Skepticism developed with regard to various disciplines in which men

claimed to have knowledge. It was questioned, for example, whether one could gain any certain knowledge in metaphysics (the study of the

nature and significance of being as such) or in the sciences. In ancient

times a chief form was medical Skepticism, which questioned whether one could know with certainty either the causes or cures of diseases. In

the area of ethics doubts were raised about accepting various mores and

customs and about claiming any objective basis for making value distinctions. Skepticisms about religion have questioned the doctrines of

different traditions. Certain philosophies, like those of Hume and

Kant, have seemed to show that no knowledge can be gained beyond the world of experience and that one cannot discover the causes of

phenomena. Any attempt to do so, as Kant argued, leads to antinomies,

contradictory knowledge claims. A dominant form of Skepticism, the subject of this article, concerns knowledge in general, questioning whether

anything actually can be known with complete or adequate certainty. This type is called epistemologicalSkepticism.

Kinds of epistemological Skepticism can be distinguished in terms of the

areas in which doubts are raised; that is, whether they be directed toward reason, toward the senses, or toward knowledge of things-in-themselves.

They can also be distinguished in terms of the motivation of the

Skeptic--whether he is challenging views for ideological reasons or for pragmatic or practical ones to attain certain psychological goals. Among the chief ideological motives have been religious or antireligious concerns. Some

Skeptics have challenged knowledge claims so that religious ones could be substituted--on faith. Others have challenged religious knowledge claims in

order to overthrow some orthodoxy. Kinds of Skepticism also can be

distinguished in terms of how restricted or how thoroughgoing they are--whether they apply only to certain areas and to certain kinds of knowledge claims or whether they are more general and universal.