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.