He was a central figure in the First Council of Ephesus in 431, which led to the deposition of Nestorius as Patriarch of Constantinople.

The conflict came to a head in 428 after Nestorius, who originated in Antioch, was made Archbishop of Constantinople.

Cyril gained an opportunity to restore Alexandria's pre-eminence over both Antioch and Constantinople when an Antiochine priest who was in Constantinople at Nestorius ' behest began to preach against calling Mary the " Mother of God ".

Nestorius argued that Mary was neither a " Mother of Man " nor " Mother of God " as these referred to Christ's two natures ; rather, Mary was the " Mother of Christ ".

Christ, according to Nestorius, was the conjunction of the Godhead with his " temple " ( which Nestorius was fond of calling his human nature ).

" However, Nestorius claimed that the Son of God was altogether incapable of suffering, even within his union with the flesh.

Ephesus was friendly to Cyril, Emperor Theodosius convoked Council of Ephesus ( in 431 ) before Nestorius's supporters from Antioch and Syria had arrived and thus Nestorius refused to attend when summoned.

The main issue that prompted this dispute between Cyril and Nestorius was the question which arose at the Council of Constantinople: What exactly was the being to which Mary gave birth?

Another theological dispute in the 5th century occurred over the teachings of Nestorius, the Patriarch of Constantinople who taught that God the Word was not hypostatically joined with human nature, but rather dwelt in the man Jesus.

Cyril was able to completely control the proceedings, completely neutralizing Candidian who favored Cyril's antagonist, Nestorius.

Nestorius took his Antiochene leanings with him when he was appointed Patriarch of Constantinople by Eastern Roman Emperor Theodosius II in 428.

Nestorius was especially criticized by Cyril, Pope ( Patriarch ) of Alexandria, who argued that Nestorius ' teachings undermined the unity of Christ's divine and human natures at the Incarnation.

Cyril had both theological and political reasons for attacking Nestorius ; on top of feeling that Nestorianism was an error against true belief, he also wanted to denigrate the head of a competing patriarchate.

Celestine found that the title Theotokos was orthodox, and authorized Cyril to ask Nestorius to recant.

Theodoret was 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 strove earnestly for the reconciliation between the Eastern churches.

Then he was constrained ( October 26, 451 ) by the friends of Dioscurus to pronounce the anathema over Nestorius.

With Diodorus and Theodore he was no less hated by the Monophysites than Nestorius himself, and held by them and their friends as a heretic.

The Church of the East was associated with the doctrine of Nestorianism, advanced by Nestorius, Patriarch of Constantinople from 428 – 431, which emphasized the disunion between the human and divine natures of Jesus.

The council was called amid a dispute over the teachings of Nestorius, Patriarch of Constantinople.

Nestorius had greatly underestimated Pulcheria's power, for she was empress, and she had Nestorius deposed from his duties as bishop of Constantinople.

Nestorius then called for a council to see what side when be made into church law.

Nothing is known of his life, save what he tells us himself in the last of the biographies he wrote: " I, Gennadius, presbyter of Massilia, wrote eight books against all heresies, five books against Nestorius, ten books against Eutyches, three books against Pelagius, a treatise on the thousand years of the Apocalypse of John, this work, and a letter about my faith sent to blessed Gelasius, bishop of the city of Rome ".

Some modern scholars argue whether Nestorianism is the proper term for the Christianity that was practiced in China, since it did not adhere to what was preached by Nestorius, and are instead preferring to refer to it as " Church of the East ", a term which encompasses the various forms of early Christianity in Asia.

Nestorius ' opponents found his teaching too close to the heresy of adoptionism – the idea that Christ had been born a man who had later been " adopted " as God's son.

Nestorius had come under fire from Western theologians, most notably Cyril of Alexandria.

Originally the church of Sassanid Persia, the Church of the East declared itself independent of other churches in 424 and over the next century became affiliated with Nestorianism, a Christological doctrine advanced by Nestorius, Patriarch of Constantinople from 428 to 431, which had been declared heretical in the Roman Empire.

Nestorius ' doctrine, Nestorianism, which emphasized the disunity between Christ's human and divine natures, had brought him into conflict with other church leaders, most notably Cyril, Patriarch of Alexandria.

Nestorius himself had requested that the Emperor convene council, hoping to prove his orthodoxy, but in the end his teachings were condemned by the council as heresy.

Nestorius ' dispute with Cyril had led the latter to seek validation from Pope Celestine I, who authorized Cyril to request that Nestorius recant his position or face excommunication.

Nestorius emphasized the dual natures of Christ, trying to find a middle ground between those that emphasized the fact that in Christ God had been born as a man, insisted on calling the Virgin Mary Theotokos ( Greek: Θεοτόκος, " God-bearer "), and those that rejected that title because God as an eternal being could not have been born.

For example, John of Antioch wrote to Nestorius urging him to submit to the Pope's judgment and cease stirring up controversy over a word that he disliked ( Theotokos ) but which could be interpreted as having an orthodox meaning especially in light of the fact that many saints and doctors of the church had sanctioned the word by using it themselves.

When John of Antioch and his Syrian bishops finally reached Ephesus five days after the council, they met with Candidian who informed them that Cyril had begun a council without them and had ratified Celestine's conviction of Nestorius as a heretic.

Philip, as papal legate, opened the proceedings by commenting that the present question regarding Nestorius had already been decided by Pope Celestine as evidenced by his letter which had been read to the assembled bishops in the first session.

The council sent a letter to Theodosius indicating that the condemnation of Nestorius had been agreed upon not only by the bishops of the East meeting in Ephesus but also of the bishops of the West who had convened at a synod in Rome convened by Celestine.

The emperor had always been a staunch supporter of Nestorius, but had been somewhat shaken by the reports of the council.

Although Emperor Theodosius had long been a staunch supporter of Nestorius, his loyalty seems to have been shaken by the reports from Cyril's council and caused him to arrive at the extraordinary decision to ratify the depositions decreed by both councils.

The purpose of the condemnation was to make plain that the Imperial, Chalcedonian ( that is, recognizing the hypostatic union of Christ as two natures, one divine and one human, united in one person with neither confusion nor division ) Church was firmly opposed to all those who had either inspired or assisted Nestorius, the eponymous heresiarch of Nestorianism — the proposition that the Christ and Jesus were two separate persons loosely conjoined, somewhat akin to adoptionism, and that the Virgin Mary could not be called the Mother of God ( Gk.

Nestorius tried to find a middle ground between those that emphasized the fact that in Christ God had been born as a man, insisted on calling the Virgin Mary Theotokos ( Greek: Θεοτόκος, " God-bearer "), and those that rejected that title because God as an eternal being could not have been born.

But while the council was in progress, John I of Antioch and the eastern bishops arrived, and were furious to hear that Nestorius had already been condemned.

Nestorius himself always insisted that his views were orthodox, though they were deemed heretical at the First Council of Ephesus in 431, leading to the Nestorian Schism, when churches supportive of Nestorius broke away from the rest of the Christian Church.

Nestorius himself retired to a monastery, always asserting his orthodoxy.

The Acoemetae took a prominent part — and always in the sense of orthodoxy — in the Christological discussions raised by Nestorius and Eutyches, and later, in the controversies of the Icons.