I first heard about “the trolley problem” as an undergraduate philosophy student in 1991, as one of the countless thought-experiments moral philosophy uses to probe our intuitions regarding right and wrong, and whether we are consistent in our judgements of what is right/wrong. The problem, for those of you who don’t know it, is presented by its creator (Philippa Foot) as follows:
Suppose that a judge or magistrate is faced with rioters demanding that a culprit be found guilty for a certain crime and threatening otherwise to take their own bloody revenge on a particular section of the community. The real culprit being unknown, the judge sees himself as able to prevent the bloodshed only by framing some innocent person and having him executed.
Beside this example is placed another in which a pilot whose aeroplane is about to crash is deciding whether to steer from a more to a less inhabited area. To make the parallel as close as possible it may rather be supposed that he is the driver of a runaway tram which he can only steer from one narrow track on to another; five men are working on one track and one man on the other; anyone on the track he enters is bound to be killed. In the case of the riots the mob have five hostages, so that in both examples the exchange is supposed to be one man’s life for the lives of five.