January 1 is the Solemnity (Holy Day) of Mary, Mother of God. To call Mary the “Mother of God” must not be understood as a claim for Mary’s motherhood of divinity itself, but in the sense that Mary was mother of Jesus, who is truly God. The Council of Ephesus in 431—long before the schisms with the Eastern churches and the Protestants—proclaimed “Mother of God” a theologically correct title for Mary.
So far from being a cause of division, the common confession of Mary as “Mother of God” should unite all Christians, and distinguish Christian orthodoxy from various confusions of it, such as Arianism (the denial that Jesus was God) or Nestorianism (in which Mary mothers only the human nature of Jesus but not his whole person).
Two themes are present in the Readings for this Solemnity: (1) the person of Mary, and (2) the name of Jesus. Why the name of Jesus? Prior to the second Vatican Council, the octave day of Christmas was the Feast of the Holy Name, not Mary Mother of God. The legacy of that tradition can be seen in the choice of Readings for this Solemnity. (The Feast of the Holy Name was removed from the calendar after Vatican II; St. John Paul II restored it as an optional memorial on January 3. This year it is not observed in the U.S., because Epiphany falls on January 3.)
1. The First Reading is Numbers 6:22-27: