# Tag: Sherlock Holmes

## Deductive vs Inductive Reasoning: Make Smarter Arguments, Better Decisions, and Stronger Conclusions

You can’t prove truth, but using deductive and inductive reasoning, you can get close. Learn the difference between the two types of reasoning and how to use them when evaluating facts and arguments.

Ok, let’s dig in and see what we can learn.

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## What Makes Something True?

As odd as it sounds, in science, law, and many other fields, there is no such thing as proof — there are only conclusions drawn from facts and observations. Scientists cannot prove a hypothesis, but they can collect evidence that points to its being true. Lawyers cannot prove that something happened (or didn’t), but they can provide evidence that seems irrefutable.

The question of what makes something true is more relevant than ever in this era of alternative facts and fake news. This article explores truth — what it means and how we establish it. We’ll dive into inductive and deductive reasoning as well as a bit of history.

### “Contrariwise,” continued Tweedledee, “if it was so, it might be; and if it were so, it would be; but as it isn’t, it ain’t. That’s logic.”

— Lewis Carroll, Through the Looking-Glass

The essence of reasoning is a search for truth. Yet truth isn’t always as simple as we’d like to believe it is.

For as far back as we can imagine, philosophers have debated whether absolute truth exists. Although we’re still waiting for an answer, this doesn’t have to stop us from improving how we think by understanding a little more.

In general, we can consider something to be true if the available evidence seems to verify it. The more evidence we have, the stronger our conclusion can be. When it comes to samples, size matters. As my friend Peter Kaufman says:

What are the three largest, most relevant sample sizes for identifying universal principles? Bucket number one is inorganic systems, which are 13.7 billion years in size. It’s all the laws of math and physics, the entire physical universe. Bucket number two is organic systems, 3.5 billion years of biology on Earth. And bucket number three is human history….

In some areas, it is necessary to accept that truth is subjective. For example, ethicists accept that it is difficult to establish absolute truths concerning whether something is right or wrong, as standards change over time and vary around the world.

When it comes to reasoning, a correctly phrased statement can be considered to have objective truth. Some statements have an objective truth that we cannot ascertain at present. For example, we do not have proof for the existence or non-existence of aliens, although proof does exist somewhere.

Deductive and inductive reasoning are both based on evidence.

Several types of evidence are used in reasoning to point to a truth:

• Direct or experimental evidence — This relies on observations and experiments, which should be repeatable with consistent results.
• Anecdotal or circumstantial evidence — Overreliance on anecdotal evidence can be a logical fallacy because it is based on the assumption that two coexisting factors are linked even though alternative explanations have not been explored. The main use of anecdotal evidence is for forming hypotheses which can then be tested with experimental evidence.
• Argumentative evidence — We sometimes draw conclusions based on facts. However, this evidence is unreliable when the facts are not directly testing a hypothesis. For example, seeing a light in the sky and concluding that it is an alien aircraft would be argumentative evidence.
• Testimonial evidence — When an individual presents an opinion, it is testimonial evidence. Once again, this is unreliable, as people may be biased and there may not be any direct evidence to support their testimony.

### “The weight of evidence for an extraordinary claim must be proportioned to its strangeness.”

— Laplace, Théorie analytique des probabilités (1812)

## Reasoning by Induction

The fictional character Sherlock Holmes is a master of induction. He is a careful observer who processes what he sees to reach the most likely conclusion in the given set of circumstances. Although he pretends that his knowledge is of the black-or-white variety, it often isn’t. It is true induction, coming up with the strongest possible explanation for the phenomena he observes.

Consider his description of how, upon first meeting Watson, he reasoned that Watson had just come from Afghanistan:

“Observation with me is second nature. You appeared to be surprised when I told you, on our ﬁrst meeting, that you had come from Afghanistan.”
“You were told, no doubt.”

“Nothing of the sort. I knew you came from Afghanistan. From long habit the train of thoughts ran so swiftly through my mind, that I arrived at the conclusion without being conscious of intermediate steps. There were such steps, however. The train of reasoning ran, ‘Here is a gentleman of a medical type, but with the air of a military man. Clearly an army doctor, then. He has just come from the tropics, for his face is dark, and that is not the natural tint of his skin, for his wrists are fair. He has undergone hardship and sickness, as his haggard face says clearly. His left arm has been injured. He holds it in a stiff and unnatural manner. Where in the tropics could an English army doctor have seen much hardship and got his arm wounded? Clearly in Afghanistan.’ The whole train of thought did not occupy a second. I then remarked that you came from Afghanistan, and you were astonished.”

