According to the Catechism of the Catholic Church,1
Since the Virgin Mary’s role in the mystery of Christ and the Spirit has been treated, it is fitting now to consider her place in the mystery of the Church. “The Virgin Mary...is acknowledged and honored as being truly the Mother of God and of the redeemer... She is ‘clearly the mother of the members of Christ’...since she has by her charity joined in bringing about the birth of believers in the Church, who are members of its head.” “Mary, Mother of Christ, Mother of the Church.”
The Council of Ephesus declared,2
If anyone does not confess that Emmanuel is God in truth, and therefore that the holy virgin is the mother of God, for she bore in a fleshly way the Word of God become flesh, let him be anathema.
The blessed virgin Mary, the mother of our Lord Jesus Christ, is referred to as ἡ Θεοτόκος, literally “the God-bearer,” and by implication, “the mother of God,” for the woman who bears a child is also the mother of that child.
Thomas Aquinas wrote,3
And some woman is called some man’s mother from this: because she conceived him and gave birth [to him].
Ex hoc autem dicitur aliqua mulier alicuius mater, quod eum concepit et genuit.
It is true that the phrase “mother of God” is not explicitly stated in scripture. Thomas Aquinas wrote,4
Concerning the fourth [article], it is thus advanced: It seems that the blessed virgin should not be called “the mother of God,” for nothing must be said concerning the divine mysteries that is not taken from sacred scripture. But nowhere in the sacred scripture is it read that she is the mother or parent of God, but that she is the mother of Christ or the mother of the child, as evident from Matt. 1:18. Therefore, it should not be said that the blessed virgin is the mother of God.
Ad quartum sic proceditur. Videtur quod beata virgo non debeat dici mater Dei. Non enim est dicendum circa divina mysteria nisi quod ex sacra Scriptura habetur. Sed nunquam in sacra Scriptura legitur quod sit mater aut genitrix Dei, sed quod sit mater Christi, aut mater pueri, ut patet Matth. I. Ergo non est dicendum quod beata virgo sit mater Dei.
However, it is implied in scripture and follows from logical necessity. Thomas Aquinas wrote,5
...although it is not found expressly stated in scripture that the blessed virgin is the mother of God, yet it is found expressly [stated] in scripture that Jesus Christ is true God, as evident in 1 John 5:20, and that the blessed virgin is the mother of Jesus Christ, as evident in Matt. 1:18. Therefore, from the words of scripture it follows of necessity that she is the mother of God.
licet non inveniatur expresse in Scriptura dictum quod beata virgo sit mater Dei, invenitur tamen expresse in Scriptura quod Iesus Christus est verus Deus, ut patet I Ioan. ult.; et quod beata virgo est mater Iesu Christi, ut patet Matth. I. Unde sequitur ex necessitate ex verbis Scripturae quod sit mater Dei.
A syllogism is a statement in which, certain things being affirmed, something other than those things affirmed follows of necessity by these being so. By “by these being so,” I mean following because of these things, and by “following because of these things,” [I mean] not even requiring one external premiss to produce the necessity.
συλλογισμὸς δέ ἐστι λόγος ἐν ᾧ τεθέντων τινῶν ἕτερόν τι τῶν κειμένων ἐξ ἀνάγκης συμβαίνει τῷ ταῦτα εἶναι. λέγω δὲ τῷ ταῦτα εἶναι τὸ διὰ ταῦτα συμβαίνειν, τὸ δὲ διὰ ταῦτα συμβαίνειν τὸ μηδενὸς ἔξωθεν ὅρου προσδεῖν πρὸς τὸ γενέσθαι τὸ ἀναγκαῖον.
That Mary is the mother of God is proven by a syllogism:
To deny the conclusion of the syllogism, that Mary is the mother of God, one must deny one of the premisses, either that Mary is the mother of the Lord Jesus Christ or that the Lord Jesus Christ is God, both of which are explicitly affirmed in scripture.8
The phrase “mother of God” is a shorthand expression for “mother of God the Son.” The blessed virgin Mary is not the mother of the Trinity, God the Holy Spirit, or God the Father. Thomas Aquinas wrote,9
Concerning the third objection, it must be said that, although this name “God” is common to the three persons, yet sometimes it applies only for the person of the Father, sometimes only for the person of the Son or of the Holy Spirit, as it is maintained above (III:16:1; I:39:4). So that when we say, “The blessed virgin is the mother of God,” this name “God” applies only for the incarnate person of the Son.
Ad tertium dicendum quod hoc nomen Deus, quamvis sit commune tribus personis, tamen quandoque supponit pro sola persona patris, quandoque pro sola persona filii vel spiritus sancti, ut supra habitum est. Et ita, cum dicitur, beata virgo est mater Dei hoc nomen Deus supponit pro sola persona filii incarnata.
But on the contrary, the Damascene says (in Book 3), “Nativity is of a person, not a nature.”
Sed contra est quod dicit Damascenus, in III libro, nativitas hypostasis est, non naturae.
However, it is appropriate to state that Mary is the mother of the Lord Jesus Christ according to his human nature or humanity. Thomas Aquinas wrote,13
Therefore, it must be said that the blessed virgin is called the mother of God, not because she is the mother of the divinity, but rather, because she is the mother according to [his] humanity of the person possessing both divinity and humanity.
Dicendum est ergo quod beata virgo dicitur mater Dei, non quia sit mater divinitatis, sed quia personae habentis divinitatem et humanitatem est mater secundum humanitatem.
Aquinas, Thomas. Summa Theologica. Vol. 6. Paris: Bloud, 1880.
Aquinas, Thomas. The Summa Theologica of St. Thomas Aquinas. Trans. Fathers of the English Dominican Province. Vol. 16. New York: Benziger, 1911–1912.
Aristotle (Ἀριστοτέλης). Aristotelis Opera. Ed. Bekker, August Immanuel. Vol. 1. Oxford: E Typographeo Academico, 1837.
Catechism of the Catholic Church. (§963–975)
Fischer, Gustavus. Latin Grammar together with a Systematic Treatment of Latin Composition. Part Second. New York: Schermerhorn, 1876.
Lewis, Charlton T.; Short, Charles. Harper’s Latin Dictionary: A New Latin Dictionary Founded on the Translation of Freund’s Latin-German Lexicon. New York: American Book, 1879.
Morris, John Brande. Jesus the Son of Mary: Or, the Doctrine of the Catholic Church upon the Incarnation of God the Son, Considered in its Bearings upon the Reverence Shewn by Catholics to His Blessed Mother. London: Toovey, 1851.
Vassall-Phillips, Oliver Rodie. The Mother of Christ: Or, the Blessed Virgin Mary in Catholic Tradition, Theology, and Devotion. London: Burns, 1922.
1 CCC, §963
2 First Anathema of the Council of Ephesus
3 ST III, Q 35, A 4, co.
4 ST III, Q 35, A 4, ad. 3
5 ST III, Q 35, A 4, ad. 1
6 Fischer, p. 141; Lewis & Short, p. 1677
7 Prior Analytics (Ἀναλυτικών Προτέρων), 24b9–11
8 Matt. 1:18; John 1:1, 1:14; Col. 2:9; Phil. 2:6
9 ST III, Q 35, A 4, ad. 3
10 Greek οὐσία or φύσις
11 Greek ὑπόστασις or πρόσωπον
12 ST III, Q 35, A 1, s. c.
13 ST III, Q 35, A 4, ad. 2
The following discourses relate to the subject of Mary, the mother of God: