If you're here from HN, and you find this criticism bizarre, you should probably read this short summary post first.

The mental model fallacy is that it’s worth it to read descriptions of mental models, written and aggregated by non-practitioners, in the pursuit of self-improvement and success.

If this sounds controversial to you, let me reframe that assertion.

Let’s say for a moment that you want to become a successful mixed martial arts (MMA) practitioner. I come up to you and tell you: “Hey Joe! I’m going to be the next MMA champion! That’s why I spend all my time listening to MMA commentators as they describe the secrets of how MMA superstars win.”

This is a ridiculous statement on the face of it. First, it’s obvious that you can’t get good at martial arts without practice. Second, it should be clear to you that listening to MMA show-commentators aren’t as valuable as listening to the MMA fighters discussing the practice of their sport. Third, even if you listen to the MMA fighters, if you lack practice, then you will lack the necessary mental architecture to understand the knowledge they possess.

I'll ... go back to reading about MMA.

We’ll spend this entire essay unpacking the implications of those three assertions, but for now, consider this: you can only learn what you are ready to learn — because humans learn by constructing knowledge from what they currently know. Therefore, without practice, and without ascending the skill tree that these MMA champions inhabit, you are unlikely to understand the insights that they have to offer. And worse, if you are listening to non-practitioners parroting what they’ve heard from the fighters themselves, you are adding a layer of indirection over something that is already difficult to communicate.

As it is for MMA fighters, so it is for business, software engineering, investing, decision making, and life.

The upshot of this argument is this: don’t read blogs written by non-practitioners, spouting insights that aren’t related to their field of practice. Don’t read Farnam Street. Don’t read self-help hacks on Medium who haven’t achieved much in life. Hell, don’t read this blog — especially if your career goals diverge from mine. I have little to offer you that practice cannot.

Instead read from the source material of practitioners in fields you inhabit, copy their actions, climb their skill trees, and reflect through trial and error.

Let’s examine why reading third party descriptions of mental models are a waste of time.

The Problem with Mental Model Writing

The central conceit of mental model education is the following:

Successful, effective people make good decisions and achieve successful outcomes in life because they have better mental models. Therefore, the secret to achieving successful outcomes in business and in life is to distill their mental models into written principles, and then learn them. This exercise can be done by a teacher who aggregates and summarises the mental models of the best practitioners in the world.

The first half of this assertion is true: successful, effective people do have better mental models that bring them success in their respective fields. They build such models through a lifetime of practice.

The second half of this assertion is false: you cannot learn the mental models that are responsible for success through reading and thinking. The reason for this is the same reason that attempting to learn how to ride a bicycle by reading a book is stupid. The most valuable mental models do not survive codification. They cannot be expressed through words alone.

The most valuable mental models do not survive codification. They cannot be expressed through words alone.

Now I can hear your objections already: “But Cedric! That’s just patently false! Look at the list of mental models over at Farnam Street! If mental models cannot survive codification, why is there such a long list of clearly codified models over at Shane Parrish’s site?”

(Farnam Street is the most famous of the ‘mental model education’ sites. I've been a subscriber to Farnam Street for over three years.)

To respond to your complaint, I propose a thought experiment. Let’s say that Warren Buffett and Charlie Munger retire tomorrow, and spend the next few years writing down every mental model that they know. Let us imagine that somehow this is possible — even if it is a difficult task, requiring hundreds of man-hours. Luckily for us, Buffett and Munger have been sharing a portion of their wisdom for a number of decades — Buffett through Berkshire Hathaway’s annual shareholder letters, Munger through Poor Charlie’s Almanack — we merely want them to write down everything else that they’ve yet to codify.

After Buffett and Munger are done, you sit down with their list and proceed to study them for a year. After a year, you are given a sum of money to invest like Buffett and Munger, and are forced to compete with them. Who will win?

I’d wager that Buffett and Munger would win.

“But —!” you say, “That’s too short! Buffett and Munger have had a lifetime of experience. At least give me some number of years to practice! With the list of mental models as guidance, I would surely do better!”

And here we come to the crux of the issue. If mental models are the key to success, why is it that reading and understanding these mental models aren’t sufficient? Where does experience fit into this? Why do we assume that a practitioner’s lifetime of experience gives them an edge, even after they have codified all their mental models?

The answer, of course, is that practice matters. Knowing something in theory and knowing something in practice aren't the same thing. But why is this the case? And why should we be suspicious of those who — unlike the practitioners who attempt to externalise their mental models — merely parrot them as shallow copies?

