A logical inference puzzle. One variety goes like this:

Some of the natives of a South Pacific island are pure-blooded and the rest are half-breeds, but they all look alike. The pure-blooded always tell the truth, but the half-breeds always lie. A visitor to the island, meeting three natives, asks them whether they are full-blooded or half-breeds. The first mumbles something inaudible. The second, points to the first and says, "He says that he is pure-blooded." The third, pointing to the second, says, "He lies." Knowing that only one is a half-breed, the visitor decides what each of the three are.

Here's a slightly different version of the same type of puzzle:

four men, one of whom was known to have committed a crime, made the following statements when questioned by the police:

Archie: Dave did it.

Dave: Tony did it.

Gus: I didn't do it.

Tony: Dave lied when he said I did it.

If only one of these four statements is true, who is guilty? On the other hand, if only one of these four statements is false, who is guilty?

Log in or registerto write something here or to contact authors.