Tuesday, March 06, 2007

221b




This Thursday the Streatham & Brixton second team are heading off to play Metropolitan 3. Hopefully we'll get revenge for our recent loss to their second team.

Metropolitan’s venue, just off Middlesex Street in East London, is an interesting location for students of criminology. Modern geographical profiling techniques suggest Jack the Ripper may have lived (or at least had a base to which he could return) in that very road. The juxtaposition of chess, the ultimate impenetrable game, and a location associated with the definitive unsolvable murder mystery seems very appropriate somehow.

Fictional detectives are often portrayed as having a keen interest in chess. I’m not sure why exactly. Perhaps it’s seen as a shorthand way of implying a logical or analytical mind.

The trouble is chess and crime detection are direct opposites. Chess is a puzzle that moves forward. The question a player asks is, ‘If I do this … he does that … then I do the other … where do we end up?’ Crime analysis, on the other hand, works in reverse. Instead of, ‘where are we going?’ the mystery to be unravelled becomes, ‘how did we get here?’

Years ago I found Raymond Smullyan’s “The Chess Mysteries of Sherlock Holmes” in some second hand book shop or other. It’s a collection of problems that require retrograde analysis to find the solution. Retrograde analysis is simply the art of working backwards on the chessboard – and thus Smullyan’s book is unique (as far as I know) in creating a true parallel between our game and amateur sleuthing.

The position at the top of this blog entry is pinched from the early pages of Smullyan’s book. The question is simple –

On what square was the White Queen captured?

You’ll need to provide proof of course. This is crime scene analysis after all.

If you need a hint, Holmes advises, “One of the main things in solving these problems is to think of the right questions to ask oneself.”

Find the right questions and I think you’ll find the answer elementary …

11 comments:

Anonymous said...

The question is: in what order did the three pawns make their captures?
(Martin)

Jonathan B said...

Yes, looking at it that way would certainly lead you to the answer...

Tom Chivers said...

Got it, I'm pretty sure. I emailed you the answer Jonathan.

Wahrheit said...

I'm sure I'm missing some subtle joke here, but...where are the White Bishops? I guess I'm no Holmes! :)

Jonathan B said...

warheit - the absence of the white Bishops is a strong clue! They are, if you like, dogs that didn't bark in the night.

Jonathan B said...

Yes, you are correct Tom. Although without supporting evidence it could have been a guess...? ;-)

Tom Chivers said...

Wahrheit - they must have been taken on their initial square by a black knight, that then escaped back to his own half.

Jonathan - actually how I worked it out is kind of funny. I don't have much patience for this kind of puzzle, and I was writing an email to you along the lines of 'I know full well a, b, and c must have happened, but I really can't be arsed to spend the time to work out how they lead to z.' Then I reread what I wrote, and realised my a, b, and c spelt out *exactly* z.

I won't spoil the puzzle for others though. If you don't believe I worked it out logically, I can email you the logic.

Let me know :D

Jonathan B said...

I believe you ... Honest Tom!

Wahrheit said...

Of course--I'm so thick. I was thinking in terms of logical game moves. With your kind reminder here, I think I've got it.

Jonathan B said...

That's the thing about retrograde analysis puzzles. Moves are ALWAYS legal but often make no sense in terms of standard chess play. I probably should have emphasised that in the original post.

There's another Holmesian saying that's appropriate here ... once you eliminate the impossible whatever remains, however improbably, must be the truth.


Glad you got there in the end.

Tom Chivers said...

The Sherlock Holmes stories are very, very good you know. Have you read them Jonathan? (I've read them all.)