Alice in Puzzle-Land: Who Really Stole the Sugar?
The sugar has gone missing, and it was either the Duchess or the Cook — no one else. Everyone agrees on one house rule: whoever stole the sugar is certain to lie about it afterward. The Cook says, 'The Duchess stole it.' The Duchess says, 'The Cook did not steal it.' Exactly one of them is the thief. Which one?
Reveal the answer
The Cook did it. Suppose instead the Duchess were the thief: her statement ('the Cook did not steal it') would have to be a lie, which would mean the Cook stole it too — impossible, since only one of them took it. That contradiction rules the Duchess out. The Cook as thief fits perfectly: her lie ('the Duchess stole it') is exactly false, as it should be. From Raymond Smullyan's 1982 book Alice in Puzzle-Land, which turns Wonderland's cast into knights-and-knaves-style logicians.
— Raymond Smullyan, Alice in Puzzle-Land: A Carrollian Tale for Children Under Eighty — William Morrow, 1982
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