(From Sir Arthur Conan Doyle’s A Study in Scarlet)

Inductive reasoning involves drawing conclusions from facts, using logic. We draw these kinds of conclusions all the time. If someone we know to have good literary taste recommends a book, we may assume that means we will enjoy the book.

Induction can be strong or weak. If an inductive argument is strong, the truth of the premise would mean the conclusion is likely. If an inductive argument is weak, the logic connecting the premise and conclusion is incorrect.

There are several key types of inductive reasoning:

• Generalized — Draws a conclusion from a generalization. For example, “All the swans I have seen are white; therefore, all swans are probably white.”
• Statistical — Draws a conclusion based on statistics. For example, “95 percent of swans are white” (an arbitrary figure, of course); “therefore, a randomly selected swan will probably be white.”
• Sample — Draws a conclusion about one group based on a different, sample group. For example, “There are ten swans in this pond and all are white; therefore, the swans in my neighbor’s pond are probably also white.”
• Analogous — Draws a conclusion based on shared properties of two groups. For example, “All Aylesbury ducks are white. Swans are similar to Aylesbury ducks. Therefore, all swans are probably white.”
• Predictive — Draws a conclusion based on a prediction made using a past sample. For example, “I visited this pond last year and all the swans were white. Therefore, when I visit again, all the swans will probably be white.”
• Causal inference — Draws a conclusion based on a causal connection. For example, “All the swans in this pond are white. I just saw a white bird in the pond. The bird was probably a swan.”

The entire legal system is designed to be based on sound reasoning, which in turn must be based on evidence. Lawyers often use inductive reasoning to draw a relationship between facts for which they have evidence and a conclusion.

The initial facts are often based on generalizations and statistics, with the implication that a conclusion is most likely to be true, even if that is not certain. For that reason, evidence can rarely be considered certain. For example, a fingerprint taken from a crime scene would be said to be “consistent with a suspect’s prints” rather than being an exact match. Implicit in that statement is the assertion that it is statistically unlikely that the prints are not the suspect’s.

Inductive reasoning also involves Bayesian updating. A conclusion can seem to be true at one point until further evidence emerges and a hypothesis must be adjusted. Bayesian updating is a technique used to modify the probability of a hypothesis’s being true as new evidence is supplied. When inductive reasoning is used in legal situations, Bayesian thinking is used to update the likelihood of a defendant’s being guilty beyond a reasonable doubt as evidence is collected. If we imagine a simplified, hypothetical criminal case, we can picture the utility of Bayesian inference combined with inductive reasoning.

Let’s say someone is murdered in a house where five other adults were present at the time. One of them is the primary suspect, and there is no evidence of anyone else entering the house. The initial probability of the prime suspect’s having committed the murder is 20 percent. Other evidence will then adjust that probability. If the four other people testify that they saw the suspect committing the murder, the suspect’s prints are on the murder weapon, and traces of the victim’s blood were found on the suspect’s clothes, jurors may consider the probability of that person’s guilt to be close enough to 100 percent to convict. Reality is more complex than this, of course. The conclusion is never certain, only highly probable.

One key distinction between deductive and inductive reasoning is that the latter accepts that a conclusion is uncertain and may change in the future. A conclusion is either strong or weak, not right or wrong. We tend to use this type of reasoning in everyday life, drawing conclusions from experiences and then updating our beliefs.

### A conclusion is either strong or weak, not right or wrong.

Everyday inductive reasoning is not always correct, but it is often useful. For example, superstitious beliefs often originate from inductive reasoning. If an athlete performed well on a day when they wore their socks inside out, they may conclude that the inside-out socks brought them luck. If future successes happen when they again wear their socks inside out, the belief may strengthen. Should that not be the case, they may update their belief and recognize that it is incorrect.

Another example (let’s set aside the question of whether turkeys can reason): A farmer feeds a turkey every day, so the turkey assumes that the farmer cares for its wellbeing. Only when Thanksgiving rolls around does that assumption prove incorrect.

