Timothy goes to the island of knights and liars searching for gold. On the way,he meets a native.

What one question could Timothy ask the native to find out if there is gold on the island?

(In reply to A Different Solution by Lewis)

The question "Would a knight say that you would say there was gold on this island?" is no different from saying "Is there gold on this island?". That is, if there is no gold on the island, a knight would say "no", but a liar would lie about what the knight would say and therefore would say "yes". If there was gold on the island a knight would say "yes" but the liar would lie about what the knight would say and say "no". Of course a knight would tell the truth about what a knight would say, and since you don't know if the native is a knight or a liar, you don't know whether there's gold on the island.

A better version of this type would be "Would the opposite kind of person say that there's gold on this island?" Then if you get a yes then there is no gold on the island and if you get a no then there is gold on the island, as there would always be one level of untruth in the path of answers.

Posted by Charlie on 2003-05-29 16:36:34