Mary “is endowed with the high office and dignity of the Mother of the Son of God, and therefore she is also the beloved daughter of the Father and the temple of the Holy Spirit” (Lumen gentium, n. 53)
- The eighth chapter of the Constitution Lumen gentium shows in the mystery of Christ the absolutely necessary reference to Marian doctrine. In this regard, the first words of the Introduction are significant: “Wishing in his supreme goodness and wisdom to effect the redemption of the world, ‘when the fullness of time came, God sent his Son, born of a woman … that we might receive the adoption of sons’ (Gal 4:4-5)” (Lumen gentium, n. 52). This son is the Messiah awaited by the people of the Old Covenant, sent by the Father at a decisive moment of history, the “fullness of time” (Gal 4:4), which coincides with his birth in our world from a woman. She who brought the eternal Son of God to humanity can never be separated from him who is found at the centre of the divine plan carried out in history.
The primacy of Christ is shown forth in the Church, his Mystical Body: in her “the faithful are joined to Christ the Head and are in communion with all his saints” (cf. Lumen gentium, n. 52). It is Christ who draws all men to himself. Since in Her maternal role she is closely united with her Son, Mary helps direct the gaze and heart of believers towards him.
She is the way that leads to Christ: indeed, she who “at the message of the angel received the Word of God in her heart and in her body” (Lumen gentium, n. 53) shows us how to receive into our lives the Son come down from heaven, teaching us to make Jesus the centre and the supreme “law” of our existence.
A unique bond between Mary and the Holy Spirit
- Mary also helps us discover, at the origin of the whole work of salvation, the sovereign action of the Father who calls men to become sons in the one Son. Recalling the very beautiful expressions of the Letter to the Ephesians: “God, who is rich in mercy, out of the great love with which he loved us, even when we were dead through our trespasses, made us alive together with Christ” (Eph 2:4), the Council gives God the title “most merciful”: the Son “born of a woman” is thus seen as the fruit of the Father’s mercy and enables us to understand better how this Woman is the “mother of mercy”.
In the same context, the Council also calls God “most wise”, suggesting a particular attention to the close link between Mary and the divine wisdom, which in its mysterious plan willed the Virgin’s motherhood.
- The Council’s text also reminds us of the unique bond uniting Mary with the Holy Spirit, using the words of the Nicene-Constantinopolitan Creed which we recite in the Eucharistic liturgy: “For us men and for our salvation he came down from heaven: by the power of the Holy Spirit he was born of the Virgin Mary, and became man”.
Lumen gentium thus shows in a Trinitarian perspective an essential dimension of Marian doctrine. Everything in fact comes from the will of the Father, who has sent his Son into the world, revealing him to men and establishing him as the Head of the Church and the centre of history. This is a plan that was fulfilled by the Incarnation, the work of the Holy Spirit, but with the essential co-operation of a woman, the Virgin Mary, who thus became an integral part in the economy of communicating the Trinity to mankind.
- Mary’s threefold relationship with the divine Persons is confirmed in precise words and with a description of the characteristic relationship which links the Mother of the Lord to the Church: “She is endowed with the high office and dignity of the Mother of the Son of God, and therefore she is also the beloved daughter of the Father and the temple of the Holy Spirit” (Lumen gentium, n. 53).
Mary’s fundamental dignity is that of being “Mother of the Son”, which is expressed in Christian doctrine and devotion with the title “Mother of God”.
This is a surprising term, which shows the humility of God’s only-begotten Son in his Incarnation and, in connection with it, the most high privilege granted a creature who was called to give him birth in the flesh.
Mother of the Son, Mary is the “beloved daughter of the Father” in a unique way. She has been granted an utterly special likeness between her motherhood and the divine fatherhood.
And again: every Christian is a “temple of the Holy Spirit”, according to the Apostle Paul’s expression (1 Cor 6:19). But this assertion takes on an extraordinary meaning in Mary: in her the relationship with the Holy Spirit is enriched with a spousal dimension. I recalled this in the Encyclical Redemptoris Mater: “The Holy Spirit had already come down upon her, and she became his faithful spouse at the Annunciation, welcoming the Word of the true God…” (n. 26).
Mary’s dignity surpasses that of every creature
- Mary’s privileged relationship with the Trinity therefore confers on her a dignity which far surpasses that of every other creature. The Council recalls this explicitly: because of this “gift of sublime grace” Mary “far surpasses all creatures” (Lumen gentium, n. 53). However, this most high dignity does not hinder Mary’s solidarity with each of us. The Constitution Lumen gentium goes on to say: “But, being of the race of Adam, she is at the same time also united to all those who are to be saved” and she has been “redeemed, in a more exalted fashion, by reason of the merits of her Son” (ibid.).
Here we see the authentic meaning of Mary’s privileges and of Her extraordinary relationship with the Trinity: their purpose is to enable Her to co-operate in the salvation of the human race. The immeasurable greatness of the Lord’s Mother therefore remains a gift of God’s love for all men. By proclaiming her “Blessed” (Lk 1:48), generations praise the “great things” (Lk 1:49) the Almighty has done in Her for humanity, “in remembrance of His mercy” (Lk 1:54). (Blessed John Paul II)
That is a good way of explaining it
) knows that Mary is the Mother of Jesus Christ, who is/was a virgin. They know that Christians believe that Christ is God. So how/why would they be confused about the reason for calling Mary, the Mother of God? 
When this confusion is claimed by professing Christians it’s even more puzzling to me. 