I am reminded of a commentary on logic puzzles of a certain kind; it was perhaps in a letter to Martin Gardner, reprinted in one of his books. The puzzles are those about getting about on an island where each native either always tells the truth or always lies. You reach a fork in the road, for example, and a native is standing there, and you want to learn from him, with one question, which way leads to the village. The “correct” question is “If I asked you if the left way led to the village, would you say yes?” But why should the native’s concept of lying conform to our own logical ideas? If the native is a liar, it means he wants to fool you, and your logical trickery will not work. The best you can do is say something like “Did you hear they are giving away free beer in the village today?” and see which way the native runs. You follow him, even if he says something like “Ugh, I hate beer!” since then he probably really is lying.

• Alexandre Borovik, quoting an unidentified colleague, paraphrasing another unidentified source, possibly Martin Gardner quoting a letter he got.