Hi Jesse, let's start at the beginning here.
You say the Old Testament clearly presents a God of one person.
Please explain two verses for me.
Genesis 1:26; "Let us make man in our image", and
Proverbs 30:4; "What is his name, and the name of his son"?
The trinity is a theological construct by man. While I do believe it has error NOT found in the NT I do read of the Father, Son, Holy Spirit that they are One and all three would be considered GOD. Man attempted to wrap all that up in the theology of the trinity.
Many claim Jesus is God the differences are usually found in the "How" as the Father is clearly presented as the God and Father of Jesus and the One true God. Only One Apostle explained the "how". "The fullness was pleased to dwell IN Him" John simply stated in the beginning was the word and the word was God and was with God. That statement in context is true. Jesus is the word of the FATHER, (God), and the creation was made through Him and He is ALL that the Father is. The image of the invisible God and the exact representation of Gods being.
But context is the key to understanding.
Is Jesus God?
He never dies. (He lives by the living Father)
Yes, He is ALL that the Father is. (The fullness was pleased to dwell in Him and all the treasures of wisdom and knowledge are hidden in Him)
No, He has always been the Son. The firstborn of every creature. As a Son Jesus has His own spirit as in "Father into your hands I commit My Spirit"
The Holy Spirit or Spirit of the Sovereign Lord or Spirit of truth can been seen as a separate person from the Father it can also be read as the Fathers OWN Spirit. That Spirit does not speak on His own but what He hears. That Spirit searches the deep thoughts of the mind of the Spirit in the same way our own spirit searches or knows our mind. (thoughts). Also the Father simple states "My Spirit" when speaking of the HS while Jesus does not.
Father =>I will place my Spirit upon Him (Jesus) and He shall proclaim justice to the nations. (With light comes accountability)
Jesus=>The Spirit of the Sovereign Lord is upon me......
The Holy Spirit bears witness, (He speaks what He hears from the mind of the Spirit), as in those who listen and learn from the FATHER go to the Son and Jesus will raise them up on the last day. That is the FATHERS will. Those that oppose Jesus fight against the FATHERS WILL.
Gods own Spirit would be divine.
All the fullness of God dwells in Jesus which includes all the treasures of wisdom and knowledge. In that context He is called God and is seen as Divine though the living in Him (The Father) is the Spirit that is divine. Again as a Son Jesus has His own spirit-Not Divine other wise we have two Gods.
Randy