At the Knights and Liars island, a logician wanted a sure fire method to know whether a native was a Knight or a Liar, but met with some problems.

First, he rashly tried simply asking "Are you a Knight?" or "Are you a Liar?", but he soon realized that this would never work. Also, there were some natives who didn't even know what they were!

Then, being logic-oriented, he started with complex combinations like "What would you answer if I asked you...?" but most persons lost interest and didn't even try to work out an answer.

Then, he changed to a simpler "Is this shirt red?" pointing at his own clothes, but that failed when he met a daltonic person.

A simple "Are you talking to me?" also failed; most thought the answer was "No" since they had been no conversation; the logician just popped up and asked his question.

Arithmetic was no good either: most natives had no use for it, and couldn't even calculate 1+1. (And they also couldn't read, by the way.)

At last, he came upon a question that could never be answered "YES" by a Knight, or "NO" by a Liar.

What simple question (up to three words is "simple"; four or more starts getting complex) could he ask?

Can you also think of some other seemingly good questions, and how they could fail?

..DO    KNIGHTS      LIE?

As a knight would always reply NO, and a liar would always reply NO.

 

-and unless you'll suddenly throw in the problem that people on this island are going to be completely deafmute, then I think this is unmistakably the right answer - I mean, if they can't even understand four words...

Posted by Cleo on 2007-08-05 11:51:26