An American tourist went sightseeing on the Greek island of Crete and met a young man  The young man said to the American, Don't trust the Crete, everything they say is a lie  I know this best because I am a Crete   The American said to the young man, I can't believe you
Since the Crete doesn't tell the truth, why should I believe that you are not lying
This is self-contradictory, for not believing what a young man says is due to believing what he says