An Autodidact's Bible, #20
Reclaiming Your Mind, Part 2, Chapter 6a
This is the twentieth installment of the serial of my forthcoming book Reclaiming Your Mind: An Autodidact’s Bible. As with other installments, part of it is behind the paywall. Become one of my supporters to get the whole thing.
Catch up on earlier installments here:
#1, #2, #3, #4, #5, #6, #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, #18, #19
If your email client chokes on this post, find the whole thing at http://jdanielsawyer.substack.com
Continuing with Part 2, Chapter 6:
Abductive Reasoning
Picture this:
Spring is in full bloom. You’re a weekend guest at an artist’s cottage on a sheep ranch. The owner thinks well enough of you to give you a deep discount on the rental fee, but he’s not a close personal friend. He’s a severe man with a morbid sense of humor, and you find him a little off-putting (though not so much that you make any great effort to avoid him).
Late in the evening on your second night there, as you’re sitting on your patio having a glass of wine and enjoying the pastoral sunset, your host happens by. He stops to talk, and despite the pleasant tenor of the conversation you can’t help but notice that his left hand is soaked in blood, and that there are blood stains and spatters on his clothes, his boots, and you think you see a little misting of it on his face (although you can’t be sure in this light).
Then you realize that you haven’t seen his wife today, nor the hired hand who’s usually puttering about the place. You politely ask after them each in the course of the conversation, and he answers that his wife has gone into town to take care of the Saturday shopping, while his assistant is attending to sheeply matters off in a distant field on the far side of the barn.
Do you worry?
The presence of blood is disturbing, but you decide quickly that it’s nothing to fret about.
But how do you know this?
Well, his demeanor doesn’t seem like that of a murderer. Why would a murderer come with his clothes covered in blood to make conversation with a guest? Nothing he says is any more threatening or morbid than normal. And you know that his wife does do the shopping on Saturday, because she’s mentioned it to you before.
But, more important than any of those things is the fact that the farmer is relaxed after a hard day’s work, and it is spring time, and this is a working ranch. Obviously he must have been culling the rams from his herd—slaughtering the yearlings before the meat grows tough and is beyond the level of gaminess that turns lamb into mutton.
Slaughtering lambs is, after all, a messy business.
This is abduction. You might recognize it as the “Sherlock Holmes method” of quickly figuring things out. If you’re interested in the practice of mentalism (a form of stage magic that creates the illusion of mind-reading), you’ll recognize it as one of the core tools in the mentalist’s bag of tricks. It’s actually a specialized form of induction where you make much wilder guesses on much slimmer evidence, and it relies on the willingness to aggressively apply outward that which you already know.
Abduction is, more-or-less, the raising of intuition to a conscious level. It works off the same cues, takes the same kinds of logical leaps, and is chiefly concerned with pragmatic matters. In the hands of someone with a sharp mind and the willingness to hone her observational skills, it can be devastatingly effective. It’s especially useful in sales, medical diagnostics, motivational coaching, clinical psychology, spycraft, politics, priestcraft, criminal investigation, con artistry, or any other discipline that requires either incisive analysis or irresistible manipulation of people.1
While the quality of your abductions is governed by the sharpness of your observations and ability to draw efficient conclusions, reasoning per se is not enough to be good at this game. Without an excellent command of relevant background material, your abductions will almost always go wide of the mark, no matter how logically defensible they are. Think of how Holmes regularly humiliates Watson with “deduction” games (Conan Doyle was not a philosopher and didn’t know the terminology, though he did describe the method perfectly). If you haven’t had the pleasure first hand, take a moment to read the opening scene from The Hound of the Baskervilles, where Holmes and Watson are puzzling over Dr. Mortimer’s walking stick:
Mr. Sherlock Holmes, who was usually very late in the mornings, save upon those not infrequent occasions when he was up all night, was seated at the breakfast table. I stood upon the hearth-rug and picked up the stick which our visitor had left behind him the night before. It was a fine, thick piece of wood, bulbous-headed, of the sort which is known as a “Penang lawyer.” Just under the head was a broad silver band nearly an inch across. “To James Mortimer, M.R.C.S., from his friends of the C.C.H.,” was engraved upon it, with the date “1884.” It was just such a stick as the old-fashioned family practitioner used to carry—dignified, solid, and reassuring.
