Nassim Taleb

My Thoughts

This book is about the "opposite of fragile", things that benefit from stress, disorder and volatility. Important concepts, unusual ideas and wise advice presented in an entertaining way.

Highlights & Summary Notes

Antifragility is beyond resilience or robustness. The resilient resists shocks and stays the same; the antifragile gets better.

The Antifragile

Black Swans

Black Swans (capitalised) are large-scale unpredictable and irregular events of massive consequence—unpredicted by a certain observer, and such unpredictor is generally called the “turkey” when he is both surprised and harmed by these events.

The Triad

Fragile — Robust — Antifragile


Hydra, in Greek mythology, is a serpent-like creature that dwells in the lake of Lerna, near Argos, and has numerous heads. Each time one is cut off, two grow back. So harm is what it likes. Hydra represents antifragility.


When a small dose of a harmful substance is actually beneficial for the organism, acting as medicine.

Domain Dependence

Humans somehow fail to recognise situations outside the contexts in which they usually learn about them.

e.g. A fellow who looked like a banker had a uniformed porter carry his luggage. About fifteen minutes later I saw the banker lifting free weights at the gym, trying to replicate natural exercises using kettlebells as if he were swinging a suitcase. Domain dependence is pervasive.

We are all, in a way, similarly handicapped, unable to recognise the same idea when it is presented in a different context.

Stressors are Information

Our antifragilities have conditions. The frequency of stressors matters a bit. Humans tend to do better with acute than with chronic stressors, particularly when the former are followed by ample time for recovery, which allows the stressors to do their jobs as messengers.

Reputation Robustness

Heuristic to detect the independence and robustness of someone’s reputation: with few exceptions, those who dress outrageously are robust or even antifragile in reputation; those clean-shaven types who dress in suits and ties are fragile to information about them.


The attempt to suck randomness out of life. Applies to soccer moms, Washington civil servants, strategic planners, social engineers, “nudge” manipulators.

Nature is Antifragile (up to a point)

While hormesis corresponds to situations by which the individual organism benefits from direct harm to itself, evolution occurs when harm makes the individual organism perish and the benefits are transferred to others, the surviving ones, and future generations.

For an illustration of how families of organisms like harm in order to evolve (again, up to a point), though not the organisms themselves, consider the phenomenon of antibiotic resistance. The harder you try to harm bacteria, the stronger the survivors will be—unless you can manage to eradicate them completely.


When you starve yourself of food, it is the bad proteins that are broken down first and recycled by your own body—a process called autophagy.

Learning From Mistakes

My characterisation of a loser is someone who, after making a mistake, doesn’t introspect, doesn’t exploit it, feels embarrassed and defensive rather than enriched with a new piece of information, and tries to explain why he made the mistake rather than moving on.


Someone who did not find something is providing others with knowledge, the best knowledge, that of absence (what does not work)—yet he gets little or no credit for it. He is a central part of the process with incentives going to others and, what is worse, gets no respect.

Most of you will fail, disrespected, impoverished, but we are grateful for the risks you are taking and the sacrifices you are making for the sake of the economic growth of the planet and pulling others out of poverty. You are at the source of our antifragility. Our nation thanks you.

Modernity and the Denial of Antifragility

The Procrustean Bed

Procrustes got people to fit perfectly into his bed by cutting or stretching their limbs. Corresponds to situations in which simplifications are not simplifications.

Mediocristan & Extremistan

Mediocristan — A process dominated by the mediocre, with few extreme successes or failures (say, income for a dentist). No single observation can meaningfully affect the aggregate. Also called “thin-tailed,” or member of the Gaussian family of distributions.

Mediocristan has a lot of variations, not a single one of which is extreme; Extremistan has few variations, but those that take place are extreme.

Extremistan — A process where the total can be conceivably impacted by a single observation (say, income for a writer). Also called “fat-tailed.” Includes the fractal, or power-law, family of distributions.

The more variability you observe in a system, the less Black Swan–prone it is.

The Turkey Problem

The turkey is fed by the butcher for a thousand days, and every day the turkey pronounces with increased statistical confidence that the butcher “will never hurt it”—until Thanksgiving, which brings a Black Swan revision of belief for the turkey. The inverse turkey error is the mirror confusion, not seeing opportunities—pronouncing that one has evidence that someone digging for gold or searching for cures will “never find” anything.

The key here is that such a surprise will be a Black Swan event; but just for the turkey, not for the butcher.

We can also see from the turkey story the mother of all harmful mistakes: mistaking absence of evidence (of harm) for evidence of absence, a mistake that we will see tends to prevail in intellectual circles and one that is grounded in the social sciences.

