In his book, The Mystery of the Trinity, renowned theologian and polymath, Vern Poythress, raises concerns with contemporary discourse on the doctrine of God. Poythress argues against the casual contemporary approaches to the doctrine of God that diminish the transcendent God to being merely a companion or “a copilot.” He refers to this error as “mutuality theology” (p. 439). At the same time, he recognizes a tendency for some classical theologians to overcorrect in the direction of an utterly transcendent deity, defined by abstract concepts of maximal immutability and simplicity, isolated from the world, and ultimately unknowable (pp. 439–40). Poythress calls this error “monadic theology” (p. 440). He writes, “If a Christian sees one extreme and becomes aware of its dangerous error, he can react by unwittingly moving closer to the other extreme” (pp. 440–41). The answer, Poythress argues, is not to reject the valuable insights from classical Christian theism, but to prioritize God’s revelation of himself in the Bible, not the fallible and flawed speculations of non-Christian philosophers. Poythress makes a case for taking the Trinity as ontologically basic and the proper foundation for Christian theologizing (p. 237).

In the opening pages, Poythress spells out his intention to address six questions that theologians and philosophers—both Christian and non-Christian—have addressed for centuries. Although Poythress spends over 600 pages answering these age-old questions, he is careful to point out that his discussion leaves the mystery of God intact (p. xxv). Using some form of the word “mystery” over three hundred times, Poythress reminds readers that talking about God means talking about realities that humans cannot comprehend (pp. 521–22).

Poythress divides his book into eight parts. Part 1 addresses some challenges in knowing God, such as human finitude and sinfulness, and overviews theologian John Frame’s “Square of Transcendence and Immanence” (pp. 18–19). Frame develops a diagram to illustrate his point by sketching two axes that illustrate the differences between a Christian understanding of God as both exalted (transcendent) and also self-revealing (immanent) compared to a non-Christian view of God as alternatively unknowable (transcendent) or subject to human standards of divinity (immanent). This diagram, which compares Christian and non-Christian views of transcendence and immanence, becomes a prominent theme throughout the book.

Parts 2–4 model Poythress’s approach to grounding theistic reflection in Scripture, and then reflecting on divine attributes in the light of the Trinitarian God that Scripture reveals. He also addresses the necessary discussion of human language and its limited-though-sufficient ability to reveal God truly if not exhaustively. These first four parts, consisting of eighteen chapters, provide the reader with a sort of prolegomena to Poythress’s approach.

Part 5 begins to tackle some issues raised by philosophy, such as the benefits and drawbacks of using technical, non-biblical terms. This section leads to an examination of Aristotle and his categories because they have greatly influenced the way thinkers analyze, conceptualize, and organize, not only language and the world, but discourse about God Himself. Poythress acknowledges Aristotle’s brilliance and the brilliance of his categories (pp. 223–24). However, calling Aristotelian categories “seductively attractive” (p. 237), Poythress critiques Aristotle’s attempt to understand the world through the power of autonomous human reasoning. Aristotle’s worldview is basically impersonal (p. 210), unlike the Christian worldview, which holds to a personal, Trinitarian God who plans, speaks, and acts.

Moving into a more direct confrontation with contemporary Christian theologians, part 6 traces the influence of Aristotle on Christian theological reflection—most notably, the thirteenth-century Scholastic theologian, Thomas Aquinas. Poythress also looks at Aristotle’s influence on Reformed theologians Francis Turretin and Stephen Charnock with respect to their writings on the attributes of God.

While Aquinas drew from many sources, Poythress notes that much of Aquinas’s work operates on the basis of Aristotle’s system of categories.“ That is a potential problem,” writes Poythress, “because Aristotle’s system not only does not have the Trinity, but also has features that, in the end, are subtly anti-Trinitarian” (p. 292). The mixture of truth and error that Aquinas learned from Aristotle “had effects on his treatment of the doctrine of God” (p. 292). Poythress argues that Aquinas takes Aristotle’s system of categories as “ontologically basic,” rather than the Trinity (p. 299). This move, says Poythress, “has the potential to corrupt everything that can be said about the attributes of God” (p. 299).

When Poythress turns his attention to Turretin, he points out that to the degree Turretin adopts Aristotelian theological language to talk about God, to that degree he introduces concepts in tension or even in contradiction with Trinitarian doctrine. According to Poythress, Turretin emphasizes the unity of God and discusses God’s attributes without self-consciously building on Trinitarian concepts, a doctrine he does not introduce until much later (p. 345). In the two chapters devoted to Charnock, Poythress praises his pastoral and biblically grounded approach to theology. Still, Poythress detects some ways in which Charnock struggles with how to both “differentiate and yet to affirm robustly the fullness of the unity of God” (p. 412). Again, Poythress believes Charnock’s theology would benefit from a more explicit Trinitarian grounding in order to avoid some of the critiques to which his work is vulnerable.

In part 7, Poythress turns from criticism to answering constructively the underlying question that his book has been investigating: “How do we mediate between transcendence and immanence?” (p. 485). Poythress suggests that we can make a step toward understanding God’s relation to the world by exploring the question in light of the Trinity. This move retains “the language of classical Christian theism,” while enhancing it “with a Trinitarian foundation” (p. 500). Poythress examines several exegetical case studies to apply his Trinitarian hermeneutic. Extending the constructive exhibition of his Trinitarian-hermeneutic to theological discussions, Part 8 considers four of God’s attributes (love, mercy, will, and knowledge) and examines how the Trinity maintains a unity of the attributes in the one God while allowing us to speak of differentiation within the attributes as expressed by each person of the Trinity. In the final chapter, Poythress reasserts his affirmation of classical Christian theism, yet again voices his concerns about relying too much on philosophy and abstract logic, instead of relying on the gospel and historically-informed biblical exegesis (pp. 594–96).

One of the strengths of this work is that Poythress achieves clarity of prose and concept without sacrificing precision. He only uses technical terms when his subject matter requires it or his interlocutors force it. And he uses such technical terminology only after carefully defining the terms. The result is a readable, meaty, and thought-provoking discussion.

Another strength is that Poythress models Christian virtue in his scholarship. He deals gently with those who may hold differing positions. He does not accuse his opponents of false teaching or of misleading others but graciously points out areas of potential weakness or misunderstanding (see chs. 30–34). A final strength is that Poythress ends every chapter with a prayer that directly flows from the preceding discussion, again modeling how contemplation of theological truths can lead to awe and worship.

One of the weaknesses of this book is that Poythress fails to answer Tertullian’s question, “What does Athens have to do with Jerusalem?” Poythress makes a largely negative evaluation of Aristotle, but he does not answer how, or to what degree, Christians can rely on human reason to lead to knowledge of the truth. Poythress focuses his critique on Aristotle and Aquinas, yet he pays little attention to Plato or Augustine, nor does he interact with early Church Fathers, who were engaged in explaining the biblical God to those steeped in Greek thought and philosophical categories. Readers may be left wondering how and to what degree Christians might be able to appropriate human reason and non-Christian philosophy.

Despite this critique, Poythress’s book, The Mystery of the Trinity, will serve a new generation of theologians who are contemplating the perennial mysteries of our Trinitarian God. Poythress aims to retain categories from classical Christian theism while also remaining firmly and primarily committed to reading and rearticulating the revealed truths given to the church by the self-revealing God of the Bible. Having rigorously defended his proposal and argued his thesis, this book provides such a massive contribution to contemporary discussions about classical theism that other theologians would be remiss to neglect it.