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Mental Models

Sextus Empiricus and Empirical Skepticism

Sextus Empiricus, an ancient Greek physician and philosopher, advocated for empirical skepticism—doubting theories and causality while relying cautiously on past experience. His Pyrrhonian skepticism promoted intellectual serenity through systematic doubt and opposition to dogma, influencing decision-making under uncertainty.

THE IDEA

Sextus the (Alas) Empirical

The violently antiacademic writer, and antidogma activist, Sextus Empiricus operated close to a millennium and a half before Hume, and formulated the turkey problem with great precision. We know very little about him; we do not know whether he was a philosopher or more of a copyist of philosophical texts by authors obscure to us today. We surmise that he lived in Alexandria in the second century of our era. He belonged to a school of medicine called “empirical,” since its practitioners doubted theories and causality and relied on past experience as guidance in their treatment, though not putting much trust in it. Furthermore, they did not trust that anatomy revealed function too obviously. The most famous proponent of the empirical school, Menodotus of Nicomedia, who merged empiricism and philosophical skepticism, was said to keep medicine an art, not a “science,” and insulate its practice from the problems of dogmatic science. The practice of medicine explains the addition of empiricus (“the empirical”) to Sextus’s name.

Sextus represented and jotted down the ideas of the school of the Pyrrhonian skeptics who were after some form of intellectual therapy resulting from the suspension of belief. Do you face the possibility of an adverse event? Don’t worry. Who knows, it may turn out to be good for you. Doubting the consequences of an outcome will allow you to remain imperturbable. The Pyrrhonian skeptics were docile citizens who followed customs and traditions whenever possible, but taught themselves to systematically doubt everything, and thus attain a level of serenity. But while conservative in their habits, they were rabid in their fight against dogma.

Among the surviving works of Sextus’s is a diatribe with the beautiful title Adversos Mathematicos, sometimes translated as Against the Professors. Much of it could have been written last Wednesday night!

Where Sextus is mostly interesting for my ideas is in his rare mixing of philosophy and decision making in his practice. He was a doer, hence classical scholars don’t say nice things about him. The methods of empirical medicine, relying on seemingly purposeless trial and error, will be central to my ideas on planning and prediction, on how to benefit from the Black Swan.

In 1998, when I went out on my own, I called my research laboratory and trading firm Empirica, not for the same antidogmatist reasons, but on the account of the far more depressing reminder that it took at least another fourteen centuries after the works of the school of empirical medicine before medicine changed and finally became adogmatic, suspicious of theorizing, profoundly skeptical, and evidence-based! Lesson? That awareness of a problem does not mean much—particularly when you have special interests and self-serving institutions in play.

When to use it

  • Using trial and error in medical treatment when theoretical knowledge is insufficient.

  • Applying skepticism to investment predictions to avoid overconfidence in historical trends.

  • Questioning assumptions that past data reliably predicts future outcomes in risk management.

  • Suspending belief about the consequences of a decision to maintain emotional imperturbability.

FROM THEORY TO EVERYDAY LIFE

In practice

01

The Turkey Problem

Sextus Empiricus formulated the turkey problem: a turkey is fed every day, so it assumes the farmer is benevolent, until the day before Thanksgiving when its past experience fails. Relying on past patterns can lead to dangerous surprises.

02

Empirical Medicine

The empirical school of medicine treated patients based on observed past outcomes rather than theoretical causes. For example, a physician might prescribe a herb because it worked in similar cases before, without understanding why, reflecting trial-and-error decision-making.

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A MOMENT TO REFLECT

Put it to work.

  1. How can you apply Pyrrhonian skepticism to your daily decisions, especially when facing uncertainty?

  2. In what areas of your life do you assume past patterns will continue, ignoring the possibility of a black swan?

  3. How does the empirical school's distrust of theories influence modern evidence-based medicine?

Connected ideas

Another lens can bring the same problem into focus.

Often confused with

CONTINUE THE CONVERSATION

Source texts

  • The Black Swan The Impact of the Highly Improbable With a new section On Robustness and Fragility (Nassim Nicholas Taleb)
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