skepticism (skĕpˈtĭsĭzəm) [key] [Gr., = to reflect], philosophic position holding that the possibility of knowledge is limited either because of the limitations of the mind or because of the inaccessibility of its object. It is more loosely used to denote any questioning attitude. Extreme skepticism holds that no knowledge is possible, but this is logically untenable since the statement contradicts itself. The first important skeptical view was held by Democritus, who saw sense perception as no certain guide to objective reality. The Sophists were the earliest group of skeptics. Protagoras taught the relativity of knowledge, and Gorgias held that either nothing could be known, or if anything were known, it could not be communicated. Pyrrho, regarded as the father of skepticism, later held a similarly extreme position, seeing reality as inaccessible. Arcesilaus taught that certitude is impossible and only probable knowledge is attainable. In the Renaissance, skepticism is seen in the writings of Michel de Montaigne, Pierre Charron, and Blaise Pascal. For René Descartes skepticism was a methodology that allowed him to arrive at certain incontrovertible truths. At the end of the 17th cent., Pierre Bayle skeptically challenged philosophical and theological theories. David Hume, a leading modern skeptic, challenged established assumptions about the self, substance, and causality. The skeptical aspect of Immanuel Kant's philosophy is exemplified by his agnosticism; his antinomies of reason demonstrate that certain problems are insoluble by reason. To some degree skepticism manifests itself in the scientific method, which demands that all things assumed as facts be questioned. But the positivism of many scientists, whether latent or open, is incompatible with skepticism, for it accepts without question the assumption that material effect is impossible without material cause.
See R. H. Popkin, The History of Skepticism from Erasmus to Descartes (rev. ed. 1968); C. L. Stough, Greek Skepticism (1969); M. Burnyeat, ed., The Skeptical Tradition (1983); B. Stroud, The Significance of Philosophical Skepticism (1984).