Trolley Problem
The thought experiment, introduced by Philippa Foot and refined by Judith Jarvis Thomson, that asks whether one may divert a runaway trolley to save five people at the cost of killing one.
The trolley problem is a thought experiment introduced by Philippa Foot in a 1967 paper on the doctrine of double effect and developed extensively by Judith Jarvis Thomson in the 1970s and 1980s. The basic scenario: a runaway trolley is heading down a track where five people are tied. You can divert it onto a side track where only one person is tied. May you do so? Most people say yes. Thomson's variant: a fat man is on a footbridge above the tracks, and pushing him off would stop the trolley, killing him but saving the five. May you do that? Most people say no.
The puzzle is that consequentialist reasoning seems to recommend the same action in both cases — five lives for one — yet our intuitions diverge sharply. The trolley problem and its many variants have become a central tool of analytic moral philosophy, used to test theories about the doctrine of double effect, the moral significance of doing versus allowing, and the role of intention in evaluating action. Recent neuroscientific and experimental philosophy work has investigated the cognitive processes that produce the divergent intuitions.
The proliferation of trolley variants — the loop, the man in front of the trolley, the transplant case, the bystander vs the bridge — has been so extensive that some philosophers (Kamm, Thomson) have made careful taxonomy a research project in its own right. The variants test different intuitions about the doctrine of double effect, the moral significance of doing versus allowing, the role of intention, and the ethics of using a person as a means.
Recent experimental philosophy and moral psychology — Joshua Greene, Fiery Cushman — have used neuroimaging to investigate the cognitive processes underlying divergent intuitions. Greene's dual-process theory argues that deontological judgments in trolley cases are driven by emotional responses while consequentialist judgments are driven by deliberate reasoning. The conclusions drawn from this work are contested: some take it to undermine deontological intuitions; others argue the experimental findings are compatible with the considered judgments of careful moral philosophy.
How philosophers have framed trolley problem
| Philosopher | Position |
|---|---|
| Philippa Foot | Introduced the case to clarify the doctrine of double effect. |
| Judith Jarvis Thomson | Developed the variants extensively, emphasizing the moral significance of using a person as a means. |
| Frances Kamm | Refined taxonomy of trolley cases; defended a sophisticated deontological framework. |
| Joshua Greene | Dual-process: deontological judgments are emotional, consequentialist judgments deliberate. |
Representative quotes
-
Philippa Foot
-
“The whole of moral philosophy, as it is now widely taught, rests on a contrast between statements of fact and evaluations. … If a man is given good evidence for a factual conclusion he cannot just refuse to accept the conclusion on the ground that in his scheme of things this evidence is not evidence at all. With evaluations, however, it is different. An evaluation is not connected logically with the factual statements on which it is based.”
Wikiquote
-
-
Judith Jarvis Thomson
-
“Many women of my generation, in many fields, had good reason to be grateful to the women's colleges.”
Judith Jarvis Thomson, "How it Was" Proceedings and Addresses of the American Philosophical Association vol. 87, November 2013, pgs. 109-121
-