How to Draw Conclusions Like Sherlock Holmes

post by abcd_z · 2011-12-27T13:29:03.419Z · LW · GW · Legacy · 28 comments


Eliezer Yudkowsky once wrote that

[...] when you look at what Sherlock Holmes does - you can't go out and do it at home.  Sherlock Holmes is not really operating by any sort of reproducible method.  He is operating by magically finding the right clues and carrying out magically correct complicated chains of deduction.  Maybe it's just me, but it seems to me that reading Sherlock Holmes does not inspire you to go and do likewise.  Holmes is a mutant superhero.  And even if you did try to imitate him, it would never work in real life.


A few days ago I was at an acquaintance's house after watching the Sherlock miniseries on Netflix. My mind whirling with the abilities displayed by the titular character and I wandered around the house while others were making small talk. I stopped by a large oil painting on one wall that was decent but had obvious problems with perspective. Additionally, it was missing a signature in the lower-right corner.



Sub-par paintings don't generally get put on the market.

If the hostess thought it was worth putting on the wall, it was most likely because she had an emotional attachment to the piece.

Painters place their signatures in the corner of the painting to identify themselves as the creator. If the painter didn't bother leaving their mark, it was because they were confident that they didn't need to.

The conclusion I drew from this was that the painter was either the hostess herself or somebody very close to her. As it turns out, it was the hostess.


Now, this anecdote hardly proves anything.  Still, I think it's a fun little thing and the ability to show off like that, even a small percentage of the time, is too good to pass up.  So I present my analysis of How to Become a Regular Sherlock Holmes.


1) Pay attention to details. Look around you at your environment.  A scratch on a wall, a limp in somebody's walk, a smudge on somebody's cheek.  At this point it's probably hard to tell what details are important, so pay attention to everything.


2) Answer these two questions:

"What am I looking at?" and

"What could it mean (if anything)?"


3) Check your guesses.

This is an important step. It's easy to make any sort of judgments about the details and what they mean, but if you accept your own conclusions without checking the facts, you're likely to create false assumptions and associations that you take as fact.  That's the opposite of what we're trying to do here.

Fortunately, checking your guesses is very easy to do in most situations with another person. Just state what you've noticed and ask for information on the context.  For example, "I've noticed a large scratch on your end-table. Do you know how it happened?"

A follow-up question might be "why haven't you changed it out for another one?", but only if you think getting the information is more important than the possibility of being seen as rude and the potential consequences thereof.


In Summary:


Pay attention to details

"What am I looking at?"

"What could it mean?"

Check your guesses


Oh, and the painting I mentioned at the beginning? I actually didn't figure it out until she told me. I just about kicked myself when I realized I could have figured it out myself and pulled off a really cool Sherlock Summation if I hadn't asked first. C'est la vie.



Comments sorted by top scores.

comment by TimS · 2011-12-27T15:02:05.006Z · LW(p) · GW(p)

Sherlock Holmes may be a rationalist, but his process is invisible to the reader.

A typical Holmes conversation (in form, at least):

Lestrade walks in.
SH: From your appearance, I can tell you just came from the morgue.
L: Gadzooks. You are correct. How did you know?
SH: I smell (some chemical) on your clothes. Also, the leather in your shoes is discolored as if (some other chemical) has dripped on it. The only places that use those two chemicals are (some ridiculous industrial location) and the morgue. Since you are a police officer, the logical conclusion is that you have just left the morgue.

But all Holmes' facts (except that Lestrade is a police officer) are invisible to the reader. Also invisible to the reader are the facts about Lestrade that are irrelevant to the story or the analysis (i.e. Lestrade was wearing a brown jacket, he recently shaved, and is carrying a note in his pocket, probably a list of items his wife wants him to buy on the way home).

Even if we wanted to, we couldn't follow along with Holmes' reasoning, including the dismissal of the irrelevant facts. In short, Holmes' "rationality" is really deus ex machina in favor of a character in a story.

comment by falenas108 · 2011-12-27T18:19:27.109Z · LW(p) · GW(p)

There's another massively important step: Check for alternative hypotheses. It's easy to think of explanations for observations, but usually they can have multiple meanings.

comment by fortyeridania · 2011-12-28T14:25:17.826Z · LW(p) · GW(p)

This is what CIA research has confirmed--that hypothesizing is easy, but staying open to new ideas after you think you already know the answer is hard (and undervalued).

