And she gave birth to her firstborn son and wrapped him in swaddling clothes and laid him in a manger.
When Jesus was baptized…the heavens were opened… and behold a voice from heaven, saying, “This is my beloved Son with whom I am well pleased.
—Matthew 3:16, 18
Jesus is both Son of Mary and Son of the Father. By contemplating his human birth, we can catch a glimpse of his divine birth mirrored in it. Charles De Koninck, founder of the Laval School of Thomism, compares the generation of the Son by Mary to his eternal generation by the Father in his two books about Mary, Ego Sapientia, and The Piety of the Son. He begins with St. Thomas’s doctrine and then develops it.
St. Thomas teaches that Christ has two births because he has two natures and the purpose of birth is to exist in a certain nature:
In Christ there is a twofold nature: one which he received from the Father from eternity, the other which he received from his mother in time. Therefore, we must attribute two births duas navitates to Christ, one by which he was born eternally from the Father; the other by which he was born in time from his mother.
St. Thomas defines birth as the “procession of a living being from a conjoined living principle . . . by way of likeness in the same specific nature.”
The first element, “The procession of a living being from a living principle,” refers to a father or mother as a living and efficient cause of the child. A father or mother generates his or her child.
The second element, “a conjoined living principle,” refers in humans to the material cause from which the child comes. The father and mother form their child from their own substance, in the case of humans, from the father’s semen and the mother’s ovum. Both are joined to their child through the intermediate gametes; the mother is also joined by the umbilical cord and the child dwelling within her womb.
The third element, “by way of likeness in the same specific nature,” refers to the final and formal cause of the process, the likeness of specific nature between the parent and son. The goal of the generation is reproduction of the nature of the parents. De Koninck argues that both Mary and the Father are true generators of the Son. Each of the three elements of generation, as defined by St. Thomas, can be found in both births of Christ.
1. Living Principle: Both the Father and Mary are living efficient causes of Christ by an activity of life. The Father is the origin of the Son in his divine nature; Mary is the origin of the Son in his human nature.
2. Conjoined Principle:
Mary generates Jesus from her own substance as the Father begets the Son from His substance. She forms in her body and contributes what the human mother forms and contributes to the child. Thus, she is a true generator. The generator draws that which is generated from its own substance while forming it . . . An assimilative action takes place formally in the production of the passive principle of conception, a production which results from the active generative power of the woman, in view of the one engendered . . . For this reason, the mother participates actively in the vital assimilation of the one engendered. She is properly a genetrix.
Today’s biology indicates that the ovum contains exactly half of the genes responsible for the development of the child. This is a sign that the ovum shares in responsibility for the form of the child; the sperm does not form the child from amorphous matter that the mother contributes, as St. Thomas believed. Once the ovum is fertilized there is a new living being that develops by its own active powers using the genes inherited from both parents as instruments. Modern biological observation thus makes clearer the active role the mother plays in generating the child because she actively produces the ovum, which together with the semen, will become the child.
In the case of Jesus, the power of the Holy Spirit, instead of semen, acted on the ovum, but it is reasonable to believe that Mary produced and contributed the ovum just as every human mother does. Mary generated Jesus from her substance as the Father generated the Son from his substance. As a result, the Son has the divine nature from His heavenly Father and human nature from his earthly mother. Mary’s gift from her substance imitates the original gift-of-self of the Father to the Son.
There is still an infinite distance between the divine and human generations of the Son, for the Father uses no intermediate, bodily, or otherwise, to beget the Son. The Son proceeds by a spiritual procession. The closest analogy for this procession, which St. Thomas finds, is the procession of knowledge, which is an immanent procession. The Son proceeds within the Father. “The nature will be expressed in itself.”
3. By Way of Likeness in the Same Specific Nature: Mary gives her nature to Jesus so that he has a complete human nature, possessing both body and soul. As De Koninck says, “[Mary was] sharing by love in the death of her Son, and in a sense dying in Him because He was bone of her bone, flesh of her flesh.” Mary was able to suffer so deeply with her Son in his agony on the Cross, because she loved him so profoundly. He had his humanity from her humanity, his body from her body. Thus it is only to the Mother that the Son of Man owes his similitude in the human species; it is from Mary that he has his whole resemblance according to perfect filiation. In this respect, he is the consubstantial image of his mother.
Jesus is consubstantial with his human mother as he is consubstantial with his divine Father. Mary’s gift of human nature to Jesus mirrors the Father’s gift of his divine nature to the Son. Hence Jesus is both the image of his mother “True human from true human” as well as the image of his Father “True God from True God.” There is also a profound difference since Mary and Jesus are not consubstantial the way the Father and Son are.
The similitude of Father and Son is not a common similitude—like the similitude between a human father and son by reason of their common species which transcends them—but a similitude in the identity of one and the same form which entails the diversity of Persons.
The Father generates the Son from his substance in such a way that there is perfect consubstantiality. The Father and the Son are both the very same God. Mary and Jesus, on the contrary, are two human beings although they have a common nature. They are two instances of human nature whereas the Father and Son are one and the same divine nature.
