Thinkers & Big Questions
The philosophers worth knowing and what they actually argued.
Which philosopher wrote "I think, therefore I am"?
Philosophy often argues through invented situations. These ten are the ones that escaped the seminar room.
A thought experiment is a way of isolating a question that real life keeps contaminating. You cannot run a controlled trial on personal identity, so you imagine a ship whose planks are replaced one at a time and see which intuitions survive. You cannot ask people to design a society without self-interest, so you imagine them choosing the rules without knowing who they will be in it. The famous ones are often remembered wrongly. The trolley problem was invented as a footnote in an argument about abortion, not as a puzzle about driverless cars. Schrodinger's cat was proposed as a criticism of a view its author found absurd, and is now quoted as though he endorsed it. These questions cover what each case was actually built to test.
Every question in this quiz is listed below with its correct answer and the reasoning behind it. Play first if you would rather not see the answers — or read through as a study sheet.
Play it insteadAnswer: D. Divert a runaway vehicle so it kills one person instead of five
Why: Philippa Foot introduced it in 1967 inside an argument about abortion and the doctrine of double effect. Most of its later fame came from variants that change only who does the killing.
Answer: C. Every one of its parts has been replaced
Why: Plutarch recorded the puzzle as an argument among Athenians. Hobbes sharpened it by asking what happens if the discarded planks are reassembled into a second ship.
Answer: B. Shadows cast on a wall
Why: The escaped prisoner's painful adjustment to daylight stands for education. His return is met with ridicule, which Plato clearly meant as a comment on Socrates.
Answer: A. Your own position within it
Why: He argued that rational people choosing blind would protect the worst-off position. He set it out in A Theory of Justice in 1971.
Answer: D. That running the right program is enough to produce understanding
Why: Searle published it in 1980, imagining himself shuffling symbols by rulebook without knowing the language. A standard reply is that understanding belongs to the whole system, not the person inside it.
Answer: C. Whether any belief survives total doubt
Why: The exercise is what drives him to the one thing he thinks cannot be faked, his own thinking. A twentieth-century version replaces the demon with a brain kept alive in a vat.
Answer: B. That a quantum description looks absurd when scaled up to everyday objects
Why: He wrote it in 1935 as a criticism, in correspondence with Einstein. It is now routinely quoted as though he was endorsing the picture rather than mocking it.
Answer: A. That you must live the same life over again without end
Why: He presents it as a test of how far a person affirms their own life. He does not argue for it as a physical claim about the universe.
Answer: D. The one requiring the fewest assumptions
Why: William of Ockham was a fourteenth-century English friar. The principle is a rule for choosing between competing theories, not evidence that the simpler one is true.
Answer: C. A lifetime of pleasant simulated experience instead of real life
Why: He observed that most people refuse, and took that as evidence against pleasure being the only thing that matters. The case is now standard in arguments about hedonism.
Thought Experiments and What They Show has 10 questions and takes about 7 minutes to finish. It is rated Medium and sits in our Philosophy & Ideas category.
Each of the 10 correct answers adds 10 XP, up to 100 XP for a clean run. Wrong answers cost you nothing, and your full question-by-question review is shown at the end.
Yes. All 10 questions carry a written explanation of why the correct answer is right, so the quiz works as a study sheet as well as a test.
Yes, as often as you like. The questions and the answer options are reshuffled on each run, and you can use Practice Mistakes afterwards to retry only the ones you missed. No account is needed to play.
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The philosophers worth knowing and what they actually argued.
Which philosopher wrote "I think, therefore I am"?
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