Edited to add: This is also the topic of Hold Off On Proposing Solutions.

comment by [deleted] · 2011-12-27T15:27:49.359Z · LW(p) · GW(p)

I have some magician/"psychic" friends, and so much of that is cold reading (which is pretty much what Sherlock does) and other Dark Arts.

In case people haven't heard of it:

Cold reading is a series of techniques used by mentalists, psychics, fortune-tellers, illusionists, and con artists to determine or express details about another person, often in order to convince them that the reader knows much more about a subject than they actually do.[1] Without prior knowledge of a person, a practiced cold reader can still quickly obtain a great deal of information about the subject by analyzing the person's body language, age, clothing or fashion, hairstyle, gender, sexual orientation, religion, race or ethnicity, level of education, manner of speech, place of origin, etc. Cold readers commonly employ high probability guesses about the subject, quickly picking up on signals from their subjects as to whether their guesses are in the right direction or not, and then emphasizing and reinforcing any chance connections the subjects acknowledge while quickly moving on from missed guesses.

-From wikipedia

comment by Oscar_Cunningham · 2012-01-01T13:15:16.007Z · LW(p) · GW(p)

Oh, and the painting I mentioned at the beginning? I actually didn't figure it out until she told me. I just about kicked myself when I realized I could have figured it out myself and pulled off a really cool Sherlock Summation if I hadn't asked first. C'est la vie.

Hindsight bias!

comment by wedrifid · 2011-12-28T16:05:31.425Z · LW(p) · GW(p)

How to Draw Conclusions Like Sherlock Holmes

Engage slow motion mode and run an annotated physics simulation in your mind.

comment by Zando · 2012-05-16T09:03:29.892Z · LW(p) · GW(p)

How to Draw Conclusions Like Sherlock Holmes? Become a fictional character and point out all the details your author has included to move the plot forward.

comment by cousin_it · 2011-12-28T10:08:47.490Z · LW(p) · GW(p)

Maybe my old comment on Rationalist Fiction is worth reposting here.

"In defense of Conan Doyle, Wikipedia says:

Sherlock Holmes remains a great inspiration for forensic science, especially for the way his acute study of a crime scene yields small clues as to the precise sequence of events... All of the techniques advocated by Holmes would later become reality, but were generally in their infancy at the time Conan Doyle was writing.

and goes off to claim that later detective fiction actually became less realistic as writers shifted attention to psychology rather than forensics."

comment by Thomas · 2011-12-28T09:11:33.065Z · LW(p) · GW(p)

What a reaction!

And what claims. That Socrates not believed in Zeus. What else did he do in Delphi? Which god did he obeyed by his own claims, if it wasn't Zeus? And what better that would be?

But let us talk about Newton who's birthday wants to replace Jesus's birthday. He was a religious man also. Mildly put. Not to mention his Demonology, the dragons an such for a lay person? See.

Hundreds of examples out there, of scientists who were rational only in there narrow field and quite deluded elsewhere.

Arthur Conan Doyle is no forum darling, I know. And his spiritualism WAS silly, I admit that. But why to bash him about it and not almost everybody else 100 and more years ago about there believes in gods (which are not inherently more real then ferries are)?

One can take Newton's laws and the Calculus and the prism and say thank you very much for the rest of him, I don't need it, it's garbage.

The same with Conan Doyle. Some of us credit him for putting logical reasoning to the highest place in his literature. The rest is mainly garbage, of course.

It is always this way in humans. Some pearls in trash.

comment by Cthulhoo · 2011-12-28T11:26:34.642Z · LW(p) · GW(p)

But why to bash him about it and not almost everybody else 100 and more years ago about there believes in gods (which are not inherently more real then ferries are)?

