The hero of this period is Athanasius (ca. 297-373), who was throughout his long life the most
intrepid champion of Nicene orthodoxy.
The period from Constantine to the Council of Chalcedon ( 451) is peculiar owing to the political
importance of theology. Two questions successively agitated the Christian world: first, the nature
of the Trinity, and then the doctrine of the Incarnation. Only the first of these was to the fore in the
time of Athanasius. Arius, a cultivated Alexandrian priest, maintained that the Son is not the equal
of the Father, but was created by Him. At an earlier period, this view might not have aroused
much antagonism, but in the fourth century most theologians rejected it. The view which finally
prevailed was that the Father and the Son were equal, and of the same substance; they were,
however, distinct Persons. The view that they were not distinct, but only different aspects of one
Being, was the Sabellian heresy, called after its founder Sabellius. Orthodoxy thus had to tread a
narrow line: those who unduly emphasized the distinctness of the Father and the Son were in
danger of Arianism, and those who unduly emphasized their oneness were in danger of
Sabellianism.
The doctrines of Arius were condemned by the Council of Nicæa ( 325) by an overwhelming
majority. But various modifications were suggested by various theologians, and favoured by
Emperors. Athanacius, who was Bishop of Alexandria from 328 till his death, was constantly in
exile because of his zeal for Nicene orthodoxy. He had immense popularity in Egypt, which,
throughout the controversy, followed him unwaveringly. It is curious that, in the course of
theological controversy, national (or at least regional) feeling, which had seemed extinct since the
Roman conquest, revived. Constantinople and Asia inclined to Arianism; Egypt was fanatically
Athanasian; the West steadfastly adhered to the decrees of the Council of Nicæa. After the Arian
controversy was ended, new controversies, of a more or less kindred sort, arose, in which Egypt
became heretical in one direction and Syria in another. These heresies, which were persecuted by
the orthodox, impaired the unity of the Eastern Empire, and facilitated the Mohammedan
conquest. The separatist movements, in themselves, are not surprising, but it is curious that they
should have been associated with very subtle and abstruse theological questions.
The Emperors, from 335 to 378, favoured more or less Arian