Trolley Problem
The trolley problem is a moral machine in miniature: a rail yard thought experiment that forces us to ask whether doing harm by hand is worse than allowing the same harm to happen by rule.
Quick Facts
- Period
- 1967 – 1967
- Region
- Americas
- Key Figures
- Diana T. Meyers, Joshua Greene, Judith Jarvis Thomson +3 more
Key Figures
Diana T. Meyers
Critic/Interlocutor
Feminist philosophy and moral psychologyDiana T. Meyers is significant to the trolley problem less as a single-case author than as a philosopher who exposes wha...
Joshua Greene
Successor
Harvard psychology and moral neuroscienceJoshua Greene brought trolley cases out of the seminar room and into the laboratory. His work in moral psychology, espec...
Judith Jarvis Thomson
Developer
Harvard philosophy; analytic ethicsJudith Jarvis Thomson was not merely a philosopher of crisp distinctions; she was a philosopher who seemed almost anatom...
Francisco Romero (editorial oversight absent; not included)
Interlocutor
Francisco Romero was a figure whose name appears in records more often than in popular memory, a reminder that power can...
Peter Unger
Critic/Interlocutor
NYU philosophy; ethics and rationalityPeter Unger belongs to the trolley story not because he wrote the most famous switch-case variants, but because he helpe...
Philippa Foot
Originator
Oxford moral philosophy; virtue ethics and normative ethicsPhilippa Foot stands at the beginning of the trolley problem not because she was trying to invent a famous puzzle, but b...
The Story
This narrative combines documented history with dramatized scenes for storytelling purposes.
The World That Made It
By the time the trolley problem appeared in print, moral philosophy had already become suspicious of easy cases. The old classroom contrasts—duty versus consequ...
The Central Idea
Judith Jarvis Thomson’s great contribution was to give the puzzle its most enduring form. In her 1976 paper “Killing, Letting Die, and the Trolley Problem,” she...
The System
The trolley problem became philosophical capital because it could be made to work for, and against, several moral frameworks at once. Judith Jarvis Thomson’s or...
Tensions & Critiques
The most powerful objections to the trolley problem begin with its artificiality. Real moral life rarely arrives in the clean shape of a track diagram. The swit...
Legacy & Echoes
The trolley problem’s legacy is unusual because it escaped the philosophy journal and became a cultural instrument. It now appears in classrooms, ethics committ...
Timeline
Birth of Philippa Foot
**1920** — Philippa Foot was born in London, entering the philosophical world that would later produce the original pressure behind the trolley problem. Her later work would challenge the dominance of simple consequentialist reasoning in moral philosophy.
Foot publishes the double effect essay
**1967** — Philippa Foot published "The Problem of Abortion and the Doctrine of the Double Effect." The essay used cases involving rescue and unintended harm to probe the moral difference between killing and letting die, laying the groundwork for the trolley problem.
Thomson formulates the trolley problem
**1976** — Judith Jarvis Thomson published "Killing, Letting Die, and the Trolley Problem." She gave the runaway trolley scenario its canonical structure and made it a central test case in analytic ethics.
Thomson's rights-based discussion expands
**1985** — Thomson's later work on rights and permissions helped deepen the philosophical use of trolley-style cases. The problem became tied not only to outcome maximization but also to questions about what may be done to persons.
Trolley cases enter broader ethical pedagogy
**1990** — By the 1990s, trolley variants had become standard classroom tools in ethics courses. Philosophers used them to probe differences between action and omission, intention and foresight, and rights versus consequences.
Joshua Greene begins influential trolley research
**2001** — Joshua Greene and collaborators began a series of studies using trolley dilemmas to investigate moral judgment. These studies helped connect normative ethics with cognitive science and neuroscience.
Neuroimaging and dual-process discussion
**2004** — Greene's work on moral dilemmas and brain activity made trolley cases central to debates about the emotional and deliberative components of ethical judgment. The thought experiment now served as a bridge between philosophy and neuroscience.
Moral psychology critique intensifies
**2007** — Critics began arguing that trolley experiments were too artificial to ground strong conclusions about ethics. Debates over framing effects, cultural variation, and the limits of laboratory dilemmas became more prominent.
Autonomous vehicle ethics popularizes trolley analogies
**2013** — Public debate about self-driving cars revived trolley-like questions about programmed trade-offs. The problem was increasingly used to discuss machine ethics, emergency planning, and algorithmic decision-making.
Moral Tribes broadens the puzzle's public reach
**2014** — Joshua Greene's Moral Tribes brought trolley-style reasoning into a wide public debate about cooperation, conflict, and modern moral life. The case became a gateway into larger questions about pluralism and social coordination.
Death of Judith Jarvis Thomson
**2020** — Judith Jarvis Thomson died after reshaping the trolley problem into a lasting philosophical instrument. Her work continued to define how philosophers think about rights, rescue, and permissible harm.
Trolley problem remains a standard reference point
**2024** — In contemporary philosophy, cognitive science, and AI ethics, trolley-like cases remain a standard reference point for moral trade-offs. The problem persists because it still exposes the unresolved tensions between outcome, agency, and constraint.
Sources
- primary_textPhilippa Foot, "The Problem of Abortion and the Doctrine of the Double Effect"
Original 1967 essay that helped generate the trolley problem.
- primary_textJudith Jarvis Thomson, "Killing, Letting Die, and the Trolley Problem"
Canonical formulation of the trolley problem in analytic ethics.
- primary_textJudith Jarvis Thomson, The Realm of Rights
Key collection for Thomson's rights-based moral philosophy.
- encyclopedia_entryStanford Encyclopedia of Philosophy, "The Doctrine of Double Effect"
Useful scholarly overview of the background problem in moral philosophy.
- encyclopedia_entryStanford Encyclopedia of Philosophy, "Philippa Foot"
Authoritative account of Foot's ethical work and intellectual context.
- encyclopedia_entryStanford Encyclopedia of Philosophy, "Judith Jarvis Thomson"
Standard reference on Thomson's moral philosophy and trolley variants.
- scholarly_bookJoshua Greene, Moral Tribes: Emotion, Reason, and the Gap Between Us and Them
Influential account connecting trolley dilemmas to moral psychology and social conflict.
- scholarly_articleJoshua D. Greene et al., "An fMRI Investigation of Emotional Engagement in Moral Judgment"
Seminal neuroscience study using trolley-style dilemmas.
- scholarly_bookPeter Unger, Living High and Letting Die
Important critique of intuitive moral distinctions between doing and allowing.
- encyclopedia_entryInternet Encyclopedia of Philosophy, "Trolley Problem"
Clear scholarly overview of the problem, its variants, and major debates.
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