Between Reason and Faith, part I
From the introduction of Between Reason and Faith: Anti-Rationalism in Italian Jewish Thought 1250-1650 (The Hague: Mouton 1967), by Isaac E. Barzilay:
During the five centuries which separate Sa'adyah Gaon (d. 942) from Joseph Albo (d. 1444) a supreme effort was made by Jewish intellectuals to reinterpret Judaism in the light of Greco-Islamic philosophy and science which, from about the tenth century on, began to penetrate the Jewish world, exerting a marked influence on it. A tenacious loyalty to an ancient law and culture, on the one hand, and a growing awareness of the intellectual and scientific trends in the milieu, on the other hand, prompted such an interpretation and made it imperative. The creative minority within Jewry, it seems, could not respond to the challenge of the philosophical and scientific awakening in both the Islamic and, at a later period, the Christian world in any way other than by absorbing the new ideas and attempting to reconcile them with Judaism.
The product of this effort was, indeed, a new synthesis necessitated by the historical reality. This synthesis had twofold implications. On the one hand, the interaction with the wider intellectual currents of the time caused Judaism to emerge from its insularity, enriched it, and demonstrated its vitality and adaptability. On the other hand, this process was wrought with grave dangers as far as the spiritual survival of the Jewish people was concerned.
Since Jewry was deprived of the natural prerequisites for a normal national existence, its preservation in the Diaspora depended primarily on the integrity of its religious beliefs and practices, as well as on the preservation of its national hopes and aspirations. These foundations rationalism, by its very nature, tended to weaken and undermine. Although the spread of rational speculation and knowledge generally constitutes a positive force in the life of normal societies, enriching their ethos and elevating them to higher cultural levels, it has proven throughout exilic Jewish history to have had a rather adverse effect on the national Jewish ethos, evoking in the people centrifugal tendencies of social dissolution and religious decline.
Being both individualistic and universal, enlightened and skeptical, rationalism is bound to have an adverse effect on Judaism, an essentially national religion centered on the community rather than the individual, and based on practices rather than abstract creeds. Notwithstanding the fact that medieval Jewish rationalism evolved its concepts and attitudes within the framework of traditional Judaism, its character was essentially individualistic.