Is anybody a Raymond Smullyan fan? Mathematician, logician, philosopher, who has written many puzzle books. I just finished (except a few appendix problems) The Chess Mysteries of the Arabian Nights. If you like chess and you’ve never seen an example of his “retrograde” chess problems, you have to check them out!
3 Likes
I’ve read his Chess Mysteries of Sherlock Holmes. Good stuff!
2 Likes
Yep, I’ve got that one too 
1 Like
What makes a chess puzzle “retrograde”?
2 Likes
In a normal chess problem you look at the board and figure out how to win in the next move, or the next N moves.
In a retrograde chess problem you look at the board and figure out what the previous moves were. Has the rook ever moved? Has the king ever been in check? Which piece captured the queen? Is that knight an original knight or a promoted knight? Questions like that.
I find them absolutely impenetrable.
5 Likes
I’m currently reading “All Tomorrows” by C.M. Kosemen, and it’s an incredible yet unsettling experience.
The book explores the future of humanity over millions of years, focusing on how alien interventions push human evolution into bizarre and often terrifying directions. The transformations and adaptations are so vividly described that they keep me on edge, blending excitement with a sense of anxiety.
To make it even better, the author plans to release a paper version with additional content.
3 Likes
Finished two books while on holiday:
-
Don Winslow: Broken
At first I thought this was a collection of short novellas (±60 pages), but as I read on I realised that although there isn’t a unifying plot, all the stories share a setting (San Diego along the 101 Pacific Highway), and a pool of characters. The protagonist of one story may be a secondary character in the next, and along the way the reader gets a good grasp of the relations between these various characters.
Short, almost brutally terse prose. The author hits the notes and signals the changes, but the reader’s mind has to fill in all the decorative stuff.
(Don Winslow - Wikipedia) -
Vera Buck: Runa
Getting through the first seventy pages is an assault on the stomach, and rightly so. Some things need to be pressed upon generation after generation’s memories. The author is intent on making it crystal-clear what kinds of horror and contempt women were made to endure when they had the gruesome misfortune of being admitted to a mental hospital in the late 19th century.
This sets the stage for a thriller about a girl lost in the bowels of Paris, a student of neurology under Jean-Martin Charcot at the Hôpital de la Salpêtrière, and a series of alchemical experiments in the catacombs under the city.
Gripping, fascinating, touching, even though I had to read parts of it between my spread fingers.
(Pitié-Salpêtrière Hospital - Wikipedia)
( Jean-Martin Charcot - Wikipedia)
( Runa (Roman) – Wikipedia ; German)
2 Likes
@Mewtamer sorry I didn’t see your question until just now!
Here’s a “simple” but still pleasing example.
Given the positions:
White bishop on a4.
Black rook on b5.
Black bishop on d5.
Black king on d1.
Is it possible for the white king to be standing legally on any square of the board? Of course we’re not looking for just “yes” or “no”, but a comprehensive case for why it is the one or the other.
Please spoiler your comments in case other folks are interested in working it out!
No, the white king can’t stand on b7 because that field is threatened both by the rook and the bishop. There is no potential move that can have caused that positioning without the white king being threatened before. And that’s against the chess rules.
3 Likes
Huh? I don’t get it.
Sure, there’s lots of them.
1 Like
This confused me too, but I think “any square” in the question actually means “every potential unoccupied square” – like, the prompt is asking whether it’s possible to place the king to create a board position that couldn’t possibly exist in real life? Peter has an answer in the post above yours.
EDIT: and as along as I’m posting in the thread, I’m currently 2/3 of the way into A.S. Byatt’s last collection of short fiction, Medusa’s Ankles. I love her novels but have never gotten deep into her short stories, but there are some real gems here – lots of magical realism, engagement with art and literary criticism, and diamond-sharp prose.
5 Likes
More precisely, a board position which could not have been reached in a valid game. Thus Peter’s answer, which is reasoning about the previous two moves that led up to a given position.
4 Likes
Ok, that makes more sense. We can see the black king is in check, so we can deduce white made the last move. Therefore any space threatened by the black king, rook, or bishop is off limits for the white king as it would mean either the white king moved into check or the white bishop moved and revealed a check on the white king, both of which would be illegal. It’s actually impossible for the white bishop to have moved last turn as there’s only two spaces it could’ve moved from, and both would have already had the black king in check. So the last move had to be the white king, but there’s no legal way the white king could have revealed the check on the black king, so there is no valid place at all to put the king. Answer: No.
2 Likes
Actually, looking at this some more, I take it back - the original understanding of “any” is right, I think.
And the answer is no, there’s no way to make this a valid board configuration - I’m on my phone now so can’t type up the full response but might edit that in later.
EDIT:the black king is currently in check, so the only way black could have had the previous move is if the white king were placed in such a way as to make d1 a safe square. b3 would block the bishop and make d1 safe, but then the white king would have been in check by the rook, so that’s not a valid position. c2 would also block the bishop, but similarly threaten d1, so that doesn’t work either. As a result, it’s impossible for black to have made the previous move.
But this same logic means that white couldn’t have made the previous move, either – white’s move would have had to put the black king in check, but there’s no place the bishop could have come from to accomplish that since the rook would have been blocking its movement from the top of the board, and the white squares to its lower-right would have already threatened the black king. So once again the only possibility is if the white king had been blocking the bishop’s angle of attack, and then moved out of the way to initiate the check. But the white king itself would have been in check if it had been in b3 or c2, so there’s no way to make that work either.
4 Likes
Btw I’m currently reading one of M. C. Beaton’s “Agatha Raisin” criminal novels. And it’s fun. It might not be high literature. But it isn’t pulp fiction either.
@Mike_G , @DeusIrae , @Pebblerubble, and @zarf, I wonder how much imaginary money you’d be willing to put on it that the answer is “no”? 
And to clarify, the question wants to know if the given position (plus a potential white king) could have been reached in a legal game.
2 Likes
I mean, very little, since I know I’m pretty bad at chess! Your comment seems to imply that the answer is yes, though I’m having a hard time finding a hole in the logic for why the answer is no… maybe the answer is there has to have been another piece on the board, which got taken in the previous turn, and that’s why the analysis doesn’t work? But I’m having a hard time seeing how that would change things, and I don’t see how pawn promotion or en passant would apply, which are the other things-just-got-weird rules I’m aware of. So yeah, curious about what actually-good-at-chess people would come up with.
2 Likes
I told you that I find these problems impenetrable!
3 Likes
I know you did, I just tagged you because you were part of the conversation… in fact it wasn’t a personal challenge to any of you, it was a silly little experiment because of this problem in particular, Raymond Smullyan wrote “It is amazing how many people will swear by the validity of this argument!” (The argument that the king can’t possibly be legally anywhere on the board.)
In full disclosure the original problem asks where the white king stands, and Smullyan’s audience would frequently swear there was no place for it.
2 Likes
You keep changing the question, don’t you?
And for the question if there’s ANY possible position: It can’t be white’s turn because then the white bishop could beat the black king, but that never happens in chess. And the white king can’t be placed between the white bishop and the black king. And it can’t be black’s turn because the white bishop can’t be moved where it is without threatening the black king earlier.
I would bet a lot of money, say 100 Euro.
Edit: Could the retrograte chess puzzle be split from the book thread?
1 Like