The Persian mind, having adjusted itself to the new political environment, soon reasserts its innate freedom, and begins to retire from the field of objectivity, in order that it may come back to itself, and reflect upon the material achieved in its journey out of its own inwardness. With the study of Greek thought, the spirit which was almost lost in the concrete, begins to reflect and realise itself as the arbiter of truth. Subjectivity asserts itself, and endeavours to supplant all outward authority. Such a period, in the intellectual history of a people, must be the epoch of rationalism, scepticism, mysticism, heresy--forms in which the human mind, swayed by the growing force of subjectivity, rejects all external standards of truth. And so we find the epoch under consideration. The period of Umayyad dominance is taken up with the process of co-mingling and adjustment to new conditions of life; but with the rise of the ‘Abbāsid Dynasty and the study of Greek Philosophy, the pent-up intellectual force of Persia bursts out again, and exhibits wonderful activity in all the departments of thought and action. The fresh intellectual vigour imparted by the assimilation of Greek Philosophy which was studied with great avidity, led immediately to a critical examination of Islamic Monotheism. Theology, enlivened by religious fervour, learned to talk the language of Philosophy earlier than cold reason began to seek a retired corner, away from the noise of controversy, in order to construct a consistent theory of things. In the first half of the 8{th} century we find Wāṣil Ibn ‘Atā--a Persian disciple of the famous theologian Ḥasan of Baṣra--starting Mu‘tazilaism (Rationalism)--that most interesting movement which engaged some of the subtlest minds of Persia, and finally exhausted its force in the keen metaphysical controversies of Bag̱ẖdād and Baṣra. The famous city of Baṣra had become, owing to its commercial situation, the playground of various forces--Greek Philosophy, Scepticism, Christianity, Buddhistic ideas, Manichaeism[47:1]--which furnished ample spiritual food to the inquiring mind of the time, and formed the intellectual environment of Islamic Rationalism. What Spitta calls the Syrian period of Muhammadan History is not characterised with metaphysical subtleties. With the advent of the Persian Period, however, Muhammadan students of Greek Philosophy began properly to reflect on their religion; and the Mu‘tazila thinkers[47:2], gradually drifted into metaphysics with which alone we are concerned here. It is not our object to trace the history of the Mu‘tazila Kalām; for present purposes it will be sufficient if we briefly reveal the metaphysical implications of the Mu‘tazila view of Islām. The conception of God, and the theory of matter, therefore, are the only aspects of Rationalism which we propose to discuss here.