Saadya ben Joseph al-Fayyumi (882-942), gaon (head) of the rabbinic academy at Sura and one of the preeminent Jewish thinkers of the medieval period, attempted to create a complete statement of Jewish religious philosophy in which all strands of philosophical thought were to be knit into a unified system. In The Book of Doctrines and Beliefs, Saadya sought to rescue believers from "a sea of doubt and the waters of confusion" into which...