John of Damascus: Exposition of the Orthodox Faith 55Concerning the Nature as viewed in Species and in Individual, and concerning the difference between Union and Incarnation: and how this is to be understood, “The one Nature of God the Word Incarnate.”

Nature is regarded either abstractly as a matter of pure thought (for it has no independent existence): or commonly in all subsistences of the same species as their bond of union, and is then spoken of as nature viewed in species: or universally as the same, but with the addition of accidents, in one subsistence, and is spoken of as nature viewed in the individual, this being identical with nature viewed in species. God the Word Incarnate, therefore, did not assume the nature that is regarded as an abstraction in pure thought (for this is not incarnation, but only an imposture and a figment of incarnation), nor the nature viewed in species (for He did not assume all the subsistences): but the nature viewed in the individual, which is identical with that viewed in species. For He took on Himself the elements of our compound nature, and these not as having an independent existence or as being originally an individual, and in this way assumed by Him, but as existing in His own subsistence. For the subsistence of God the Word in itself became the subsistence of the flesh, and accordingly "the Word became flesh" clearly without any change, and likewise the flesh became Word without alteration, and God became man. For the Word is God, and man is God, through having one and the same subsistence. And so it is possible to speak of the same thing as being the nature of the Word and the nature in the individual. For it signifies strictly and exclusively neither the individual, that is, the subsistence, nor the common nature of the subsistences, but the common nature as viewed and presented in one of the subsistences.

Union, then, is one thing, and incarnation is something quite different. For union signifies only the conjunction, but not at all that with which union is effected. But incarnation (which is just the same as if one said "the putting on of man's nature") signifies that the conjunction is with flesh, that is to say, with man, just as the heating of iron implies its union with fire. Indeed, the blessed Cyril himself, when he is interpreting the phrase, "one nature of God the Word Incarnate," says in the second epistle to Sucensus, "For if we simply said 'the one nature of the Word' and then were silent, and did not add the word 'incarnate,' but, so to speak, quite excluded the dispensation, there would be some plausibility in the question they feign to ask, 'If one nature is the whole, what becomes of the perfection in humanity, or how has the essence like us come to exist?' But inasmuch as the perfection in humanity and the disclosure of the essence like us are conveyed in the word 'incarnate,' they must cease from relying on a mere straw." Here, then, he placed the nature of the Word over nature itself. For if He had received nature instead of subsistence, it would not have been absurd to have omitted the "incarnate." For when we say simply one subsistence of God the Word, we do not err. In like manner, also, Leontius the Byzantine considered this phrase to refer to nature, and not to subsistence. But in the Defence which he wrote in reply to the attacks that Theodoret made on the second anathema, the blessed Cyril says this: "The nature of the Word, that is, the subsistence, which is the Word itself." So that "the nature of the Word" means neither the subsistence alone, nor "the common nature of the subsistence," but "the common nature viewed as a whole in the subsistence of the Word."

It has been said, then, that the nature of the Word became flesh, that is, was united to flesh: but that the nature of the Word suffered in the flesh we have never heard up till now, though we have been taught that Christ suffered in the flesh. So that "the nature of the Word" does not mean "the subsistence." It remains, therefore, to say that to become flesh is to be united with the flesh, while the Word having become flesh means that the very subsistence of the Word became without change the subsistence of the flesh. It has also been said that God became man, and man God. For the Word which is God became without alteration man. But that the Godhead became man, or became flesh, or put on the nature of man, this we have never heard. This, indeed, we have learned, that the Godhead was united to humanity in one of its subsistences, and it has been stated that God took on a different form or essence, to wit our own. For the name God is applicable to each of the subsistences, but we cannot use the term Godhead in reference to subsistence. For we are never told that the Godhead is the Father alone, or the Son alone, or the Holy Spirit alone. For "Godhead" implies "nature," while "Father" implies subsistence, just as "Humanity" implies nature, and "Peter" subsistence. But "God" indicates the common element of the nature, and is applicable derivatively to each of the subsistences, just as "man" is. For He Who has divine nature is God, and he who has human nature is man.

Besides all this, notice that the Father and the Holy Spirit take no part at all in the incarnation of the Word except in connection with the miracles, and in respect of good will and purpose.