First published Wed Feb 24, 2010; substantive revision Wed Sep 21, 2022
The Greek word skepsis means investigation. Literally, a “skeptic” is an inquirer. Not all ancient philosophers whom in retrospect we call “skeptics” refer to themselves as such. Nevertheless, they all embrace ways of life that are devoted to inquiry. Ancient skepticism is as much concerned with belief as with knowledge. As long as knowledge has not been attained, the skeptics aim not to affirm anything. This gives rise to their most controversial ambition: a life without belief.
Ancient skepticism is, for the most part, a phenomenon of Post-Classical, Hellenistic philosophy. The Academic and Pyrrhonian skeptical movements begin roughly in the third century BCE, and end with Sextus Empiricus in the second century CE. Hellenistic philosophy is a large-scale conversation, not unlike philosophy today. The skeptics (among them Pyrrho, Timon, Arcesilaus, Carneades, Aenesidemus, and Sextus Empiricus) do engage with Pre-Socratic philosophy, Socrates, Protagorean relativism, Plato, and perhaps Aristotle. But their contemporary and principal interlocutors are Epicureans, Stoics, Cynics, and Megarian logicians (cf. Long 2006, ch. 4 and 5).