We saw in a previous article that the Incarnation is the means by which God shares his divine life with human beings, transforming them into his likeness, so that they can eternally enjoy perfect fellowship and union with him. As I will now argue, this has some interesting implications for (as it were) the specific 'mechanics' of the Incarnation.
How exactly does the eternal God 'become Man'? The most straightforward interpretation would have God literally transforming himself into a human being, exchanging his divine nature for a human one. But this is a non-starter. For losing his divine nature would surely entail losing the power to share the divine life with human beings. Hence on this simple account, the incarnation not only fails to fulfil its purpose, it makes said purpose impossible to fulfil.
The divine nature, then, must remain intact in order for the Incarnation to achieve its goals. That is why Christian theology has consistently taught that the Incarnation consists in the union of a divine nature and a human nature, not the transformation of a divine being into a human being.
But what exactly is this 'human nature' that the divine Word unites itself to? Well, one view is that it is simply a human body. The fourth century Christian bishop Apollinaris argued that in the Incarnation, God the Son simply took the place that an ordinary human soul would normally occupy. This sort of position is sometimes referred to as 'Word-flesh' (Logos-sarx) Christology. Its opponents charged that, here again, the view jeopardizes the efficacy of the Incarnation. Another bishop and contemporary of Apollinaris, Gregory of Nazianzus, put it like this:
The unassumed is the unhealed, however, that which is united to his Godhead is saved. If only half of Adam fell, then Christ assumes and saves only that half of his nature. But if his nature fell in its totality, then it must all be united to the nature of him who was begotten, and thus be saved in its totality. Let them not begrudge us our salvation in its totality, or clothe the savior with nothing more than bones and nerves and something which looks like humanity.
Let's try to unpack this a bit. If it is human nature as a whole that is to be regenerated and deified, and not simply its bodily component, God must unite himself to a complete humanity, both body and soul. Otherwise, God would not really be sharing his divine life with humanity at all. Further, and as we saw in the last article, the most important aspects of deification have to do with the character of the human soul, which is called to partake of God's love, perception, joy etc. Hence an Incarnation that failed to deify the soul would fall well short of what it promised.
For these reasons and others, the opposing 'Word-man' ( Logos-anthropos ) Christology eventually won out and became normative to mainstream Christianity, which affirmed that the divine Word of the Father and a particular human body-soul complex were perfectly unified in the person of Christ. The Third Council of Constantinople (680) went as far as to declare that there exist two distinct wills in Christ, one divine and one human.
This raises questions about the unity of the person of Christ, as it seems to imply two 'Christs', one divine and one human. I hope to discuss this i a future article.