The Guide For The Perplexed consists of three books. The first book deals with the nature of God, concluding that God cannot be described in positive terms. The second book examines natural philosophy, particularly Aristotle's system of concentric spheres, and theories of the creation and duration of the universe, and the theory of angels and prophecy. In the last Book, he expounds the mystical Merkabah section of Ezekiel, skirting the traditional prohibition of direct explanation of this passage. After this he covers the 613 laws of the Pentateuch, organized into 14 branches, attempting to present rational explanations for each law. Throughout, Maimonides stresses that the student needs to consider all theories.