I contest your claim, and have concrete reasons to think that ferries are indeed real! ;)

Jokes aside, I partly second your claim that Sherlock Holmes methods are in fact rational. Yes, you don't get to see the whole process. Indeed, it looks like magic. But my mobile phone also looks almost like magic to me. Holmes' reasoning is evidence based. He constantly challenges the most common beliefs to see if they match with reality. He holds off on proposing solutions until he has gathered a sufficient mass of evidence. He updates his beliefs and shows no bias in how he analyzes the facts. He's maybe not a black belt bayesian, but this doesn't mean there something good to be taken from the character.

comment by gwern · 2011-12-29T02:28:39.357Z · LW(p) · GW(p)

And what claims. That Socrates not believed in Zeus. What else did he do in Delphi? Which god did he obeyed by his own claims, if it wasn't Zeus? And what better that would be?

Apollo, I gathered from my classes; at least the Socrates presented by Plato. (I'm not well-read enough in Xenophon or the Straussian esoteric interpretations to summarize their versions.) Most obviously, Delphi wasn't Zeus's; that'd be Dodonna or one of the other oracles. As well, the text of things like the Apology or The Republic are vague enough that one could - and many like medieval Christians have - make Socrates out to be a monotheist, which allows for disbelief in Zeus.

comment by benelliott · 2011-12-28T14:10:10.198Z · LW(p) · GW(p)

All your arguments are simply points about why we should not consider him irrational because he was religious, but so far you have not given me any reason to consider him irrational. If Newton was just an alchemist I would not suggest studying him at all, it is because he has real achievements to counter-act the failures that he is interesting. What does Conan-Doyle have, beyond writing a character who uses magic and calls it reason.

comment by Thomas · 2011-12-27T14:16:08.519Z · LW(p) · GW(p)

I think, Arthur Conan Doyle - the author of Sherlock Holmes - was one of the great rationalists of the 19th century. So was his mental child, the famous detective. And his methods are very rational in essence.

Dos not matter what Yudkowsky thinks or writes.

comment by drethelin · 2011-12-27T15:10:53.434Z · LW(p) · GW(p)

"Conan Doyle, as a spiritualist, was enthusiastic about the photographs, and interpreted them as clear and visible evidence of psychic phenomena."

comment by FiftyTwo · 2011-12-27T21:06:56.267Z · LW(p) · GW(p)

To be fair, believing in supernatural phenomena based on seemingly good photographic evidence rather than on the basis of faith is at least a step in the right direction. But refusing to examine the flaws in the evidence is the problem, good example of motivated cognition there.

comment by billswift · 2011-12-28T01:02:35.971Z · LW(p) · GW(p)

on seemingly good photographic evidence

Have you seen the photos in question? The girls cut them out of a children's picture book and it shows. There is no chance anyone could take them seriously without previous belief.

comment by Thomas · 2011-12-27T15:37:21.292Z · LW(p) · GW(p)

He could not have known everything we know now in his times. Spiritualism was much on the table in those days.

It is easy to judge Socrates now, how ignorant was he about Zeus. Despite, he was more rational than most.

As was A. C. Doyle.

comment by ArisKatsaris · 2011-12-27T22:27:42.844Z · LW(p) · GW(p)

It is easy to judge Socrates now, how ignorant was he about Zeus.

Downvoted for making an unsubstantiated claim that Socrates believed in Zeus. This is sheer clumsiness. You make assumptions about what every ancient Greek must have believed because you underestimate them -- though some of them were indeed rational enough to not believe in Zeus. And then you use that false assumption about false failings to support the argument that we must excuse away Arthur Conan Doyle's real failings.

Also, it's you who argued that A.C. Doyle "was one of the great rationalists of the 19th century" -- that's a rather strong claim that argues he exhibited significantly better reasoning than most of his contemporaries.

If he was taken in by spiritualism, when Houdini wasn't, and he was taken in by crude child-produced fakes of fairies, when many of his contemporaries weren't -- what's even slight evidence that he can be called a rationalist, let alone a great one?

comment by orthonormal · 2011-12-27T17:09:10.496Z · LW(p) · GW(p)

Socrates didn't believe in Zeus- he was executed for atheism and corrupting the youth.

