That the elements are those mentioned above and nothing else is proved by the definition of element and its distinction from "principle." A principle is something which, while being the cause of change, and even possibly at the basis of change, is not itself subject to change. Thus God is undoubtedly the cause of everything that happens in the world. He may therefore be called a principle of the world, but he does not enter with his essence the changing things. Hence it is absurd to speak of God as an element of the sublunar world. Matter, i. e., primary formless matter, does enter all changing things and is at the basis of all change; but it does not itself change. Hence matter also is a principle but not an element. An element is something which is itself a composite of matter and form, and changes its form to become something else in which, however, it is contained potentially, not actually. The product ultimately goes back to the element or elements from which it was made. When we follow this resolution of a given composite into its elements back as far as we can until we reach a first which is no longer produced out of anything in the same way as things were produced from it, we have the element. Such is the nature of fire, air, water, earth. All things are made from them in the manner above indicated. But there is nothing prior to them which changes its form to become fire, continues to reside potentially in fire and returns to its original state by the resolution of fire. The same applies to the other three. The matter is now clear. The elements stand at the head of physical change and take part in it. Prior to the elements are indeed matter and form, but as logical principles, not as physical and independent entities. Hence it would seem, according to Israeli, that matter and form are side-tracked in the gradual evolution of the lower from the higher. For the elements, he tells us, come from the motion of the Sphere, the Sphere from the shadow of the Soul, the Soul from the shadow of the Intelligence, the Intelligence is created by God. To be sure he tells us that the Sphere is not body, but the matter of body. Yet the Sphere cannot take the place of prime matter surely, for it is undoubtedly endowed with form, nay is rational and intelligent, as we have seen. When Israeli says that prior to the four elements there is nothing but the Omnipotence of God, he means that the sublunar process of change and becoming stops with the elements as its upper limit. What is above the elements belongs to the intelligible world; and the manner of their production one from the other is a spiritual one, emanation. The Sphere stands on the border line between the corporeal and the intelligible, itself a product of emanation, though producing the elements by its motion--a process apparently neither like emanation nor like sublunar becoming and change.