Sextus Empiricus

Sextus Empiricus was a Greek physician and philosopher who held Roman citizenship, as his name suggests, and he is one of the principal representatives of Pyrrhonian scepticism. He is thought to have lived around the late second and early third centuries, though his dates are not known with certainty. He matters for two reasons: his writings are the most complete surviving account of Pyrrhonism, and because he argues against other Hellenistic schools, he preserves a great deal of information about them.

Little is known about his life. He probably lived in Alexandria, Rome or Athens, and his birthplace is unknown. The nickname "Empiricus" links him to the empirical school of medicine, which focused on clinical experience rather than general theory. Some ancient sources, such as the Suda, identify him with a Sextus of Chaeronea, an identification that is now widely doubted. In his medical writings he seems, at least twice, to place himself closer to the methodist school.

His surviving Greek works are the Outlines of Pyrrhonism and two collections gathered under the title Adversus Mathematicos. The Outlines give the general presentation of his scepticism. The second work is traditionally divided into Books I to VI, often called "Against the Professors," and Books VII to XI, sometimes called "Against the Dogmatists," which survive in fragmentary form. According to ancient reports he also wrote ten books on Pyrrhonism and a work on ethics, both now lost.

His thought begins with a critique of dogmatism. Sextus holds that we cannot know things as they are in themselves, only how they affect us. Against Carneades, whom he accuses of dogmatism for claiming that nothing can be known, he recommends suspending judgment (epoché) about whether anything is knowable, which he links to ataraxia, or tranquillity. His position is less radical than Pyrrho's: he allows everyday life to be guided by experience, the testimony of the senses, the needs of the body and the rules of the crafts. He criticises the syllogism as circular, questions the Stoic notion of the sign, and attacks Stoic theology: if god is corporeal, he argues, it must be either compound and mortal or simple and lifeless.

His influence was considerable. Henricus Stephanus published a Latin translation of the Outlines in Geneva in 1562, followed in 1569 by Gentian Hervet's complete Latin edition, and the Greek text first appeared in 1621. He was widely read in Europe during the sixteenth, seventeenth and eighteenth centuries, and his work left a mark on Montaigne, Hume and Hegel, as well as on much of the later French sceptical tradition.