Again, if you're going to make a statement, then you need to support it. Hey, I'm helping you learn to be a better debater. ;)
For example (note this is NOT a essential-for-salvation doctrine):
Agreed belief: there is one God.
Agreed belief: the Father, Son, and Spirit are three different divine persons.
Point of disagreement: how are the three persons Father, Son, and Spirit one God?
The classical Creedal statement is:
“that our Lord Jesus Christ, the Son of God, is God and Man; God, of the Substance [Essence] of the Father; begotten before the worlds; and Man, of the Substance [Essence] of his Mother, born in the world. Perfect God; and perfect Man, of a reasonable soul and human flesh subsisting. Equal to the Father, as touching his Godhead; and inferior to the Father as touching his Manhood. Who although he is God and Man; yet he is not two, but one Christ. One; not by conversion of the Godhead into flesh; but by assumption of the Manhood into God. One altogether; not by confusion of Substance [Essence]; but by unity of Person. For as the reasonable soul and flesh is one man; so God and Man is one Christ” -- The Athanasian Creed.
I personally simply don’t find this talk of substance/essence to be straight up from the Bible and cannot ethnically believe likewise. What I do find in the Bible is support for the view that they are one through unity, particular in John 17. The whole chapter is great, but especially:
21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.
22 And the glory which thou gavest me I have given them; that they may be one, even as we are one:
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
I acknowledge and respect people whom do believe as the Athanasian Creed states. I'm not remotely attack anyone about that. I'm just explaining my beliefs on this particular issue. Again, this is a non-essential-for-salvation doctrine.