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The islander who says "I am not a knight"

knights-and-knaveslogicnormals

On a certain island there are three kinds of people: knights, who always tell the truth; knaves, who always lie; and normals, who sometimes tell the truth and sometimes lie.

You meet an islander who says: "I am not a knight."

What is this islander? As follow-ups, decide who could say "I am a knight", who could say "I am a knave", and who could say "I am a normal".

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Test the sentence against each of the three types. A type can say a sentence only if doing so is consistent with that type's rule.

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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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