Knights always tell the truth,liars always lie,and knaves alternate between truths and lies.

Two people named Jimmy and Johnny make the following claims.

Jimmy:I am a knave.
Johnny:Jimmy is not a knight.
Jimmy:Johnny is a knave.
Johnny:Jimmy is a knave.

What are each?

Jimmy says 'I am a knave', so he is either a liar or a knave telling the truth, which would make his other statement false.

Johnny says that Jimmy is not a knight, which is true, so he is either a knave or a knight. If he is a knave his other statement would also be false.

Seeing as they both claim each other are knaves, if they were knaves that would be the lying statement, but thats a contradiction.

This means that Johnny is a knight and Jimmy is a knave who's first statement was true.

Posted by Lewis on 2003-07-07 05:15:57