Psychological/Decision
Unexpected Hanging Paradox
A judge says you'll be hanged on a day you don't expect
Overview
A paradox involving prediction and surprise that challenges our reasoning about knowledge and time.
A judge tells a prisoner he'll be hanged on a weekday, but it will be a surprise. The prisoner reasons: it can't be Friday (he'd know Thursday night), so it can't be Thursday (he'd know Wednesday night), etc. He concludes he won't be hanged. Then he's surprised when hanged on Wednesday.