But, who is this god?

In the end, putting the question “who is God?” to the Pauline letters elicits an answer that entirely resists simplicity. It requires instead a nimble movement between three distinct but inseparably related terms, with a willingness to hold onto the oneness of Israel’s God all the while. To tell the story that names who God is according to Paul, therefore, we have to speak distinctly and concurrently of God the Father, Jesus of Nazareth, and the Holy Spirit that is their Spirit. To leave out one of these would reduce Paul’s theological language to the point of destroying it; or, to say it another way, refusing the Pauline complexity results in the telling of another story and thus in the naming of someone other than the God about whom Paul writes. The fillip for the complexity, of course, is Paul's reflection on Jesus.—One True Life: The Stoics and Early Christians as Rival Traditions, 91