The issue with overusing inductive reasoning is that cognitive shortcuts and biases can warp the conclusions we draw. Our world is not always as predictable as inductive reasoning suggests, and we may selectively draw upon past experiences to confirm a belief. Someone who reasons inductively that they have bad luck may recall only unlucky experiences to support that hypothesis and ignore instances of good luck.

In The 12 Secrets of Persuasive Argument, the authors write:

In inductive arguments, focus on the inference. When a conclusion relies upon an inference and contains new information not found in the premises, the reasoning is inductive. For example, if premises were established that the defendant slurred his words, stumbled as he walked, and smelled of alcohol, you might reasonably infer the conclusion that the defendant was drunk. This is inductive reasoning. In an inductive argument the conclusion is, at best, probable. The conclusion is not always true when the premises are true. The probability of the conclusion depends on the strength of the inference from the premises. Thus, when dealing with inductive reasoning, pay special attention to the inductive leap or inference, by which the conclusion follows the premises.

… There are several popular misconceptions about inductive and deductive reasoning. When Sherlock Holmes made his remarkable “deductions” based on observations of various facts, he was usually engaging in inductive, not deductive, reasoning.

In Inductive Reasoning, Aiden Feeney and Evan Heit write:

…inductive reasoning … corresponds to everyday reasoning. On a daily basis we draw inferences such as how a person will probably act, what the weather will probably be like, and how a meal will probably taste, and these are typical inductive inferences.

[…]

[I]t is a multifaceted cognitive activity. It can be studied by asking young children simple questions involving cartoon pictures, or it can be studied by giving adults a variety of complex verbal arguments and asking them to make probability judgments.

[…]

[I]nduction is related to, and it could be argued is central to, a number of other cognitive activities, including categorization, similarity judgment, probability judgment, and decision making. For example, much of the study of induction has been concerned with category-based induction, such as inferring that your next door neighbor sleeps on the basis that your neighbor is a human animal, even if you have never seen your neighbor sleeping.

### “A very great deal more truth can become known than can be proven.”

— Richard Feynman

## Reasoning by Deduction

Deduction begins with a broad truth (the major premise), such as the statement that all men are mortal. This is followed by the minor premise, a more specific statement, such as that Socrates is a man. A conclusion follows: Socrates is mortal. If the major premise is true and the minor premise is true the conclusion cannot be false.

Deductive reasoning is black and white; a conclusion is either true or false and cannot be partly true or partly false. We decide whether a deductive statement is true by assessing the strength of the link between the premises and the conclusion. If all men are mortal and Socrates is a man, there is no way he can not be mortal, for example. There are no situations in which the premise is not true, so the conclusion is true.

In science, deduction is used to reach conclusions believed to be true. A hypothesis is formed; then evidence is collected to support it. If observations support its truth, the hypothesis is confirmed. Statements are structured in the form of “if A equals B, and C is A, then C is B.” If A does not equal B, then C will not equal B. Science also involves inductive reasoning when broad conclusions are drawn from specific observations; data leads to conclusions. If the data shows a tangible pattern, it will support a hypothesis.

For example, having seen ten white swans, we could use inductive reasoning to conclude that all swans are white. This hypothesis is easier to disprove than to prove, and the premises are not necessarily true, but they are true given the existing evidence and given that researchers cannot find a situation in which it is not true. By combining both types of reasoning, science moves closer to the truth. In general, the more outlandish a claim is, the stronger the evidence supporting it must be.

We should be wary of deductive reasoning that appears to make sense without pointing to a truth. Someone could say “A dog has four paws. My pet has four paws. Therefore, my pet is a dog.” The conclusion sounds logical but isn’t, because the initial premise is too specific.

## The History of Reasoning

The discussion of reasoning and what constitutes truth dates back to Plato and Aristotle.

Plato (429–347 BC) believed that all things are divided into the visible and the intelligible. Intelligible things can be known through deduction (with observation being of secondary importance to reasoning) and are true knowledge.

Aristotle took an inductive approach, emphasizing the need for observations to support knowledge. He believed that we can reason only from discernable phenomena. From there, we use logic to infer causes.

Debate about reasoning remained much the same until the time of Isaac Newton. Newton’s innovative work was based on observations, but also on concepts that could not be explained by a physical cause (such as gravity). In his Principia, Newton outlined four rules for reasoning in the scientific method:

1. “We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.” (We refer to this rule as Occam’s Razor.)
2. “Therefore, to the same natural effects we must, as far as possible, assign the same causes.”
3. “The qualities of bodies, which admit neither intensification nor remission of degrees, and which are found to belong to all bodies within the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.”
4. “In experimental philosophy, we are to look upon propositions collected by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, ’till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.”

