Sextus Empiricus
Greek sceptic philosopher and physician (2nd–3rd century AD), about whom almost no reliable biographical information survives beyond his own name, his membership of the 'empiricist' medical school — hence his surname — and his probable activity as head of the Pyrrhonist school toward the end of his life, his work being the only extensive source to survive intact from the entire Pyrrhonist sceptical tradition of antiquity, transmitted and preserved precisely because, unlike other earlier sceptical texts, it managed to survive complete through medieval manuscripts. His fundamental work, Outlines of Pyrrhonism, offers the most complete and detailed surviving systematic exposition of Pyrrhonism, the most radical form of ancient philosophical scepticism, founded by Pyrrho of Elis centuries earlier, which held that on any serious philosophical question it is possible to construct equally persuasive arguments for and against, reaching a state of 'equipollence' (isostheneia) that makes it impossible to decide rationally between opposing positions, and that therefore the only philosophically coherent attitude is the suspension of judgement (epoché) regarding all dogmatic claims about the ultimate nature of reality. Sextus systematised with notable methodological rigour the various 'modes' or argumentative tropes through which Pyrrhonist sceptics generated this suspension of judgement — variations in perception among animal species, among individuals, according to circumstances, the relativity of all perception, among others — and argued that, paradoxically, this suspension of judgement, far from leading to paralysis, leads to ataraxia, the tranquillity and inner peace constituting the ultimate goal of all Hellenistic philosophy. One of the most original and influential aspects of his work is his systematic critique not only of philosophical dogmatism (Stoic, Epicurean, Academic) but of all the technical and scientific disciplines of his time — grammar, rhetoric, music, geometry, astrology — a work collected as Against the Professors (Adversus Mathematicos), which constitutes one of the most exhaustive critiques in all antiquity of the epistemological foundations of specialised knowledge. Rediscovered during the Renaissance, Sextus Empiricus's work exerted decisive influence on modern thought, especially on Montaigne, Pierre Bayle and, through them, on the philosophical scepticism that would run through modernity all the way to Hume.