What We Believe

The Trinity: An Introduction, by Scott R. Swain. Wheaton: Crossway, 2020, 154 pages, $15.99, paper.

The Mystery of the Trinity: A Trinitarian Approach to the Attributes of God, by Vern S. Poythress. Phillipsburg, NJ: P&R, 2020, xxx + 688 pages, $39.99.

Books on the Trinity have abounded in recent years. By no means all have been satisfactory. Social trinitarianism has prevailed, with God portrayed as a community, akin to a human family. Some evangelicals have propounded a form of subordinationism. The books being reviewed are two quite distinct contributions produced by highly regarded Reformed scholars, neither of which fall into these categories.

Swain focuses on the doctrine of the Trinity. This is not a historical discussion as such nor is there a consideration of recent scholarly work, although Swain is more than capable of addressing both. It is a primer, one that can conceivably be used in adult Sunday school, for elder training, in college or seminary classes, or simply for general reading. That is not to say that scholars could not benefit from it; they certainly could. Swain gets to the heart of the matter and expresses complicated and profound ideas in cogent ways, doing so in a remarkably succinct and accessible manner.

This is the best concise introduction to the doctrine of the trinity that is available in print. The Roman Catholic scholar, Gilles Emery, has written an almost definitive work on a similar scale, more advanced and technical, but Swain has the field to himself both for the tyro and for anyone wanting a concentrated distillation of the biblical and historical doctrine with clear and accurate delineation of major heresies and errors. Sessions, ministers, anyone should get hold of a copy.

Poythress’s latest tome is more speculative and complex. It also raises some significant questions that require a lengthier discussion. In this, I will refer to matters that may be a cause of concern if the book were to be read in a particular way. However, it becomes clear that the author does not intend these outcomes. As we shall see, the concluding section (591–94) is perhaps not as carefully expressed as it might be and should be tightened up when the time comes for a second edition in order to avoid possible misunderstandings.

Poythress is a polymath, equally at home in mathematics, science, and linguistics as well as New Testament studies and theology. Even critical reviewers have agreed that he has made “a significant achievement.” They have noted his irenic and humble example. This is greatly needed at present in view of a welter of sulfurous writing belching forth in recent years. “Blessed are the peacemakers,” our Lord taught; it is evident that Poythress wishes to bring together warring factions, not create more of them. In this, he is on the side of the angels.

Poythress discusses successively the classical attributes of God, the doctrine of the Trinity, the trinitarian basis of language, philosophical conundrums, and challenges in classical Christian theism, focusing mainly on Aquinas and his use of Aristotle. He aims to enhance Christian theism by encouraging a more pervasive trinitarian focus.

Each chapter has study questions, suggestions for further reading, and a prayer. The book abounds in diagrams, reminiscent of the profusion of charts in Ramist works of the sixteenth and seventeenth centuries. Both Poythress and his close collaborator, John Frame, have a penchant for diagrams. These may be helpful for some readers, but I must be visually challenged as diagrams generally leave me bemused, so I stick to the text!

Poythress has a similar readership in view as Swain does, although we have a comment on that later. He writes, as usual, in a very simple, direct style, readily comprehensible but not simplistic.


One cannot but be struck by Poythress’s pervasive use of Scripture and commitment to a faithful rendering of it. The book throughout is worshipful. Its focus is on the mystery of the Trinity, which goes beyond the powers of human reason. This is not the Palamite idea[1] in orthodoxy, where the mind is to be emptied and where God is in his essence unknowable, but rather is to be understood in Van Tilian terms, in the sense of the transcendent greatness of God. This is vital in thinking of God. Considering the Trinity is inevitably a life-changing practice; it will either lead us to greater love for and communion with the living God, or if not, we would be better off never having begun. We approach with reverence and awe for our God is a consuming fire. If we come from this book with nothing other than that, it will be a lesson well learned.


