The simplicity of God was proved by arguing that if he is composite, his parts are prior to him, and he is neither the first, nor is he eternal, and hence not God; and the incorporeality followed from his simplicity, for all body is composite. Maimonides proved with one stroke God's existence, unity and incorporeality. For his argument from motion leads him to conceive of the first mover as a "separate" form or intellect. This clearly denotes incorporeality, for body is composed of matter and form. But it also denotes unity, for the immaterial is not subject to numerical distinction unless the one be the cause and the other the effect. But in that case the cause alone is God. Next in importance to the proof of God's existence, unity and incorporeality, is the doctrine of attributes. We have seen (p. xxiii) how much emphasis the Arabian Mutakallimun placed upon the problem of attributes. It was important to Jew, Christian and Mohammedan alike for a number of reasons. The crude anthropomorphism of many expressions in the Bible as well as the Koran offended the more sophisticated thinkers ever since Alexandrian days. Hence it was necessary to deal with this question, and the unanimous view was that the Biblical expressions in question are to be understood as figures of speech. The more difficult problem was how any predicates at all can be applied to God without endangering his unity. If God is the possessor of many qualities, even though they be purely spiritual, such as justice, wisdom, power, he is composite and not simple. The Christian theologians found indeed in this problem of attributes a philosophical support for the doctrine of the Trinity. Since God cannot be devoid of power, reason and life, he is trinitarian, though he is one. The difficulty was of course that the moment you admit distinctions within the Godhead, there is no reason for stopping at three. And the Jewish critics were not slow to recognize this weakness in the system of their opponents. At the same time they found it necessary to take up a positive attitude toward the question of attributes so as to harmonize the latter with God's absolute unity. And the essence of the solution of the problem was to explain away the attributes. Saadia says that the ascription of life, power and knowledge to God does not involve plurality in his essence. The distinction of three attributes is due to our limited mind and inadequate powers of expression. In reality the essence of which we predicate these attributes is one and simple. This solution did not seem thoroughgoing enough to Saadia's successors, and every one of the Jewish philosophers tried his hand at the problem. All agreed that the attributes cannot apply to God in the same signification as they have when we use them in our own experience. The meaning of the term attribute was investigated and the attributes were divided into classes, until finally in the system of Maimonides this question too received its classical solution.