By St. John of Damascus
(Exact Exposition of the Orthodox Faith, Bk. 3, Ch. 12)
Moreover we proclaim the holy Virgin to be in strict truth the Mother of God [Theotokos]. For inasmuch as He who was born of her was true God, she who bare the true God incarnate is the true mother of God. For we hold that God was born of her, not implying that the divinity of the Word received from her the beginning of its being, but meaning that God the Word Himself, Who was begotten of the Father timelessly before the ages, and was with the Father and the Spirit without beginning and through eternity, took up His abode in these last days for the sake of our salvation in the Virgin's womb, and was without change made flesh and born of her. For the holy Virgin did not bare mere man but true God: and not mere God but God incarnate, Who did not bring down His body from Heaven, nor simply passed through the Virgin as channel, but received from her flesh of like essence to our own and subsisting in Himself. For if the body had come down from heaven and had not partaken of our nature, what would have been the use of His becoming man? For the purpose of God the Word becoming man was that the very same nature, which had sinned and fallen and become corrupted, should triumph over the deceiving tyrant and so be freed from corruption, just as the divine apostle puts it, "For since by man came death, by man came also the resurrection of the dead" [1 Cor. 15:21]. If the first is true the second must also be true.
Although, however, he says, "The first Adam is of the earth earthy; the second Adam is Lord from Heaven" [1 Cor. 15:47], he does not say that His body is from heaven, but emphasizes the fact that He is not mere man. For, mark, he called Him both Adam and Lord, thus indicating His double nature. For Adam is, being interpreted, earth-born: and it is clear that man's nature is earth-born since he is formed from earth, but the title Lord signifies His divine essence.
And again the Apostle says: "God sent forth His only-begotten Son, made of a woman" [Gal. 4:4]. He did not say "made by a woman." Wherefore the divine apostle meant that the only-begotten Son of God and God is the same as He who was made man of the Virgin, and that He who was born of the Virgin is the same as the Son of God and God.
But He was born after the bodily fashion inasmuch as He became man, and did not take up His abode in a man formed beforehand, as in a prophet, but became Himself in essence and truth man, that is He caused flesh animated with the intelligent and reasonable to subsist in His own subsistence, and Himself became subsistence for it. For this is the meaning of "made of a woman." For how could the very Word of God itself have been made under the law, if He did not become man of like essence with ourselves?
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, manifestly 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 [Christotokos (χριστοτόκος), as opposed to Theotokos (θεοτόκος)] because it was in order to do away with the title Mother of God, and to bring dishonor on the Mother of God, who alone is in truth worthy of honor above all creation, that the impure and abominable Judaizing Nestorius, that vessel of dishonor, invented this name for an insult. For David the king, and Aaron the high priest, are also called Christ [which means "the anointed one"], for it is customary to make kings and priests by anointing: and besides every God-inspired man may be called Christ, but yet he is not by nature God. Truly, the accursed Nestorius insulted Him Who was born of the Virgin by calling Him God-bearer [Theophoros (θεόφορος)]. 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 marvelous 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 were 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 coming 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 marvelous 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.