Experiment #16 · Thought experiment

The Trolley Problem

Doing vs allowing, intending vs foreseeing

Philippa Foot (original); Judith Jarvis Thomson (modern variants) · 1967 / 1976 · Ethics, moral psychology

First published: P. Foot, "The Problem of Abortion and the Doctrine of the Double Effect" (1967); J. J. Thomson, "Killing, Letting Die, and the Trolley Problem", *The Monist* 59 (1976).

A runaway trolley will kill five; you can divert it onto a track where it will kill one. May you? Must you? And does pushing a man off a bridge to stop it change the answer?

In Foot's original case, the driver of a runaway trolley can steer it onto a side-track, killing one instead of five. Most respondents say diverting is permissible. Thomson varies the case: a bystander pushes a large man off a footbridge to stop the trolley by his body, again killing one to save five. Most now say no. The asymmetry between these otherwise outcome-identical cases is the central data point for modern deontology, for double-effect reasoning, and for moral psychology research on dual-process moral cognition. The case has expanded into an entire literature — loop variants, fat-villain variants, autonomous-vehicle adaptations.

Formulation

(Switch) Trolley → 5 workers; divert track → 1 worker. May you divert? (Footbridge) Trolley → 5 workers; push large bystander off bridge to stop trolley, killing him. May you? Standard responses: switch yes, footbridge no, despite identical 1-vs-5 trade-off.

Compare this experiment

Dimensions Engaged

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Observer

Engages Observer · Agency and Metaphysical Agency: what is the morally relevant difference between bringing about an outcome and merely permitting it, and between intending a death and foreseeing one?

Responses — How Schools Engage

Affirms / takes the bait 1

Catholic/Thomistic

The doctrine of double effect explains the asymmetry: in the switch case the one death is foreseen but not intended; in the footbridge case the death is the means. Intention is morally constitutive in a way consequentialists miss.

Denies / rejects the premise 1

Existentialism

The case forces a false dilemma: real moral life is not a series of stipulated trolley choices, and imagining oneself into them trains us in the wrong kind of moral reasoning — abstract, instrumentalised, shorn of context.

Reframes the question 3

Naturalism

Modern moral-psychology naturalism (Greene): the asymmetry reflects dual-process cognition — an emotional alarm at personal force versus a more utilitarian deliberative response. The case reveals how morality is implemented, not what is right.

Pragmatism

Both pure consequentialism and pure deontology mishandle the case; the right approach is contextual judgment informed by the social practices that shape our reactions. The thought experiment trains intuition, it does not adjudicate theory.

Phenomenology

The phenomenological difference between flipping a switch and pushing a person is itself morally significant; the asymmetry reflects the structure of agency-as-encountered, not a deontic distinction read from above.

Holds it inconclusive 1

Analytic Metaphysics / Logical Atomism

A canonical battleground: deontologists read the asymmetry as tracking real moral structure (doctrine of double effect; agent-relative constraints); consequentialists read it as moral illusion.