The answer is that the mental models that make Buffett and Munger so effective are divided into two types: mental models that are explicit knowledge and mental models that are tacit knowledge.

The explicit mental models lend themselves to codification, and consist of lenses for seeing the world — know-what frameworks (facts) and know-why frameworks (science). They include things like “winner-take-all markets exist, and these are its properties” as well as “this is how a deflationary debt cycle affects the equity markets.”

But there also exist mental models that are nearly impossible to communicate. We call this tacit knowledge. These mental models are the ones that I believe best explains a practitioner’s success. It is what execution feels like. It is the sequence of moves that an MMA fighter displays when he lunges in for a throw. It is what goes through your head when you make a decision, barely noticeable to your conscious mind. It is what I feel when I need to convince my boss of something, or when I need to introduce a new policy while navigating the political terrain of my organisation.

When Warren Buffett studies a company, he doesn’t see a checklist of mental models he has to apply.

When Warren Buffett studies a company, he doesn’t see a checklist of mental models he has to apply. He doesn’t even see a sheaf of financial statements that he has to go through. Instead, he sees an embodied model of a company, a place that he can navigate in his mind as surely as you or I might navigate a room.

Building this model is what is valuable. No matter how inscrutable it is, no matter how impossible to describe, the central challenge of building expertise in any field as a practitioner is to build up models that allow you to act effectively in the pursuit of your goals.

Some people call this ‘expert’s intuition’. But we can get more specific than that.

A Little Bit of Epistemology Goes a Long Way

Teachers have to struggle with mental models every day.

I was surprised to learn that mental models have been known to learning science researchers for decades. There is nothing special about mental models as a concept — you and I have models of reality in our heads, and will do so for as long as we continue to have a pulse. It is how humans naturally learn.

Similarly, the idea that knowledge can be divided into explicit and tacit is not new: the Ancient Greeks called the former epistêmê and the latter technê, loosely translated into ‘knowledge’ and ‘art’. (I personally prefer the use of ‘technê’, and have used it interchangeably with tacit knowledge throughout this blog).

The term tacit knowledge, on the other hand, was introduced by Michael Polanyi in his 1958 book Personal Knowledge, originally conducted as the 1951-52 Gifford Lectures. Polanyi argued that there is knowledge that cannot be adequately articulated by verbal means, and asserted that most of human knowledge is rooted in tacit knowing.

I don’t want to drag us into the weeds of epistemology, so I’ll point instead to the field of knowledge management.

Knowledge management is primarily concerned with tacit knowledge in the context of organisational learning. Researchers in the field believe that tacit knowledge — not explicit knowledge! — constitutes the bulk of a firm’s operational ability and competitive advantage. Lam, 2000 summaries the three qualities of tacit knowledge:

(First): Knowledge which is tacit is intuitive and unarticulated. It resides in Popper’s ‘World two’ where knowledge cannot be communicated, understood, or used without the ‘knowing subject’. (…) This is particularly true of operational skills and know-how acquired through practical experience. Knowledge of this type is action-oriented and has a personal quality that makes it difficult to formalize or communicate.



Second, the main methods for the acquisition and accumulation of these two knowledge forms also differ. Explicit knowledge can be generated through logical deduction and acquired by formal study. Tacit knowledge, in contrast, can only be acquired through the practical experience in the relevant context i.e. ‘learning-by-doing’.



Third, the two forms of knowledge differ in their potential for aggregation and modes of appropriation. Explicit knowledge can be aggregated at a single location, stored in objective forms and appropriated without the participation of the knowing subject. Tacit knowledge, in contrast, is personal and contextual. It is distributive, and cannot be easily aggregated. The realization of its full potential requires the close involvement and cooperation of the knowing subject.

It’s also worth knowing that tacit and explicit knowledge, while separately categorised, are not separate and discrete in practice. For example, understanding how markets work may be an explicit mental model that Buffett and Munger have in their heads, but learning this model is not sufficient to act as they do. You also need to have the iceberg under that model — their tacit knowledge of how to apply it, when to apply it, and what can be ignored in which situations.

I’ve often noticed that when a practitioner describes an explicit model, he or she describes it in a usable form — usable, that is, if you were a fellow practitioner. Part of it is is describing it at the right level of detail, but another part of it is to describe it in ways that may be tested and made available for application.