“Well, Watson, what do you make of it?”
Holmes was sitting with his back to me, and I had given him no sign of my occupation.
“How did you know what I was doing? I believe you have eyes in the back of your head.”
“I have, at least, a well-polished, silver-plated coffee-pot in front of me,” said he. “But, tell me, Watson, what do you make of our visitor’s stick? Since we have been so unfortunate as to miss him and have no notion of his errand, this accidental souvenir becomes of importance. Let me hear you reconstruct the man by an examination of it.”
“I think,” said I, following as far as I could the methods of my companion, “that Dr. Mortimer is a successful, elderly medical man, well-esteemed since those who know him give him this mark of their appreciation.”
“Good!” said Holmes. “Excellent!”
“I think also that the probability is in favour of his being a country practitioner who does a great deal of his visiting on foot.”
“Why so?”
“Because this stick, though originally a very handsome one has been so knocked about that I can hardly imagine a town practitioner carrying it. The thick-iron ferrule is worn down, so it is evident that he has done a great amount of walking with it.”
“Perfectly sound!” said Holmes.
“And then again, there is the ‘friends of the C.C.H.’ I should guess that to be the Something Hunt, the local hunt to whose members he has possibly given some surgical assistance, and which has made him a small presentation in return.”
“Really, Watson, you excel yourself,” said Holmes, pushing back his chair and lighting a cigarette. “I am bound to say that in all the accounts which you have been so good as to give of my own small achievements you have habitually underrated your own abilities. It may be that you are not yourself luminous, but you are a conductor of light. Some people without possessing genius have a remarkable power of stimulating it. I confess, my dear fellow, that I am very much in your debt.”
He had never said as much before, and I must admit that his words gave me keen pleasure, for I had often been piqued by his indifference to my admiration and to the attempts which I had made to give publicity to his methods. I was proud, too, to think that I had so far mastered his system as to apply it in a way which earned his approval. He now took the stick from my hands and examined it for a few minutes with his naked eyes. Then with an expression of interest he laid down his cigarette, and carrying the cane to the window, he looked over it again with a convex lens.
“Interesting, though elementary,” said he as he returned to his favourite corner of the settee. “There are certainly one or two indications upon the stick. It gives us the basis for several deductions.”
“Has anything escaped me?” I asked with some self-importance. “I trust that there is nothing of consequence which I have overlooked?”
“I am afraid, my dear Watson, that most of your conclusions were erroneous. When I said that you stimulated me I meant, to be frank, that in noting your fallacies I was occasionally guided towards the truth. Not that you are entirely wrong in this instance. The man is certainly a country practitioner. And he walks a good deal.”
“Then I was right.”
“To that extent.”
“But that was all.”
“No, no, my dear Watson, not all—by no means all. I would suggest, for example, that a presentation to a doctor is more likely to come from a hospital than from a hunt, and that when the initials ‘C.C.’ are placed before that hospital the words ‘Charing Cross’ very naturally suggest themselves.”
“You may be right.”
“The probability lies in that direction. And if we take this as a working hypothesis we have a fresh basis from which to start our construction of this unknown visitor.”
“Well, then, supposing that ‘C.C.H.’ does stand for ‘Charing Cross Hospital,’ what further inferences may we draw?”
“Do none suggest themselves? You know my methods. Apply them!”
“I can only think of the obvious conclusion that the man has practised in town before going to the country.”
“I think that we might venture a little farther than this. Look at it in this light. On what occasion would it be most probable that such a presentation would be made? When would his friends unite to give him a pledge of their good will? Obviously at the moment when Dr. Mortimer withdrew from the service of the hospital in order to start a practice for himself. We know there has been a presentation. We believe there has been a change from a town hospital to a country practice. Is it, then, stretching our inference too far to say that the presentation was on the occasion of the change?”
