This conception of unity underwent further modifications; until in the hands of Mu‘ammar and Abu Hās̱ẖim it became a mere abstract possibility about which nothing could be predicated. We cannot, he says, predicate knowledge of God[50:1], for His knowledge must be of something in Himself. The first necessitates the identity of subject and object which is absurd; the second implicates duality in the nature of God which is equally impossible. Aḥmad and Faḍl[50:2]--disciples of Nazzām, however, recognised this duality in holding that the original creators are two--God--the eternal principle; and the word of God--Jesus Christ--the contingent principle. But more fully to bring out the element of truth in the second alternative suggested by Mu‘ammar, was reserved, as we shall see, for later Ṣūfī thinkers of Persia. It is, therefore, clear that some of the rationalists almost unconsciously touched the outer fringe of later pantheism for which, in a sense, they prepared the way, not only by their definition of God, but also by their common effort to internalise the rigid externality of an absolute law. [50:1] S̱ẖahrastānī: Cureton's ed., p. 48. See also Steiner--Die Mutaziliten, p. 59. [50:2] Ibn Ḥazm (Cairo, ed. I) Vol. IV, p. 197. See also S̱ẖahrastānī: Cureton's ed., p. 42. But the most important contribution of the advocates of Rationalism to purely metaphysical speculation, is their explanation of matter, which their opponents--the Ash‘arite--afterwards modified to fit in with their own views of the nature of God. The interest of Nazzām chiefly consisted in the exclusion of all arbitrariness from the orderly course of nature[51:1]. The same interest in naturalism led Al-Jāḥiẓ to define Will in a purely negative manner[51:2]. Though the Rationalist thinkers did not want to abandon the idea of a Personal Will, yet they endeavoured to find a deeper ground for the independence of individual natural phenomena. And this ground they found in matter itself. Nazzām taught the infinite divisibility of matter, and obliterated the distinction between substance and accident[51:3]. Existence was regarded as a quality superimposed by God on the pre-existing material atoms which would have been incapable of perception without this quality. Muḥammad Ibn ‘Uṯẖmān, one of the Mu‘tazila S̱ẖaiḵẖs, says Ibn Ḥazm,[51:4] maintained that the non-existent (atom in its pre-existential state) is a body in that state; only that in its pre-existential condition it is neither in motion, nor at rest, nor is it said to be created. Substance, then, is a collection of qualities--taste, odour, colour--which, in themselves, are nothing more than material potentialities. The soul, too, is a finer kind of matter; and the processes of knowledge are mere mental motions. Creation is only the actualisation of pre-existing potentialities[52:1] (Ṭafra). The individuality of a thing which is defined as "that of which something