And yet, when I read Farnam Street on topics that I have some expertise in — for instance, on the nature of business competition in, say, winner-takes-all markets, I find a distinct lack of actionable handles. This is what I’ve hinted at when I say that you should be suspicious of non-practitioners writing about the mental models of practitioners. Without actual experience running a business, Parrish’s writing works at the wrong resolution.

(To summarise my misgivings about that post, ask yourself the following questions as you read it: if you are in a winner-takes-all market, what strategies are available to you to win? If you are not in a winner-takes-all market — which, contrary to Parrish’s assertion, do not make up the vast majority of markets — what do you do against your competitors? Is there anything in Parrish’s post that will help you? Is Parrish’s post merely to explain that winner-take-all markets exist? But what good is that? In fact: ask this of every post in Farnam Street: how is this useful? How may I test this idea in practice? I suspect that you’ll find yourself more often disappointed than not.)

The alert reader should now begin to realise: if you want to learn the tacit mental models that are responsible for the success of practitioners, your question must reduce down to: how do you learn technê?

To answer this, we must turn to domains that have to teach technê, and have huge financial incentives for getting good at it. We must turn to professional sports.

The Inner Game of Tennis

When Timothy Gallwey was a new tennis pro, fresh out of Harvard, he often observed that the students he coached would perform worse when he gave them verbal instructions, and that they would perform better when he asked them to mimic his strokes and to silence the mutterings of their conscious mind. Gallwey wrote The Inner Game of Tennis shortly after starting on his coaching career, never expecting it to sell more than 20,000 copies.

To his complete shock, and to his publisher’s delight, the book sold over a million copies in the decades since, turning into a phenomenon used by tennis amateurs and pros alike. Buzzfeed reports that NFL defensive end Lawrence Jackson used The Inner Game to up his game, and further explained:

It has become the most influential tennis book ever published, praised by professionals — Billie Jean King told Gallwey the book was her tennis bible — and amateurs alike. Jimmy Carter admitted to reading it to help in White House matches with Zbigniew Brzezinski, his national security adviser, while Rainn Wilson — Dwight from The Office — told the Los Angeles Times that training under a coach who had given him the book was "basically like playing tennis with Yoda." Gallwey himself is still an in-demand teacher and guru — trying to schedule an interview with him for this piece was like trying to get a few minutes of face time with an entertainer on a press tour.

When I first read the book, I found myself less captivated by the sports psychology element of Inner Game as I was by the central mystery Gallwey explores in the opening:

Imagine what goes on inside the head of an eager student taking a lesson from an equally eager new tennis pro. Suppose that the student is a middle-aged businessman bent on improving his position on the club ladder. The pro is standing at the net with a large basket of balls, and being a bit uncertain whether his student is considering him worth the lesson fee, he is carefully evaluating every shot. “That’s good, but you’re rolling your racket face over a little on your follow-through, Mr. Weil. Now shift your weight onto your front foot as you step into the ball… Now you’re taking your racket back too late … Your backswing should be a little lower than on that last shot… That’s it, much better.” Before long, Mr. Weil’s mind is churning with six thoughts about what he should be doing and sixteen thoughts about what he shouldn’t be doing. Improvement seems dubious and very complex, but both he and the pro are impressed by the careful analysis of each stroke and the fee is gladly paid upon receipt of the advice to “practice all this, and eventually you’ll see a big improvement.



(…) My next lesson that day was with a beginner named Paul who had never held a racket. I was determined to show him how to play using as few instructions as possible; I’d try to keep his mind uncluttered and see if it made a difference. So I started by telling Paul I was trying something new: I was going to skip entirely my usual explanations to beginning players about the proper grip, stroke and footwork for the basic forehand. Instead, I was going to hit ten forehands myself, and I wanted him to watch carefully, not thinking about what I was doing, but simply trying to grasp a visual image of the forehand. He was to repeat the image in his mind several times and then just let his body imitate. After I had hit ten forehands, Paul imagined himself doing the same. Then, as I put the racket into his hand, sliding it into the correct grip, he said to me, “I noticed that the first thing you did was to move your feet.” I replied with a noncommittal grunt and asked him to let his body imitate the forehand as well as it could. He dropped the ball, took a perfect backswing, swung forward, racket level, and with natural fluidity ended the swing at shoulder height, perfect for his first attempt! But wait, his feet; they hadn’t moved an inch from the perfect ready position he had assumed before taking his racket back. They were nailed to the court. I pointed to them, and Paul said, “Oh yeah, I forgot about them!” The one element of the stroke Paul had tried to remember was the one thing he didn’t do! Everything else had been absorbed and reproduced without a word being uttered or an instruction being given!



