Skepticism — A philosophical attitude of systematic doubt about whether certain, justified knowledge can be attained. The word derives from the Greek skeptesthai, “to examine” or “to inquire,” so that the skeptikós is first of all one who keeps inquiring without either affirming or denying. In antiquity, radical skepticism is represented by Pyrrho of Elis and by Pyrrhonism, whose systematic exposition has reached us in the Outlines of Pyrrhonism by Sextus Empiricus. The method consists in setting arguments of equal force against one another on any question; faced with this equipollence, the skeptic arrives at epoché (suspension of judgment) and, through it, at ataraxia, the tranquility of a mind freed from the disturbance caused by dogmatic beliefs. Distinct from this is the Academic skepticism that developed in two phases. In the Middle Academy, Arcesilaus radicalised the Socratic inheritance by defending total suspension of judgment (epoché) and, to guide action without dogmatism, appealed to “the reasonable” (eúlogon). In the New Academy, Carneades went further: while retaining epoché as a theoretical ideal, he introduced the concept of tò pithanón (the plausible or probable) as a practical criterion for action, admitting degrees of plausibility as a sufficient guide for living. In the modern era, Descartes turns skeptical doubt into a methodical device: he doubts everything that can be called into question—the senses, the external world, even mathematical truths—until he reaches an indubitable certainty, the cogito, “I think, therefore I am.” Doubt thus ceases to be an end and becomes an instrument for grounding knowledge. Skepticism remains a central theme in epistemology, especially in contemporary debates over the justification of belief and over hypothetical error scenarios, such as the evil demon. It is closely related to epoché and to the problem of the criterion of truth.
← Glossary