Little is known of Cyril’s early life. He was born at Alexandria and first became known as a young presbyter who was the nephew of the bishop of Alexandria, Theophilus, whom he succeeded in 412. Cyril’s intransigent vigor was soon expressed in attacks on the Novatianists, the Neoplatonists, the Jews, and the imperial governor Orestes. (The Novationists were Christians who were doctrinally identical with the catholics, but whose ancestors in the faith had stood firm against persecution. The Novationists kept themselves separate ecclesiastically from Christian churches whose leaders had been less firm in their faith against Roman persecution. Nearly a century earlier, the emperor Constantine had exasperatedly told a leader of the Novationists to set up a ladder and climb to heaven by himself. The Neoplatonists were a school of mostly pagan philosophers.) Historians disagree over the extent of Cyril’s involvement in the explusion of the Novationists and of the Jews from Alexandria. Some of the Alexandrian Christians believed that the imperial prefect Orestes had been influenced against Cyril by the mathematician and philosopher Hypatia, who was lynched by some of Cyril’s followers. The Orthodox historian John Anthony McGuckin wrote, “At this time Cyril is revealed as at the head of dangerously volatile forces: at their head, but not always in command of them.”
Cyril’s controversy with Nestorius, the bishop of Constantinople, was the most important of his life. The different exegetical traditions of Antioch (where Nestorius received his education) and Alexandria, sharpened by the rivalry of the sees of Constantinople and Alexandria for pre-eminence, embittered the quarrel. Nestorius was believed to have taught that there were two distinct persons in Christ who were joined by a merely moral union. Consequently, Nestorius taught that the Blessed Virgin Mary should be called Christotokos (Christ-bearer), since she was the mother only of the humanity of Christ, but not Theotokos (God-bearer). Cyril taught that Christ’s two natures, divine and human, were intimately joined in a hypostatic union. Cyril certainly and Nestorius probably appealed to Celestine, the bishop of Rome, who after examining the question in a council at Rome, condemned Nestorius’ teaching, excommunicated and deposed him unless he retracted, and appointed Cyril to carry out the sentence. Nestorius refused, and the Council of Ephesus was summoned in 431.
Two hundred bishops took part in the council. Cyril presided and proceeded to the condemnation of Nestorius, who had refused to appear, before the arrival of the bishops of the patriarchate of Antioch. These bishops in turn condemned Cyril first but later (in 443) reached agreement with him. The emperor upheld the condemnation of Nestorius and the title Theotokos became a touchstone of orthodoxy as the Council of Ephesus was recognized as the third Ecumenical Council.
Whatever may be thought of his intransigence and (sometimes) misunderstanding of his opponents, Cyril’s ability and distinction as a theologian are beyond dispute. Traditionally he is regarded as the fearlessly outspoken defender of orthodox thought on the Person of Christ. In addition to this, his writings contain fine passages on the Real Presence of Christ in the Eucharist and the place of Mary in the Incarnation. His writings, which are marked by precision in exposition, accuracy in thought, and skill in reasoning, include sermons and letters besides more formal theological treatises and biblical commentaries. He died at Alexandria in the year 444.
taken from The Oxford Dictionary of Saints, with amendments
Heavenly Father, whose servant Cyril steadfastly proclaimed your Son Jesus Christ to be one person, fully God and fully man: Keep us, we pray, constant in this faith and worship; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, for ever and ever. Amen.
Cyril, Bishop of Alexandria, is commemorated in only one Anglican calendar: that of the Church of England. He is revered as a Teacher of the Church by the Catholic and Orthodox Churches in the West and in the East.