However, several significant questions arise. In some way, they are interconnected—unified, distinct, and co-inherent, we might say, to use categories that Poythress himself adopts. Each one relates to how far philosophy is and should be deployed in service of the truth, to what extent its use has been beneficial, and in consequence how the past teaching of the church and its leading figures should inform our reading of Scripture. My comments are more reflections that flow from my reading, addressing common dangers and possible misconstruals.

First, there are questions of hermeneutics. Poythress does not adopt these problematic positions, but the general stance he takes may give rise in the reader to the suggestion that they follow from what he says. This is particularly the case in his final summary where he calls us to abandon a primary reliance on tight, abstract logical argument in theology (592-94). Much depends on what is meant by that. From elsewhere in the text, it appears that “perfect being theology” is in view, where an abstract notion of perfection is applied to God, without recourse to the Bible. This warning would serve a salutary purpose. On subsequent readings it is clear that Poythress is opposed to the influence he detects from Aristotle, especially as mediated by Thomas Aquinas. The Bible is enough, he asserts.

At this point his language might lead the reader to suspect, wrongly, that behind this lies a common and false view of the slogan sola Scriptura. It is thought by many that this principle commits us to base our thought, theology, and language exclusively on the Bible, without recourse to any extrinsic authority. However, when the slogan was devised—various proposals locate it from the eighteenth to the early twentieth century—it merely asserted the belief and practice of the generality of Reformers and their successors that the Bible is the supreme authority. This is the position of the Westminster Standards. It does not exclude other authorities but rather subordinates them to Scripture. This is the position Poythress actually and correctly takes, since he interacts at length with a range of such figures.

B. B. Warfield pointed to the absurdity of rejecting reason and logic. He wrote,

the re-emergence in recent controversies of the plea that … human logic is not to be trusted in divine things, is, therefore, a direct denial of a fundamental position of Reformed theology, explicitly affirmed in the Confession, as well as an abnegation of fundamental reason, which would not only render thinking in a system impossible, but would discredit at a stroke many of the fundamentals of the faith, such e.g. as the doctrine of the Trinity, and would logically involve the denial of the authority of all doctrine whatsoever, since no single doctrine of whatever simplicity can be ascertained from Scripture except by the use of the process of the understanding.[2]

In line with this, Poythress states that God is supremely rational (594). However, there can arise a potential danger of misunderstanding when revelation and faith are apparently set against philosophical language.

The outcome of such a misunderstanding is that so many times one is faced by books that attempt to construct doctrinal arguments based on biblical exegesis without recourse to the history of discussion. These are effectively attempts to reinvent the wheel. This is a recipe for heresy. By ignoring the consensus of the historic church, one ignores the biblical exegesis that underlay that consensus. The Socinians, Arians, and Jehovah’s Witnesses are but a few instances of how this can work out in practice. The Socinians had a high view of the Bible and would have passed presbytery exams on that question, but by rejecting past tradition, in practice they privileged their own exegesis over the accumulated centuries of the biblical exegesis of others. Of course, Poythress is most emphatically not to be associated with these aberrations. I know that he will repudiate them with every atom of his being, as his outline of his interlocutors demonstrates (3–5).

However, the not uncommon methodology by which the Bible is pitted against the traditional formularies ultimately leads in that direction. That is an exceedingly dangerous path to follow. Calvin did not go that way, neither did the Westminster divines, as the minutes and papers of the Assembly amply illustrate. 

Second, pressing the issue further, Poythress calls for changes in technical terms and abandonment of both Aristotelian metaphysics and tight, abstract reasoning in theology (592–94). His particular target is Thomas Aquinas (283–338).  

The argument is undermined by Poythress’s ahistorical reading of Aquinas. Poythress accuses Aquinas of constructing an approach to the Christian faith heavily reliant on reason with heavy doses of Aristotle. The context in which Aquinas wrote was the threat posed by the Islamic interpretations of the recently rediscovered corpus of Aristotle. There are hints that some form of “double truth” theory was in vogue, by which theological integrity could be maintained while accepting the new criticism, with theology and reason held in contrasting tension. Into this confusion, Aquinas sought to demonstrate that while Christian truth depends on revelation, it is compatible with reason and can be rationally explained and defended.

