that all things are composed of elements. Since elements combine to form composite substances, and because these substances differ from each other, there must be different elements: in other words, "b or a cannot be the same as ba". Number of movers Near the end of Metaphysics, Book , Aristotle introduces a surprising question, asking "whether we have to suppose one such [mover] or more than one, and if the latter, how many". Aristotle concludes that the number of all the movers equals the number of separate movements, and we can determine these by considering the mathematical science most akin to philosophy, i.e., astronomy. Although the mathematicians differ on the number of movements, Aristotle considers that the number of celestial spheres would be 47 or 55. Nonetheless, he concludes his Metaphysics, Book , with a quotation from the Iliad: "The rule of many is not good; one ruler let there be." Influence John Burnet (1892) noted Aristotle's principles of being (see section above) influenced Anselm's view of God, whom he called "that than which nothing greater can be conceived." Anselm thought that God did not feel emotions such as anger or love, but appeared to do so through our imperfect understanding. The incongruity of judging "being" against something that might not exist, may have led Anselm to his famous ontological argument for God's existence. Many medieval philosophers made use of the idea of approaching a knowledge of God through negative attributes. For example, we should not say that God exists in the usual sense of the term; all we can safely say is that God is not nonexistent. We should not say that God is wise; but, we can say that God is not ignorant (i.e. in some way God has some properties of knowledge). We should not say that God is One; but, we can state that there is no multiplicity in God's being. Aristotelian theological concepts were accepted by many later Jewish, Islamic, and Christian philosophers. Key Jewish philosophers included Samuel Ibn Tibbon, Maimonides, and Gersonides, among many others. Their views of God are considered mainstream by many Jews of all denominations even today. Preeminent among Islamic philosophers who were influenced by Aristotelian theology are Avicenna and Averroes. In Christian theology, the key philosopher influenced by Aristotle was undoubtedly Thomas Aquinas. There had been earlier Aristotelian influences within Christianity (notably Anselm), but Aquinas (who, incidentally, found his Aristotelian