In the field of science and philosophy, where we get such abundant evidence in the `Abbasid period, we are left with very little material under the `Umayyads. We know that the medical school at Alexandria continued to flourish, and we read of one Adfar, a Christian, who was distinguished as a student of the books of Hermes, the occult authority which did most to divert Egyptian science into a magical direction, and we are informed that he was sought out by a young Roman named Morienus (Marianos) who became his pupil and at his master’s death retired to a hermitage near Jerusalem. Later on the prince Khalid b. Yazid, of the `Umayyad family (d. 85 A.H.--704 A.D.) is said to have become the pupil of Marianos and to have studied with him chemistry, medicine, and astronomy. He was the author of three epistles, in one of which he narrated his conversations with Marianos, another relates the manner in which he studied chemistry, and a third explains the enigmatical allusions employed by his teachers. Long before this medical and scientific studies had passed over to Persia, but Alexandria retained its reputation as the chief centre of such work throughout the `Umayyad period. Towards the end of the `Umayyad age the influence of Hellenistic thought begins to appear in the nature of criticism upon accepted views of Muslim theology. As in jurisprudence, we have no ground for supposing that Muslims at this stage were directly acquainted with Greek material, but general ideas were obtained by intercourse with those who had been long under Hellenistic influences, and especially by intercourse with Christians amongst whom the premises of psychology, metaphysics, and logic had encroached very largely upon the field of theology by the nature of the subjects debated in the Arian, Nestorian, and Monophysite controversies which turned mainly upon psychological and metaphysical problems. The ideas with which the Muslims were brought into contact suggested difficulties in their own theology, as yet only partially formulated, and in religious theories which had taken form in a community entirely ignorant of philosophy. Some of the older fashioned believers met these questions with a plain negative, simply refusing to admit that there was a difficulty or any question for consideration: reason (_`aql_), they said, could not be applied to the revelation of God, and it was alike an innovation to dispute that revelation or to defend it. But others felt the pressure of the questions proposed and, whilst strictly faithful to the statements of the Qur´an, endeavoured to bring their expression into conformity with the principles of philosophy. The questions first proposed were concerned with (a) the revelation of the Word of God, and (b) the problem of free will.