[citation needed] The following facts about his life are gleaned mainly from his Epistles and his Religious History (Philotheos historia).

He paid weekly visits to Peter the Galatian, was instructed by Macedonius and other ascetics, and at an early age became a lector among the clergy of Antioch.

He clearly also received an extensive classical education, unsurprisingly for the child of prosperous parents in a city which had long been a centre of secular learning and culture.

In 423 he left as he had been appointed Bishop of Cyrrhus, over a diocese about forty miles square and embracing 800 parishes, but with an insignificant town as its see city.

Theodoret, supported only by the appeals of the intimate hermits, himself in personal danger, zealously guarded purity of the doctrine.

His philanthropic and economic interests were extensive and varied: he endeavoured to secure relief for the people oppressed with taxation; he divided his inheritance among the poor; from his episcopal revenues he erected baths, bridges, halls, and aqueducts; he summoned rhetoricians and physicians, and reminded the officials of their duties.

To the persecuted Christians of Persian Armenia he sent letters of encouragement, and to the Carthaginian Celestiacus, who had fled the rule of the Vandals, he gave refuge.

[citation needed] Theodoret stands out prominently in the Christological controversies aroused by Cyril of Alexandria.

John, reconciled to Cyril by the emperor's order, sought to bring Theodoret to submission by entrenching upon his eparchy.

But Cyril refused to compromise and when he opened his attack (437) upon Diodorus of Tarsus and Theodore, John sided with them and Theodoret assumed the defence of the Antiochian party (c. 439).

Here, because of his Epistle 151 against Cyril and his defence of Diodorus and Theodore, he was condemned without a hearing and excommunicated and his writings were directed to be burned.

His conduct shows (though hindered from a statement to that effect) that he performed this with his previous reservation; namely, without application beyond the teaching of two sons in Christ and the denial of the theotokos.

[citation needed] The only thing known concerning him following the Council of Chalcedon is the letter of Leo charging him to guard the Chalcedonian victory (PG, lxxxiii.

Theodoret's last exegetical works were the interpretations of difficult passages in the Octateuch and Quaestiones dealing with the books of Samuel, Kings, and Chronicles, written about 452 to 453.

[citation needed] Excepting the commentary on Isaiah (fragments preserved in the catenae) and on Galatians ii.6-13, the exegetical writings of Theodoret are extant.

Exegetical material on the Gospels under his name in the catenae may have come from his other works, and foreign interpolations occur in his comments on the Octateuch.

[citation needed] The biblical authors are, for Theodoret, merely the mouthpieces of the Holy Spirit, though they do not lose their individual peculiarities.

He is clear and simple in thought and statement; and his merit is to have rescued the exegetical heritage of the school of Antioch as a whole for the Christian Church.

These florilegia provide evidence of Theodoret's considerable learning, with 238 texts drawn from 88 works, including pre-Nicene writers such as Ignatius, Irenaeus and Hippolytus, as well as theologians such as Athanasius and the Cappadocian Fathers.

[12][13] Two works, On the Holy and Life-giving Trinity and On the Incarnation of the Lord, have survived through ascription to his opponent Cyril of Alexandria.

[16] He detects Apollinarianism in Cyril's teaching, and declines a "contracting into one" of two natures of the only begotten, as much as a separation into two sons (Epist.

Among apologetic writings was the Ad quaestiones magorum (429-436), now lost, in which Theodoret justified the Old Testament sacrifices as alternatives in opposition to the Egyptian idolatry,[20] and exposed the fables of the Magi who worshipped the elements (Church History v. 38).

[21] The Ecclesiastical History of Theodoret, which begins with the rise of Arianism and closes with the death of Theodore in 429 (despite being completed in 449–450) is very different in style from those of Socrates Scholasticus and Sozomen.

It contains many sources otherwise lost, specially letters on the Arian controversy; however, the book is extremely partisan, the heretics being consistently blackened and described as afflicted with the 'Arian plague'.

These letters provide glimpses of rural Christianity in northern Syria, as well as insight into episcopal relationships; hints of the development of Christological issues between the Councils of Ephesus and Chalcedon can be seen; there are letters of consolation and commendation; throughout there is revealed the generous and sensitive soul of a pastor.

Aware of regional diversities of Aramaic dialects, he recorded that "the Osroënians, the Syrians, the people of the Euphrates, the Palestinians, and the Phoenicians all speak Syriac, but with many differences in pronunciation".