St. Cyril, Patriarch of Alexandria for thirty-two years in the first half of the fifth century, was a great champion of the faith against heresy; he opposed Novatianism, Neoplatonism, and Judaism. His principal struggle, however, was with Nestorius, Patriarch of Constantinople. Cyril vehemently defended the application of the word Theotokos, which means 'Godbearer', to the Blessed Virgin Mary. Nestorius, representative of the Antiochene theological...