In 1843, philosopher John Stuart Mill published A System of Logic, which further refined our understanding of reasoning. Mill believed that science should be based on a search for regularities among events. If a regularity is consistent, it can be considered a law. Mill described five methods for identifying causes by noting regularities. These methods are still used today:

• Direct method of agreement — If two instances of a phenomenon have a single circumstance in common, the circumstance is the cause or effect.
• Method of difference — If a phenomenon occurs in one experiment and does not occur in another, and the experiments are the same except for one factor, that is the cause, part of the cause, or the effect.
• Joint method of agreement and difference — If two instances of a phenomenon have one circumstance in common, and two instances in which it does not occur have nothing in common except the absence of that circumstance, then that circumstance is the cause, part of the cause, or the effect.
• Method of residue — When you subtract any part of a phenomenon known to be caused by a certain antecedent, the remaining residue of the phenomenon is the effect of the remaining antecedents.
• Method of concomitant variations — If a phenomenon varies when another phenomenon varies in a particular way, the two are connected.

Karl Popper was the next theorist to make a serious contribution to the study of reasoning. Popper is well known for his focus on disconfirming evidence and disproving hypotheses. Beginning with a hypothesis, we use deductive reasoning to make predictions. A hypothesis will be based on a theory — a set of independent and dependent statements. If the predictions are true, the theory is true, and vice versa. Popper’s theory of falsification (disproving something) is based on the idea that we cannot prove a hypothesis; we can only show that certain predictions are false. This process requires vigorous testing to identify any anomalies, and Popper does not accept theories that cannot be physically tested. Any phenomenon not present in tests cannot be the foundation of a theory, according to Popper. The phenomenon must also be consistent and reproducible. Popper’s theories acknowledge that theories that are accepted at one time are likely to later be disproved. Science is always changing as more hypotheses are modified or disproved and we inch closer to the truth.

## Conclusion

In How to Deliver a TED Talk, Jeremey Donovan writes:

No discussion of logic is complete without a refresher course in the difference between inductive and deductive reasoning. By its strictest definition, inductive reasoning proves a general principle—your idea worth spreading—by highlighting a group of specific events, trends, or observations. In contrast, deductive reasoning builds up to a specific principle—again, your idea worth spreading—through a chain of increasingly narrow statements.

Logic is an incredibly important skill, and because we use it so often in everyday life, we benefit by clarifying the methods we use to draw conclusions. Knowing what makes an argument sound is valuable for making decisions and understanding how the world works. It helps us to spot people who are deliberately misleading us through unsound arguments. Understanding reasoning is also helpful for avoiding fallacies and for negotiating.

## Peter Bevelin: A Few Lessons From Sherlock Holmes

Peter Bevelin‘s first book, Seeking Wisdom from Darwin to Munger, is one of the best books you’ve probably never heard of. He’s just released another book, A Few Lessons from Sherlock Holmes (Kindle), aimed at those who want to improve their thinking.

### “Peter Bevelin is one of the wisest people on the planet.”

— Nassim Taleb

I’m a big fan of Sherlock Holmes, and Peter is not the first person to explore the wisdom that can be drawn. Maria Konnikova’s book, Mastermind: How To Think Like Sherlock Holmes, takes a deep look at Sherlock Holmes’s methodology to develop the habits of mind that will allow us to mindfully engage the world.

Peter’s book is shorter than Maria’s and encourages you to draw your own conclusions. He’s distilled Arthur Conan Doyle’s famous detective Sherlock Holmes into principles and quotes.

This book will appeal to both Sherlock fans as well as those who want to think better. It contains useful and timeless methods and questions applicable to a variety of important issues in life and business. We could all benefit from A few lessons from Sherlock Holmes.

Let’s look at some of the lessons Bevelin brings to our attention.

“What distinguishes Holmes from most mortals,” Bevelin writes, “is that he knows where to look and what questions to ask. He pays attention to the important things, and he knows where to find them.”

Many ideas over a wide range of disciplines help us gain perspective (queue mental models).

