Notwithstanding the eternity of his five principles, Razi thus speaks of a Creator and even gives a story of Creation. First then a simple, pure, spiritual Light was created, the material of Souls, which are simple, spiritual substances, of the nature of Light. That Light-material or Upper-world, from which souls descended, is also called Reason, or Light of the Light of God. The Light is followed by the Shadow, from which the Animal Soul is created, for the service of the Rational Soul. But simultaneously with the simple, spiritual light, there existed from the first a composite form, which is Body, from the shadow of which now issue the four “natures”, Warmth and Cold, Dryness and Moistness. From these four natures at last are formed all heavenly and earthly bodies. The whole process, however, is in operation from all eternity, without beginning in time, for God was never inactive. That Razi was an astrologer is plain from his own utterances. The heavenly bodies consist indeed, according to him, of the same elements as earthly things, and the latter are continually exposed to the influences of the former. 6. Razi had to maintain a polemical attitude in two directions. On the one side he impugned the Muslim Unity of God, which could not bear to be associated with any eternal soul, matter, space or time; and on the other side he attacked the Dahrite system, which does not acknowledge any Creator of the world. This system, which is frequently mentioned by Muslim authors, with due aversion of course, appears to have found numerous representatives, though none of any importance. The adherents of the ‘Dahr’ (v. I, 2, § 2) are represented to us as Materialists, Sensualists, Atheists, Believers in the transmigration of souls, and so on; but we learn nothing more definite about their doctrines. In any case the Dahrites had no need to trace all that exists to a principle which was of spiritual essence and creative efficiency. Muslim Philosophy, on the other hand, did stand in need of such a principle, if it should only conform in some degree to the teaching of the faith. Natural Philosophy was not suited for the furtherance of this object, as it showed more interest in the manifold and often contrary operations of Nature than in the One Cause of all. Such aim was better attained by Neo-Platonic Aristotelianism, whose logico-metaphysical speculations endeavoured to trace all existence to one highest existence, or to derive all things from one supreme operative principle. But before we attend to this direction of thought, which commenced to appear even in the ninth century, we have still to give some account of an attempt to blend Natural Philosophy and the teachings of the Faith into a Philosophy of Religion. 2. The Faithful Brethren of Basra.