The Value of Randomness

Some systems like randomness. e.g. Systematically preventing forest fires from taking place “to be safe” makes the big one much worse.

Brudian's Donkey — A donkey equally famished and thirsty caught at an equal distance between food and water would unavoidably die of hunger or thirst. You can see here that absence of randomness equals guaranteed death.

The ancients evolved hidden and sophisticated ways and tricks to exploit randomness.

We seek vaccination at every new school year (injecting ourselves with a bit of harm to build immunity) but fail to transfer the mechanism to political and economic domains.


Harm done by the healer, as when the doctor’s interventions do more harm than good.

Naive Intervention

Intervention with disregard to iatrogenics. The preference, even obligation, to “do something” over doing nothing. While this instinct can be beneficial in emergency rooms or ancestral environments, it hurts in others in which there is an “expert problem.

It is mostly about having a systematic protocol to determine when to intervene and when to leave systems alone. And we may need to intervene to control the iatrogenics of modernity—particularly the large-scale harm to the environment and the concentration of potential (though not yet manifested) damage, the kind of thing we only notice when it is too late.


Few understand that procrastination is our natural defense, letting things take care of themselves and exercise their antifragility; it results from some ecological or naturalistic wisdom, and is not always bad—at an existential level, it is my body rebelling against its entrapment.

Granted, in the modern world, my tax return is not going to take care of itself—but by delaying a non-vital visit to a doctor, or deferring the writing of a passage until my body tells me that I am ready for it, I may be using a very potent naturalistic filter.

Since procrastination is a message from our natural willpower via low motivation, the cure is changing the environment, or one’s profession, by selecting one in which one does not have to fight one’s impulses. Few can grasp the logical consequence that, instead, one should lead a life in which procrastination is good, as a naturalistic-risk-based form of decision making.

Information and Antifragility

The previous two chapters showed how you can use and take advantage of noise and randomness; but noise and randomness can also use and take advantage of you, particularly when totally unnatural, as with the data you get on the Web or through the media.

That is two hundred times more noise than signal—which is why anyone who listens to news (except when very, very significant events take place) is one step below sucker.

There is a biological dimension to this story. I have been repeating that in a natural environment, a stressor is information. Too much information would thus be too much stress, exceeding the threshold of antifragility.

Now let’s add the psychological to this: we are not made to understand the point, so we overreact emotionally to noise. The best solution is to only look at very large changes in data or conditions, never at small ones.

A Nonpredictive View of the World

Fat Tony and The Fragalistas

Fat Tony — the smeller of fragility.

Fat Tony did not believe in predictions. But he made big bucks predicting that some people—the predictors—would go bust.

Curiosity is antifragile, like an addiction, and is magnified by attempts to satisfy.


Someone who causes fragility because he thinks he understands what’s going on. Often Fragilistas fragilize by depriving variability-loving systems of variability and error-loving.

Fundamental Asymmetry / Seneca's Asymmetry

When someone has more upside than downside in a certain situation, he is antifragile and tends to gain from (a) volatility, (b) randomness, (c) errors, (d) uncertainty, (e) stressors, (f) time. And the reverse.

The traditional understanding of Stoicism in the literature is of some indifference to fate.

Success brings an asymmetry: you now have a lot more to lose than to gain. Seneca’s practical method to counter such fragility was to go through mental exercises to write off possessions, so when losses occurred he would not feel the sting—a way to wrest one’s freedom from circumstances. It is hard to stick to a good discipline of mental write-off when things are going well, yet that’s when one needs the discipline the most.

The antifragile package has more to gain than to lose from being shaken. Simple test: if I have “nothing to lose” then it is all gain and I am antifragile.

Fragility implies more to lose than to gain, equals more downside than upside, equals (unfavorable) asymmetry. Antifragility implies more to gain than to lose, equals more upside than downside, equals (favorable) asymmetry

The Barbell Strategy

A dual strategy, a combination of two extremes, one safe and one speculative, deemed more robust than a “monomodal” strategy; often a necessary condition for antifragility.

The barbell (or bimodal) strategy is a way to achieve antifragility and move to the right side of the Triad.

The first step toward antifragility consists in first decreasing downside, rather than increasing upside; that is, by lowering exposure to negative Black Swans and letting natural antifragility work by itself.

I find it preferable (and less painful) to work intensely for very short hours, then do nothing for the rest of the time (assuming doing nothing is really doing nothing), until I recover completely and look forward to a repetition.

Optionality, Technology, and the Intelligence of Antifragility

Teleological Fallacy

The illusion that you know exactly where you are going, and that you knew exactly where you were going in the past, and that others have succeeded in the past by knowing where they were going.