Breadth of view, my dear Mr. Mac, is one of the essentials of our profession. The interplay of ideas and the oblique uses of knowledge are often of extraordinary interest.(Holmes; The Valley of Fear)

## The Memory Attic

I consider that a man’s brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things so that he has a difficulty in laying his hands upon it.

Now the skillful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones. (Holmes; A Study in Scarlet)

So says the statistician.

You can, for example, never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant. (Holmes; The Sign of the Fear)

## Knowledge Doesn’t Make us Wise

One of the best things about Peter is how he adds outsiders to the mix. He inserts this quote from Montaigne:

Judgment can do without knowledge but not knowledge without judgment. (Montaigne)

I have not all my facts yet, but I do not think there are any insuperable difficulties. Still, it is an error to argue in front of your data. You find yourself insensibly twisting them round to fit your theories. (Holmes; Wisteria Lodge)

## Don’t theorize before data.

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Holmes; A Scandal in Bohemia)

Make sure the facts are facts.

I realize that if you ask people to account for “facts”, they usually spend more time finding reasons for them than finding out whether they are true. … They skip over the facts but carefully deduce inferences. They normally begin thus: “How does this come about?” But does it do so? That is what they ought to be asking. (Montaigne)

## See the Forest

The principal difficulty in your case … lay in the fact of there being too much evidence. What was vital was overlaid and hidden by what was irrelevant. Of all the facts which were presented to us we had to pick just those which we deemed to be essential, and then piece them together in their order, so as to reconstruct this very remarkable chain of events. (Holmes; The Naval Treaty)

Small things may be important.

The smallest point may be the most essential. (Holmes; A Study in Scarlet)

## We see but don’t Observe

What we see is all we think is there — What often leads us astray in an investigation is that we adopt the theory which is most likely to account for the “visible” and found facts but what if the important is left out? What is not reported, withheld, hidden?

Take time to think things over.

Sherlock Holmes was a man … who, when he had an unsolved problem upon his mind, would go for days, and even for a week, without rest, turning it over, rearranging his facts, looking at it from every point of view until he had either fathomed it or convinced himself that his data were insufficient. (Dr. Watson; The Man with the Twisted Lip)

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Peter’s books tend to become very hard to find a few months after they are released. Used editions often sell well above cover price, so if you’re interested, I encourage you to order A Few Lessons From Sherlock Holmes today.

## How to Think Like Sherlock Holmes

When it comes to using our minds, we all want to learn how to think like Sherlock Holmes. This isn’t just a way of solving a crime. It’s a way of thinking.

Maria Konnikova’s book, Mastermind: How To Think Like Sherlock Holmes, takes a deep look at Sherlock Holmes’s methodology to develop the habits of mind that will allow us to mindfully engage the world.

Holmes has a step up on most people. “For most of his life, he had been honing a method of mindful interaction with the world.” To him, this was a skill that came naturally. “What Sherlock Holmes offers isn’t just a way of solving a crime. It is an entire way of thinking. … It is an approach born out of the scientific method that transcends science and crime both and can serve as a model for thinking, a way of being, even, just as powerful in our time as it was in Conan Doyle’s.”

The idea of mindfulness itself is by no means a new one. As early as the end of the nineteenth century, William James, the father of modern psychology, wrote that, ‘The faculty of voluntarily bringing back a wandering attention, over and over again, is the very root of judgment, character, and will. … An education which should improve this faculty would be the education par excellence.’ That faculty, at its core, is the very essence of mindfulness. And the education that James proposes, an education in a mindful approach to life and to thought.

Ellen Langer, in the 1970s demonstrated that mindfulness could even improve “judgment, character, and will.”

In recent years, studies have shown that meditation-like thought (an exercise in the very attentional control that forms the center of mindfulness), for as little as fifteen minutes a day, can shift frontal brain activity toward a pattern that has been associated with more positive and more approach-oriented emotional states, and that looking at scenes of nature, for even a short while, can help us become more insightful, more creative, and more productive. We also know, more definitively than we ever have, that our brains are not built for multitasking — something that precludes mindfulness altogether. When we are forced to do multiple things at once, not only do we perform worse on all of them but our memory decreases and our general wellbeing suffers a palpable hit.

But for Sherlock Holmes, mindful presence is just a first step. It’s a means to a far larger, far more practical and practically gratifying goal. Holmes provides precisely what William James had prescribed: an education in improving our faculty of mindful thought and in using it in order to accomplish more, think better, and decide more optimally. In its broadest application, it is a means for improving overall decision making and judgment ability, starting from the most basic building block of your own mind.

