Why Christ's Enhypostatic Union Matters to Our Salvation
Theology matters. Christianity hangs on the conviction that the invisible God can transform the visible world. If he cannot, then how can Christ's death and resurrection save us from our sins? Sin against God, after all, exists invisibly as a genuine concept. Sin against God only makes sense if we believe that the invisible God exists and that our actions transgress his laws.
If none of this matters, then theology does not matter. Yet God does exist, sin does exist, and salvation does exist. So theology matters. What we believe and do reaches to the spiritual realm; and the spiritual realm reaches to the physical realm. And these realities require careful thinking about what Christ did for us when he became flesh (John 1:14). In light of this requirement, here are a few thoughts on Christ's incarnation and specifically why his enhypostatic union matters.
Enhypostatic Union Means that Christ Assumes a Human Nature and not a Person
The enhypostatic union of Christ means that the Word did not assume a person but a nature. The Word assumed a common human nature but not a particular instantiation of humanity—a person/hypostasis.
The Word, the second Hypostasis of the Trinity assumed a human nature but not a human person. He united humanity and divinity. He remained what he was, namely, divinity and Word, while assuming what he was not: human nature.
Is important to note here that, in classical Christian theology, a person/hypostasis means a concrete instantiation of a substance. It's about genus and species. Someone named "Joe" is an instantiation of humanity. He is a substance (human) and person ("Joe").
Divinity Cannot Submit to Itself Because It Has One Will
Given the enhypostatic union, it's impossible for Christ to be subordinate to the Father before the incarnation since he was divinity: and divinity by definition has one will, power, and energy. It's one God. One will. One power. One energy. Or else why in the world would we confess: "Hear, O Israel: The LORD our God, the LORD is one" (Deut 6:4)?
Consequently, for the one God of Israel and Paul to submit to himself would necessarily require two wills; but God is one. So that's impossible. Hence, only by assuming a common human nature could he will to obey the divine on behalf of humanity.
Christ's submission to the Father on our behalf can thus only happen if he assumes a human nature. And human nature is what he heals through assuming it; it is the material means by which imputation can occur. He can impute to all because he has a common nature to all.
