The mother of the messiah has been called many things in the last 2000 years — the Virgin Mary, Our Lady, the Blessed Mother. But call her “the Mother of God†and you’ll see some Christians squirm.This is nothing new. One day in the early fifth century, a priest preached a stirring sermon in the presence of the patriarch of Constantinople. His subject was the holy mother of Jesus. The preacher continually referred to Mary as the “Theotokos†meaning “God-bearer†or mother of God. This was no innovation — Christians had invoked Mary under this title for at least two...