The Perfectly Simple Triune God: Aquinas and His Legacy

D. Stephen Long. The Perfectly Simple Triune God: Aquinas and His Legacy. Minneapolis: Fortress Press, 2016. 448 pp. $49.00, paper.

In recent decades, theologians and historians have come to a greater appreciation of the depth of the thought of Thomas Aquinas. Older stereotypes of a Thomas who cared nothing for the Trinity are disappearing chiefly as a result of the herculean work of Gilles Emery, Professor at the University of Fribourg, as well as a host of others, including Timothy L. Smith and John Baptist Ku. Central to this has been the defense of the idea that the Trinity plays a prominent role in Thomas’ thought, and is not relegated to a minor place in his theology. D. Stephen Long’s recent book The Perfectly Simple Triune God: Aquinas and His Legacy is an attempt to pursue a similar treatment of Thomas’ thought by arguing that divine simplicity and perfection in Thomas serve primarily to aid the doctrine of the Trinity.

Long’s argument in this book is that the proper context for the traditional understanding of God is the question, “How do we speak well of the mystery of the Holy Trinity?”(xx) For Long, the traditional understanding of God as perfectly simple is most coherent when it is utilized in explaining the nature of divine Triunity. Simplicity explains that the three divine Persons are not parts of the one God. Thus for Long, divine simplicity serves to exposit the mystery of the Holy Trinity. Where simplicity is not used for this purpose, or it is used for other purposes, then Long claims that the doctrine is detrimental to Christian theology. In order to argue for this point, Long examines the first forty-three questions of the Prima Pars (first part) of Thomas Aquinas’ great work, the Summa Theologiae. Long does this because he sees Thomas as the great expounder of the traditional doctrine of the Triune God, who is both perfect and simple.

The book is divided into three parts: Part I is titled “Exposition of the Traditional Understanding of the Perfectly Simple Triune God.” In this section, Long exposits the first 43 questions of the Summa Theologiae. In some cases he goes into detail, and other times he merely gives summaries. He then examines authorities for Thomas’ traditional understanding of the Triune God, including Sacred Scripture, Augustine, and Pseudo-Dionysius.

Part II is entitled, “The Ecumenical Consensus on the Perfectly Simple Triune God.” Here he primarily examines the legacy of Aquinas among those emerging from the Reformed tradition. Long compares Thomas’ thought to that of Calvin and Luther, and then examines Thomas’ influence in Peter Martyr Vermigli, Jerome Zanchi, and John Owen. Here Long argues that these authors begin to diverge from Thomas’ traditional answer because they emphasized predestination. Long finds the work of Jacob Arminius and John Wesley much more valuable due to their aversion to predestination and reprobation.

In Part III, Long addresses “challenges to the traditional understanding of the perfectly simple Triune God.” Here Long examines critiques of the traditional doctrine of God that have been made since the eighteenth century. The chief objects of concern here are process theism, open theism, analytic theology, cultural and political theologies that have challenged the traditional response, and metaphysical challenges to traditional thought. Long concludes the book with an examination of three theologians whom he feels have appropriately engaged the traditional Thomistic understanding of the Perfectly Simple Triune God: Kathryn Tanner, Katherine Sonderegger, and Sarah Coakley.

Long is to be commended for bringing attention to Thomas’ doctrine of the Trinity and the central role that it possesses in his theology. Far too many myths abound regarding the supposed “Western” emphasis upon the unity of the nature over the Triunity of the Persons. Long also writes very clearly and plainly, and the work is highly readable. He also articulates very well the threat that modern theology has posed to the traditional understanding of the doctrine of God.

However, Long’s book possesses several structural issues which pose grave problems for it as an understanding of traditional Christian theology in general, and Thomas’ theology in particular. The primary issue is that Long limits his examination of Thomas’ doctrine of God to only the first forty three questions of the Prima Pars of the Summa Theologiae. While there is a substantial amount of material here, this most certainly does not exhaust Thomas’ writings on the doctrine of God. Not only are there other writings where Thomas wrote extensively upon the Triune God, such as the Summa Contra Gentiles and the Commentary on the Sentences, but there is much more that Thomas wrote about God in the Summa Theologiae itself. One example of this is questions 109-144 of the first part of the second part of the Summa Theologiae, the Prima Secundae. This is the section in which Thomas examines the necessity of grace for human salvation. Here Thomas argues for the necessity of divine causality in order for any man to know and believe the truth. This causality is directly related to divine simplicity. Thomas makes this explicit, stating, “all movements, both corporeal and spiritual, are reduced to the simple First Mover, Who is God.” (IaIIae, q. 109 art. 1, resp.) Thomas thus explicitly ties simplicity to predestination and providence. This important aspect of the nature of divine simplicity in Thomas is not addressed by Long because these questions lie outside of the purview of the first forty three questions of the Summa Theologiae to which Long has restricted his study.

