Lesson · 4 min Steady
The Trolley Problem
In one line When two cases with the same numbers pull your judgment apart, look for the difference that explains both.
A runaway trolley will kill five workers unless it is turned onto a side track, where it will kill one. Philippa Foot raised a version of this case in 1967, in a paper on the doctrine of double effect. Most people say turning it is allowed.
Judith Jarvis Thomson named the puzzle in 1976, and she and others added variants. In the best known, you stand on a footbridge and could stop the trolley only by pushing a large man into its path. The numbers are the same, one for five, yet most people say pushing is wrong.
The trolley problem asks why. Is the difference between redirecting a harm and using a person? Between harm you foresee and harm you intend? The point is to test which principle explains your judgments.
Go deeper
Later research asked many people about these cases. In 2001 the psychologist Joshua Greene and colleagues found that the footbridge case engages brain regions linked to emotion more than the switch case does, and argued that moral judgment runs on a fast emotional system and a slower calculating one.
Critics reply that knowing where a judgment comes from does not settle whether it is right. The philosophical question is still which difference, if any, justifies treating the cases apart.
Two ways to save a show
Jovan runs a small theater, and five actors will lose their jobs if the season fails. He can move the show to a cheaper hall, which costs one stagehand her job. Or he can leak a false rumor about the lead actor to draw curious crowds.
Both plans cost one person to save five. Jovan feels the first is hard but fair and the second is wrong, and he finds the difference: the second uses the actor as a means to sell tickets.
Try this today Take two cases you judge differently and write down the one difference that explains why.
Cite or share this lesson
A plain reference you can paste into notes or an essay:
Quest2Reason. “The Trolley Problem.” https://quest2reason.com/learn/lesson/the-trolley-problem. Accessed 13 November 2026.
Sources
- “Trolley problem,” Wikipedia — Foot’s 1967 case, Thomson’s naming of the problem in 1976, the footbridge variant and Greene’s brain-imaging studies.
- Judith Jarvis Thomson, “The Trolley Problem,” Yale Law Journal 94(6) (1985) — Thomson’s fullest treatment of the cases and the search for the principle behind them.
- “Doctrine of Double Effect,” Stanford Encyclopedia of Philosophy — The distinction between intended and merely foreseen harm that many use to explain the cases.
- Philippa Foot, “The Problem of Abortion and the Doctrine of the Double Effect,” Oxford Review 5 (1967) — The paper where the runaway trolley case first appears.