Today we reflect with St Thomas Aquinas on the sublime mystery of Christ conception in the womb of Mary, His Mother. The Son of God in His divine nature was already begotten of God the Father, therefore God the Holy Spirit does not beget the child similar to Himself in the divine nature in the womb of Mary but He forms the human nature of the Son of God in the hypostatic union of two natures, divine and human.
The Son of God, Jesus Christ, was conceived of the flesh of Mary, the Virgin of Nazareth. He was, therefore, a man like other men. He was of the race of Adam. He was also, as had been foretold by the prophets, of the family of David, a member of the royal house of Israel. But the active principle of His conception in the womb of Mary was the Holy Spirit, God Himself. Of course, it is true that it was God, all three Persons of the Trinity, Who conceived Christ in the womb of Mary. but God Himself attributes this action to the Third Person, the Holy Spirit, because it is work of divine love, and in God the Holy Spirit is the love of the Father and the Son. This does not mean that the Holy Spirit is the father of Christ. To be a father, a person must beget a child who is similar to himself in nature. God the Father begets in God a Son Who is like to Him in the divine nature, Who is, in fact, identical with Him in the divine nature, A human father begets a child who is like to himself in human nature. But the Holy Spirit when He conceives Christ in the womb of Mary, does not beget a child similar to Himself in the divine nature. As God, the Son of God is already divine, begotten only of God the Father. The action of the Holy Spirit forms in Mary the human nature of the Son of God.
Text from "My Way of Life- The Summa simplified" by Msgr Austin P. Bennett, Confraternity of the Precious Blood, 1952
Text from "My Way of Life- The Summa simplified" by Msgr Austin P. Bennett, Confraternity of the Precious Blood, 1952