The following quote from Fr. John Behr was something I found of interest, commenting on Basil the Great’s understanding of Who the “one God” of the Christian faith is:
“For the Christian faith there is, unequivocally, but one God, and that is the Father: “There is one God the Father.” For Basil, the one God is not the one divine substance, or a notion of “divinity” which is ascribed to each person of the Trinity, nor is it some kind of unity or communion in which they all exist; the one God is the Father. But this “monarchy” of the Father does not undermine the confession of the true divinity of the Son and the Spirit. Jesus Christ is certainly “true God from true God,” as the Nicene Creed puts it, but he is such as the Son of God, the God who is thus the Father. If the term “God” (Θεός) is used of Jesus Christ, not only as a predicate, but also as a proper noun with an article (ὁ Θεός), this is only done on the prior confession of him as “Son of God, and so as other than “the one God” of whom he is the Son; it is necessary to bear in mind this order of Christian theology, lest it collapse in confusion.” (John Behr, The Formation of Christian Theology – Volume 2: The Nicene Faith – Part 2, pp. 307, 308.)
Thanks to David at http://articulifidei.blogspot.com/ for providing the source for this quotation.