The Ecclesiastical History of Sozomen

Basil and Gregory were contemporaries, and they were recognized to be equally intent, so to speak, upon the cultivation of the virtues. They had both studied in their youth at Athens, under Himerius and Proæresius, the most approved sophists of the age; and afterwards at Antioch, under Libanius, the Syrian. But as they subsequently conceived a contempt for sophistry and the study of the law, they determined to study philosophy according to the law of the Church. After having spent some time in the pursuit of the sciences, taught by pagan philosophers, they entered upon the study of the commentaries which Origen and the best approved authors who lived before and after his time, have written in explanation of the Sacred Scriptures.

They rendered great assistance to those who, like themselves, maintained the Nicene doctrines, for they manfully opposed the dogmas of the Arians, proving that these heretics did not rightly understand either the data upon which they proceeded, nor the opinions of Origen, upon which they mainly depended. These two holy men divided the perils of their undertaking, either by mutual agreement, or, as I have been informed, by lot. The cities in the neighborhood of Pontus fell to the lot of Basil; and here he founded numerous monasteries, and, by teaching the people, he persuaded them to hold like views with himself. After the death of his father, Gregory acted as bishop of the small city of Nazianzus, but resided on that account in a variety of places, and especially at Constantinople. Not long after he was appointed by the vote of many priests to act as president of the people there; for there was then neither bishop nor church in Constantinople, and the doctrines of the council of Nicæa were almost extinct.