Aëtius of Antioch, surnamed "the Atheist" by his trinitarian enemies, had studied successively under the Arian bishops Paulinus of Antioch and Athanasius of Anazarbus, and the presbyter Antonius of Tarsus.

Ordained a deacon in 350 by Leontius of Antioch, he had shortly afterwards been forced by the trinitarian party to leave that town.

At the first synod of Sirmium in 351, he had won a dialectic victory over the homoiousian bishops, Basilius and Eustathius, who seek in consequence to stir up against him the enmity of Constantius Gallus.

Roman authorities make an attempt on February 8, 356, to arrest Athanasius on the accusation of supporting the late usurper Magnentius.

Athanasius eludes them, fleeing to the desert to hide among the monks of Mount Nitria.

Aëtius of Antioch goes to Alexandria with his Cappadocian protégé Eunomius in order to advocate Arianism, but he is banished by Constantius.

Eunomius, who had studied theology at Alexandria under Aëtius, and afterwards come under the influence of Eudoxius of Antioch, who ordained him deacon, had in 360 been appointed bishop of Cyzicus, in Mysia, on the recommendation of Eudoxius.

Propounding an extreme form of Arianism that refutes the divinity of Christ and constructing his argument on a Platonist philosophical structure, Eunomius teaches that Christ was not equal to God the Father but only resembled him.

Here his free utterance of extreme Arian views have led to popular complaints, and Eudoxius is compelled, by command of Constantius, to depose him from the bishopric within a year of his elevation to it.

Julian had recalled Aëtius of Antioch from exile, bestowed upon him an estate in Lesbos, and retained him for a time at his court in Constantinople.

Having been consecrated as a bishop, Aëtius had used his office in the interests of Arianism by creating other bishops of that party.

At the accession of Valens in 364, Aëtius had retired to his estate at Lesbos, but soon returned to Constantinople, where he dies in 367.

Eunomius of Cyzicus, deposed from his bishopric by Constantius for his extreme Arianist views, had resided in Constantinople during the reigns of Julian and Jovian, in close intercourse with his mentor Aëtius, consolidating an heretical party and consecrating schismatical bishops.

He had then gone to live at Chalcedon, whence in 367 he is banished to Mauretania for harboring the rebel Procopius.

He is recalled, however, before he reaches his destination.