In the beginning was the Word, and the Word was with a God, and God was the Word. John 1:1
John cannot be clearer in establishing that the Word, while being the outward expression of God, is also in essence God.
And it is this Word that is the subject of John’s writing, and having worked through a number of aspects related to the Word, we then read:
And the Word was made flesh and dwelt among us, (and we beheld His glory, the glory as of the only begotten of the Father) full of grace and truth. John 1:14
From this he draws a further link based upon character, establishing that this Word, which is God, now made flesh, is one and the same as the person of Jesus Christ.
Grace and truth came by Jesus Christ
So, if Jesus Christ is God, does that mean that while Jesus was here there was no God in heaven?
No, for remember in John 1:1, while the Word is God, it is also true to say the Word was with God.
One way to think of it, as I mentioned at the start, is to think of the Word as the outward expression of the invisible God.
The revealed Word cannot exist separately from God. It is in essence the fullness of God, and yet at the same time functionally subject unto God.
And this is further established in the next verse as John makes clear we are not talking about an abstract relationship between the mind of God and the Word of God, but rather a real and personal relationship between two persons – Father and Son – who are eternally one is essence, but have functional distinction, with the Son coming into this world in voluntary subjection and in human form to reveal to us to Father.
No man has seen God at anytime. The only begotten Son, which is in the bosom of the Father, he has declared Him. John 1:18
If we don’t understand this, we will not understand the Gospels or indeed the New Testament at large.