As you correctly say, according to scripture, these three are One, so why does the trinitrian diagram say the Father is NOT the Son, the Holy Spirit is NOT THE Father ETC?
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I don’t know anything about a “Trinitarian diagram”.
I don’t use the word Trinity. I use the word Godhead.
The scripture says
these three are one, not this one is three.
That’s Modalism.
For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these
three are
one. 1 John 5:7
If the scripture said this one is three, then that would make your theory correct.
Do you understand that the Son and is God, and is YHWH the Lord God?
The Son created the heavens and the earth.
But to the Son He says:
“Your throne, O God, is forever and ever;
A scepter of righteousness is the scepter of Your kingdom.
You have loved righteousness and hated lawlessness;
Therefore God, Your God, has anointed You
With the oil of gladness more than Your companions.”
And:
“
You, LORD, in the beginning laid the foundation of the earth,
And the heavens are the work of Your hands.
Hebrews 1:-10
Jesus is the only begotten Son of God.
Here He is in the Old Testament.
Now Moses was tending the flock of Jethro his father-in-law, the priest of Midian. And he led the flock to the back of the desert, and came to Horeb, the mountain of God. And
the Angel of the LORD appeared to him in a flame of fire from the midst of a bush. So he looked, and behold, the bush was burning with fire, but the bush was not consumed. Then Moses said, “I will now turn aside and see this great sight, why the bush does not burn.”
So when
the LORD saw that he turned aside to look,
God called to him from the midst of the bush and said, “Moses, Moses!”
And he said, “Here I am.”
Then He said, “Do not draw near this place. Take your sandals off your feet, for the place where you stand is holy ground.” Moreover He said, “I am the God of your father—the God of Abraham, the God of Isaac, and the God of Jacob.” And Moses hid his face,
for he was afraid to look upon God. Exodus 3:1-6
JLB