Sherlock as a Mathematical Logician?

December 12, 2012 7:01 PM

A colleague alluded to a passage from Sherlock Holmes where all the evidence is re-written as formal logic propositions, leading to a mathematical solution that matches Holmes' solution (and is far from trivial). Does anyone else know where I could find this passage?

I'm a maths teacher and will be teaching Logic to top level year 11s in the new year, and this sounded interesting. Unfortunately, my google-fu is only turning up introductions to logic with quotes from Sherlock Holmes, rather than the full passage with formal logic notation beside it - I would *really* appreciate any help.

Thanks :)

posted by Anon Ymous to Education (11 answers total)

I don't remember that in the original Sherlock Holmes stories, but this sounds like something they might have done in Conned Again, Watson.
posted by RobotHero at 7:11 PM on December 12, 2012

The logician Raymond Smullyan wrote a Holmes-themed book, but I am not very confident that this is what your friend was describing. I leave it here anyway, since Smullyan's books may be of use in your teaching.
posted by thelonius at 7:23 PM on December 12, 2012

That doesn't happen in any of the canonical Holmes stories, unfortunately...you'd have to look into the many volumes of criticism out there (eep) or hope that Smullyan is your guy.
posted by like_a_friend at 7:34 PM on December 12, 2012

Just to let you know - I've read all of the original Sherlock Holmes stories, and I'm almost pretty sure that it doesn't happen. If I recall correctly, the only story that has any non-english-language letters or symbols is The Adventure of the Dancing Men.
posted by suedehead at 7:35 PM on December 12, 2012

Response by poster: Okay, sorry, I wasn't clear... My colleague described a passage taken from Sherlock Holmes, with *beside* the story all the propositions given in logic symbols - as in, an annotated version of the story.

I'll definitely have a look at the books mentioned, but it doesn't look right, just from the excerpts available.
posted by Anon Ymous at 7:41 PM on December 12, 2012

Could it be the book Sherlock's Logic, by William Neblett? From a user review:

The first third of the book is a rather weak murder mystery starring the grandson of the great detective Sherlock Holmes....

The balance is designed to teach formal logic, using references to the mystery story that has just been solved. It begins with propositions and then formal reasoning using deduction rules such as modus ponens. Predicate logic, the most common types of fallacious reasoning and equivalent logical forms are presented. As such it is a complete introduction to the predicate calculus, propositional calculus and formal reasoning. It could possibly be used as a text in such a course.

Another description.
posted by dhartung at 10:54 PM on December 12, 2012

This sounds like something that might have been on Sherlock (the recent BBC TV show), which often has notes/annotations/doodles written on the screen as Sherlock figures something out.
posted by EndsOfInvention at 1:30 AM on December 13, 2012

I know exactly what you're talking about - it was an analysis of some deduction clips from the BBC Sherlock show using flowcharts and diagrams to identify the nested formal logic propositions. I think it was done by a math professor on his blog. I thought I'd had it bookmarked, but apparently it's gone. If I find it I'll post
posted by Wulfhere at 6:24 AM on December 13, 2012

Best answer: Found it! Post 1, Post 2. Upon reading the posts, maybe this isn't exactly what you're talking about at the top, but it definitely could be used as an "in" for some formal logic style propositions (have the students rewrite the flowcharts in formal form!)
posted by Wulfhere at 6:31 AM on December 13, 2012 [1 favorite]

Isn't Holmes typically doing induction, not deduction? I don't know if Conan Doyle understood the difference.

He notices, say, a tattoo of a fish on a man's arm, and concludes that the man has been in the German Navy, where they tattoo fish on people to haze them. That is not deductive reasoning, since it is possible that the man has gotten the tattoo somewhere else. The conclusion is merely probable.
posted by thelonius at 6:38 AM on December 13, 2012

Frustratingly, I can't lay my hands on my copy, but it sounds like it could be from one of the essays in Umberto Eco and Thomas Albert Sebeok's The Sign of Three: Dupin, Holmes, Peirce (Indiana University Press, 1983).
posted by davemack at 1:05 PM on December 13, 2012