In meditating on the eternal and temporal processions of the Son, De Koninck discovers further similarities between them. I will mention five.
I. By Speaking a Word: De Koninck says the temporal generation of the Son is like the divine generation because each was a “procession according to knowledge.” According to the psychological analogy of the Trinity, Father speaks the Word from all eternity; Mary’s generation of the Son was also by a word, fiat (Luke 1:38):
Wisdom implies knowledge, a procession according to knowledge. In order that the Blessed Virgin be truly Wisdom, she must, even in relation to God, in addition to her divine maternity according to the flesh, attain to the nature of a first principle according to intellect. That is what she declares in her Fiat—may it be done unto me according to thy word . . . M. Olier, in the most express way tells us that in her Fiat the Blessed Virgin imitated the procession of the Son in God according to knowledge.
Gabriel announces to Mary the identity of the son she is to bear: “Jesus . . . the Son of the Most High . . . the Son of God” (Luke 1:31, 32 and 35). As a result, she can assent to her maternity, knowing that her son will be both man and God. She utters her fiat with knowledge and by her word causes the generation of the Son in her womb, although only through “the power of the Most High,” who deigns to wait for her consent (Luke 1:35):
Just as [the eternal Father] engenders His Word through all eternity by His Knowledge, by a return upon and vision of Himself, so He wills that Mary the supremely perfect and holy image of His virginal fruitfulness, should engender the Word with knowledge; and for that reason He decrees that she shall give her consent to the generation of the word in flesh in an express and solemn way presupposing knowledge and reason.
God sends Gabriel to ask for Mary’s consent so that she could mirror his generation of the Son more perfectly. Nevertheless, Mary engenders the Word by knowledge, in a very different way from the Father. The Father expresses his knowledge of himself in a spiritual Word that is the very Person of the Son. Mary expresses her consent to God’s plan in a human word, which God accepts. Then it is God who overshadows her and engenders the Son physically in her womb, using the ovum, which she has prepared.
II. Virginal Generation: De Koninck says that Mary’s generation of the Word made flesh also mirrors the Father’s generation of the Word by its virginal character. Mary conceives Jesus without a human Father. “How can this be since I have no husband?” (Luke 1:34). In this way, too, she mirrors the Father, the fountainhead of the divinity, who begets the Son from His substance with no partner in His begetting. Thus “Mary [is] the supremely perfect and holy image of His virginal fruitfulness,” as De Koninck, citing M. Olier affirms.
This virginity differs from the Father’s virginity, however, since the Father is the unique fountainhead of the Trinity, the principle without a principle, while Mary is a principle of Jesus through the power of the Holy Spirit. St. Thomas agrees with St. Augustine that Mary is a co-principle of the generation of the Word. “As Augustine says (Enchiridion xi), Christ is said to be conceived or born of the Holy Spirit in one sense; of the Virgin Mary in another—of the Virgin Mary materially; of the Holy Spirit efficiently.”
III. Silent Generation: As De Koninck notes, there is no sound in the eternal speaking of the Word because it is a spiritual procession within the Godhead, just as there is no sound in the conception and nine-month gestation of Jesus in the womb of Mary. “By this silence in the womb of His mother, the Word imitated at the same time in a most striking way His silent procession from the bosom of the Father.”
Not only were the conception and gestation of Jesus silent; St. Thomas teaches that the birth of Jesus was also silent. It was painless without the cries of anguish or deep breaths of labor that usually accompany giving birth in the fallen state. It was silent like the silent procession of the Son from the Father. “But the pain of giving birth of his mother did not pertain to Christ, who came to make satisfaction for our sins. And therefore, it was not necessary that his mother should give birth with pain.” This is not certain doctrine; however, if it is true, it increases the similarity between the two generations.
IV. Remaining of the Son in Mary: The Son remains within the Father eternally, as the Gospel of John makes clear. “I am in the Father” (John 10:38); “the only-begotten Son, who is in the bosom of the Father, he has made him known” (John 1:18). Similarly, the Son remains in his mother’s womb for nine months and in her heart perpetually. De Koninck cites a beautiful passage from St. Albert on the dwelling of Christ within the womb of his mother:
But in the womb of the Blessed Virgin, a womb prepared by the Holy Spirit, all the divinity and all the humanity of Christ were placed and established, and it was thus the proper place of the kingdom: therefore she has been mercy itself and at the same time has been, not without reason, Queen of Mercy.
St. Thomas speaks of the Son dwelling in Mary’s soul as well as in her womb, “The Son of God, who is the ‘Divine Wisdom’ dwelt in her, not only in her soul but in her womb.” Even after Jesus is born, the Son remains perpetually in his mother by faith, hope, and charity. Since she is confirmed in grace, she is confirmed in the theological virtues by which the Trinity dwells in the soul. “Confirmation in goodness was fitting for the Blessed Virgin Mary, because she was the mother of divine Wisdom, in which there is nothing defiled.” But the one who has charity has the Trinity in his soul. “If a man loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him” (John 14:23).
