The Omawîyah, or descendants of Muawîyah, retained the khalifate for less than a century (661–750 A. D.); their strength lay in Syria and Egypt, and their weakness in Arabia and in the East. The battle of the Zâb was fatal to Ibrahîm, the thirteenth and last khalîfah of Damascus, and the white banner of this great house fell before the black ensign of Abu el ’Abbas, who was yet more closely connected with the prophet as a descendant of Muḥammad’s uncle. Thus the political centre of Islâm was transferred to Baghdâd, and the influence of Persia and India, under the ’Abbasides, began to mingle with that of Greek philosophy, which had been learned from the Syrian and Chaldean monks who preserved in their monasteries the works of Plato and Aristotle, which were lost in Europe. The Ṣûfi bore a Greek name (_sophos_, or “wise”), and the term originally denoted an Arab student of Greek science; but the mysticism of India attracted the cultivated Moslem, and undermined gradually the simple faith of the first century, causing a deep schism between the Sunnî, or follower of “tradition,” and the Persian Shi’ah, or “sectarian.” Philosophic scepticism, concealed at first, developed under the ’Abbasides with the growth of a culture learned by the Arab from the ancient Aryan races whom he had conquered, and was only repressed by the reaction which began when the Turks superseded the Arabs as masters of Islâm. The age of the ’Abbasides, for about a century (750–860 A. D.), was the culminating period of Moslem civilisation, at a time when Europe was sunk in Gothic barbarism; and though Spain never acknowledged the ruler of Baghdâd as suzerain, Egypt and the whole of Western Asia obeyed these khalifs till the rise of the Fâṭemite dynasty in 916 A. D. at Ḳairwân. [Sidenote: THE AḲṢA MOSQUE]