In epistemology, the branch of philosophy concerned with the nature and scope of knowledge, skepticism refers to the position that questions, doubts, or denies the possibility of certain or absolute knowledge. It challenges the idea that humans can attain justified, true beliefs about the external world, other minds, the past, future, or even fundamental logical and mathematical principles. Skepticism is not merely a single doctrine but rather a spectrum of philosophical views, ranging from global skepticism (the denial that any knowledge is possible) to local skepticism (the denial of knowledge in specific domains, such as metaphysics, morality, or theology). The central concerns of epistemological skepticism involve issues of justification, certainty, truth, and the relationship between belief and reality.

Historical Roots of Skepticism

The roots of skepticism trace back to ancient Greek philosophy, particularly the works of Pyrrho of Elis, who is often regarded as the founder of Pyrrhonian skepticism. The Pyrrhonists advocated for epoché (suspension of judgment) due to the equal weight of opposing arguments (equipollence) and believed that suspending judgment leads to ataraxia (peace of mind). In contrast, Academic skepticism, associated with philosophers like Arcesilaus and Carneades, emerged in Plato’s Academy and held the view that knowledge is impossible, though some beliefs may be more reasonable or probable than others. These ancient forms of skepticism deeply influenced later Western philosophical traditions, notably during the Renaissance and Enlightenment, when skepticism resurfaced in critical engagement with religious, scientific, and metaphysical claims.

In modern philosophy, skepticism is prominently addressed by René Descartes, who utilized methodological skepticism to find a secure foundation for knowledge. Descartes doubted everything that could be doubted, including sensory experience, the existence of the external world, and even mathematical truths, until he reached the indubitable truth of cogito, ergo sum (“I think, therefore I am”). This foundationalist approach opposed radical skepticism by establishing certain knowledge on the basis of reason, but it also revealed the depth and strength of skeptical challenges, particularly concerning the mind-world relation.