The Trolley Problem Variations

The Trolley Problem

First posed by Philippa Foot (1967) and expanded by Judith Jarvis Thomson, the trolley problem is a thought experiment in ethics that asks: Is it morally permissible to divert a runaway trolley from killing five people by switching it to a track where it will kill one person?

Classic Variants

• Classic: Pull a lever to divert the trolley from 5 people to 1 person. Most people say "yes."
• Fat Man: Push a large person off a bridge to stop the trolley and save 5 people. Most people say "no."
• Loop: The side track loops back, so the 1 person stops the trolley from killing 5. Complicates means/ends.
• Transplant: Kill 1 healthy patient to harvest organs for 5 dying patients. Nearly everyone says "no."

Moral Theories

• Consequentialism/Utilitarianism: Maximize good outcomes. Always save 5 over 1 (pull lever, push person, harvest organs).
• Deontology: Respect moral rules and rights. Don't use people as mere means. Pulling lever may be okay (redirecting threat), but pushing person is not (using them).
• Virtue Ethics: What would a virtuous person do? Focus on character and practical wisdom rather than rules or outcomes alone.
• Doctrine of Double Effect: Harm as side effect may be permissible if you don't intend it. Distinguishes intended vs foreseen consequences.

Psychological Research

Studies show people's judgments depend on: Personal vs impersonal harm (pushing vs lever-pulling), action vs omission (doing vs allowing), means vs side effect (using someone vs collateral damage). Emotional responses (tracked by brain imaging) differ between personal and impersonal dilemmas.

Parameters in This Toy

• Survival Probability: Add uncertainty to outcomes. Expected value = (people) × (1 - survival prob).
• Utilitarian Weight: How much you weight total lives saved/lost.
• Deontological Constraint: Cost for actively causing harm (pulling lever). Higher values make action worse.
• Responsibility Factor: Multiplier on harm from action vs inaction. Models intuition that causing harm feels worse than allowing it.