Sextus Empiricus was a Pyrrhonian Skeptic living probably in the second or third century CE, many of whose works survive, including the Outlines of Pyrrhonism, which is the best and fullest account we have of Pyrrhonian skepticism. (Book I of that work consists of Sextus' codification of the nature of Pyrrhonian skepticism, which he contrasts with the outlooks of other schools of philosophy.) Fittingly, we know little or nothing about the life of Sextus Empiricus, including when and where he lived. Best estimates put him anywhere between 100 CE and the first half of the third century CE (House 1980), but it has been suggested that he was already well known by the end of the second century (Barnes 2000: xii). Sextus is called ‘Empiricus’ because he belonged to the Empirical School of Medicine (Deichgräber 1965: 40–1). There were three main schools of medicine, the Rationalists, the Empiricists, and the Methodists. Confusingly, even though Sextus was an Empiricist, he actually states in Outlines of Pyrrhonism I 236 that while Pyrrhonism is very similar to the Empirical School of Medicine, Pyrrhonists ‘might rather adopt’ Methodism. This is a standing puzzle for interpreters of Sextus.

Morison, Benjamin, “Sextus Empiricus”, The Stanford Encyclopedia of Philosophy (Spring 2014 Edition), Edward N. Zalta (ed.), forthcoming URL = <http://plato.stanford.edu/archives/spr2014/entries/sextus-empiricus/>.