Lost in the woods, you finally happen upon a rickety old bridge across a deep ravine. The ravine is too steep to go down and climb back up. You need to know if the bridge is safe. As 'luck' would have it, you recognize that on the other side of the bridge is that dreadful town, "Knight-and-Liarville". Everyone who lives there is a knight (who always tells the truth) or a liar (who always lies). You are tired and you've been lost in Knight-and-Liarville before. You see three men on the other side of the bridge.

You shout out: "Are you a knight?"

The first man says something, but you can't hear what he said.

The second man shouts, "He said he was a knight."

The third man shouts, "No, he didn't. He said he was a liar."

Which man do you ask to find out whether or not the bridge is safe?

(In reply to maybe... by logischer Verstand)

First of all, your interpretation is wrong.  There is nothing to suggest that only one man is a knight, or even that there is only one correct person to ask.  Even with your interpretation, there could be other people who might be knights, but you are not sure of it. 

Also, the second man does not claim that the first is a knight, nor does the third man claim the first is a liar.  Read more carefully.

Some people might argue that you could ask a liar and derive the truth from his lie.  IMHO, though, in the world of real, there is more than just "yes" and "no"...  A liar can say, "I don't know," if he knows, but a knight can't.  And if the liar doesn't know, he's more likely to throw you off.

Posted by Tristan on 2004-03-26 17:09:49