Three brothers—Arthur, Bernard, and Charles—live in a house with a single front door. One of them always lies, one always tells the truth, and one alternates. Arthur says, 'Charles always tells the truth.' Bernard says, 'Arthur is the alternating brother.' Charles says, 'Bernard always lies.' Who is the liar?
Charles
If Charles tells the truth, his statement that Bernard lies contradicts Arthur's claim that Charles tells the truth. Testing the truth values reveals Charles must be the liar.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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