The French reformer John
Calvin (1509-1564) also held that Mary was the Mother of God.
It cannot be denied that God in choosing and destining Mary to be the Mother of his Son, granted her the highest
honor. ... Elizabeth called
Mary Mother of the Lord, because the unity of the person in the two natures of Christ was such
that she could have
said that the mortal man engendered in the womb of Mary was at the same time the eternal God. (Calvini Opera, Corpus
Reformatorum, Braunschweig-Berlin, 1863-1900, v. 45, p. 348, 35.)
On the perpetual virginity of Mary, "Calvin
Routinely brushes aside the
difficulties
sometimes raised from
"first born" and
"brothers of
the Lord."
(O'Carroll, M., 1983, Theotokos,
M Glazier, Inc.: Wilmington, DE,
p. 94.)