The Council of Ephesus (431 AD)

If anyone shall dare to say that the Christ is a Theophorus [that is, God-bearing] man and not rather that he is very God, as an only Son through nature, because “the Word was made flesh,” and “hath a share in flesh and blood as we do:” let him be anathema.

If any one ventures to say that, even after the assumption of human nature, there is only one Son of God, namely, he who is so in nature (naturaliter filius = Logos), while he (since the assumption of the flesh) is certainly Emmanuel; let him be anathema.

It is manifest that this anathematism is directed against the blasphemy of Nestorius, by which he said that Christ was in this sense Emmanuel, that a man was united and associated with God, just as God had been said to have been with the Prophets and other holy men, and to have had his abode in them; so that they were properly styled Θεοφόροι, because, as it were, they carried God about with them; but there was no one made of the two. But he held that our Lord as man was bound and united with God only by a communion of dignity.

Nestorius [in his Counter Anathematism] displays the hidden meaning of his heresy, when he says, that the Son of God is not one after the assumption of the humanity; for he who denied that he was one, no doubt thought that he was two.

Theodoret in his criticism of this Anathematism remarks that many of the Ancients, including St. Basil had used this very word, Θεοφόρος, for the Lord; but the objection has no real foundation, for the orthodoxy or heterodoxy of such a word must be determined by the context in which it is used, and also by the known opinions of him that uses it. Expressions which are in a loose sense orthodox and quite excusable before a heresy arises, may become afterwards the very distinctive marks and shibboleths of error. Petavius has pointed out how far from orthodox many of the earliest Christian writers were, at least verbally, and Bp. Bull defended them by the same line of argument I have just used and which Petavius himself employs in this very connection.