II.

Greek Skepticism

The Greek Sophists of the 5th century bc were for the most part skeptics. Their point of view is reflected in their maxims “Man is the measure of all things” and “Nothing is; or if anything is, it cannot be known.” Thus, the Sophist Gorgias declared that all statements concerning reality are false and that, even if true, their truth can never be proved. Another Sophist, Protagoras of Abdera, taught that human beings can know only their perceptions of things, not the things themselves.

The principles of skepticism were first explicitly formulated by the Pyrrhonists, a school of Greek philosophy deriving its name from its founder, Pyrrho of Elis. Pyrrho, whose primary concern was ethics, maintained that human beings can know nothing of the real nature of things, and that consequently the wise person will suspend judgment. Timon of Philius (flourished about 280 bc), Pyrrho's pupil, carried skepticism to its logical conclusion by asserting that equally good reasons can be adduced both for and against any philosophical proposition.

The members of the Middle Academy (the school that developed in the 3rd century bc from Plato's Academy) and the New Academy (2nd century bc) of Carneades were more systematic but somewhat less radical in their skepticism than the Pyrrhonists. Carneades maintained that no beliefs can be proved conclusively but that some can be shown to be more probable than others. The most important skeptics of later antiquity were the Greek philosopher Aenesidemus, who classified ten arguments in support of the skeptical position, and the Greek physician Sextus Empiricus (flourished early 3rd century ad), who emphasized observation and common sense as opposed to theory.