“He comes forth, God with what he assumed, one from two opposites, flesh and spirit, the one deifying and the other deified. O the new mixture! O the paradoxical blending! He who is comes into being, and the uncreated is created, and the uncontained contained” (Or. 38.13). Thus declaims St Gregory the Theologian in his magnificent Theophany oration.
It’s a striking and dangerous image—the blending and mixing of divinity and humanity to form the one incarnate Christ. Striking—as it intimates the most intimate union. The divine and human natures stand neither over against each other nor alongside each other nor kept at a distance. They are joined and blended together, as one blends together lettuce, tomatoes, and bell peppers to create a delicious salad. Dangerous—because it can be easily misunderstood as suggesting that the two natures are mixed together to create a bizarre hybrid that is neither God nor man, much as one might mix Coca-Cola and a fine single malt whisky (there is no name for such a travesty).
Apollinarius also invoked the language of mixture to describe the Incarnation: “O new creation and God-spoken mixture! God and flesh made up one and the same nature!” (frag. 10; cf. frag. 93). Note how Apollinarius can speak of the incarnate Christ as possessing one nature. Because he conceives of the divine Word as functioning as the directing principle of Jesus, instead of a human mind, Apollinarius thinks of Jesus as possessing only a divine nature. Quite literally, and non-paradoxically, God walks on earth dressed in a physical form. His human body is the Word’s passive instrument. To speak of the one divine nature of Christ is therefore the most accurate way to speak of the Lord’s primary identity.
The language of mixing and blending would later be proscribed by the Council of Chalcedon as inappropriate to express the mystery of the hypostatic union; “yet for Gregory,” as Christopher Beeley explains, “such terms helpfully convey the dynamic unifying movement of the incarnation and the mysteriously intimate union of God with humanity in Christ” (The Unity of Christ, p. 187). Gregory protects himself from misunderstanding in two ways:
First, by insisting that the incarnate Son is a composite being. Human nature (including, most critically, a human mind) is not absorbed into deity, much as the Borg might assimilate the various races and peoples of the galaxy into its alien cybernetic collective. In Jesus Christ divinity and humanity perfectly coalesce and interpenetrate without in any way annulling or eradicating the other. As Kenneth Paul Wesche explains: “In contrast to Apollinaris and the Antiochenes, the union of God and man in Christ κατ’ ούσίαν is simply for Gregory an affirmation that when man himself comes in contact with God himself his nature is not destroyed: rather, it is truly made human. In other words, man does not cease to be man, but in fact becomes truly man only in communion with God. In the Incarnation, God can indeed assume a full human nature, including the human nous, without there having to be some kind of barrier erected between the two natures in order to protect the integrity of the humanity” (“The Union of God and Man in Jesus Christ in the Thought of Gregory of Nazianzus,” St Vladimir’s Theological Quarterly 28.2 : 93). In the theanthropic union human existence retains its creaturely integrity.
Second, by asserting that in the Incarnation divinity and humanity has been made one reality:
because he took upon himself your thickness, associating with flesh through the intermediary of a [human] mind, and being made a human being who is God on earth, since [human existence] was blended with God and he was born as a single entity, because the One who is more powerful prevailed [over his assumed humanity], so that he might be made divine to the same extent that he was made human. (Or. 29.19)
What he was he set aside; what he was not he assumed. Not that he became two things, but he deigned to be one thing out of two. For both are God, that which assumed and that which was assumed, the two natures meeting in one thing. (Or. 37.2)
God together with what he assumed, one thing made out of two opposites, flesh and Spirit, of which the latter deifies and the former is deified. (Or. 38.13)
We treat the Son of God, who was begotten of the Father and who was later [born] of the Virgin Mary, as a single entity (εἰς ἕν ἄγομεν) and we do not name two sons. Rather we worship one and the same in undivided Divinity and honor. (Ep. 102.4)
When the eternal Son unites himself to human existence by “blending” it with his own, Jesus is born as a single reality, not a human being distinct from God but God himself as Man—hence Gregory’s preference for numerical values (“one”—hen [neut.], heis [masc.]) to speak of Theanthropos.
With this repeated stress on the singularity of Christ, Gregory draws near to the “one incarnate nature” phraseology of St Cyril of Alexandria. Cyril favored speaking of the theandric union as taking place “out of two natures.” “After the union has occurred,” he writes to Succensus, “we do not divide the natures from one another, nor do we sever the one and indivisible into two sons, but we say that there is One Son, and as the holy Fathers have stated: One Incarnate Nature of The Word” (1 Succ. 6). After the theanthropic union is accomplished, we may only speak theoretically and notionally of two natures, for in reality there is only the one and indivisible Savior, the Lord Jesus Christ (1 Succ. 7).
Gregory tends to avoid the language of two natures, fearing that such language will only underwrite the dualism of Diodore and his assertion of two sons. Beeley elaborates further:
Finally, Gregory also tends to speak of Christ as possessing one divine nature, a choice that will have enormous repercussions in later centuries. Gregory’s preference for single-nature expressions reflects the crucial asymmetry that exists between God and humanity in Christ. Because the nature of the divine Son is radically transcendent of creation, the composition of divinity and humanity is not like a mixture of two similar types of things like different ingredients in a food recipe, which the common term “natures” could suggest. Gregory’s practice of speaking of Christ’s one divine nature also emphasizes that Christ is fundamentally divine—he is “God made visible” to those who are able to perceive his true identity (Or. 30.20); and it reinforces the idea that Christ never exists as a human being independent of the life of the divine Son. While it is also possible to speak of Christ as possessing two natures, in Gregory’s view it is less desirable. When Gregory does speak of Christ’s two natures, it is almost always to express the two different things from which Christ is composed, after which he has become “one thing” (Or. 37.2). Otherwise, the distinction between two natures in the incarnate Christ is possible only through human abstraction, like differentiating a human soul from its body (Or. 30.8). The confession that Christ possesses a single, divine nature expresses his most fundamental identity; and in doing so it reiterates the basic rationale and saving purpose of the incarnation: the divine Son’s union and mixture of fallen human existence within his eternal, divine life in order to heal and save it. (p. 188)
I’m not sure how hard one should push Beeley’s construal of the Gregorian Christ’s “one divine nature.” As far as I can tell St Gregory never explicitly says that the incarnate Christ has “one nature” (mia physis). On the other hand, his unitive emphasis is unmistakeable and even shares verbal similarities with Apollinarius. In the Incarnation divinity and humanity have been mixed and blended together: Jesus Christ, son of Mary, is God the eternal Son and second person of the Holy Trinity.