 For Avicenna, as for al-Fārābī, God moves the universe not just as final cause, but as that from which emanate the series of Intelligences and celestial spheres, down to the Agent Intellect, giver of forms to our sublunar world and so assurer of the continued regularity of nature. His innovation was to identify this first cause as the one necessary being, that which is necessary through itself: its nature is to exist and so it cannot but exist. All other things are merely possible in themselves, but necessary through another—that is, through God, the necessary being. Since Avicenna’s God, like that of al-Fārābī, the Platonists and Aristotle himself, is not a being that chooses and wills, his theory of necessity in itself and through another binds the whole history of the universe to a very strict Principle of Sufficient Reason.