The modalities – necessity, possibility, and impossibility – are not topics like the existence of God, creation versus eternity, prophecy, divine attributes, or providence whose “secrets” Maimonides investigates in the Guide. They belong instead to the philosophical and logical framework within which these topics are explored. But they are no less perplexing. The modal terms often differ in meaning in different contexts, depending on whether the subject is physics or metaphysics, and for the falasifa and the mutakallimun. Therefore, in order to address any of the central controversies of the Guide, we must first sort out these modal notions, distinguishing the different conceptions in different contexts.