Saint Celestine was Bishop of Rome from 422 to 432 and is remembered in the Orthodox Church as a learned champion of Orthodox doctrine during the Christological controversies of the fifth century. The synaxarion describes him as a man of excellent education who knew philosophy well but devoted himself above all to the study of Holy Scripture and to theological questions. His virtuous life and his standing as a theologian won him the esteem of clergy and people alike, and after the death of his predecessor Saint Boniface he was chosen to occupy the see of Rome.
His pontificate fell during the reign of the Emperor Theodosius the Younger and coincided with the rise of the teaching of Nestorius, Patriarch of Constantinople, who divided the person of Christ and refused to confess the Virgin Mary as Theotokos, the Mother of God. At a local council held at Rome in 430 Celestine denounced this teaching and condemned Nestorius as a heretic. He afterward wrote to Saint Cyril, Archbishop of Alexandria, directing that unless Nestorius renounced his error within ten days he should be deposed and excommunicated, and he sent letters to the churches of Constantinople and Antioch exposing the heresy.
When the Third Ecumenical Council assembled at Ephesus in 431 to settle the controversy, Celestine sent legates to represent the Roman church, instructing them to act in concert with Cyril of Alexandria, whose cause he had already endorsed. The council condemned Nestorius and affirmed the unity of Christ and the title Theotokos for the Virgin Mary. Celestine also opposed the Pelagian teaching on grace and supported efforts to combat it in the West.
Beyond the doctrinal struggles of the East, Celestine took an interest in the spread of the faith in the British Isles. In 431 he consecrated and sent Palladius as bishop to the Christians of Ireland. He reposed peacefully in 432; he is commemorated on April 8 in the East and on April 6 in the West.