Rational Optionality

Not being locked into a given program, so one can change his mind as he goes along based on discovery or new information.

Optionality will take us many places, but at the core, an option is what makes you antifragile and allows you to benefit from the positive side of uncertainty, without a corresponding serious harm from the negative side.

Any options, by allowing you more upside than downside, are vectors of antifragility.

I am fond of the brand of the unexpected one finds at parties (going to parties has optionality, perhaps the best advice for someone who wants to benefit from uncertainty with low downside).

Option = asymmetry + rationality: The rationality part lies in keeping what is good and ditching the bad, knowing to take the profits. As we saw, nature has a filter to keep the good baby and get rid of the bad. The difference between the antifragile and the fragile lies there. The fragile has no option. But the antifragile needs to select what’s best—the best option.

Rational Flaneur

Someone who, unlike a tourist, makes a decision opportunistically at every step to revise his schedule (or his destination) so he can imbibe things based on new information obtained. In research and entrepreneurship, being a flâneur is called “looking for optionality.” A non-narrative approach to life.

Things That Like Dispersion

Beyond books, consider this simple heuristic: your work and ideas, whether in politics, the arts, or other domains, are antifragile if, instead of having one hundred percent of the people finding your mission acceptable or mildly commendable, you are better off having a high percentage of people disliking you and your message (even intensely), combined with a low percentage of extremely loyal and enthusiastic supporters. Options like dispersion of outcomes and don’t care about the average too much.

Lecturing Birds How to Fly

Definition — Inverting the arrow of knowledge to read academia → practice, or education → wealth, to make it look as though technology owes more to institutional science than it actually does.

Just as great geniuses invent their predecessors, practical innovations create their theoretical ancestry.

We need some randomness to help us out—with a double dose of antifragility. For randomness plays a role at two levels: the invention and the implementation.

But why is it that when we anthropomorphize and replace “birds” with “men,” the idea that people learn to do things thanks to lectures becomes plausible? When it comes to human agency, matters suddenly become confusing to us.

The lecturing-birds-how-to-fly effect is an example of epiphenomenal belief: we see a high degree of academic research in countries that are wealthy and developed, leading us to think uncritically that research is the generator of wealth.

Cherry Picking (Fallacy of Confirmation)

In institutional research, one can selectively report facts that confirm one’s story, without revealing facts that disprove it or don’t apply to it.

Someone with optionality—the right to pick and choose his story—is only reporting on what suits his purpose. You take the upside of your story and hide the downside, so only the sensational seems to count.

The Green Lumber Fallacy

Mistaking the source of important or even necessary knowledge—the greenness of lumber—for another, less visible from the outside, less tractable one. How theoreticians impute wrong weights to what one should know in a certain business or, more generally, how many things we call “relevant knowledge” aren’t so much so.

Prometheus and Epimetheus

Prometheus and Epimetheus. Prometheus means “fore-thinker” while Epimetheus means “after-thinker,” equivalent to someone who falls for the retrospective distortion of fitting theories to past events in an ex post narrative manner.

Optionality is Promethean, narratives are Epimethean—one has reversible and benign mistakes, the other symbolizes the gravity and irreversibility of the consequences of opening Pandora’s box.

Expert problems put you on the wrong side of asymmetry.

When you are fragile you need to know a lot more than when you are antifragile. Conversely, when you think you know more than you do, you are fragile (to error).

Antifragile risk taking—not education and formal, organized research—is largely responsible for innovation and growth, while the story is dressed up by textbook writers.


The difference between humans and animals lies in the ability to collaborate, engage in business, let ideas copulate. Collaboration has explosive upside, what is mathematically called a superadditive function, i.e., one plus one equals more than two, and one plus one plus one equals much, much more than three.

Crucially, this is an argument for unpredictability and Black Swan effects: since you cannot forecast collaborations and cannot direct them, you cannot see where the world is going. All you can do is create an environment that facilitates these collaborations, and lay the foundation for prosperity.

Corporate Teleology

Corporations are in love with the idea of the strategic plan. They need to pay to figure out where they are going. Yet there is no evidence that strategic planning works—we even seem to have evidence against it. A management scholar, William Starbuck, has published a few papers debunking the effectiveness of planning—it makes the corporation option-blind, as it gets locked into a non-opportunistic course of action.

Rules for Optionality

Let me stop to issue rules based on the chapter so far. (i) Look for optionality; in fact, rank things according to optionality, (ii) preferably with open-ended, not closed-ended, payoffs; (iii) Do not invest in business plans but in people, so look for someone capable of changing six or seven times over his career, or more; one gets immunity from the backfit narratives of the business plan by investing in people. It is simply more robust to do so; (iv) Make sure you are barbelled, whatever that means in your business.

