With Tertullian we have an early voice attributing his basic understanding of the Trinity to a Scripturally-based tradition handed down in the Church. Furthermore, he engages polemically with Praxeas on the basis of Scripture, expounding a plethora of verses from the Gospel of John. Remember that the Marcionites, modalists, and others claimed support from the Gospel of John specifically because it did not have an “earthly” genealogy of Christ. Thus, Tertullian succeeded in beating them at their own game, even pressing them to utilize all of Scripture in the Old and New Testaments.
The Trinitarian formulations of the early Church often seem to our postmodern culture as the inevitable brainchild of monastic orders, burlap habits, deserts, and Neoplatonic philosophy. Austere, abstract, and unconnected from everyday life—just like the stereotypical image of a monk. Even worse, in a fit of postmodern amnesia, it is no less than the Christian community who has lost sight of the significance of the Trinity for the Christian life. Does it really matter whether we refer to God as Father, Son, and Holy Spirit? Are these not simply human conventions imposed upon an infinitely loving being? Have we not outgrown such small-mindedness? What could detailed, protracted arguments over the terms perichoresis, hypostasis, communicatio idiomatum, monarchia, and oikonomia possibly offer the 21st century Church in terms of its devotion to Christ and the growth of His Church? Won’t our God-consciousness simply choke and die on the dust of such dogmatic doctrine?
It is precisely this modern God-forgetfulness in reference to the doctrine of the Trinity that belies much of the modern lack of depth, awe, and reverence. First and foremost, the debates about the Trinity were not simply semantic spats among would-be philosophers. These controversies generally arose like Church controversies arise today: In the pew and the pulpit. And thus, the men that answered the challenges were generally pastors and laity committed to the Word of God and salvation by God’s grace.
If you read authors like Tertullian (c.155–230 A.D.) and note an undercurrent of impatience, sorrow, and brokenness, it is because these men witnessed the declension of many Christian friends and brethren from the faith. Why would Tertullian—who lived through at least three major Roman persecutions of Christians—defend the Trinity so fervently?
Because he cared about how we should speak and think about God. How do we make sense of the revelation of Scripture that God is Father, Son, and Holy Ghost? How do we grant full weight to all of what is revealed? And how does this impact our salvation? These are the vital questions that Tertullian and others sought to answer.
The doctrine of the Trinity is by no means the easiest doctrine to articulate—and not because most of the theological terminology is developed from patristic Latin and Greek. It is a difficult doctrine to understand because we are touching upon the question of how God exists as God. Our creaturely minds cannot comprehend how God exists as God, but only that God exists as God and, furthermore, only in what manner God reveals himself to us in Scripture. Here a strong and much needed caveat is in order, one with which I think the Church Fathers would heartily agree: We may only assert ultimately what Scripture asserts, and speak guardedly about what we infer from it. We cannot plumb the depths of this doctrine. Thus, the doctrine of the Trinity is the grammar of what we must say and of what we may not say. It consists in boundary markers, as it were.