Question to determine if a cannibal always lies or always tells the truth

[Mr Davis 97]

Homework Statement

An explorer is captured by a group of cannibals. There are two types of cannibals--those who always tell the truth and those who always lie. The cannibals will barbecue the explore unless he can determine whether a particular cannibal always lies or always tells the truth. He is allowed to ask the cannibal exactly one question. Find a question that the explorer can use to determine whether the cannibal always lies or always tells the truth.

Homework Equations

The Attempt at a Solution

I am not sure where to start. Is there a systematic way to formulate the appropriate question with propositional logic and truth tables, or must one just have divine inspiration?

 

[PeroK]

You could always ask the cannibal whether he is a dolphin. If he says he is a dolphin then he's a liar.

But, I guess that's not the sort of question you are expected to find?

 

[member 587159]

You could always ask the cannibal whether he is a dolphin. If he says he is a dolphin then he's a liar.

But, I guess that's not the sort of question you are expected to find?

I actually laughed on that one, but it's a correct answer.