Theodoret, a friend of Nestorius, has become embroiled in the controversy with Cyril of Alexandria, whose views, he argues, imply a confusion of the divine and human natures of Christ.
Theodoret had shared in the petition of John I of Antioch to Nestorius to approve of the term theotokos ("mother of God"), and upon the request of John wrote against Cyril's anathemas.
He may have prepared the Antiochian symbol, which is to secure the emperor's true understanding of the Nicene Creed, and he is a member and spokesman of the deputation of eight from Antioch called by the emperor to Chalcedon.
To the condemnation of Nestorius he could not assent.
John, reconciled to Cyril by the emperor's order, seeks to bring Theodoret to submission by entrenching upon his eparchy.
Theodoret is determined to preserve the peace of the Church by seeking the adoption of a formula avoiding the unconditional condemnation of Nestorius, and toward the close of 434 had striven earnestly for the reconciliation between the Eastern churches.
But Cyril had refused to compromise and when he opened his attack upon Diodorus of Tarsus and Theodore in 437, John had sided with them and Theodoret had assumed the defense of the Antiochian party around 439.
Domnus II, who had succeeded John, his uncle, in 441, had taken him as his counselor.
After the death of Cyril in 444, adherents of the Antiochian theology are appointed to bishoprics.
Irenaeus the friend of Nestorius, with the cooperation of Theodoret, becomes bishop of Tyre, in spite of the protests of Dioscorus, Cyril's successor, who now turns specially against Theodoret; and, by preferring the charge that he teaches two sons in Christ, he secures the order from the court confining Theodoret to Cyrrhus.
