A prisoner is told "If you tell a lie we will hang you; if you tell the truth we will shoot you." What can he say to save himself?
Think you have it? The answer is below.
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Answer: He says: 'You will hang me.' (If true they must shoot him — making it false; if false they must hang him — making it true. The paradox saves him.)
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📖 The answer, explained
The trick here is that the prisoner turns the punishment into the very thing his statement predicts, so the guards can never enforce either rule without breaking it. Say "you will hang me" and check what happens: if it's true, the rule says liars get hanged and truth-tellers get shot, so a true statement demands he be shot — but shooting him makes the sentence false. Flip it around and the same knot appears from the other side. There's no stable outcome, no matter which punishment they pick, because the punishment itself decides whether the sentence was true or false, and each choice contradicts itself. It's less a clever lie than a self-devouring loop, a sentence that eats its own tail. The guards' rigid either/or system simply has no room for a statement that refers to its own consequence, so the whole trap jams.
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