The 'Doctor of the Incaration' is hailed in the Syrian and Maronite Mass as the "tower of truth and interpreter of the Word of God made flesh".
Saint Cyril of Alexandria is known to have read of the Faith adhering to orthodoxy, but read profane writers as well, this being known mainly by his written attacks on Julian the Apostate. After his uncle Theophilus' death, in 412, he was raised to the See of Alexandria.
Cyril exerted authority by closing the churches of the Novations, and expelled the Jews from his See. This caused a major backlash within the society of northern Eygpt, and the pagan philosopher Hypatia took advantage. She had many followers including the governor, but the suspicion that she had turned the governor against their Bishop, the laity of Cyril took hold on and dismembered her.
Also at this time, the priest-monk Nestorius of Antioch, perpetuated the notion that Christ had two distinct persons - one God, one man - united in moral dimension only in effect denying the humanity of Christ. This was rebuked in kind by Cyril, but Nestorius was obstinate. The matter was sent to Pope Celestine I, who in turn allowed Cyril to excommunicate Nestorius.
The debate over Nestorianism caused the convention of the general council of Ephesus. Nestorius skated the council, refusing to appear. He was condemned and the excommunication upheld. As it would happen, the Antiochene delegation arrived after this decree. They did not support his errors, but did support the person of Nestorius. They decried Cyril's original excommunication, and in turn excommunicated Cyril.
Celestine I gave notice from Rome that Cyril had acted properly, overturned his condemnation, and upheld the finding of the Council. The Antiochene Church schismed for a time, but reconciled themselves to Cyril and issued a statement of their orthodoxy.
St. Cyril was made Doctor of the Univeral Church in 1882.