(His Ideal of the Good did have a theistic flavor, but you can't accuse him of believing in the Greek pantheon.)

comment by dlthomas · 2011-12-27T18:21:17.935Z · LW(p) · GW(p)

That he was executed for it does not necessarily mean it was true, particularly in this case. I don't think we have reliable enough reporting to tell one way or the other what was actually going on inside the man's head.

comment by orthonormal · 2011-12-28T01:06:02.988Z · LW(p) · GW(p)

Oh, come on. Thomas wrote a comment on the assumption that because Socrates lived in Greek times, he must have believed in Zeus. I've read about half of the many surviving primary sources on Socrates' life (the dialogues of Plato and plays of Aristophanes). According to that evidence, Socrates would be classified today as an atheist, agnostic or at worst Deist, and both his detractors and his students claimed he disbelieved in the Greek pantheon.

I wasn't making a claim with 100% certainty, because you can't do that, but if Omega had me stake my life to that assertion, I'd feel a lot better about it than about plenty of other historical claims.

comment by dlthomas · 2011-12-28T01:21:32.430Z · LW(p) · GW(p)

I was not demanding 100% certainty, I was demanding reasonable certainty. I am certainly not a scholar of the period, but I have done more than a little reading of my own, and my recalled interpretation clearly differs from yours. I don't know if we'll get further without citing sources in detail.

comment by Thomas · 2011-12-28T13:03:48.475Z · LW(p) · GW(p)

I did some readings, too! Socrates, for example, refers to accusations of being a believer in a Moon as a rock as ridiculous. For those ideas were commonly known as cheap and can be (text) bought on the market in Athens for a little money. Socrates was not keen for a cheap knowledge to distribute.

At least, that was his defense.

My dear Meletus, do you think you are prosecuting Anaxagoras? Are you so contemptuous of the jury and think them so ignorant of letters as not to know that the books of Anaxagoras of Clazomenae are full of those theories, and further, that the young men learn from me what they can buy from time to time for a drachma, at most, in the bookshops, and ridicule Socrates if he pretends that these theories are his own, especially as they are so absurd? (26d)

comment by Manfred · 2011-12-27T17:26:50.394Z · LW(p) · GW(p)

However popular spiritualism was, there was plenty of evidence against it by 1920, and many people did indeed reject it. Thus demonstrating that they were greater rationalists, at least in this area, than Arthur Conan Doyle.

comment by ArisKatsaris · 2011-12-27T22:21:16.885Z · LW(p) · GW(p)

Arthur Conan Doyle believed in fairies, for Cthulhu's sake. He argued that their existence explains the divine purpose behind those parts of nature that aren't immediately visible to mankind. (basically God made those parts of nature for the sake of fairies)

Arthur Conan Doyle wasn't even one of the minor rationalists of the 19th century, let alone of the great ones.

comment by shminux · 2011-12-27T18:55:45.826Z · LW(p) · GW(p)

You probably would not have been downvoted as badly if you provided some arguments in support of your assertion. Or against it.

comment by Thomas · 2011-12-27T19:16:03.256Z · LW(p) · GW(p)

Maybe, yes.

ACD was an agnostic when the large majority was theistic. He was wrong about "paranormal", yes! But who is always right? Was that Newton who's birthday has been widely celebrated some days ago? No, he wasn't. One can pick to Newton just as much as to Doyle, even much more.

But that is not the point. It counts what he discovered in physics and mathematics. His alchemy and the relation to the Holy Trinity is a side joke, unimportant.

Also Socrates spoke about "god" all the time. And so on and on.

Why to blame Conan Doyle now for his weaknesses? It just isn't fair. He gave us his confidence to the human reason through Holmes.

comment by benelliott · 2011-12-27T19:54:40.971Z · LW(p) · GW(p)

So far, all you've told me is a reason to somewhat ignore one of his negative traits. Can you give one reason why I should consider him more rational than Joe Bloggs.

Furthermore, Yudkowsky has made what seems to me a good point about why Holmes is a crap rationalist role model, do you have any rebuttal at all other than asserting that I should not care what Yudkowsky thinks.