It is a curious fact that many modern Evangelicals (if not their majority, not to mention folk from more historical Protestant bodies) would not want to refer to the Blessed Virgin as the Mother of God (neither as “Blessed Virgin” for that matter, even though the Holy Spirit, trough the lips of Elizabeth, tells her “blessed are you among women and blessed is the fruit of your womb!”)
Apparently they are unaware that refusing to do so is to embark in a serious Christological heresy that was refuted by the whole Church over 1,600 hundred years ago – not to mention that it is to reject the Christology espoused by all the Reformers of the 16th century (Reformation from which Evangelicals come) and the theology of their confessions of faith.
The Third Ecumenical Council took place in Ephesus in 431 with 200 bishops being present. The council was to address the teachings of Patriarch Nestorius, who overemphasized the distinction between the human and divine natures of Jesus Christ, to the expense of the hypostatic union – therefore dividing him into parts that were hardly united in one Person.
As one of the consequences of this heresy (among many, including making our salvation impossible if we cannot be united to God through the Person of Christ, but only to his human nature), Nestorius argued that the Virgin Mary gave birth to a man, Jesus Christ, not God the Logos. The Logos only dwelt in Christ, as in a Temple, and the Virgin Mary should be called Christotokos (“Mother [or Bearer] of Christ”) and not Theotokos (“Birth-giver of God”).
The Council decreed that Christ was one Person, not two separate “people”: fully God and fully man, with a rational soul and body. The Virgin Mary is Theotokos because she gave birth not to a mere man, nor to a mere nature, but to a Person, who is God and Man.
By virtue of this union, attributes are communicable and so we can say, for example, that God (not the divine nature) died on the cross. The union of the two natures of Christ took place in such a fashion that one did not disturb the other, perfectly united in a Person of whom she is the Mother and who is God incarnate.
The Council also declared the text of the Nicene-Constantinopolitan Creed to be final and forbade any additional change to it. It also condemned Pelagianism.
“The holy virgin is more accurately termed mother of Christ than mother of God”
Cyril of Alexandria’s response:
“. . . Therefore, because the holy virgin bore in the flesh God who was united hypostatically with the flesh, for that reason we call her mother of God, not as though the nature of the Word had the beginning of its existence from the flesh (for “the Word was in the beginning and the Word was God and the Word was with God”, and he made the ages and is coeternal with the Father and craftsman of all things), but because, as we have said, he united to himself hypostatically the human and underwent a birth according to the flesh from her womb. . . . ”
We confess, then, our lord Jesus Christ, the only begotten Son of God perfect God and perfect man of a rational soul and a body, begotten before all ages from the Father in his godhead, the same in the last days, for us and for our salvation, born of Mary the virgin, according to his humanity, one and the same consubstantial with the Father in godhead and consubstantial with us in humanity, for a union of two natures took place.
Therefore we confess one Christ, one Son, one Lord. According to this understanding of the unconfused union, we confess the holy virgin to be the mother of God because God the Word took flesh and became man and from his very conception united to himself the temple he took from her. As to the evangelical and apostolic expressions about the Lord, we know that theologians treat some in common as of one person and distinguish others as of two natures, and interpret the god-befitting ones in connexion with the godhead of Christ and the lowly ones with his humanity.
Decree of the Council Against Nestorius
As, in addition to other things, the impious Nestorius has not obeyed our citation, and did not receive the holy bishops who were sent by us to him, we were compelled to examine his ungodly doctrines. We discovered that he had held and published impious doctrines in his letters and treatises, as well as in discourses which he delivered in this city, and which have been testified to. Compelled thereto by the canons and by the letter (ἀναγκαίως κατεπειχθέντες ἀπό τε τῶν κανόνων, καὶ ἐκ τὴς ἐπιστολῆς, κ.τ.λ.) of our most holy father and fellow-servant Cœlestine, the Roman bishop, we have come, with many tears, to this sorrowful sentence against him, namely, that our Lord Jesus Christ, whom he has blasphemed, decrees by the holy Synod that Nestorius be excluded from the episcopal dignity, and from all priestly communion.
Definition of the faith at Nicaea [6th session 22 July 431]
The synod of Nicaea produced this creed: We believe … [the Nicene Creed follows]
It seems fitting that all should assent to this holy creed. It is pious and sufficiently helpful for the whole world. But since some pretend to confess and accept it, while at the same time distorting the force of its expressions to their own opinion and so evading the truth, being sons of error and children of destruction, it has proved necessary to add testimonies from the holy and orthodox fathers that can fill out the meaning they have given to the words and their courage in proclaiming it. All those who have a clear and blameless faith will understand, interpret and proclaim it in this way.
When these documents had been read out, the holy synod decreed the following.
1. It is not permitted to produce or write or compose any other creed except the one which was defined by the holy fathers who were gathered together in the holy Spirit at Nicaea.
2. Any who dare to compose or bring forth or produce another creed for the benefit of those who wish to turn from Hellenism or Judaism or some other heresy to the knowledge of the truth, if they are bishops or clerics they should be deprived of their respective charges and if they are laymen they are to be anathematised.
3. In the same way if any should be discovered, whether bishops, clergy or laity, thinking or teaching the views expressed in his statement by the priest Charisius about the incarnation of the only-begotten Son of God or the disgusting, perverted views of Nestorius, which underlie them, these should be subject to the condemnation of this holy and ecumenical synod. A bishop clearly is to be stripped of his bishopric and deposed, a cleric to be deposed from the clergy, and a lay person is to be anathematised, as was said before.
Later ratification by the Council of Chalcedon:
The Council of Chalcedon has accepted the synodical letters of the blessed Cyril, pastor of the church in Alexandria, to Nestorius and to the Orientals, as being well-suited to refuting Nestorius’s mad folly and to providing an interpretation for those who in their religious zeal might desire understanding of the saving creed [of Nicea]”.