Recall that man has his material, efficient, and final causes within, but his formal cause, the answer to the question, “What am I?” is external to him and is determined by God.
God in turn has all 4 Aristotelian causes inside natively. This has two implications.
First, God is His own eternal act of self-actualization, such that His self-discovery and self-creation are one and the same act. God “comes to be” upon understanding Himself, as His act, essence, and existence are numerically identical with each other.
Second, God must agree to be God. He must approve of it and like it. As a result, God even upon grasping His own simple essence is free to become anything. If God had been annoyed at being God and preferred to be a horse instead, He had the right to become a horse. Thankfully for all concerned, it pleased God immensely to be Himself.