God created humanity in God’s own Image. God’s Image is the Trinity. Therefore God created humans as Triune beings.
This is my basic starting point which you have no way refuted. Casper tried to refute it by saying humans cannot compare God or the Trinity to “earthly things” including humans who are created in God’s Image. I used Augustine to refute that particular point, and you agreed!
Now you insist that I must prove my point by citing some passage from Augustine or other theologian. Have you forgotten Sola Scriptura? Why do you want to return to the theological tradition as the only true basis of our understanding of God?
My understanding of Reality as Triune is based on Scripture and the understanding of God as Trinity, not as Duality. It is giving the Triune God all the honor and glory that is due God by accepting the fact that God made humans and the rest of the Created Order in God’s Triune Image. Sola Scriptura, Soli Deo Gloria.
Maybe I haven’t proven this to you yet, but you have not given me the opportunity to do so either.