Never mistake mindlessness for mindfulness. “We have to move from passive absorption to active awareness. We have to engage.”

— W. H. Auden

## Engagement

As children, we are remarkably aware. We absorb and process information at a speed that we’ll never again come close to achieving. New sights, new sounds, new smells, new people, new emotions, new experiences: we are learning about our world and its possibilities. Everything is new, everything is exciting, everything engenders curiosity. And because of the inherent newness of our surroundings, we are exquisitely alert; we are absorbed; we take it all in. Who knows when it might come in handy?

But as we grow older, the blasé factor increases exponentially. Been there, done that, don’t need to pay attention to this, and when in the world will I ever need to know or use that. Before we know it, we have shed that innate attentiveness, engagement, and curiosity for a host of passive, mindless habits. And even when we want to engage, we no longer have that childhood luxury. Gone are the days where our main job was to learn, to absorb, to interact; we now have other, more pressing (or so we think) responsibilities to attend to and demands on our minds to address. And as the demands on our attention increase—an all too real concern as the pressures of multitasking grow in the increasingly 24/7 digital age—so, too, does our actual attention decrease. As it does so, we become less and less able to know or notice our own thought habits, and more and more allow our minds to dictate our judgments and decisions, instead of the other way around.

## Pitfalls of the Untrained Brain

One of the things that characterizes Holmes’s thinking —and the scientific ideal—is a natural skepticism and inquisitiveness toward the world. Nothing is taken at face value.

It’s awfully easy to get tripped up. In fact, not only do we believe everything we hear, at least initially, but even when we have been told explicitly that a statement is false before we hear it, we are likely to treat it as true. For instance, in something known as the correspondence bias (a concept we’ll revisit in greater detail), we assume that what a person says is what that person actually believes—and we hold on to that assumption even if we’ve been told explicitly that it isn’t so; we’re even likely to judge the speaker in its light.

Daniel Kahneman believes there are two systems for organizing and filtering knowledge: system one and system two. System one is real-time. Think about the way we recognize speech or make an intuitive decision. This system makes judgments and decisions before our mental apparatus can consciously catch up. System two, on the other hand, is a slow process of thinking based on critical examination of evidence. Konnikova refers to these as System Watson and System Holmes.

In essence it comes down to one simple formula: to move from a System Watson- to a System Holmes-governed thinking takes mindfulness plus motivation. (That, and a lot of practice.) Mindfulness, in the sense of constant presence of mind, the attentiveness and hereness that is so essential for real, active observation of the world. Motivation, in the sense of active engagement.

### “Powers of observation can be developed by cultivating the habit of watching things with an active, enquiring mind. It is no exaggeration to say that well-developed habits of observation are more important in research than large accumulations of academic learning.”

— W. I. B. Beveridge

And of course, applying these skills is incredibly difficult, when our brains want to default into quick, intuitive, thinking.

It is most difficult to apply Holmes’s logic in those moments that matter the most. And so, all we can do is practice, until our habits are such that even the most severe stressors will bring out the very thought patterns that we’ve worked so hard to master.

Of course, what you allow into your brain is the starting point for how we think. And whether we think intuitively (system one) or more rationally (system two) what’s in our head affects our decisions.

## Respect the Memory Attic

As Holmes tells Watson, “I consider that a man’s brain originally is like a little empty attic, and you have to stock it with such furniture as you choose.”

When I first heard the term brain attic, all I could picture in my seven-year-old head was the cover of the black-and-white Shel Silverstein book that sat prominently on my bookshelf, with its half-smiling, lopsided face whose forehead was distended to a wrinkled triangle, complete with roof, chimney, and window with open shutters. Behind the shutters, a tiny face peeking out at the world. Is this what Holmes meant? A small room with sloped sides and a foreign creature with a funny face waiting to pull the cord and turn the light off or on?

As it turns out, I wasn’t far from wrong. For Sherlock Holmes, a person’s brain attic really is an incredibly concrete, physical space. Maybe it has a chimney. Maybe it doesn’t. But whatever it looks like, it is a space in your head, specially fashioned for storing the most disparate of objects. And yes, there is certainly a cord that you can pull to turn the light on or off at will. As Holmes explains to Watson, “A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skillful workman is very careful indeed as to what he takes into his brain-attic.”

