The Hardest Logic Puzzle Ever is a logic puzzle by American philosopher and logician George Boolos and published in The Harvard Review of Philosophy in 1996.
Three gods A, B, and C are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions, which you must correctly come up with yourself ; each question must be put to exactly one god at a time. Each god knows the true nature of the other gods, and they understand English, but will answer all questions in their own language, in which the words for yes and no are da and ja, in some order. You do not know which word means which.
Boolos provides the following clarifications : a single god may be asked more than one question, questions are permitted to depend on the answers to earlier questions, and the nature of Random's response should be thought of as depending on the flip of a fair coin hidden in his brain: if the coin comes down heads, he speaks truly; if tails, falsely. Random's response of da or ja is random per question (ie. might not be consistently True or False throughout the 3 questions asked, which makes the puzzle slightly harder), and not per session (ie. will be consistently either True or False throughout the 3 questions asked, which makes the puzzle slightly easier).
See attached image for the Solution (the 3 required correct questions you need to ask are in quotation marks).