Gospel Guidebook: Getting and Keeping It Right 
When Did "One God the Father" Become the "Triune God"?
by Robert P. Terry based on an article by Andrew DavisUpdated July 8, 2026
Philip Schaff in his book "Creeds of Christendom, Volume II" provides a "Comparative Table of the Ante-Nicene Rules of Faith" (available here) that shows that up until the end of the fourth century, the "one God" of the creeds (including the Nicene Creed of 381) and patristic writings was unanimously the Father. At some point in time, however, the church apostatized and replaced "one God the Father" with the "Triune God." Knowing how jealous God is for His name, this ought to send shivers down our spines. How could this have happened?
It appears that the initial culprit behind this departure from the "Ante-Nicene Rules of Faith" was Augustine of Hippo. He wrote 15 volumes on the Trinity and referred to God as the Trinity, prayed to God as the Trinity, and worshiped God as the Trinity. And because of his popularity and influence, most of the Christian church (at least in the West) adopted Augustine's new "rule of faith." Here are just a few examples of Augustine referring to God as the Trinity:
In Book 2, Chapter 10 speaking of Abraham he says, "...neither here does it appear plainly whether it was any person of the Trinity that appeared to Abraham, or God Himself the Trinity, of which one God it is said, You shall fear the Lord your God, and Him only shall you serve" (available here). Augustine quotes Deuteronomy 6:13, which is in the same context of the Shema, and refers to the Lord God as the Trinity, even using the singular personal pronoun "himself." Reading the above quote carefully shows that, for Augustine, the Trinity is a person who consists of persons (for a total of four persons: the Trinity, the Father, the Son, and the Holy Spirit).
In Book 15, Chapter 28, Augustine prays to the Trinity, saying "O Lord our God, we believe in You, the Father and the Son and the Holy Spirit. For the Truth would not say, Go, baptize all nations in the name of the Father and of the Son and of the Holy Spirit, unless You were a Trinity. Nor would you, O Lord God, bid us to be baptized in the name of Him who is not the Lord God. Nor would the divine voice have said, Hear, O Israel, the Lord your God is one God, unless You were so a Trinity as to be one Lord God...O Lord the one God, God the Trinity, whatever I have said in these books that is of Yours, may they acknowledge who are Yours; if anything of my own, may it be pardoned both by You and by those who are Yours. Amen" (available here).
As one more example, in Section 11 in his debate with Maximinus, Augustine speaks of worshiping the Trinity and quotes the Shema. "Hence, we worship the Trinity, because the Father is not the Son and the Son is not the Father and the Holy Spirit is neither the Father nor the Son, but we still worship one God, because the ineffable and lofty union of the Trinity reveals that there is one God, one Lord. Thus scripture said, Hear, O Israel, the Lord is your God, the Lord is one (Dt 6:4)" (available here).