That comparison, as it turns out, is remarkably accurate. Subsequent research on memory formation, retention, and retrieval has proven itself to be highly amenable to the attic analogy.

Attics have two components: structure and contents.

This sounds a lot like Charlie Munger’s view espoused in A Lesson on Worldly Wisdom: storing key ideas on a latticework of mental models.

Well, the first rule is that you can’t really know anything if you just remember isolated facts and try and bang ‘em back. If the facts don’t hang together on a latticework of theory, you don’t have them in a usable form.

You’ve got to have models in your head. And you’ve got to array your experience both vicarious and direct on this latticework of models. You may have noticed students who just try to remember and pound back what is remembered. Well, they fail in school and in life. You’ve got to hang experience on a latticework of models in your head.

What are the models? Well, the first rule is that you’ve got to have multiple models because if you just have one or two that you’re using, the nature of human psychology is such that you’ll torture reality so that it fits your models, or at least you’ll think it does…

It’s like the old saying, ”To the man with only a hammer, every problem looks like a nail.” And of course, that’s the way the chiropractor goes about practicing medicine. But that’s a perfectly disastrous way to think and a perfectly disastrous way to operate in the world. So you’ve got to have multiple models.

And the models have to come from multiple disciplines because all the wisdom of the world is not to be found in one little academic department. That’s why poetry professors, by and large, are so unwise in a worldly sense. They don’t have enough models in their heads. So you’ve got to have models across a fair array of disciplines.

You may say, “My God, this is already getting way too tough.” But, fortunately, it isn’t that tough because 80 or 90 important models will carry about 90% of the freight in making you a worldly wise person. And, of those, only a mere handful really carry very heavy freight.

Konnikova carries the systems (Watson and Holmes) into how we remember.

Our default System Watson attic is jumbled and largely mindless. Gregson may have once known about Van Jansen but has lacked the requisite motivation and presence to retain his knowledge. Why should he care about old cases? Holmes, however, makes a conscious, motivated choice to remember cases past; one never knows when they might come in handy. In his attic, knowledge does not get lost. He has made a deliberate decision that these details matter. And that decision has, in turn, affected how and what – and when – he remembers.

## Cultivating knowledge

To cultivate our knowledge actively, we need to realize that items are being pushed into our attic space at every opportunity. In our default state, we don’t often pay attention to them unless some aspect draws our attention—but that doesn’t mean they haven’t found their way into our attic all the same. They sneak in if we’re not careful, if we just passively take in information and don’t make a conscious effort to control our attention—especially if they are things that somehow pique our attention naturally: topics of general interest; things we can’t help but notice; things that raise some emotion in us; or things that capture us by some aspect of novelty or note.

It is all too easy to let the world come unfiltered into your attic space, populating it with whatever inputs may come its way or whatever naturally captures your attention by virtue of its interest or immediate relevance to you. When we’re in our default System Watson mode, we don’t “choose” which memories to store. They just kind of store themselves—or they don’t, as the case may be.

## Observation

Before we include something in our brain attic we must first observe it. Konnikova writes:

Observation with a capital O — the way Holmes uses the word when he gives his new companion a brief history of his life with a single glance — does entail more than, well, observation (the lowercase kind). It’s not just about the passive process of letting objects enter into your visual field. It is about knowing what and how to observe and directing your attention accordingly: what details do you focus on? What details do you omit? And how do you take in and capture those details that you do choose to zoom in on? In other words, how do you maximize your brain attic’s potential? You don’t just throw any old detail up there, if you remember Holmes’s early admonitions; you want to keep it as clean as possible. Everything we choose to notice has the potential to become a future furnishing of our attics — and what’s more, its addition will mean a change in the attic’s landscape that will affect, in turn, each future addition. So we have to choose wisely.

Choosing wisely means being selective. It means not only looking but looking properly, looking with real thought. It means looking with the full knowledge that what you note — and how you note it — will form the basis of any future deductions you might make. It’s about seeing the full picture, noting the details that matter, and understanding how to contextualize those details within a broader framework of thought.

In his book, The Art of Scientific Investigation, W. I. B. Beveridge writes:

Training in observation follows the same principles as training in any activity. At first one must do things consciously and laboriously, but with practice the activities gradually become automatic and unconscious and a habit is established. Effective scientific observation also requires a good background, for only by being familiar with the usual can we notice something as being unusual or unexplained.