Educating the Flaneur

As a child of civil war, I disbelieve in structured learning—actually I believe that one can be an intellectual without being a nerd, provided one has a private library instead of a classroom, and spends time as an aimless (but rational) flâneur benefiting from what randomness can give us inside and outside the library.

The trick is to be bored with a specific book, rather than with the act of reading.

Much of what other people know isn’t worth knowing.

The Nonlinear and the Nonlinear

Convexity, Concavity and Convexity Effects

Nonlinearities, Convexity Effects (smiles and frowns): Nonlinearities can be concave or convex, or a mix of both. The term convexity effects is an extension and generalization of the fundamental asymmetry. The technical name for fragility is negative convexity effects and for antifragility is positive convexity effects. Convex is good (a smiley), concave is bad (a frowny).

In spite of what is studied in business schools concerning “economies of scale,” size hurts you at times of stress; it is not a good idea to be large during difficult times.

The Philosopher's Stone

Philosopher’s Stone, also called Convexity Bias (very technical): The exact measure of benefits derived from nonlinearity or optionality. For instance, such bias can quantify the health benefits of variable intensity of pulmonary ventilation over steady pressure, or compute the gains from infrequent feeding. The Procrustean bed from the neglect of nonlinearity (to “simplify”) lies in assuming such convexity bias does not exist.

Via Negitiva (by subtraction)

In theology and philosophy, the focus on what something is not, an indirect definition. In action, it is a recipe for what to avoid, what not to do—subtraction, not addition, say, in medicine.

So the central tenet of the epistemology I advocate is as follows: we know a lot more what is wrong than what is right, or, phrased according to the fragile/robust classification, negative knowledge (what is wrong, what does not work) is more robust to error than positive knowledge (what is right, what works).

Subtractive knowledge is a form of barbell. Critically, it is convex. What is wrong is quite robust, what you don’t know is fragile and speculative, but you do not take it seriously so you make sure it does not harm you in case it turns out to be false.


A love of change for its own sake, a form of philistinism that does not comply with the Lindy effect and understands fragility. Forecasts the future by adding, not subtracting.

Lindy Effect

A technology, or anything nonperishable, increases in life expectancy with every day of its life—unlike perishable items (such as humans, cats, dogs, and tomatoes). So a book that has been a hundred years in print is likely to stay in print another hundred years.

Because all surviving technologies have some obvious benefits, we are led to believe that all technologies offering obvious benefits will survive.

We notice what varies and changes more than what plays a large role but doesn’t change. We rely more on water than on cell phones but because water does not change and cell phones do, we are prone to thinking that cell phones play a larger role than they do.

Treadmill Effect

We even rapidly tire of what we have, continuously searching for versions 2.0 and similar iterations. And after that, another “improved” reincarnation. These impulses to buy new things that will eventually lose their novelty, particularly when compared to newer things, are called treadmill effects.

Empedocles' Tile

A dog sleeps on the same tile because of a natural, biological, explainable or nonexplainable match, confirmed by long series of recurrent frequentation. We may never know the reason, but the match is there. Example: why we read books.


Simple, quite simple decision rules and heuristics emerge from this chapter. Via negativa, of course (by removal of the unnatural): only resort to medical techniques when the health payoff is very large (say, saving a life) and visibly exceeds its potential harm, such as incontrovertibly needed surgery or lifesaving medicine (penicillin).

e.g. Antibiotics. Every time you take an antibiotic, you help, to some degree, the mutation of germs into antibiotic-resistant strains. Add to that the toying with your immune system. You transfer the antifragility from your body to the germ. The solution, of course, is to do it only when the benefits are large.

e.g. Hygiene, or excessive hygiene, has the same effect, particularly when people clean their hands with chemicals after every social exposure.

Let me phrase the last point a bit differently. If there is something in nature you don’t understand, odds are it makes sense in a deeper way that is beyond your understanding.

What Mother Nature does is rigorous until proven otherwise; what humans and science do is flawed until proven otherwise.

Diet, Health & Antifragility

Another application of via negativa: spend less, live longer is a subtractive strategy. We saw that iatrogenics comes from the intervention bias, via positiva, the propensity to want to do something, causing all the problems we’ve discussed. But let’s do some via negativa here: removing things can be quite a potent (and, empirically, a more rigorous) action.

Happiness is best dealt with as a negative concept; the same nonlinearity applies. The “pursuit of happiness” is not equivalent to the “avoidance of unhappiness".

