A Biblical defense and the historicity of the Solemnity known as Mary, Mother of God

1) Mary the “Mother of God” (Theotokos) The official, dogmatic proclamation of this dogma was made at the Ecumenical Council of Ephesus in 431, in response to the heresy of Nestorianism.

Scripture implicitly affirms Mary’s Divine motherhood by attesting, on the one hand, the true Divinity of Christ, and on the other hand, Mary’s true motherhood. Thus Mary is called: “Mother of Jesus” (John 2:1) ... “Mother of the Lord” (Luke 1:43). Mary’s true motherhood is clearly foretold by the Prophet Isaiah: “Behold a virgin shall conceive and bear a Son, and his name shall be called Emmanuel” (Isaiah 7:14) . . . . the woman who bore the Son of God is Progenitress of God, or the Mother of God [ see also Matt. 1:18, 12:46, 13:55; Luke 1:31, 35; Gal 4:4]. (Ott, Fundamentals of Catholic Dogma, 196-197)

The doctrine of Mary as Theotokos flows consistently and straightforwardly from the doctrine of the Holy Trinity and the Incarnation of the Second Person of the Trinity, the Son, Jesus. Cardinal Gibbons explains:

We affirm that the Second Person of the Blessed Trinity, the Word of God, who in His divine nature is from all eternity begotten of the Father, consubstantial with Him, was in the fullness of time, begotten, by being born of the Virgin, thus taking to Himself, from her maternal womb, a human nature of the same substance with hers.

But it may be said the Blessed Virgin is not the Mother of the Divinity. She had not, and she could no have, any part in the generation of the Word of God, for that generation is eternal; her maternity is temporal. He is her Creator; she is His creature. Style her, if you will, the Mother of the man Jesus or even of the human nature of the Son of God but not the Mother of God.

I shall answer this objection by putting a question. Did the mother who bore us have any part in the production of our soul? Was not this nobler part of our being the work of God alone? And yet who would for a moment dream of saying “the mother of my body,” and not “my mother”? . . . (Gibbons, The Faith of Our Fathers, 137-138)

In like manner . . . the Blessed virgin, under the overshadowing of the Holy Ghost, by communicating to the Second Person of the Adorable Trinity, as mothers do, a true human nature of the same substance with her own, is there really and truly His Mother.