Monday 7 September 2026

How it works

Every witness is either honest or a liar. An honest witness only says true things, and a liar only says false ones, like the knights and knaves in Raymond Smullyan's puzzles. Each of them makes one statement below. Your job is to mark every witness honest or liar so that all the statements hold up together. Exactly one way of doing that works, and you can reach it by reasoning alone: try a guess, follow what it forces, and drop it the moment two statements clash.

The statements

1. The LocksmithThe Postman is a liar.
2. The PostmanThe Locksmith and the Carpenter are different kinds.
3. The CarpenterThe Postman and the Librarian are different kinds.
4. The LibrarianThe Carpenter is honest.