This leads to the second issue, related to the first. Long ignores and downplays those aspects of Thomas’ thought with which he disagrees. Long not only avoids questions such as those on grace in the Prima Secundae, but he also minimizes the significance of divine causality in Thomas’ thought. A glaring example of this is when he discusses the Five Ways found in Question 1, article 2, section 3 of the Summa. Long writes, “Too much should not be made of Thomas’s five ways. They have limited use in his work; he refers to them again in his later questions, but not with the frequency to which he appeals to divine simplicity and perfection.” (17) The problem with this is that divine simplicity and perfection are inseparable from the Five Ways. Thomas’ discussion on simplicity immediately follows the Five Ways, and is dependent upon them (Ia, q. 3, art.1 resp.), while his discussion of perfection is found in the argument for the Fourth Way. Thomas’ Five Ways are not merely arguments for the existence of God, separable and able to be read in abstraction. Thomas lays down in them a theological logic and set of principles to which he returns again and again in the Summa Theologiae. The principles found in the Five Ways are utilized in sections as diverse as the nature of grace and the constitution of the hypostatic union (IIIa, q. 2, art. 1. resp.). Long’s rejection of important aspects of Thomas’ use of simplicity and perfection results in an inaccurate picture of Thomas’ thought on these attributes.

A further problem with this is that he is claiming to appropriate Thomas’ thought on simplicity and the Trinity. This appropriation fails because he has both mischaracterized Thomas thought, and he has rejected Thomas’ thought. Long’s project is to develop a theological paradigm where simplicity and perfection are useful in defending the Trinity, but are not utilized in the doctrine of predestination. He clearly has a distaste for the idea of predestination and especially reprobation, even going so far as to state that he prefers universalism to reprobation (169). These theological commitments are likely due to the fact that Long is a Methodist minister, and is thus ministering in the Arminian Wesleyan tradition. This aversion to predestination and reprobation, however, are inconsistent with the thought of Thomas.

Thomas’ thought finds a more natural ally to Reformed understandings of providence and predestination, as he argues that the creature cannot move in any way, physically or spiritually, apart from the work of God in the creature. The creature needs God to instill faith in his heart (ST IaIIae, q. 62, art. 1, resp), to move him through grace to reach his final end (ST Ia-IIae, q. 109, art. 1, resp.) and to provide supernatural light to the intellect by which he is able to believe (Ia-IIae, q. 62, art. 3, resp.). This is a theme that is present throughout the Summa Theologiae, and it is an essential aspect of Thomas’ thought.

Moreover, the provenance of Thomas’ views demonstrate their consistency with Reformed thought on predestination and providence. There was a great controversy in the late sixteenth and early seventeenth century in the Roman Catholic Church over the nature of predestination. In the de Auxiliis controversy, Dominican Thomists such as Domingo Banez and Diego Alvarez argued against Jesuits such as Luis de Molina. The Thomists believed that God moved all things in providence and predestination as He was the First Mover. The Jesuits argued for Middle knowledge, wherein God saw who would respond to grace and who would not. This controversy impacted Reformed thought in the seventeenth century as theologians such as John Owen and Francis Turretin borrowed from the arguments of the Dominican Thomists in their argumentation against Arminian thought. This genetic influence is never addressed in Long’s book.

While there is much to like about Long’s book, it is safe to say that he goes to Thomas with an agenda, and forces Thomas to fit it, rather than finding what he actually says, and attempting to work with it. Ultimately, the Thomas of Long’s book is not the Thomas of history, nor is the theological understanding that he presents as consistent or as logical as that of Thomas and his Reformed heirs. Other resources are better for understanding Thomas and the impact that he has had upon history, and his value for contemporary theology.


Christopher Cleveland