Saadya's intellectual career was characterized by polemic and defense of rabbinic Judaism. As head (gaon) of the rabbinic academy of Sura in Babylonia in the first third of the tenth century, Saadya felt compelled to respond to the Karaites, those who challenged the authority of rabbinic Judaism. Saadya's major philosophical work, written in Arabic, Kitāb al-Āmānāt wa'l-Iʿtiqādāt (The book of doctrines and beliefs) should be understood in large part as a defense against the Karaites. Following the Muslim Muʿtazilites, who emphasized divine justice and unity, Saadya's Āmānāt focuses on creation, divine unity, divine law and justice, and reward and punishment in this world and posthumously.

Prefacing the particular discussions just noted, Saadya outlines the sources of human knowledge and understanding, and of error. The senses can be unreliable, reason may be derailed if inferential...