In the early centuries of our era, the two fundamental articles of the Gentile-Christian creed, the Trinity and the Incarnation, neither of them Jewish, were formulated in terms of Platonic philosophy, of which the distinctive tenet is, that the real and eternal is the universal, not the individual. On this assumption it was possible to say that the same real substance could exist in three, or indeed in any number of persons. In the case of God, the dogma-builders were careful to say, essence is one with existence, and therefore in Him the individuals are as real as the universal. Platonism, having lent the formula for the Trinity, became the favorite philosophy of many of the Church fathers, and so introduced into Christian thought and life the Platonic dualism, that sharp distinction between the temporal and the eternal which belittles the practical life and glorifies the contemplative. This distinction, as aggravated by Neo-Platonism, further affected Eastern Christianity in the sixth century, and Western Christianity in the ninth, chiefly through the writings of (the pseudo-) Dionysius Areopagita, and gave rise to Christian mysticism. It was then erected into a rule of conduct through the efforts of Pope Gregory VII., who strove to subject practical and civil life entirely to the control of ecclesiastics and monks, standing for contemplative, supernatural life. The latter included all purely mental work, which more and more tended to concentrate itself upon religion and confine itself to the clergy. In this way it came to be considered an utter disgrace for any man engaged in mental work to take any part in the institutions of civil life, and particularly to marry. He might indeed enter into illicit relations, and rear a family of "nephews" and "nieces," without losing prestige; but to marry was to commit suicide. Such was the condition of things in the days of Abélard. But while Platonism, with its real universals, was celebrating its ascetic, unearthly triumphs in the West, Aristotelianism, which maintains that the individual is the real, was making its way in the East. Banished as heresy beyond the limits of the Catholic Church, in the fifth and sixth centuries, in the persons of Nestorius and others, it took refuge in Syria, where it flourished for many years in the schools of Edessa and Nisibis, the foremost of the time. From these it found its way among the Arabs, and even to the illiterate Muhammad, who gave it (1) theoretic theological expression in the cxii. surah of the Koran: "He is One God, God the Eternal; He neither begets nor is begotten; and to Him there is no peer," in which both the fundamental dogmas of Christianity are denied, and that too on the ground of revelation; (2) practical expression, by forbidding asceticism and monasticism, and encouraging a robust, though somewhat coarse, natural life. Islam, indeed, was an attempt to rehabilitate the human.