God’s triune nature is an essential part of who God is and how He relates to man. All of God is eternal. Every attribute, every nature, every part of His being is eternal. Scripture proclaims in Jeremiah 10:10 “But the Lord is the true God; He is the living God, the eternal King.” Also consider, Habakkuk 3:6, “His ways are eternal.”
When we speak of God the Father, the first person of the Trinity , we are speaking of an eternal Father. Therefore, for God to be a Father to man, He must first have always been a Father by His eternal nature. He was a Father before creation to the eternal Son, Jesus. If God became a Father because He created then He would have become something He had not been. This is impossible. For God never changes for He is never lacking anything. He has always been perfect in His eternalness. He spoke a great reality when He told Moses that His name is “I AM.” He spoke of His eternality, His completeness. Thus, for God to be a Father, He has always had a Son who was of the same substance of Himself, being fully God. The Son had to also be eternally the Son. He didn’t gain Son status, for He always existed as the Son of God. Jesus said to the Pharisees, “before Abraham was born, I Am” (John 8:58). If one denies the eternal God nature of the Son, then the Father nature of God is denied as well. One cannot exist without the other. John 17:24 says that God loved Jesus before the creation of the world. The Holy Spirit is also eternally binding the love of God to the love of the Son and is our Counselor, because He has eternally been thus. Romans 5:5 reads “God has poured out His love into our hearts by the Holy Spirit, whom He has given us.”
To break this down in a natural analogy, man gains his identity in relation to other people. A father becomes a father when he has a child. A wife becomes a wife when she gains that identity in relation or in reference to having a husband. Without a husband she is not a wife. Without a child, a person is not a parent. A human woman, contrary to popular sentiment, does not become a mother because she loves her pet like a child. Her pet is different from her and not her offspring. God did not become a father of mankind because He created mankind. He always is a Father because He always has a Son. He is a Father to mankind because He is first a Father to the Son of God.
God is a personal God because He has relationship within the Trinity. He doesn’t gain His personal nature from His creation. If there is no interpersonal God being such as the Christian God, there can be no personal God to creation. In fact, if God was this cosmic static entity with no persons of the Trinity He could not be self-existing. He would then not even be God at all for He would need something else outside Himself to sustain His identity. The finite creation cannot lend the framework to support an infinite God. God’s identity has to be secure before creation or separate from creation. He must be self-referencing. He must be His own identity framework. Thus any religion that posits a non-relational God cannot logically support the existence of God. Moreover polytheism fails to be a foundational system of belief for each of the many gods would have to be finite for you cannot have more than one all powerful God. It isn’t logically possible. Thus multiplicity of gods lends itself to finiteness of gods and that is not an adequate foundation for they would be in need of a self-evident eternal God themselves.
In conclusion, the nature of God being: God the Father, God the Son, and God the Holy Spirit, is essential belief about who God is and how we can have a personal relationship with Him. For without His personal nature within the Trinity there would be no personal relationship between Him and all creation.