I was beginning to learn what all good pros and students of tennis must learn: that images are better than words, showing better than telling, too much instruction worse than none, and that trying often produces negative results. One question perplexed me: What’s wrong with trying? What does it mean to try too hard?

I know that this sounds like utter rubbish to anyone who hasn’t played a competitive sport before. But stories like this aren’t uncommon.

I used to play Judo seriously, having represented my state in Malaysia’s Nationals Championships in 2007. I remember a drought, early in my Judo career, where I could not throw anyone during competition. It took me many months to learn to stop listening to my master’s instructions, and to focus on acquiring the feeling of executing my throw successfully. I slowed down, mimicked the black belters in my dojo, and was finally rewarded in my second year by a string of wins.

The aftermath of this insight was that I could suddenly see — like a series of ascending doors unlocking above me — slightly further up the path of expertise. My sensei’s instructions about constant movement and control didn’t make sense until I understood how to do my throw successfully.

The difficulty with learning technê is that you can't learn by talking. The best part of Inner Game is when Gallwey finally gets around to discussing technique. Technique, he says, is but a series of ‘feelings’ learnt by a pro and passed on only by shared experience; notice how closely what Gallwey says corroborates what we just learnt about tacit knowledge:

Tennis was brought to America from Europe in the late 1800s. There were no professional tennis teachers to teach technique. The best were players who experienced certain feelings in their swings and tried to communicate those feelings to others. In the effort to understand how to use technical knowledge or theory, I believe that it is most important to recognize that, fundamentally, experience precedes technical knowledge. We may read books or articles that present technical instructions before we have ever lifted a racket, but where did these instructions come from? At some point did they not originate in someone’s experience? Either by accident or by intention someone hit a ball in a certain way and it felt good and it worked. Through experimentation, refinements were made and finally settled into a repeatable stroke.



Perhaps in the interest of being able to repeat that way of hitting the ball again or to pass it on to another, the person attempts to describe that stroke in language. But words can only represent actions, ideas and experiences. Language is not the action, and at best can only hint at the subtlety and complexity contained in the stroke. Although the instruction thus conceived can now be stored in the part of the mind that remembers language, it must be acknowledged that remembering the instruction is not the same as remembering the stroke itself.

This applies not just to tennis, but to all of technê.

How do you know if a computer program is badly designed? You don’t go through a mental checklist; instead, you feel disgust, coloured by your experience.

Think of learning to ride a bicycle. Think of how difficult it is to communicate what you know to a child just beginning to take off her training wheels.

If you write software: think of how you feel when you’re manipulating a program. How do you know if the program is badly designed? You don’t go through a mental checklist; instead, you feel disgust, coloured by your experience.

If you’re a designer, how do you know that something looks good? Sure, you have explicit principles that you learned in design school: rules like the golden ratio, and ‘form ever follows function.’ But when you’re in the middle of creating, what guides your hand as you make aesthetic decisions? Perhaps taste, you say, but how is this taste learnt?

In an earlier series of posts on Commonplace I argued that family-run conglomerates in Asia operated by having father show son (or father show daughter) the ropes of running a complicated portfolio of businesses. I then argued that their success at doing so tells us that business is most likely a form of technê — a skill that can be learnt by a combination of apprenticeship and practice.

The common element to all of this is that true success is not in learning explicit mental models, but in developing tacit ones. The explicit models are merely the tip of the iceberg, poking above the ocean, hiding a huge mass of competency beneath.

Stop Falling for the Mental Model Fallacy

I’d like to close here with a series of questions.

First, if technê is so difficult for a professional practitioner to communicate, what makes you think you’re getting anything out of a non-practitioner? What makes you think that this writer is likely to succeed at getting it right? Remember that words are just hints when it comes to technê; what you’re really after is the feeling — the deep principles and embodied knowledge that the expert can only grasp at communicating.

If the writer you read lacks practice, it’s unlikely that he or she has the mental models necessary to understand what the pro is trying to say. You will find that non-practitioners will write overly-complicated treatises about the mental models of pros. You'll find that they lack the wisdom to make things useful.

And so I’ll leave you with my original recommendation:

Read from the source material of master practitioners, copy their actions, climb their skill trees, and reflect through trial and error. Don't read third-party accounts of technê. And stop reading this blog if my career goals diverge from yours.

I've written a follow-up series to serve as a constructive version of these ideas. You can find that here: A Framework for Putting Mental Models to Practice.