St. Cyril of Alexandria

Cyril was born around the year 378 at Alexandria in  Egypt. He succeeded his uncle Theophilus as patriarch of Alexandria on Theophilus' death in 412. In 430 Cyril became embroiled with Nestorius, patriarch of Constantinople, who was preaching that Mary was not the Mother of God, and consequently she should not have the word theotokos (God-bearer) applied to her. In 431, Cyril presided over the third General Council at Ephesus, attended by some two hundred bishops, which condemned all the tenets of Nestorius and his followers.

During the rest of his life, Cyril wrote treatises that clarified the doctrines of the Trinity and the Incarnation and that helped prevent Nestorianism and Pelagianism from taking long-term deep root in the Christian community. He was the most brilliant theologian of the Alexandrian tradition. His writings are characterized by accurate thinking, precise exposition, and great reasoning skills.

He died in 444, and was declared a doctor of the Church by Pope Leo XIII in 1882. His feast day is June 27th.