"Another scintillating collection of brilliant problems and paradoxes by the most entertaining logician and set theorist who ever lived." -- Martin Gardner"Smullyan is not your run-of-the-mill puzzlemeister; he polishes up old chestnuts, spins variations on a theme, and peoples his logical world with a delightful cast of characters." -- Science 82"I believe Ray Smullyan to be the Lewis Carroll of our times. His little books of logic puzzles will be remembered long after most of us are forgotten." -- Peter Denning, Chairman of the Computer Science Department, Naval Postgraduate School"You may experience small frissons of delight as you follow Smullyan into the dizzying heights of Gödel's proof and the very nature of proof, truth, and logic in mathematics." -- Kirkus ReviewsDiscover scintillating new perspectives on the principles of mathematical logic with this puzzle treasury. Inspired by the classic tale of a prisoner's choice between two doors, these whimsically themed challenges allow readers to base their decisions on logic rather than luck. Nineteen chapters advance from relatively simple puzzles and meta-puzzles to highly complex paradoxes involving probability, time, and change. The author, a well-known philosopher and magician as well as a celebrated mathematician and logician, was acclaimed by The New York Times as "a master at translating difficult ideas into stories and puzzles that require no formal background, only patience and a passion to learn."