To understand the outright denial of antifragility in the way we seek wealth, consider that construction laborers seem happier with a ham and cheese baguette than businessmen with a Michelin three-star meal. Food tastes so much better after exertion.

We need modern civilization for many things, such as the legal system and emergency room surgery. But just imagine how by the subtractive perspective, via negativa, we can be better off by getting tougher (e.g. no sunscreen, no sunglasses, no orange juice)

Religion and Naive Interventionism

We rarely look at religion’s benefits in limiting the intervention bias and its iatrogenics: in a large set of circumstances (marginal disease), anything that takes you away from the doctor and allows you to do nothing (hence gives nature a chance to do its work) will be beneficial.

So going to church (or the temple of Apollo) for mild cases—say, those devoid of trauma, like a mild discomfort, not injuries from a car accident, those situations in which the risk of iatrogenics exceeds the benefit of cure, to repeat it again, the cases with negative convexity—will certainly help.

The Ethics of Fragility and Antifragility


A sense of grandeur that was superseded by the Christian value of “humility.” There is no word for it in Romance languages; in Arabic it is called Shhm—best translated as nonsmall. If you take risks and face your fate with dignity, there is nothing you can do that makes you small; if you don’t take risks, there is nothing you can do that makes you grand, nothing. And when you take risks, insults by half-men (small men, those who don’t risk anything) are similar to barks by nonhuman animals: you can’t feel insulted by a dog.

The Agency Problem

Situation in which the manager of a business is not the true owner, so he follows a strategy that cosmetically seems to be sound, but in a hidden way benefits him and makes him antifragile at the expense (fragility) of the true owners or society. When he is right, he collects large benefits; when he is wrong, others pay the price. Typically this problem leads to fragility, as it is easy to hide risks. It also affects politicians and academics. A major source of fragility.

Skin in the Game

Every captain goes down with every ship. This removes the agency problem and the lack of doxastic commitment.

So counter to the entire idea of the intellectual and commentator as a detached and protected member of society, I am stating here that I find it profoundly unethical to talk without doing, without exposure to harm, without having one’s skin in the game, without having something at risk.

If you see fraud and don’t say fraud, you are a fraud.

Soul in the Game

You must only believe predictions and opinions by those who committed themselves to a certain belief, and had something to lose, in a way to pay a cost in being wrong.

The psychologist Gerd Gigerenzer has a simple heuristic. Never ask the doctor what you should do. Ask him what he would do if he were in your place. You would be surprised at the difference.

Frequency and Arguments

On paper, the frequency of being right matters, but only on paper—typically, fragile payoffs have little (sometimes no) upside, and antifragile payoffs have little downside.

One makes pennies to lose dollars in the fragile case; makes dollars to lose pennies in the  antifragile one. So the antifragile can lose for a long time with impunity, so long as he happens to be right once; for the fragile, a single loss can be terminal.

Accordingly if you were betting on the downfall of, say, a portfolio of financial institutions because of their fragilities, it would have cost you pennies over the years preceding their eventual demise in 2008, as Nero and Tony did. (Note again that taking the other side of fragility makes you antifragile.)

You were wrong for years, right for a moment, losing small, winning big, so vastly more successful than the other way (actually the other way would be bust).

To put in Fat Tony terms: suckers try to be right, nonsuckers try to make the buck, or: Suckers try to win arguments, nonsuckers try to win.

Antifragility and the Ethics of Large Organisations

The problem of the commercial world is that it only works by addition (via positiva), not subtraction (via negativa).

Pharmaceutical companies don’t gain if you avoid sugar; the manufacturer of health club machines doesn’t benefit from your deciding to lift stones and walk on rocks (without a cell phone); all these firms have to produce “growth in revenues” to satisfy the metric of some slow thinking or, at best, semi-slow thinking MBA analyst sitting in New York. Of course they will eventually self-destruct, but that’s another conversation.

By definition, what is being marketed is necessarily inferior, otherwise it would not be advertised. Marketing beyond conveying information is insecurity.

We accept that people who boast are boastful and turn people off. How about companies? Why aren’t we turned off by companies that advertise how great they are?

We have three layers of violations:

  1. The mild violation: companies are shamelessly self-promotional
  2. The more serious violation: companies trying to represent themselves in the most favourable light possible, hiding the defects of their products—still harmless, as we tend to expect it and rely on the opinion of users.
  3. The even more serious violation: companies trying to misrepresent the product they sell by playing with our cognitive biases, our unconscious associations, and that’s sneaky.


Remember that food would not have a taste if it weren’t for hunger; results are meaningless without effort, joy without sadness, convictions without uncertainty, and an ethical life isn’t so when stripped of personal risks.