No phrase in modern evangelicalism is more cringe-worthy than “Mary, mother of God.”
There was a time when I couldn’t stand this designation. “Mother of God?” I’d ask myself, “God is un-created! He can’t have a mother!” It seemed so impious and blasphemous to suggest that God the Son had an earthly mother.
But, what happens if we reject this phrase, or downplay it?
Rather than asking the question, “Did God have a mother?” a better question we could ask is, “What would the implications be if God did not have a mother?”
Nestorius was a 4th to 5th century Archbishop of Constantinople who developed a theory of Christology which would eventually come to be known as Nestorianism. This theory suggested that the Son of God took unto Himself not a human nature but a human person in His incarnation. For Nestorius, Jesus was a composite of both an eternal divine person and a finite human person.
Historical-creedal Christianity would come to reject this as a heresy because, biblically, Jesus is only ever referred to as a singular person, not a composition of persons. Perhaps the best elucidation of the Son’s singular personhood would be in John 1:1-17. The Christ, in v. 17, cannot be separated from the Word (logos) in vv. 1-3. They are one in the same, not two persons coming together to form some type of composed being. Moreover, if the Son were really two persons, then the Son could not be the Christ and the Christ could not be the Son, they would in fact be two different persons manifesting in a singular body. But as it is, the Son must be the Christ and the Christ must be the Son if we are taking Scripture seriously.
The church has, therefore, rejected Nestorianism as heresy. It is unsupported both biblically and historically.
Mary is Mother of God or Nestorius is Right
The implication for rejecting Mary’s motherhood in relation to the Son of God is Nestorianism. If Mary is the mother of Jesus—and she was (Jn. 2:1, 3; Acts 1:14); and if Jesus was God—and He was (Jn. 1:1-3; 20:28; Tit. 2:13); then it is right to say Mary is the mother of God (Gk. Theotokos).
However, there are qualifications we need to make.
First, Mary is not the mother of God in the sense that God came into existence according to His divine nature. We are not saying that the divine Being is created or finite in any way.
Second, we need to remember the doctrine of the incarnation. Properly formulated, it is this: The Son of God took into union with Himself the fullness of a human nature. The 2nd London Confession states it this way:
The Son of God, the second person in the Holy Trinity, being very and eternal God, the brightness of the Father’s glory, of one substance and equal with him who made the world, who upholdeth and governeth all things he hath made, did, when the fullness of time was come, take upon him man’s nature, with all the essential properties and common infirmities thereof, yet without sin (2nd LBC, 8.2).
Therefore, third, we can accurately say that Mary is the mother of God according to the human nature God (the Son) took unto Himself in the incarnation. Our words, “Mary, mother of God,” do not extend to the immutable divine nature which fully subsists in the Person of the Son. Rather, our words extend only to the human nature taken up by the Son at the point of His incarnation.
We need to qualify our use of the term nature.
When we make a linguistic distinction between the divine and human natures of Christ, we do not mean to indicate that those two natures are divided nor do we want to flee to the other side of the spectrum and say that they are confused.
These natures are distinct yet perfectly and harmoniously unified in the one Person of the Son. Our language fails us to a certain extent because we simply do not have a sufficient way to exhaustively describe the incarnation.
It is incomprehensible to us.