A Doctor and a Lawyer

A Doctor and a lawyer are being interviewed. "I am a Doctor", says the man. "I am a Lawyer", says the woman. Assume that at least one of them is lying. Which one is it?

Answer:

Both of them are liars! If the woman was lying, then there would be two doctors. If the man was lying, there would be two lawyers. We are told that one is a Doctor and one a lawyer and that at least one of them is lying. Therefore, both are lying.