It appears that Poythress is relying on outdated scholarship on Aquinas. In fact, Aquinas was primarily a biblical commentator, and his doctrine of the Trinity was founded in biblical exegesis, especially in his commentary on the gospel of John (which is on my desk at the moment). He was thoroughly trinitarian. His great Summa Theologia needs to be read in the light of his biblical commentaries. Indeed, right at the start of the Summa he insisted that the teachings of the fathers and doctors, and the philosophers, are all subject to the supreme authority of Holy Scripture:

Since therefore grace does not destroy nature but perfects it, natural reason should minister to faith as the natural bent of the will ministers to charity … (2 Cor. 10:5). Hence sacred Scripture makes use of the philosophers in those questions in which they were able to know the truth by natural reason, as Paul quotes a saying of Aratus … (Acts 17:28)… . Nevertheless, sacred doctrine makes use of these authorities as extrinsic and probable arguments: but properly uses the authority of the canonical Scriptures as an incontrovertible proof, and the authority of the doctors of the church as one that may properly be used, yet merely as probable. For our faith rests on the revelation made to the apostles and prophets, who wrote the canonical books, and not on the revelations (if any such there are) made to other doctors. Hence Augustine says (Letter to Jerome, 19:1): “Only those books of Scripture which are called canonical have I learned to hold in such honor as to believe their authors have not erred in any way in writing them. But other authors I so read as not to deem anything in their works to be true, merely on account of their having so thought and written, whatever may have been their holiness and learning.”[3]

Aquinas considers reason to be compatible with revelation and faith if grounded upon it. We should remember that Aquinas was not attempting to convince unbelievers for there were few if any self-identifying unbelievers around at the time. Rather, the mystery of the Trinity engendered a determined, focused, and highly refined engagement of the intellect. Faith was seeking understanding.

While many in Reformed circles have adopted a dismissive attitude towards Aquinas, Poythress, to his credit, has taken the trouble to read him. While I am being a touch critical here, it is clear to me that Poythress has seriously engaged with ‘the angelic doctor’ and recognizes the primacy he accords to the Scriptures over all human opinions.

It appears to me that the use of thought patterns and methodologies not found in the Bible is unavoidable, indeed necessary, if we are to communicate the truth clearly in our own context. The key question to ask ourselves is from where does the control come? How far do we go before the message is shaped by the contextual language rather than being expressed by it?

Third, Poythress suggests areas where theology has been corrupted by Greek philosophy, specifically by Aristotelian metaphysics. He is critical of a range of theologians down the years who he considers have tainted their work by imbibing alien philosophical ideas. In some cases, such as Dionysius the Areopagite (458–62), this is evidently so. This may seem superficially akin to the theory of Adolf von Harnack, which led to a widespread distaste for the historic Christian faith as expressed in its creeds and confessions. Systematic theology went through a period when it was regarded with disfavor for this very reason, and biblical theology was held out as the ideal. Yet systematic theology distinctively provides the tools to defend the church from heresy and error.

Harnack’s theory has been undermined many times over, from the days of Kelly, Pelikan, and Grillmeier onwards. His argument was invalid. For example, the incarnation and resurrection were nonsensical to Greek philosophy of whatever stripe. Moreover, the evidence demonstrates that the church took Greek words and gave them new meanings, adapted and fitted to reflect the truth. The agreement on the use of ousia and hypostasis brokered by Basil is an obvious instance. In the face of teaching that would have destroyed the gospel, the classic councils distilled their reading and understanding of Scripture by borrowing language from elsewhere to elucidate “the sense of Scripture,” as Gregory of Nazianzus put it. They stretched such language and accorded it meaning appropriate to the mystery of the Holy Trinity.

These criticisms are of a general nature and highlight the dangers that can arise when the historic formularies of the church are questioned or relativized. While Poythress does not go in that direction, it is easy to come away from the reading, if not better informed, with a sense that the cumulative wisdom and biblical exegesis underlying the historic ecumenical councils is somehow damaged.

