The trolley problem was never really about trolleys.
Philippa Foot introduced it in 1967: a runaway tram will kill five people unless you divert it onto a track where it will kill one. Most people say pull the lever. Change it so you must push someone off a bridge instead, and most refuse. Why does the difference matter?
The British philosopher Philippa Foot introduced a version of the trolley problem in a 1967 paper on the ethics of abortion and the 'doctrine of double effect'. A driver of a runaway tram can steer onto a side track, killing one worker instead of five. Most people feel it is permissible, even required, to steer.
The American philosopher Judith Jarvis Thomson developed the puzzle in the 1970s and 80s and gave it its name. In her 'footbridge' variant, you stand on a bridge above the track next to a large stranger. Pushing him off would stop the tram and save the five, at the cost of his life. The arithmetic is the same, one life for five, yet most people say pushing him would be wrong.
Philosophers have spent decades trying to explain the gap. One idea is the difference between killing someone as a means to an end, using his body to stop the tram, and killing as a foreseen side effect of diverting a threat. Another is the difference between doing harm and allowing it. Psychologists have found that the footbridge case triggers stronger emotional responses, and people's answers vary across cultures.
The problem has gained new urgency with self-driving cars. MIT's 'Moral Machine' experiment collected tens of millions of decisions from people around the world on how an autonomous vehicle should choose between lives. Real engineering rarely looks like the thought experiment, but the question it isolates, whether outcomes are all that matter, sits beneath many hard decisions.
Source: Wikipedia — Trolley problem · Text summarised from Wikipedia (CC BY-SA 4.0)
