Philosophical scepticism

Philosophical skepticism (UK spelling scepticism; from Greek σκέψις skepsis, "inquiry") is both a philosophical school of thought and a method that questions the possibility of certainty in knowledge. It is generally agreed that knowledge requires justification. It is not enough to have a true belief: one must also have good reasons for that belief. Skeptics claim that it is not possible to have only an adequate justification.

Skepticism is not a single position but covers a range of different positions. In the ancient world there were two main skeptical traditions. Academic skepticism took the dogmatic position that knowledge was not possible; Pyrrhonian skeptics refused to take a dogmatic position on any issue—including skepticism. Radical skepticism ends in the paradoxical claim that one cannot know anything—including that one cannot know about knowing anything.

Skepticism can be classified according to its scope. Local skepticism involves being skeptical about particular areas of knowledge, e.g. moral skepticism, skepticism about the external world, or skepticism about other minds, whereas global skepticism is skeptical about the possibility of any knowledge at all.

Skepticism can also be classified according to its method. In the Western tradition there are two basic approaches to skepticism.Cartesian skepticism —named somewhat misleadingly after René Descartes, who was not a skeptic but used some traditional skeptical arguments in his Meditations to help establish his rationalist approach to knowledge— attempts to show that any proposed knowledge claim can be doubted. Agrippan skepticism focuses on the process of justification rather than the possibility of doubt. According to this view there are three ways in which one might attempt to justify a claim but none of them are adequate: one can keep on providing further justification but this leads to an infinite regress; one can stop at a dogmatic assertion; or one can argue in circular reasoning, never reaching a viable conclusion.

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