Thus, the Son dwelt in the womb of his mother and dwells perpetually in the heart of his mother as he dwells in the bosom of his Father. Again, the caveat must be made that there is a great difference in the indwelling in Mary and in the Father. The Son dwelt physically in the womb of his mother; he dwells in his Father in the mysterious spiritual manner of perichoresis. He dwells in Mary’s heart by being joined to her mind and will first by faith and charity and now by the beatific vision and charity.
The remaining of the Son in his heavenly Father and in his mother Mary both have the nature of the completion of a circular motion. The Son comes forth from the Father (without ever leaving him) and returns to him in love. He comes forth from his mother physically at his birth and returns to dwells within her by love and brings her physically back to him in heaven at the Assumption.
V. Permanent Relation of Origin to Mary: The Son is always related to the Father as his origin; there is no Father without the Son; nor is there any Son without the Father. The Father reveals the Son and the Son reveals the Father because a relative always manifests its correlative. The Father reveals the Son at his Baptism and Transfiguration. “This is my beloved Son, with whom I am well pleased” (Matt 3:17) and (Matt 17:5). Similarly the Son reveals the Father. “If you had known me, you would have known my Father also; henceforth you know him and have seen him” (John 14:7). “He who has seen me has seen the Father” (John 14:9).
Similarly, the Son is now permanently related to his mother, his human origin. De Koninck says: “The mother is inconceivable without the Son, nor is the Son . . . conceivable without the mother. She proceeds from Him who made her in order that He might proceed from her.” The Son points to his mother on the cross. “Behold your mother” (John 19:20). However, it is usually she who reveals her Son rather than vice versa. At the Visitation, Mary says, “My soul magnifies the Lord” (Luke 1:46); at the wedding at Cana, she says, “Do whatever he tells you” (John 2:5).
There are again immense differences in the relationships. The relation of the Son to the Father is essential; the Son is his subsistent relation to the Father, whereas he is not his relation to his mother. The Son always points to his Father, whereas, in a reversed mirror image, it is usually his mother who points to her Son.
Nevertheless, these similarities allow the temporal procession of the Son to mirror and manifest to humanity the eternal procession of the Son. This imitation is merciful because it is an elevation of a creature, Mary, to be more like God by imitating the immanent life of the Trinity. By imitating the divine generation, she partakes more profoundly in the mystery of the Trinity, the very knowledge of which is eternal life. “And this is eternal life, that they know you the only true God, and Jesus Christ whom you have sent” (John 17:3).
By making Mary the mother of God, God allows the human and cosmic to imitate the eternal and divine. Mary becomes, like God the Father, principle of God the Son; Christ is God from God and God from Woman. St. Thomas writes that each creature desires to imitate the divine in some way: “All things, by desiring their own perfection, desire God Himself inasmuch as the perfections of all things are so many similitudes of the divine being.” The Incarnation is a supernatural and superabundant fulfillment of the creaturely desire to be like God. It could never be anticipated that a creature could be God, as Jesus is; nor that a creature could mirror the Father’s begetting of the Son as Mary does.
My soul magnifies the Lord,
And my spirit rejoices in God my Savior . . .
For He who is mighty has done great things for me and holy is his name (Luke 1: 46,47,49).
 ST III,35.2.c.
 ST I, 27.2.c.
 Charles De Koninck, Ego Sapientia: The Wisdom that is Mary in The Writings of Charles De Koninck, vol. 2, trans. and ed. Ralph McInerny (Notre Dame: UNDP, 2009), 7. De Koninck refers to ST III 32.4. De Koninck also refers to Cajetan’s commentary on this question (Cajetan, Commentary on ST III 32.3: n. VI-X).
 Charles De Koninck, The Cosmos in The Writings of Charles De Koninck, vol. 1, trans. and ed. Ralph McInerny (Notre Dame, IN: UNDP, 2008), 332. The fuller context preceding this quotation: “Let us suppose a living being which does not proceed from potency to act, which proceeds immediately from the activity alone of the generating principle, he will have the second sort of generation [procession of a living thing from a living thing] without the first [passage from non-being to being], that is, without the imperfection that an intermediate element introduces, namely the potentiality from which the engendered is drawn.”
Cornelius a Lapide, In Canticum Canticorum,1:4, t.7, p. 496a, quoted in Ego Sapientia, 37.
 Charles De Koninck, The Piety of the Son, trans. Ralph McInerny, privately circulated, 36. Emphasis added. De Koninck refers to ST III 32.3 ad 1.
 The Cosmos, 333.
 Ego Sapientia, 8.
 Ego Sapientia, 8-9.
 M. Olier, Vie intérieure de la Très Sainte Vierge (Paris, 1875), 5-6. Cited by De Koninck in Ego Sapientia, 9.
ST III 32.2 ad 3.
Ego Sapientia, 31.
 ST III 36.6.
 St. Albert, Mariale, p. 236 b; cited by De Koninck in Ego Sapientia, 39.
 ST III 27.4.
 St. Thomas Aquinas, de Veritate 24.9 ad 2.
 Ego Sapientia, 10.
 ST I 6.1 ad 2.