Here's the backstory to why I'm interested in this question.
There's a very famous formulation from Gregory of Nazianzus in one of his Letters to Cledonius. Defending the Christian belief in the Incarnation, Gregory writes: "For what is not assumed is not healed, but what is united to God is saved."
Much of the patristic understanding of salvation is expressed in this succinct formulation: What is not assumed is not healed. As has been pointed out many times, the patristic vision of salvation was more ontological than forensic. Humanity, and indeed the entire created order, upon its separation from God began to suffer the effects of its finitude and contingency. Separated from God and lacking the power to hold itself in being, creation began its slide into non-existence. Witnessing this drift, God acted in the Incarnation to reconnect creation to Himself.
As Athanasius described:
Man, who was created in God's image and in his possession of reason reflected the very Word Himself, was disappearing, and the work of God was being undone. The law of death, which followed from the Transgression, prevailed upon us, and from it there was no escape. The thing that was happening was in truth both monstrous and unfitting. It would, of course, have been unthinkable that God should go back upon His word and that man, having transgressed, should not die; but it was equally monstrous that beings which once had shared the nature of the Word should perish and turn back again into non-existence through corruption.
Seeing this slide into non-existence, God acts in Christ to ontologically stabilize the created order. As Athanasius continues:
For this purpose, then, the incorporeal and incorruptible and immaterial Word of God entered our world. In one sense, indeed, He was not far from it before, for no part of creation had ever been without Him Who, while ever abiding in union with the Father, yet fills all things that are. But now He entered the world in a new way, stooping to our level in His love and Self-revealing to us... Thus, taking a body like our own, because all our bodies were liable to the corruption of death, He surrendered His body to death instead of all, and offered it to the Father. This He did out of sheer love for us, so that in His death all might die, and the law of death thereby be abolished because, having fulfilled in His body that for which it was appointed, it was thereafter voided of its power for men. This He did that He might turn again to incorruption men who had turned back to corruption, and make them alive through death by the appropriation of His body and by the grace of His resurrection. Thus He would make death to disappear from them as utterly as straw from fire.
Returning to Gregory of Nazianzus' more succinct description, humanity had become subject to dissolution. Thus Christ assumes human nature, and by assuming it—thereby reconnecting human nature to God—human nature is stabilized and healed.
Okay, all that is just a summary of the patristic vision, one I expect you've heard before. The key point, again, is that salvation in this view is ontological stabilization rather than a penal, forensic declaration of pardon. To be sure, the patristic tradition recognized the penal and forensic aspects of salvation, but its primary concerns were ontological. Human nature had been ontologically "wounded" in the Fall, made subject to the forces of dissolution. So in the Incarnation Christ assumes human nature, reunites it with God, and thereby heals its ontological wound.
And it's precisely here where I started asking some questions about the unity of human nature.
I asked myself, "What exactly does it mean that Christ 'assumed' human nature?" To be sure, Christ became a human being. But how, exactly, was what happened in Christ's body connected with, or implicated in, my own body? It seems to me that, as a matter of logic, the human nature Christ assumed in the Incarnation had to be connected to my own. And not merely as two individual members of the same class, but as participants in a shared ontological reality.
To make the point more clearly: Yes, Christ's human body defeated death. That's a truth about that one human body. But how or why would the resurrection of that single body have any effect upon my separate human body? How, to borrow from Gregory, was my particular humanity "assumed" in Christ's particular humanity? What's the connection between us? How does what happens to Christ's body affect or implicate my own?
It seems to me that if there is no shared ontological connection between Christ's body and my own, then what was assumed in Christ has no relation to me. And if that's true, then the entire patristic vision of salvation begins to fall apart. If Christ ontologically stabilized the whole of humanity, then the whole of humanity had to be connected to Christ's body. What Christ assumed in the Incarnation has to be the whole of humanity.
Thus, human nature is a single, shared ontological whole. While there are many human persons, those persons share one human nature. When Christ became incarnate as an individual person, he made ontological contact, through that individual point, with the whole of humanity. And when Christ's individual humanity was resurrected, the whole of humanity, as a single united nature, was resurrected with him.
In short, as I read the patristic vision, one of the logical implications of its ontological understanding of salvation—what is not assumed is not healed—is that human nature is a single, shared, united whole. There are many individual persons, but they all participate in one human nature. And yet, while this seems to me to be a logical entailment of the patristic soteriological vision, I've not come across much discussion of it. There is an anthropological issue here that, it seems to me, needs to be sorted out and nailed down.














