the other person is in the other car and will die if you push his car off the bridge, but you must act immediately, or the trolley will be past the bridge, so you do not have time to talk with the other driver or pull him out of his car; you either ram his car immediately, knocking it in the way of the trolley, or the trolley goes by and kills the five people. What should you do?
Just in case these details matter to you, I will now provide three variants:
1. If the car is knocked off the bridge, the car lands on the tracks, and when the trolley hits the car, the man in it dies.
2. If the car is knocked off the bridge, the man dies on impact with the tracks, so he is dead before the trolley hits the car.
3. The car is a convertible, and if the car is knocked off the bridge, the man will fall out of the car to the side of the tracks, but onto some rocks, which will kill him, but not immediately, so that he will still be alive at the time that the trolley comes to a complete stop from hitting his car, and then he dies within a minute, without being able to speak or do anything.”
The idea of these examples is to deal with people that think that the practical imperative shows why we think that which we think (or that which most people’s intuitions are). Clearly, if that was the case, then it would be permissible to push the car off the bridge because one does not use the man as a means to end end, he just happens to be in the car that we use. But still, most people’s intuitions disagree with this. Thus, the practical imperative does not explain (or is the cause of) our intuitions.