## Paying Attention Is Anything but Elementary

Attention is a limited resource. Paying attention to one thing necessarily comes at the expense of another. Letting your eyes get too taken in by all of the scientific equipment in the laboratory prevents you from noticing anything of significance about the man in that same room. We cannot allocate our attention to multiple things at once and expect it to function at the same level as it would were we to focus on just one activity. Two tasks cannot possibly be in the attentional foreground at the same time. One will inevitably end up being the focus, and the other — or others — more akin to irrelevant noise, something to be filtered out. Or worse still, none will have the focus and all will be, albeit slightly clearer, noise, but degrees of noise all the same.

Attentional blindness, paying attention to one thing at the expense of another, is often how pickpocketing works. Yet all is not lost.

## The Holmes solution? Habit.

The Holmes solution? Habit, habit, habit. That, and motivation. Become an expert of sorts at those types of decisions or observation that you want to excel at making. … If you learn first how to be selective accurately, in order to accomplish precisely what it is you want to accomplish, you will be able to limit the damage that System Watson can do by preemptively teaching it to not muck it up. The important thing is the proper, selective training — the presence of mind — coupled with the desire the motivation to master your thought process.

No one says it’s easy. When it comes right down to it, there is no such thing as free attention; it all has to come from somewhere. And every time we place an additional demand on our attentional resources — be it by listening to music while walking, checking our email while working, or following five media streams at once — we limit the awareness that surrounds any one aspect and our ability to deal with it in an engaged, mindful, and productive manner.

## Take a Step Back

To think we also need distance.

One of the most important ways to facilitate imaginative thinking is through distance. In ‘The Adventure of the Bruce-Partington Plans,’ a case that comes quite late in the Holmes-Watson partnership, Watson observes:

One of the most remarkable characteristics of Sherlock Holmes was his power of throwing his brain out of action and switching all his thoughts on to lighter things whenever he had convinced himself that he could no longer work to advantage. I remember that during the whole of that memorable day he lost himself in a monograph which he had undertaken upon the Polyphonic Motets of Lassus. For my own part I had none of this power of detachment, and the day, in consequence appeared to be interminable.

Forcing your mind to take a step back is a tough thing to do. It seems counterintuitive to walk away from a problem that you want to solve. But in reality, the characteristic is not so remarkable either for Holmes or for individuals who are deep thinkers. The fact that it is remarkable for Watson (and that he self-admittedly lacks the skill) goes a long way to explaining why he so often fails when Holmes succeeds.

Not only does distance facilitate imaginative thinking but it also helps counter short-term emotions.

A final thought on Mindfulness comes from Sam McNerney. Referencing a recently published paper by Erika Carlson, a PhD candidate at Washington University, he writes:

Carlson proposes that mindfulness, defined as “paying attention to one’s current experience in a nonevaluative way,” may provide an effective means for acquiring self-knowledge. The “mindful” individual, as opposed to his introspective peer, does not analyze or interpret nor does he ask questions that lend themselves to intricate narratives that confirm his intuitions. As Carlson puts it, “[mindfulness] involves noticing thoughts and emotions as they arise without elaboration or rumination. This kind of detached observation … allows people to experience fairly aversive thoughts and emotions as temporary events rather than experiences that require a response or an explanation.”

How can we achieve mindfulness? Carlson mentions two strategies that both stress observation over questioning and introspection. The first is nonevalution observation, which encourages people to consider information even if it threatens the ego. Carlson cites a study that primed participants with morbid thoughts about their death. The researchers noted that the typical response to “mortality salience” is to hunker down, bolster self-esteem, and defend your worldview. However, individuals who scored higher on tests of mindfulness “defended their worldviews less, thought about death longer, and suppressed negative thoughts about death less.” An observant ego, in sum, is a healthy ego.

Second, we should pay attention to all the available information in a given moment (i.e., all thoughts, feelings, and behaviors). If this sounds obvious consider that compared to untrained individuals, people with mindfulness training preform better on conflict monitoring tasks, orientation tasks, standardized tests and working memory tasks.* Like impartial spectators, they consider all of the facts and avoid jumping to conclusions.

Mastermind: How to Think Like Sherlock Holmes was a great read.