Skepticism in philosophy refers to the principle that all knowledge, whether sensory or conceptual, is subject to the limitations of the human mind and, thus, unreliable. No certain or absolute knowledge can be attained by man. This position was advanced by such Greek schools as the Sophists and the Pyrrhonists. They did not, however, consider revelation. In religious philosophy some thinkers, while accepting the skeptical view concerning knowledge acquired by natural means, have held that certain knowledge can be attained through the supernatural act of revelation. But others, while denying the skeptics' claim about natural knowledge, have found the claim of certain supernatural knowledge open to unresolvable doubt, requiring either rejection or suspension of judgment regarding its validity.
Although medieval Jewish thinkers offered varied interpretations of Judaism, none subscribed to extreme skepticism about man's ability to acquire certain knowledge naturally, though the historical forms of this skepticism were known to them (cf. Saadiah Gaon, Emunot ve-De'ot, ch. 4). All affirmed the existence of positive knowledge upon which the truths of Judaism, however understood, could be based. Joseph *Albo epitomized this viewpoint in his specific rejection of philosophic skepticism. Moreover, unlike such medieval Christian mystics as Peter Damian (1007–1072) and Bernard of Clairvaux (1091–1153), who minimized the possibilities of natural against supernatural knowledge, most Jewish philosophers
*Judah Halevi and Ḥasdai *Crescas came closest among Jewish thinkers to skepticism about naturally acquired knowledge. But natural knowledge to medievals consisted of neoplatonic Aristotelian metaphysics and physics, and Judah Halevi and Crescas denied the adequacy of these theories as ultimate theological truths. However, in their refutations of neoplatonic Aristotelianism, Judah Halevi and Crescas relied on reason and assumed the validity of empirical knowledge.
The question whether any medieval Jewish thinkers were skeptical of revelations as a source of knowledge cannot be unequivocally determined. This issue arises particularly in the thought of *Maimonides and *Levi b. Gershom. Maimonides specifically rejected the opinion that non-Mosaic prophecy arose supernaturally, but his view of Mosaic prophecy was deliberately obscure. From a number of veiled remarks, Maimonides' view appears to be that Moses' prophecy arose naturally as well. Levi b. Gershom's position seems, in the main, similar to that of Maimonides.
Guttmann, Philosophies, 67, 122, 226; Husik, Philosophy, 152–3, 389; A.J. Reines, in: HUCA, 40–41 (1969–70), 325–61; H.A. Wolfson, in: Hebrew Union College Jubilee Volume (1925), 263–315; idem, in: HTR, 28 (1935), 69–133; S. Horowitz, in: Judaica, Festschrift zu Hermann Cohens 70. Geburtstag (1912), 235–52.