Fourth, I have a series of observations that are broadly sympathetic, with certain qualifications. Poythress attempts to read trinitarian distinctions back into the divine attributes. The orthodox teaching is that the attributes of God are identical with his being, with who he is, and are so eternally. Poythress agrees. To oppose this would be to suggest that God has parts less than the whole of himself, or else that there are eternal entities other than God, or that God has accidents (things that are not inherent and necessary to God’s being).

At the same time, the attributes are manifested in distinct hypostatic ways. The love of God is indivisibly common to all three hypostases, which Poythress affirms, yet in the external works of God, love is demonstrated in the Son in a manner peculiar to him, for only the Son, in our nature, went to the cross. However, since the Trinity is indivisible, and the works of the Trinity are inseparable, all three hypostases are involved in all such works, the cross included. Poythress’s diagram of unity, distinction, and coinherence embraces all these aspects. Focus on the unity to the exclusion of distinction and you are on the road to modalism. Stress distinction and the perils of social trinitarianism are not far off. Ironically, Poythress’s recognition of this is reminiscent of Aquinas’s treatment of essential love and personal love in God.[4]

There are some fine balancing acts required here. Poythress states that the “mercy [of God] is differentiated: the Father initiates, the Son accomplishes, and the Spirit applies” (569). This has echoes of Calvin, who wrote that to the Father “is attributed the beginning of activity … to the Son … the ordered disposition of all things; but to the Spirit is assigned the power and efficacy of that activity.”[5] However, it may convey a possible suggestion that the three are separable, exercising different functions. In reality, all three are engaged indivisibly in initiation, accomplishment, and application, since in all God’s works all three hypostases work inseparably. Poythress appreciates this, for unity and coinherence are integral to his trinitarian thought, together with distinction (90–100). The point is that such elements, as Vermigli put it, terminate hypostatically (personaliter) on, or as the Latin tradition calls it, are appropriated to, one particular person.[6] John Owen wrote of the one indivisible will of God as coming to hypostatic manifestation as the will of the Son, the will of the Father, or the will of the Spirit, not as divided into three wills but as distinct hypostatic manifestations of the one will.[7] This is reiterated by Poythress (571–74). If each hypostasis had its own will, one would have tritheism. If there were no hypostatic distinctions in the one will of God, one would have modalism. This is an example of where someone may go astray through a simple, basic reading of the Bible but where refined theoretical or metatheoretical tools, clarified over centuries, can keep us from danger—philosophy, in other words, in the service of the truth revealed in Scripture.

In summary, Poythress calls us “to abandon tight, abstract logic in theological reasoning” (594). On one level, that was how the trinitarian crisis was resolved in the fourth century, in the Greek church. The Nicene Creed was confessed at the Council of Constantinople by bishops, not philosophers, mainly through biblical exegesis, particularly of Old Testament passages. The problem was that the anti-Nicenes, Homoian Arians and Eunomians, insisted on the Bible only, to the exclusion of the cumulative wisdom of the church’s interpretation of the Bible. In rebuttal, the church, through figures such as Gregory of Nazianzus, defended what they called “the sense of Scripture.” In later years, Article 8 of the Thirty-Nine Articles of the Church of England, a document that profoundly influenced the Westminster Confession, put this brilliantly: “The Three Creeds, Nicene Creed, Athanasius’s Creed, and that which is commonly called the Apostles’ Creed, ought thoroughly to be received and believed: for they may be proved by most certain warrants of holy Scripture.”[8]

Moreover, the fathers achieved this from a perspective that held to the simplicity and immutability of God every bit as much as Aquinas did. Both they and he were saying the same thing in differing ways. Both affirmed the mystery of the Trinity. However, at Nicaea in 325 it had become evident that biblical language could be cited by orthodox and heretics alike, the latter using it in support of their own beliefs. To mark the boundaries between truth and heresy new terminology was needed. This call to abandon tight, abstract logic in theological reasoning should be carefully reconsidered in a second edition of the book.

