As for the Blessed Virgin Mary herself, she is a creature. She is the greatest creature the Son of God ever created for Himself in all creation. For He created her “full of grace” as a human being, as the All Holy Daughter of Israel, through her Immaculate Conception to prepare her to become His Mother “in the fullness of time”. Accordingly, from the beginning of her creation, she was fully sanctified, far above all other creatures, by a singular grace of justification, the immaculate grace of God, through the Gift of the Holy Spirit. As such, she received this grace from her conception as a human being in anticipation of the merits of her Son’s saving actions as man. In this sense, He saved her through her immaculate creation. For this reason, she has a natural debt to honor Him in justice and charity as her God by offering Him prayer of latria or worship, for God alone merits such prayer as her Creator and Savior. She is, in this sense, subject to Him. She is subject to His divine dignity and authority. For He is not only her Son, but also her God. Nevertheless, in a certain sense, by His human conception and birth as man to the Blessed Virgin Mary, God the Son subjects Himself to her maternal dignity and authority. In becoming man through Blessed Mary, He establishes a relationship of nature, a relationship of consanguinity, with her. This means that as man He proceeds from the same substance or nature of Blessed Mary as to natural, bodily descent. His humanity descends from hers. Consequently, as a natural Son of Mary through His created human nature, He becomes naturally indebted to her as to filial justice and charity. As a result, this is a debt He is morally required to pay her by nature. For as her natural Son, He has a filial duty to offer her the just and loving actions she has merited for herself by conceiving and bearing Him as man. Accordingly, He honors her as His Mother, as the Mother of God, by such actions, for He is the Son of God who has become man through her.
All the same, in professing that the Blessed Virgin Mary is the Mother of God through the human incarnation of God the Son in her womb, the Church is not saying that Mary is the "Mother of a human person." On the contrary, the Church is saying that Mary is the "Mother of a Divine Person," the Second Person of the Blessed Trinity, God the Son, who became man through His incarnation. For the terminus or end of the act of Mary conceiving God as man through the Holy Spirit is not the generation of a created human subject or person in her womb. There remains only one "personal subjectum" in the incarnation of God the Son as man. This subjectum, called the "suppositum" or "hypostasis," is the Uncreated Divine Person of the Son of God, the Second Person of the Blessed Trinity. As such, this is the subjectum that proceeds eternally from God the Father. For this reason, the Church professes that the subject or suppositum of the created human nature of Jesus Christ is His Uncreated Divine Person. In this sense, He remains "one and the same Divine Person" eternally in becoming man. Accordingly, Mary’s conception of the Son of God as man terminates not in the creation of a human person, but in the incarnation of the Uncreated Person of God the Son as man through a created human nature. As a result, God the Son acquires a "second nature or mode of being" in becoming man, not a second suppositum or person. This means that He remains the Son of God in becoming the son of man. For this reason, the subject of His created manhood or nature is His Uncreated Divine Person as the Son of God. In this sense, He unites this second created nature or mode of being to Himself in the incarnation of His Divine Person. This is called the "hypostatic union," the union of the divine nature and the human nature, in the One Divine Person of Jesus Christ, the Son of God. Hence, the Blessed Virgin Mary is rightly called the Mother of God, not the Mother of a human person. For She is more than the Mother of a man. She is the Mother of the Divine Person of God the Son who has become man. She is the Mother of the Second Person of the Blessed Trinity who remains fully God in becoming fully man.
On this basis, St. Thomas says that as the Mother of God, the Blessed Virgin Mary has a certain infinite dignity by her maternal relationship to the infinite Good, God Himself. As such, he says that there is nothing that can be conceived of as greater than Mary’s Maternity, because there is nothing greater than God as the end or terminus of this Maternity. This is the basis for St. Thomas’s teaching concerning hyperdulia, a special honor or veneration due to Blessed Mary alone as Mother of God. According to him, "hyperdulia" is the highest form of dulia, because the reverence or honor due any person increases with that person’s relation to God. The greater this relation, the greater the honor due the person. As a result, because the Maternity of the person of Blessed Virgin Mary terminates in the Uncreated Person of God the Son, she is personally due the greatest honor or reverance among human persons called hyperdulia through acts of justice and love. This would include prayer of veneration and intercession. Accordingly, during this Christmas season, I hope and pray that you will consider honoring the Blessed Virgin Mary as the Mother of the Divine Person of God the Son.