Sextus Empiricus
160 CE – 210 CE · Ancient Era
“For every argument there exists an equal counter-argument; therefore we should suspend judgment.”
Biography
Sextus was the most systematic exponent of ancient Skepticism. He compiled and refined the arguments of the Pyrrhonian skeptics into a rigorous philosophical method. His works, rediscovered in the Renaissance, launched modern epistemology by forcing philosophers to take the challenge of skepticism seriously.
Major Works
Key Arguments
Click “Philosophy 101” to read the full exploration of each argument.
The Ten Modes of Skepticism
Sextus compiled ten systematic arguments (tropes) demonstrating that our sensory experience is unreliable and that we have no basis for choosing one appearance over another. The same wine tastes sweet to a healthy person and bitter to a sick one; the same tower appears round from a distance and square up close; the same bath water feels hot to one hand and cold to the other; different species perceive entirely different worlds. Objects appear differently depending on the species observing (Mode 1), the individual perceiver (Mode 2), the sense organ involved (Mode 3), the circumstances (Mode 4), the position and distance (Mode 5), the surrounding conditions (Mode 6), the quantity (Mode 7), the relation to other things (Mode 8), the frequency of observation (Mode 9), and the cultural framework of the observer (Mode 10). Since we cannot step outside all perspectives to determine how things 'really' are, we should suspend judgment (epochē).
Why it matters: The Ten Modes were rediscovered during the Renaissance and directly catalyzed modern epistemology: Montaigne drew heavily on Sextus in his Apology for Raymond Sebond, and the skeptical crisis Sextus provoked forced Descartes to develop his method of doubt, Hume his empiricism, and Kant his critical philosophy.
Suspension of Judgment and Tranquility (Ataraxia)
The Pyrrhonian skeptic does not claim that knowledge is impossible (that would itself be a knowledge claim). Instead, the skeptic finds that for every argument supporting a position, an equally strong counter-argument can be constructed. Unable to determine which side is correct, the skeptic suspends judgment, and discovers, unexpectedly, that tranquility (ataraxia) follows. The person who stops making dogmatic claims about the hidden nature of things is freed from the anxiety that comes with defending beliefs. The skeptic continues to live by appearances, customs, and natural impulses, eating when hungry, following local laws, practicing a craft, but without the dogmatic conviction that these appearances correspond to ultimate reality.
Why it matters: The Pyrrhonian insight that peace of mind follows from the abandonment of dogmatic certainty challenged the assumption, shared by Stoics, Epicureans, and Platonists, that happiness requires discovering the truth about reality. The skeptic suggests that perhaps the relentless pursuit of truth is itself a source of suffering, and that contentment is found not in answers but in the suspension of the question.
The Problem of the Criterion
How do we know that our methods of acquiring knowledge are reliable? We might appeal to reason, or to sensory evidence, or to some other criterion. But how do we know that this criterion is itself reliable? We would need another criterion to validate the first, and another to validate that one, generating an infinite regress. Alternatively, we might argue in a circle (using reason to validate reason) or simply assert our criterion without justification. None of these options provides a genuine foundation for knowledge. Sextus called this the problem of the criterion and argued it shows that no dogmatic philosophy can get off the ground without begging the question.
Why it matters: The problem of the criterion was revived by Montaigne, troubled Descartes (who attempted to solve it with the cogito and God's guarantee), and remains unresolved in contemporary epistemology. Roderick Chisholm's 20th-century discussion of the problem directly cites Sextus. It is, in essence, the question of how knowledge can have a non-circular foundation, a question that some philosophers believe has no satisfying answer.
Lasting Influence
Catalyzed modern philosophy by forcing Descartes, Hume, and Kant to confront bold skepticism.
Your Reading Path
The Companion Guide
Seven eras of philosophy in one volume — reading lists, key terms, journal prompts · $19.99