The Thought Experiment Library

Robert Nozick's challenge to hedonism: if a machine could give you any experience you desired, would you plug in? Most people say no — suggesting we value something beyond mere experience.

Given enough time, a monkey hitting keys at random on a typewriter will almost surely type any given text — including the complete works of Shakespeare. A lesson in probability, infinity, and the difference between possible and probable.

Imagine a being physically identical to you in every way — same brain, same behaviour — but with no conscious experience at all. If such a being is conceivable, what does that tell us about the nature of consciousness?

John Rawls asks: what principles of justice would you choose if you did not know your place in society — your race, wealth, intelligence, or talents? The answer, he argues, is fairness.

A contemporary version of Descartes' demon: if your brain were in a vat being fed artificial signals, how could you know? The scenario sharpens foundational questions about knowledge, reference, and the limits of radical skepticism.

John Searle's 1980 thought experiment argues that a system manipulating symbols according to rules cannot be said to understand or have genuine intelligence, however convincingly it mimics comprehension.

In 1867, James Clerk Maxwell imagined a tiny creature that could sort fast and slow molecules, seemingly violating the second law of thermodynamics — a puzzle that took a century to resolve and transformed our understanding of information, entropy, and the physical basis of knowledge.

If every plank of Theseus' ship is gradually replaced, is it still the same ship? The oldest thought experiment in the Western tradition poses questions about identity, persistence, and what it means for anything — a ship, a person, an institution — to remain itself through change.

First articulated by Philippa Foot in 1967 and extended by Judith Jarvis Thomson, the trolley problem forces a choice between killing one person to save five, exposing deep tensions in moral theory.