Entries in Raymond Smullyan (2)
Raymond Smullyan, 1919-2017
Raymond Smullyan was primarily a mathematician and logician, but he achieved a degree of fame in the chess world for his ingenious retrograde analysis puzzles. The idea is that one is given a position, and the task is not to figure out what to do next, but what must have happened for the current position to arise, for it to be legally possible. Ken Regan has a couple of recent posts on Smullyan on his blog, here and here. (They're not only about Smullyan, though, but the second one in particular presents a couple of retrograde problems from Smullyan's work, though the first is given with a small modification by Regan.)
Smullyan was a very entertaining writer, so if those retrograde analysis puzzles pique your interest I'd heartily recommend checking out or getting his books on the subject (here and here - but find a cheaper copy, obviously).
Raymond Smullyan, R.I.P.