SPROUL: The first part is very easy—He certainly does not change. In His being, He is immutable.
In the incarnation, He took upon Himself a human nature. He didn’t stop being God and become a human being. To affirm He did is to fall into the old kenotic heresy that was popular in the nineteenth century, which taught that God gave up certain attributes in order to become incarnate.
You hear this kind of thing among evangelicals all the time: “God, in order to understand what sin and suffering are, had to become a man and change His nature to be able to be empathetic, so He gave up His deity.” Another thing you hear is this: “God chooses to limit Himself.” Does God really choose to limit His knowledge, His power, and His omnipresence? No. God is eternally, perfectly, and immutably God.
This is one of the things we see in theology all the time. Almost every denomination has the same fundamental confession of the being and character of God, but I think the uniqueness of the Reformed faith is that when we get to page two of our systematic theology, we don’t forget what we confessed on page one. Our doctrine of God informs every other doctrine in that respect. What was the second part of your question?
AUDIENCE MEMBER: “If not, why? And how do we respond to the question?”
SPROUL: We respond by a clear statement of the nature and character of God.
WEBB: Do you want to add anything to that, Dr. Thomas?
THOMAS: Yes—the incarnation was not by subtraction; it was by addition. God is immutable. God cannot change, and the incarnation cannot involve a change in the being of God. He added to Himself something that He didn’t have before; that is, human nature. But that human nature is not a divinized human nature, nor is the divine nature a humanized divine nature. They are two separate natures. So, there is no change whatsoever in the divine nature.