Thinking Theologically About the Holy Trinity

BOOK PICK: Dominican Father Thomas Joseph White lucidly synthesizes teaching on the Triune God.

‘The Trinity: On the Nature and Mystery of the One God’
‘The Trinity: On the Nature and Mystery of the One God’ (photo: CUA Press)

The Trinity: On the Nature and Mystery of the One God

By Thomas Joseph White, OP

The Catholic University of America Press, 2022

734 pages, $34.95

To order:


“How would your life be different if God were not triune?” That’s an essential question on Trinity Sunday. But it’s not the first question. No, the first thing to ask is “What does it mean that God is triune?” Only after we grasp (as much as we are able) the eternal truth of the Trinity can we then appreciate its existential importance for us.

Some years ago, a priest friend observed, “We don’t think theologically.” The “we” refers to the Church in general and priests in particular. What he meant was that we fail, first, to think about God for his own sake. We typically think about him only in relation to something else, usually ourselves and our problems. We give short shrift to God in himself and skip quickly to what is to be done. Further, in addressing problems, we fail to think them through from theological principles to pastoral application. Again, we jump straight to fixing a situation or “being pastoral.” It’s the “Do something!” mistake applied to the apostolate. We want or are pressured to act so quickly that we fail to think theologically.

One reason for do-something-ism is the poor theological education many of us received in the seminary years ago. Some instructors just gave a survey of theological opinions, as if the Church had no specific teaching or tradition about the topic. That gave the impression that we can’t really know the truth, much less teach it or reason from it. Other instructors provided little more than a catechesis — important content, to be sure, but future priests need something more. Still others provided their own theories, again giving the impression that we can only speculate and not actually know. Needless to say, these approaches don’t have a happy result in the pulpit.

Trinity Sunday suffers from this theological poverty disproportionately. It’s hard to de-theologize and “Do something!” about the Trinity. Still, many priests try. “God is so big; it takes three Persons to live him!” one preacher proclaimed. Other priests let themselves off the hook by claiming that you can’t speak about the Trinity for more than five minutes without falling into heresy (an adage I’ve heard attributed to Pope St. John XXIII, but I have never seen any evidence for that claim). One blessing of the Solemnity of the Holy Trinity is that it forces us to think about God for God’s sake and from there to think theologically. 

Into this theological poverty comes Dominican Father Thomas Joseph White’s The Trinity: On the Nature and Mystery of the One God. Father Thomas Joseph is rector magnificus of the Pontifical University of St. Thomas Aquinas in Rome (The Angelicum). The book is clearly the fruit of his teaching future priests. The Trinity gives a lucid presentation of what, after all, we hope to contemplate for eternity and sets the course for thinking theologically. 

The book has a simple structure: theological history, Thomistic synthesis and modern consideration. Father Thomas Joseph first walks the reader through the theological controversies and developments of the Church’s first centuries. Although striving to be unoriginal, he acts like an expert guide leading hikers up a mountain. Many who travel this path fall prey to one mistake or another. The author identifies the pitfalls, hazards and loose rocks along the ascent. By the end, he has identified that era’s theological insights as well as its errors — which many still fall into today.

Not surprisingly, the heart of the book is an examination of St. Thomas Aquinas’ treatises on God as one and God as triune. Father Thomas Joseph doesn’t present Aquinas’ theology as “one account among many,” but as “a kind of Greenwich time in Christian theology.” It’s refreshing to know that there is a standard in theology, that it’s not just a jumble of opinions.

For the Dominican priest, Aquinas provides a standard because he gives the great synthesis of the theology of the East and the West as it developed in the ancient Church. But Aquinas’ work isn’t reducible to a synthesis of the past. Precisely because he presents the Church’s teaching so clearly, he also provides a way forward. So he doesn’t confine Aquinas to the 13th century. He uses his synthesis to engage and answer some modern speculations about the Trinity. It is also on that clear Thomistic synthesis that Father Thomas Joseph provides his own thoughts in the book’s last section.

The Trinity can be dense and technical at times. That’s no surprise, given the topic. But it’s also due to the method. To think about the Triune God requires a consideration of how to do theology, how to engage philosophy and how to use language properly. 

This is an important book for priests, first of all. It’s an effective instrument for us to engage in that theological thought that serves as the reservoir of good pastoral practice. As I sat down to write this review, a classmate texted me his response to the book: “I feel only now am I learning what I never fully learned in the seminary.” I suspect that many priests (including me) will share that reaction. Again, it’s not only the content that would benefit many priests but also the method: examining revelation and navigating the theological controversies with a confidence that there is a truth to be known and we can know it, even if only in part. The book will compensate for what many of us didn’t receive in the seminary. For that reason, The Trinity is also good for anyone who desires to deepen his understanding of the faith and to nourish his prayers with clear doctrine.

That classmate of mine gave another compliment to this book: “It seems to me you first have to have a clear understanding of the Trinity before you move on to grace.” His reading about the Trinity produced an awareness of how we relate to and, indeed, are introduced into the life of the Trinity. Now, that is thinking theologically, and such thinking always leads to good pastoral practice.