There is something of a puzzle over the precise readership Poythress has in mind. He writes in such a way as to engage the general reader, with basic language, diagrams, and prayers, yet he calls for an abandonment of abstract logic and philosophical terminology they are unlikely ever to encounter. On the other hand, if his aim is to persuade specialist theologians and others of that ilk, a more extensive and informed historical analysis is required that would go well beyond the bounds of this volume.

This is not at all to negate the fact that this is a most stimulating piece of work, indicated by the questions it provokes. It is a book replete with wisdom, insights, and perspectives, too many to enumerate here. However, as with anything written on the Trinity by whomever it may be, it is well to read it critically, under Scripture, with deference to the considered biblical exegesis that underlay the Niceno-Constantinopolitan creed (Nicene creed) and the tradition that stemmed from it, confessed down the centuries. It is clear that Poythress wishes to operate within these bounds, and, at the end, he acknowledges that he does not want to change “what orthodox Christians have believed through the centuries” (591). Thank God, we have no need to reinvent the wheel.


[1] Gregory Palamas, a fourteenth century Orthodox theologian, taught that the essence of God is inaccessible, our knowledge of God limited to his energies (his workings), an unacceptable division in the Trinity.

[2] B. B. Warfield, The Westminster Assembly and Its Work (New York: Oxford University Press, 1934), 226. I am grateful to Sherman Isbell for pointing out the following works which address the question of inferences from Scripture; George Gillespie, A Treatise of Miscellany Questions (Edinburgh: Gedeon Lithgow for George Swintoun, 1649), 243. Wing /G371; Aldis, H.G. Scotland /1367. James Bannerman, Inspiration: The Infallible Truth and Divine Authority of the Holy Scriptures (Edinburgh: T. & T. Clark, 1865), 582–88; Francis Turretin, Institutes of Elenctic Theology (Phillipsburg, NJ: Presbyterian and Reformed, 1992), 1:37–43. 

[3] Aquinas, Summa Theologica, 1a.1.8. Responsio, obieictio 2.

[4] Aquinas, Summa Theologica, 1.37.1

[5] John Calvin, Institutes of the Christian Religion, 1:13:18.

[6] Peter Martyr Vermigli, Commonplaces, 2:17, trans. Anthonie Marten (London, 1583), 599–600.

[7] The Works of John Owen, ed. William H. Goold, 23 vols. (1850–1855; repr., London: Banner of Truth, 1965–1968), 19:86–88.

[8] The Book of Common Prayer and Administration of the Sacraments (Oxford: Oxford University Press, n.d.), 636.

Robert Letham is a minister in the Evangelical Presbyterian Church in England and Wales, serving as professor of systematic and historical theology at Union School of Theology in Bryntirion in Bridgend, South Wales, and is senior fellow at Newton House, Oxford, United Kingdom. Ordained Servant Online, December 2021.

Publication Information

Contact the Editor: Gregory Edward Reynolds

Editorial address: Dr. Gregory Edward Reynolds,
827 Chestnut St.
Manchester, NH 03104-2522
Telephone: 603-668-3069

Electronic mail: reynolds.1@opc.org

Submissions, Style Guide, and Citations


Editorial Policies

Copyright information

Ordained Servant: December 2021

A Congregational Charge

Also in this issue

A Charge to the Congregation

New Polish translation of the Westminster Confession of Faith

The Writings of Meredith G. Kline on the Book of Revelation: Chapter 6, “The Apocalypse of Jesus Christ” (1992)

A Study in the Structure of the Revelation of John

Commentary on the Form of Government of the Orthodox Presbyterian Church, Chapter 23, Part 1

Exodus Old and New: A Biblical Theology of Redemption by L. Michael Morales

The Rise and Triumph of the Modern Self by Carl Trueman


Download PDFDownload MobiDownload ePubArchive


+1 215 830 0900

Contact Form

Find a Church