On Smullyan's island live knights, who always tell the truth, and knaves, who always lie. Knights and knaves cannot be told apart by their looks.
In each problem you have to work out, when possible, which of the speakers is a knight and which is a knave.
Can an inhabitant of the island say “I am a knave”?
No, because a knight says he is a knight; but a knave too, when asked what he is, will lie and say he is a knight.
