ultimate being, but some cause would lie behind him; and he would not be perfection, since some potentiality, the characteristic of matter, would still reside in him. As a matter of fact Aristotle in a number of passages identifies his ultimate material and form (ἡ ἐσχάτη ὔλη καὶ ἡ μορφὴ ταὐτό);[219] not that he would have granted that there was a material element in the Supreme Being; but in the light of what we have just said we can understand how he might have held that the ultimate material and God were identical.[220] It readily follows from Aristotle’s concept of God as the prime mover, the source of all activity in the world, that God can be but one. Monotheism is the logical result of the Aristotelian reasoning. Moreover it was inevitable that Aristotle should make God transcendent, that is, that he should place him above all objects of the natural world, since if the First Cause is pure thought unmixed with matter, he cannot be immanent in material things. The immateriality which Plato gave to his ideas, his pupil transferred to God. Midway between the natural and the supernatural worlds Aristotle placed man, whom he regarded as bound to the world of nature by his body and the lower elements of his mind, but connected with God through his reason, for he held that the human mind possessed attributes of the divine intelligence. Aristotle’s psychology was based on his belief that there was a purpose in all nature, and on his view that in the individual were always united form and material. With reference to animate beings he showed that they had their formative principle within them, which brought to actuality the material which had the potentiality of life, and which determined the purpose for which the individual creature existed. This formative principle was then for him the soul of the animate being, whether plant, lower animal, or man; it was the internal principle which determined the processes of nutrition, growth, and decay common to all animate creatures, and no less the functions peculiar to the lower and the higher animals throughout the scale of life. The soul of a plant, then, he defined as the assimilative principle (τὸ θρεπτικόν) But creatures of the next, higher stage, the so-called lower animals, he saw had senses, desires, and self-movement; to their souls therefore he assigned the additional elements of sensation (τὸ αἰσθητικόν), appetite (tὸ ὀrektikόn), and motion (τὸ κινητικόν). Finally, he said, the human soul had mind (νοῦς) in addition to the elements possessed by the lower animals and plants, for man has the power of thought and reflection. Therefore man is the highest creature, the most perfect organism in the natural order.