58. He who does not distinguish the two natures in Christ has no basis for affirming that the Logos became flesh without change. He does not acknowledge that after the union that which assumed and that which was assumed are preserved according to their nature in the single person of the one Christ, our God and Savior.
That which assumed was the divine Logos, the eternally begotten Son. That which was assumed was sarx or flesh — our human nature. (I will note here that there’s a section in Romans where the NIV over the course of a few sentences translates sarx as sometimes sinful human nature and sometimes flesh. It’s a good illustration of the way bias can distort translation efforts.) And both the divine nature and our full human nature are completely preserved in Christ. This is hard to wrap our heads around, but it’s important because “that which is not assumed is not healed or saved.”