At the close of the second century of the Hegira, Al Mâmûn succeeded to the throne. His mother was a Persian lady; and he had imbibed from her, and the society in which he was reared at Merve, the principles of the Motázilites. [Sidenote: Motázilite creed.]This strange system, which had recently sprung up in the East, was grafted by the sectarians of Aly (Shîyites) on the transcendental philosophy of the Persians. It was, in fact, a new and altogether unlooked-for development, or rather perversion, of Islam. Heretofore, the sole ground of faith had been the Corân, and the _Sunnat_ or deliverances preserved by tradition from the lips of Mahomet. Now, under the Divine Imâmate, or spiritual leadership vested in some member of the house of Aly, there might be other infallible sources of guidance from above. There arose, in fact, a new school of interpretation, one might almost say, a new dispensation. The Corân was treated allegorically; and such difficulties as beset the Orthodox, offended reason, or cramped the growth of society, were thus easily evaded.[607] In the system so evolved, the Prophet, had he revisited the earth, would hardly have recognised his own religion. This elastic development of the Faith, sublimated by the mysticism of Persia, and refined by the subtleties of Indian philosophy, was eagerly embraced by the natives of the Eastern provinces. And Al Mâmûn, who on his accession remained still for a time at Merve, fell deeply under its influence. [Sidenote: Embraced by Al Mâmûn.]So inclined was he to the house of Aly, that he gave a daughter of his own in marriage to one of that lineage, and he even adopted their green ensign;--hoping thus to unite the lines of Aly and Abbâs in one new dynasty. Although, on transferring his court to Baghdad, he abandoned the design,[608] Mâmûn still remained faithful to the rationalistic creed. He surrounded himself at the capital with the learned of all persuasions; and in company with them was used to hold discussions, at which such grave questions as those affecting man’s relations with the Deity, and the nature of the Godhead itself, were freely handled. In opposition to the Orthodox, he believed in the doctrine of Free-will. From the received teaching that the Corân is uncreated and eternal, he recoiled, as at variance with the unity of the Godhead; and, in the end, he proclaimed, with pains and penalties for dissent, that it was created. Thus, though a Free-thinker himself, Al Mâmûn, as often happens, denied the free right of judgment to others; and he persecuted cruelly, and on one or two occasions even to the death, those who ventured to differ with him. [Sidenote: Comparative freedom and toleration under Motázilites.]Still freedom of opinion and open discussion were, beyond comparison, more tolerated under the régime of the Motázilites than of the Orthodox.[609] For forty or fifty years, the tenets of the Rationalists prevailed under the Motázilite Caliphs at Baghdad.