Discuss the question below:
Suppose you were in a country where each person was either a truth teller or a liar. (A truth teller always tells the truth, a liar always lies.) What single question could you ask a person that would allow you to detect whether that person was a truth teller or a liar?
Suppose that the truth-teller is named A and the liar is named B. You would say to A: If I asked B if you always told the truth, what would he say?
Let us consider the two possible situations.
A is the liar
B is the ...
This solution provides a clear solution, with explanation, of the truth-teller problem.