Herb,
some background to the Third Ecumenical Council, the Council of Ephesus.
The Alexandrian school made use use of the term
Theotokos("the one who gave birth to God") at least as early as 319-324 AD when Alexander, Bishop of Alexandria, refered to Mary as
Theotokos in his Letter to Alexander of Byzantium about the heresy of Arius. In Alexandria and other regions, the title
Theotokos as ascribed to Mary enjoyed popular liturgical usage.
After the priest, Nestorius, ascended to the episcopal throne of Constantinople in April of 428, he criticized the notion of Mary as
Theotokos, because in his opinion it gave the impression that she gave birth to the divine nature. Nestorious preferred the term
Christotokos, "the one who gave birth to Christ." This teaching caused a stir among the faithful who had been following established popular liturgical devotion of Mary as
Theotokos. Nestorius wrote to Pope Celestine, but even after two letters to the pope no answer was to come.
As a result of that teaching and its refutation by St Cyril of Alexandria, Nestorius accused St Cyril of doctrinal error. St Cyril sought in vain for help from the emperor, Theodosius II. With no imperial assistance forthcoming, St Cyril turned to Rome.
St Cyril sent a dossier on Nestorius and his teachings to Rome. Archdeacon, and future pope, Leo of Rome asked St John Cassian to give his learned opinion upon the teachings of Nestorius. Cassian opined that Nestorius held teachings related to the heresy of Paul of Samosata and Pelagius. Pope St Celestine convoked a synod in August, 430, and condemned Nestorius. Under pain of excommunication, the synod required Nestorius to recant his opinions and teachings within ten days. In November, 430, at the instigation of Nestorius,Emperor Thedosius II called for a council to convene in Ephesus on Pentecost, 431.
We know of course, the Third Ecumenical Council upheld the doctrinal purity of the liturgical Marian title of
Theotokos. The title "Mother of God" had not been used as a Marian title in the Greek, although this is how
Theotokos had been translated in the Latin, ("Mater Dei") and the subsequent Romance languages. In German it has been translated as
Mutter Gottes.
Pelikan notes:
Therefore when Athanasius spoke of the Logos "taking flesh of a Virgin, Mary the Theotokos," he was echoing the language of popular devotion; but he had already begun to provode the title with the very rationale that was to help defend it against attack half a century after his death. As Newman suggested in The Arians of the Fourth Century, the people were orthodox even when the bishops were not. In his use of the Theotokos, as in his use of other titles and metaphors, Athanasius aligned himself with the orthodoxy of popular devotion and vindicated it. The idea of lex orandi, lex credendi, that implicit in Christian worship there was a normative doctrinal content, which needed to be made explicit, seems to have been formulated shortly after the time of Athanasius, but he evidently worked on the basis of some such idea. Mary Through the Centuries , p 59.
The controversy surrounding the Nestorian heresy was primarily Christological. As a result, the Church was able to elaborate upon the principle of the
communicatio idiomatum , "communication of the properties". This rule holds that as a result of the Incarnation, the
Theanthropos, the God-man, Jesus Christ, can be described in both human and divine attributes and they can be used interchangeably since the terms refer to the one and the same Person. Although the Eastern Fathers could have made use of the title "Mother of God" by
communicatio idiomatum , the title
Theotokos already had an orthodox Christological understanding among the faithful because of its popular liturgical usage.