'Mother of God' or 'Mother of Christ?'
There are tons of great writings from the Church Fathers available on the internet. One of them is Saint John Damascene's 'Exposition of the Orthodox Faith.' In Book III Saint John discusses why the Church of his time used the title 'Mother of God.' Perhaps we as Catholics take this for granted today, because I have seen many use the term 'Mother of Christ' instead of 'Mother of God.' In fact there are even Catholic parishes now named, 'Mother of Christ.' While there is no doubt that the Blessed Mother of God was the mother of Christ, the title 'Mother of God' is certainly a more appropriate title to use, because it tells us who Christ truly is, that is God incarnate. Although The Blessed Mother of God has been given many titles over the history of the Church, I know of no other formal dogmatic declarations by the Church demanding a specific title in regard to Mary's motherhood other than what Canon 1 of the Council of Ephesus demanded, "If anyone does not confess that God is truly Emmanuel, and that on this account the Holy Virgin is the Mother of God (for according to the flesh she gave birth to the Word of God become flesh by birth), let him be anathema."
While certainly other titles also clearly convey central theological truths of our faith, such as 'Mother of the Savior,' Mother of the Redeemer,' etc, none strike as clear of a picture as to who Mary is the mother of, as the 'The Mother of God' does. When we use titles like 'Mother of God,' Mother of the Savior,' or Mother of the Redeemer, a clear message is conveyed as to the who the person of Christ is as a divine person, while when using the term 'Mother of Christ' we loose the divine nature of who it is that Mary is the mother of. Was she just the mother of Christ, a mere man from Nazareth, or was He God incarnate, born in Bethlehem, who has come upon us to save and redeem us? Saint John understood well the implications of using the title 'Mother of God', and how important it was to maintain its use. This title has always been held in high esteem in the Church, both the East and the West. With all of the efforts made today to dismiss Christ as just another "guru" among others, we should do well to continue to use the title to exalt Christ as God Incarnate. Of course I am not saying that using other titles such as 'The Blessed Virgin Mary,' 'The Queen of Heaven,' 'Our Lady of Sorrows,' etc, etc, should not be used. I am merely pointing out the fact that many today are using the title 'Mother of Christ' as a substitute for 'Mother of God' and it can have serious implications as to how the world views the divine person of Jesus Christ. Below is small excerpt from the chapter concerning the title, 'Mother of God.'
Hence it is with justice and truth that we call the holy Mary the Mother of God. For this name embraces the whole mystery of the dispensation. For if she who bore Him is the Mother of God, assuredly He Who was born of her is God and likewise also man. For how could God, Who was before the ages, have been born of a woman unless He had become man? For the son of man must clearly be man himself. But if He Who was born of a woman is Himself God, man He Who was born of God the Father in accordance with the laws of an essence that is divine and knows no beginning, and He Who was in the last days born of the Virgin in accordance with the laws of an essence that has beginning and is subject to time, that is, an essence which is human, must be one and the same. The name in truth signifies the one subsistence and the two natures and the two generations Of our Lord Jesus Christ.But we never say that the holy Virgin is the Mother of Christ because it was in order to do away with the title Mother of God, and to bring dishonour on the Mother of God, who alone is in truth worthy of honour above all creation, that the impure and abominable Judaizing Nestorius, that vessel of dishonour, invented this name for an insult. For David the king, and Aaron, the high priest, are also called Christ, for it is customary to make kings and priests by anointing: and besides every God-inspired man may be called Christ. but yet be is not by nature God: yea, the accursed Nestorius insulted Him Who was born of the Virgin by calling Him God-bearer. May it be far from us to speak of or think of Him as God-bearer only, Who is in truth God incarnate. For the Word Himself became flesh, having been in truth conceived of the Virgin, but coming forth as God with the assumed nature which, as soon as He was brought forth into being, was deified by Him, so that these three things took place simultaneously, the assumption of our nature, the coming into being, and the deification of the assumed nature by the Word. And thus it is that the holy Virgin is thought of and spoken of as the Mother of God, not only because of the nature of the Word, but also because of the deification of man's nature, the miracles of conception and of existence being wrought together, to wit, the conception the Word, and the existence of the flesh in the Word Himself. For the very Mother of God in some marvellous manner was the means of fashioning the Framer of all things and of bestowing manhood on the God and Creator of all, Who deified the nature that He assumed, while the union preserved those things that wesaint re united just as they were united, that is to say, not only the divine nature of Christ but also His human nature, not only that which is above us but that which is of us. For He was not first made like us and only later became higher than us, but ever from His first coating into being He existed with the double nature, because He existed in the Word Himself from the beginning of the conception. Wherefore He is human in His own nature, but also, in some marvellous manner, of God and divine. Moreover He has the properties of the living flesh: for by reason of the dispensation the Word received these which are, according to the order of natural motion, truly natural.