On The Union

Τὰ μὲν οὖν πρὸ τῆς ἑνώσεως καὶ μετὰ τὴν ἕνωσιν ἐπ᾿ αὐτῷ λεχθήσεται, τὰ δὲ μετὰ τὴν ἕνωσιν πρὸ τῆς ἑνώσεως οὐδαμῶς, εἰ μήτιγε προφητικῶς, ὡς ἔφημεν. Τῶν δὲ ἐν τῇ ἑνώσει τρόποι εἰσὶ τρεῖς. Ὅτε μὲν γὰρ ἐκ τοῦ κρείττονος τὸν λόγον ποιούμεθα, θέωσιν τῆς σαρκὸς καὶ λόγωσιν καὶ ὑπερύψωσιν λέγομεν καὶ τὰ τοιαῦτα, τὸν προσγενόμενον τῇ σαρκὶ πλοῦτον ἐκ τῆς πρὸς τὸν ὕψιστον Θεὸν Λόγον ἑνώσεώς τε καὶ συμφυΐας ἐμφαίνοντες. Ὅτε δὲ ἀπὸ τοῦ ἐλάττονος, σάρκωσιν τοῦ Λόγου, ἐνανθρώπησιν, κένωσιν, πτωχείαν, ταπείνωσίν φαμεν· ταῦτα γὰρ καὶ τὰ τοιαῦτα ἐκ τῆς πρὸς τὸ ἀνθρώπινον κράσεως ἐπιλέγεται τῷ Λόγῳ τε καὶ Θεῷ. Ὅταν δὲ ἐξ ἀμφοῖν ἅμα, ἕνωσιν, κοινωνίαν, χρίσιν, συμφυΐαν, συμμόρφωσιν καὶ τὰ τοιαῦτα φάσκομεν. Διὰ τοῦτον οὖν τὸν τρίτον τρόπον οἱ προλελεγμένοι δύο τρόποι λέγονται. Διὰ γὰρ τῆς ἑνώσεως δηλοῦται, τί ἔσχεν ἑκάτερον ἐκ τῆς τοῦ συνυφεστῶτος αὐτῷ ἁρμογῆς καὶ περιχωρήσεως· διὰ γὰρ τὴν καθ᾿ ὑπόστασιν ἕνωσιν ἡ σὰρξ τεθεῶσθαι λέγεται καὶ Θεὸς γενέσθαι καὶ ὁμόθεος τῷ Λόγῳ· καὶ ὁ Θεὸς Λόγος σαρκωθῆναι καὶ ἄνθρωπος γενέσθαι καὶ κτίσμα λέγεσθαι καὶ ἔσχατος καλεῖσθαι, οὐχ ὡς τῶν δύο φύσεων μεταβληθεισῶν εἰς μίαν φύσιν σύνθετον, ἀδύνατον γὰρ ἐν μιᾷ φύσει ἅμα τὰ ἐναντία φυσικὰ γενέσθαι, ἀλλ᾿ ὡς τῶν δύο φύσεων καθ᾿ ὑπόστασιν ἑνωθεισῶν καὶ τὴν εἰς ἀλλήλας περιχώρησιν ἀσύγχυτον καὶ ἀμετάβλητον ἐχουσῶν. Ἡ δὲ περιχώρησις οὐκ ἐκ τῆς σαρκός, ἀλλ᾿ ἐκ τῆς θεότητος γέγονεν· ἀμήχανον γὰρ τὴν σάρκα περιχωρῆσαι διὰ τῆς θεότητος, ἀλλ᾿ ἡ θεία φύσις ἅπαξ περιχωροῦσα διὰ τῆς σαρκὸς ἔδωκε καὶ τῇ σαρκὶ τὴν πρὸς αὐτὴν ἄρρητον περιχώρησιν, ἣν δὴ ἕνωσιν λέγομεν. Άγιος Ιωάννης ο Δαμασκηνός, Ἔκδοσις Ὰκριβὴς Τῆς Ὀρθοδόξου Πίστεως, Τομος Δ, Κεφαλ ΙΗ' Source: Migne PG 94.1183b-d

The things said, then, concerning Him before the union are sayable also after the union, but those things after the union not at all, unless indeed in a Prophetic manner, as we have said. Those things that refer to the union have three modes. For when we make speech about the higher, we speak of the deification of the flesh and the assumption of the Word and exceeding exaltation, and so forth, declaring manifestly the wealth added to the flesh from the union with the must high God the Word and conjunction. And when we speak of the lower, we speak of the incarnation of the Word, His becoming man, His emptying of Himself, His poverty, His humility. For these things, and such like, by His mixing with humanity are imposed upon the Word and God. And when we speak of both together, we speak of union, communion, anointing, conjunction, conformation and such things. Thus the former two modes have their reason in this third mode. For by the union it is made clear what each has from the intimate conjunction and permeation with the other, for by the union in subsistence the flesh is said to be deified and to become God and to be equally God with the Word, and God the Word is said to be made flesh, and to become man, and is called a creature and last, not that the two natures are converted into one compound nature, for it is impossible that at the same time in the same nature opposite natural qualities exist, but the two natures are united in subsistence and permeate one another without confusion or transmutation. And the permeation is not from the flesh but from the Divinity, for it is impossible that the flesh should permeate through the Divinity, but the Divine nature permeating through the flesh gave to the flesh that same ineffable permeation, and this indeed we call union. Saint John of Damascus, An Exact Exposition of the Orthodox Faith, Book 4, Chap 18