Divine Simplicity is the Orthodox Christian doctrine of the oneness of God. It teaches that God is simple—that is to say, not complex—that He is not composed of parts, but is one pure, simple substance.
When God said to Moses, “I am that I am,” He was speaking of His boundless existence—His essence and very being. Because He is simple, God does not exist by means of another thing, but He is identical to His own existence. He is self-sufficient, whole, boundless, and one.