There were once three friends. Abe is a Knight, Bill is a Liar, and Carl is neither, having been brought up in a foreign country. (This means he can either lie or tell the truth depending on what he feels like.)
One day, the three were sitting on a bench when the king's herald stopped by to deliver a message to one of them.
He asked the man sitting on the left side of the bench:
"Who's that sitting in the middle? To which the man replied: "Why that's Abe".
He then asked the man in the middle directly:
"What's your name?" and got the answer "My name's Carl."
Confused, he asked the man on the right:
"Who is that sitting in the middle?" and was immediately told: "That's Bill, of course!"
Can you help the king's herald figure out who is who?
(In reply to Answer
by K Sengupta)
At the outset, we know that Abe is a Knight and if he was the man on the left he would have truly identified himself. Since, the actions of the man on the left was otherwise, it follows that he was not Abe.
The man on the middle couldn't have been Abe, since as a Knight Abe would never proclaim himself as Carl. Therefore, the man on the right must be Abe, and accordingly, in terms of his true statement, it follows that the man on the middle must be Bill.
Consequently, the man on the left must be the remaining individual, that is, Carl.