“It certainly seems probable.”
“Now, you will observe that he could not have been on the staff of the hospital, since only a man well-established in a London practice could hold such a position, and such a one would not drift into the country. What was he, then? If he was in the hospital and yet not on the staff he could only have been a house-surgeon or a house-physician—little more than a senior student. And he left five years ago—the date is on the stick. So your grave, middle-aged family practitioner vanishes into thin air, my dear Watson, and there emerges a young fellow under thirty, amiable, unambitious, absent-minded, and the possessor of a favourite dog, which I should describe roughly as being larger than a terrier and smaller than a mastiff.”
I laughed incredulously as Sherlock Holmes leaned back in his settee and blew little wavering rings of smoke up to the ceiling.
“As to the latter part, I have no means of checking you,” said I, “but at least it is not difficult to find out a few particulars about the man’s age and professional career.” From my small medical shelf I took down the Medical Directory and turned up the name. There were several Mortimers, but only one who could be our visitor. I read his record aloud.
“Mortimer, James, M.R.C.S., 1882, Grimpen, Dartmoor, Devon. House-surgeon, from 1882 to 1884, at Charing Cross Hospital. Winner of the Jackson prize for Comparative Pathology, with essay entitled ‘Is Disease a Reversion?’ Corresponding member of the Swedish Pathological Society. Author of ‘Some Freaks of Atavism’ (Lancet 1882). ‘Do We Progress?’ (Journal of Psychology, March, 1883). Medical Officer for the parishes of Grimpen, Thorsley, and High Barrow.”
“No mention of that local hunt, Watson,” said Holmes with a mischievous smile, “but a country doctor, as you very astutely observed. I think that I am fairly justified in my inferences. As to the adjectives, I said, if I remember right, amiable, unambitious, and absent-minded. It is my experience that it is only an amiable man in this world who receives testimonials, only an unambitious one who abandons a London career for the country, and only an absent-minded one who leaves his stick and not his visiting-card after waiting an hour in your room.”
“And the dog?”
“Has been in the habit of carrying this stick behind his master. Being a heavy stick the dog has held it tightly by the middle, and the marks of his teeth are very plainly visible. The dog’s jaw, as shown in the space between these marks, is too broad in my opinion for a terrier and not broad enough for a mastiff. It may have been—yes, by Jove, it is a curly-haired spaniel.”
He had risen and paced the room as he spoke. Now he halted in the recess of the window. There was such a ring of conviction in his voice that I glanced up in surprise.
“My dear fellow, how can you possibly be so sure of that?”
“For the very simple reason that I see the dog himself on our very door-step, and there is the ring of its owner.”
Here we see Watson making a number of perfectly plausible abductions, almost all of which turn out to be tragically wrong because either he overlooks something (failure of observation) or fails to connect it with a bit of knowledge that Holmes has ready to hand but Watson does not (lack of command of background).
While all reasoning works from available knowledge and experience, abduction relies on them more extensively and acutely than other methods. It’s important to bear this in mind when you consider that abduction is actually a part of the inductive process—which, I’m sure you’ll realize, means that both science and criminal justice depend upon it.
How?
If you are an aficionado of Internet debates, you may have heard the phrase: “Anecdotes are not data.” Science doesn’t have much respect for personal experience and personal interpretations of that experience, because (as we’ve discussed at length) human perception and reasoning and experience are so very, very fallible. Science’s clever hack—the thing that makes it science—is that it does a pretty good (but far from perfect) job at separating the “personal” from generalizable “experience.” Scientific research is always quantitative, not qualitative.
Well, almost always. There is one exception.
Qualitative research is deployed during the exploratory phase, when a researcher is trying to develop a good hypothesis or determine if a mostly-formed hypothesis is worth his attention. Abductive reasoning—that ability to draw conclusions from very thin data, to make leaps of insight based on the consilience of various sparse lines of evidence—is the very ability that cops call “hunches” and that scientists use when formulating hypotheses.
Abduction is the lubrication that allows induction to work. It also is very good on its own—just bear in mind the particular kinds of errors it is prone to.