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At least one of us is a knave

knights-and-knaveslogic

On an island every inhabitant is a knight (always truthful) or a knave (always lying). You meet two of them, A and B.

A says: "At least one of us is a knave." B says nothing.

What are A and B?

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Try assuming A is a knave and see what his statement would then have to be.

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The theory behind this question.

Cheryl's Birthday and Iterated KnowledgeLogic and QuantifiersOne Question, Two Guards, One DoorProof Techniques: Direct, Contrapositive, ContradictionAdaptive Versus Pre-Committed Weighing Strategies

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