Trolley Problem
Trolley Dilemma
A thought experiment asking whether it is right to divert a runaway trolley onto a track where it will kill one person in order to save five — probing the tension between action and inaction in moral reasoning.
Origin
British philosopher Philippa Foot introduced the scenario in her 1967 paper "The Problem of Abortion and the Doctrine of Double Effect," using a runaway tram to explore when it is permissible to cause harm as a side effect of preventing a greater harm. American philosopher Judith Jarvis Thomson expanded the problem in 1985 with new variations — most famously the "fat man" version — that sharpened the moral stakes and turned the thought experiment into a staple of ethics courses worldwide.
Everyday Use
"Would you pull the lever?" has become shorthand for any agonizing moral trade-off. You'll hear it invoked in debates about self-driving car algorithms, public-health triage, and even workplace layoffs — anywhere someone must weigh one harm against a greater one.