Sextus Empiricus

Of Sextus' life only two things are known: he was a physician of the Empiric school, hence his name, and he was active around the end of the second century and the beginning of the third, perhaps in Alexandria or Rome. He is the last major representative of the Pyrrhonist tradition and the only one whose works survive complete.

The three books of Outlines of Pyrrhonism are the most systematic account of scepticism. Unlike the dogmatist, the sceptic neither claims to have found the truth nor claims it cannot be found; he simply keeps inquiring. The method sets the arguments for and against any proposition side by side, finds them equally strong, suspends judgement, and tranquillity follows. The book summarises the sceptical 'ten modes' and 'five modes', the latter showing that any proof either regresses infinitely, or runs in a circle, or stops at an arbitrary assumption.

Against the Professors attacks each discipline and each philosophical school in turn. His works were barely read in the Middle Ages, but the Latin translation of 1562 shook Europe at once: Montaigne carved 'What do I know?' into the beams of his study, Descartes invented universal doubt to answer scepticism, and Hume called him a profound sceptic. The whole agenda of modern epistemology was set by his questions.