[piasa]

Philosophers compare this problem to a second scenario, sometimes called the footbridge problem, in which a train is again heading toward five people, but there is no spur. Two bystanders are on a bridge above the tracks and the only way to save the five people is for one bystander to push the other in front of the train, killing the fallen bystander.

I can't figure out how dumping yet another person in front of a train would save any of them. Wouldn't that just kill 6 people instead of five? What about the folks on the train?

But let's assume the one you, the other bystander, would push could cause the train to derail and somehow save the others... it isn't right to toss someone else in to do the job when you can do it yourself. So their belief that the situations they propose are essentially the same is a bit of a stretch.

[Nebullis]

But let's assume the one you, the other bystander, would push could cause the train to derail and somehow save the others... it isn't right to toss someone else in to do the job when you can do it yourself.

That's why they use these kinds of problems. The numbers work out the same, but one situation feels wrong while the other doesn't.