In Smullyan's "Logical Labyrinths" there is the following problem 1.11:
(INTRODUCING THE NELSON GOODMAN PRINCIPLE). Suppose that you visit the Island of Knights and Knaves because you have heard a rumor that there is gold buried there. You meet a native and you wish to find out from him whether there really is gold there, but you don't know whether he is a knight or a knave. You are allowed to ask him only one question answerable by 'yes' or 'no'. What question would you ask? (The answer involves an important principle discovered by the philosopher Nelson Goodman.)
I'm somewhat stuck on the problem. I looked into Goodman's work and his work on the "Problem of Induction" which seems to be somewhat related to this puzzle while about induction and not deduction.
The premises are, that knights always tell the truth and knaves always lie.
Is the "Problem of Induction" the right place to look for a solution? Thank you.