A trolley is careening toward an unsuspecting group of workers. You have the power to derail the trolley onto a track with just one worker. Do you do it? It might not matter.
"Suppose you're the driver of a trolley car, and your trolley car is hurtling down the track at 60 miles an hour. You notice five workers working on the track. You try to stop, but you can't, because your brakes don't work. You know that if you crash into these five workers, they will all die. You feel helpless until you notice that off to the side, there's a side track. And there's one worker on the side track."
The question: Do you send the trolley onto the side track, thus killing the one worker but sparing the five, or do you let events unfold as they will and allow the deaths of all five? (Most people, for what it's worth, say they would turn.)
Then Sandel asked about a popular variation on the same problem. The same trolley is careening toward unsuspecting innocents, but this time, you're an onlooker on a footbridge, and, "you notice that standing next to you, leaning over the bridge, is a very fat man."
A ripple of laughter rises from the packed auditorium.
"You could give him a shove," he continues. "He would fall over onto the track, right in the way of the trolley car. He would die, but he would spare the five. How many would push the fat man over the bridge?"
A few hands go up, but most of the students just erupt in giggles.
And that's exactly why, some scientists argue, this well-known "trolley dilemma," shouldn't be used for psychology experiments as much as it is.