Augustine is that rare ancient Christian writer whose two great works — The Confessions and The City of God — are widely known far beyond the confessional boundaries of the Church. In contrast, Augustine’s third masterpiece, De Trinitate, is hardly even known within them.
It’s probably too much to hope that De Trinitate — which is Augustine’s exposition of the traditional doctrine of the Trinity — will ever reach the broad acclaim of his other two magnum opi. But it absolutely deserves more attention within the Church.
In purely structural terms, De Trinitate forms a kind of trilogy with the other two. The Confessions could be considered to be the dramatic story of an individual Christian, namely Augustine. The City of God, in turn, is the dramatic story of the body of Christians, the Church. De Trinitate then tells the story of God. (I’m paraphrasing translator Edmund Hill, the source of this insight. His translation is available here. An older version can also be accessed here.)
God, of course, does not have a story in one important way: as one who is eternal and unchanging, He is above and beyond time (as Hill points out). But He does have a story in another important way: the manner in which He chose to reveal Himself in time to man. That story is fundamentally the content of Sacred Scripture and De Trinitate is an earnest attempt to understand that story.
The overarching issue at the core of De Trinitate is how we can know God. Augustine stakes out a paradoxical, yet theologically necessary stance: at the end of the day, we can’t really know God directly. Or, as he puts it,
For it is no small part of knowledge, when we emerge from these depths to breathe in that sublime atmosphere, if before we can know what God is, we are at least able to know what He is not. … Nor if you increase the light of the sun in your imagination as much as you can, whether to make it greater or brighter a thousand times even or to infinity, not even that is God (De Trinitate, trans. Hill, 243 ).
So what are Christians to do? Are we condemned to know nothing certain about God? Is Christian faith a blind faith?
Not quite. Here Augustine makes one of great ingenious moves of the book. Though we cannot know God directly, we know him through the image of Him that we see in ourselves. Here Augustine is building upon two foundational Scriptural texts: the declaration in Genesis that we are created in the image of God and Paul’s statement in 1 Corinthians 13:12 that we ‘see through a glass darkly’—a likely reference to ancient mirrors.
So no, we are not quite like the hapless men of Plato’s proverbial cave, grasping at shadows, never to see the light. But we are not among the enlightened elite either, able to gaze directly upon the truth. We are something in between: seeing the light as it is reflected in ourselves.
Have made this ‘psychological’ turn, Augustine proceeds to identify what it is in us that reflects the triune God. Thus commences a great exploration that not only outlines the basis for all subsequent Trinitarian theology in the West, but also unveils a number of other critical insights.
De Trinitate, for example, contains one of the source texts for Augustine’s doctrine of original sin. It offers an explanation for why the Second Person of the Trinity became Incarnate. And the book contains one of the earliest formulations of the ‘analogy of being’ — the all-important principle of theology that governs how we talk about the relationship between man and God. (For more, see these explanations here and here.)
As Augustine meanders towards his topic, he proceeds to identify triads in mankind that are potential images of the Trinity. Early on, for example, he discerns an inner Trinitarian structure to love: there is the lover, the beloved, and the love they share. He then proceeds to identify another triad that is a potential reflection of the Trinity: mind, knowledge, and love. This yields one of the many great insights of the work—Augustine’s explanation for why the Word is ‘begotten’ but not the Holy Spirit. The explanation comes by way of ‘analogy’ with how the individual mind of a man works:
But the reason it is not right to say that love is begotten by it like the knowledge of itself by which it knows itself, is that knowledge is a kind of finding out what is said to be brought forth or brought to light, which is often preceded by an inquisitiveness that is going to rest in that end. Inquisitiveness is an appetite for finding out, which amounts to the same thing as ‘bringing to light.’ But things that area brought to light are so to speak brought forth, which makes them similar to offspring. And where does all this happen but in knowledge? It is there that they are as it were squeezed out and formed. Even if the things we have found out by inquiry already existed, still knowledge of them did not yet exist, and it is this that we reckon as offspring coming to birth (284-285).
In other words, the process of acquiring knowledge is a kind of bringing forth of something—or a ‘begetting.’ That initial appetite for finding out and the resulting will which joins knowledge to the mind that knows it is what Augustine calls love. These three—the mind, its knowledge, and the love they share—are an image of the Trinity.
Augustine himself is relentlessly inquisitive and reflective. He does not rest here. Instead, he wrestles with the question of how a mind can really know itself. This leads him to revise his initial thoughts on what it is that constitutes the image of the Trinity in a human being. The final triad is refined to one of memory, understanding, and will.
As one follows Augustine on this theological quest, it becomes rapidly apparent that he is not aiming to write an abstract tome of theology. His theology, by its very nature, is devotional. His Trinitarian image immediately engages readers on a personal level, inviting them to, as the ancient saying put it, know themselves.
But De Trinitate is not an exercise in spiritual naval-gazing. In probing the depths of the human soul, Augustine finds God’s fingerprints. Rather than turning us inward, the reflection of the Trinity within us, by design, points us outwards towards the Trinity. Who, looking upon something amazing in a mirror, does not want to turn around to see the actual thing? Or, who, upon seeing a beautiful photograph, does not yearn to see the reality pictured?
This leads us to yet another turn of Augustine’s genius. The image of the Trinity that we see in ourselves is not a fact that concerns only theologians endeavoring to better understand and explain the Trinity. The image turns into an imperative for all Christians: it points us the way forward in our spiritual lives. For, as with all images, it directs our attention to its perfect exemplar. For us, as image bearers, this means that we are called to turn our memory, understanding, and will towards God. For only when we remember, understand, and love God is His image within us perfected, Augustine says.
Augustine’s deep exposition of the doctrine of the Trinity thus provides a spiritual program for all Christians. The search for God that began in The Confessions reaches its conclusion in De Trinitate. In a way, the trilogy forms a kind of ascent to God, but it is an ascent made possible only by God’s prior descent to man.