In one major respect, Jewish thinkers of the medieval period were no different from Islamic philosophers: they were interested in reconciling their philosophy with their faith. The greatest medieval Jewish philosopher was Moses Maimonides (1135–1204), born in Cordova at Spain.

In his major work, entitled Guide of the Perplexed, he addressed all those readers who studied philosophy but were unsure of how to get philosophy to harmonize with faith. Maimonides, like Avicenna and Averroes before him, was heavily influenced in his thinking by the works of Aristotle. Nonetheless, he recognized an inconsistency in accepting both Aristotle's belief in the eternity of the world and revealed theology that maintained that the universe was created by God. After all, Scripture claims that the world had a beginning. Maimonides' “solution” was to show that Aristotle's arguments are inconclusive and needn't be accepted.

A century before Thomas Aquinas, Maimonides anticipated three of Aquinas's proofs for the existence of God. Using portions of Aristotle's metaphysics and physics, and relying on concepts like possible and necessary beings, Maimonides proved the existence of a Prime Mover, the existence of a necessary Being (relying here also on Avicenna), and the existence of a primary cause.

In his commentary on the Mishna Torah, Maimonides formulated his thirteen “principles of faith.” They summarized what he viewed as the required beliefs of Judaism with regards to:

• God's existence

• God's unity

• God's spirituality and incorporeal essence

• God's eternity

• God alone as the object of worship

• Revelation through God's prophets

• The pre-eminence of Moses among the prophets

• God's law given on Mount Sinai

• The immutability of the Torah as God's law

• God's foreknowledge of human actions

• The reward of good and retribution of evil

• The coming of the Jewish Messiah

• The resurrection of the dead

Unlike Aquinas, he said one could not say what God was like; no positive attributes can be ascribed to God. Rather, one can only use negative descriptors, by saying what God is not like. This was his “via negative,” or negative way.