To engage with the medieval Italian priest Thomas Aquinas (1224–74) is to approach one of history’s greatest theological giants. Aquinas is second only to Augustine in his influence on Western Christianity—and his legacy of Thomism is a vast ocean. Academic discussions in theology and philosophy demand Aquinas and Thomism as conversation partners.

Yet evangelicals, in particular, have had an unresolved relationship with Aquinas over the years. The pendulum of 20th-century evangelical scholarship on Aquinas has swung between strongly negative appraisals (from Francis Schaeffer and Cornelius Van Til, for example) and, since the 1980s, more appreciative receptions (such as from Norman Geisler and Arvin Vos). Yet in the last decade or so, there has been a Thomist renaissance within evangelical circles.

Evangelical apologists were first attracted to his epistemology, especially his defense of an evidentialist view of the relationship between faith and reason, which assumes that reason can ascertain the existence of God. Evangelical theologians then began retrieving his “classical” doctrine of God’s oneness in the face of modern Christological and Trinitarian trends, which they perceived as slippery slopes to unorthodox views—which promote a social trinity and a hierarchical subordination of Jesus to the Father, for instance.

In the face of pressures from secularization and the identity crisis felt in some evangelical quarters, Aquinas can be perceived as a bulwark of a “traditional” theology that needs to be urgently recovered—and is thus in danger of being idealized in an uncritically positive retrieval.

Previous generations of Protestant scholars could not avoid Aquinas, given his stature and importance for theology, but he was always read with selective eyes. Today, however, there is an increasing tendency to think that you cannot be properly orthodox (in the “catholic” sense) if you don’t embrace the fundamental tenets of Thomism.

What is often overlooked by these evangelical retrievers is the controversial history of Aquinas. From the Reformation and beyond, Roman Catholicism has considered Aquinas as its chief champion in its anti-Reformation stance and resulting antibiblical developments, such as the 1950 Marian dogma of the bodily ascension of Mary.

What are we to make of this divide over Aquinas? What are the strengths and weaknesses, if not dangers, in retrieving Aquinas for theology today? The point is not to avoid Aquinas, nor to study him uncritically, but to provide the theological map with which evangelicals might approach him.

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As an evangelical theologian who has been working on Roman Catholic theology for 25 years—and, more recently, working toward an evangelical appreciation of pre-Reformation theology, including Aquinas—I’d like to offer five principles that can be useful in affirming the evangelical interest in Aquinas without veering into heterodox territory.

1. Scripture alone is ultimate, and tradition (Aquinas included) is always second.

In reading Aquinas, evangelical theology must always practice the sola Scriptura principle (the Bible alone is the inspired written Word of God and the ultimate authority in all matters of life), the tota Scriptura principle (the whole Bible is inspired by God and needs to be received as a whole), and the Scriptura sui ipsius interpres principle (the Bible is its own interpreter).

At the end of his letter to Sadoleto, John Calvin wrote, “We hold that the Word of God alone lies beyond the sphere of our judgment, and that Fathers and Councils are of authority only in so far as they accord with the rule of the Word, [but] we still give to Councils and Fathers such rank and honor as it is meet for them to hold, under Christ.”

This leads to a theologically sober and realistic view of tradition, including Aquinas’s substantial legacy. In J. I. Packer’s words, “Tradition, after all, is the fruit of the Spirit’s teaching activity from the ages as God’s people have sought understanding of Scripture. It is not infallible, but neither is it negligible, and we impoverish ourselves if we disregard it.”

That is all to say that Aquinas is important but not decisive; he can be useful but never definitive—especially where he is distorting or deviant from God’s Word. In other words, Aquinas can be enriching, but only to the extent that he is faithful to Scripture.

2. Aquinas is a giant of church history whose teachings need to be appropriated eclectically.

All Protestant theologians have studied Aquinas as the primary exponent of medieval theology. But the best readers of Aquinas have had neither reverential fears nor inferiority complexes—they have faced Aquinas head-on with an evangelical boldness undergirded by the biblical principle of “Prove all things; hold fast that which is good” (1 Thess. 5:21, KJV).

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Responsible retrievers of Aquinas—such as Peter Martyr Vermigli and Herman Bavinck, through Francis Turretin—have exercised a theological discernment allowing them to appreciate the aspects of Aquinas’s teachings that are in line with biblical faith and to reject those that conflict with Scripture.

In other words, they did not embrace the Thomist system as such but broke it down into its parts—as far as possible while maintaining their integrity—and used them eclectically. That said, eclecticism has its own risks, and we must not lose sight of the fact that Aquinas is a “worldview” thinker and that any analysis of the Thomist system must be done as a whole.

Evangelical scholarship can neither reject Aquinas as a hopelessly compromised theologian (the anti-Aquinas temptation) nor elevate him as the chief parameter of Christian orthodoxy (the Roman Catholic temptation). Rather, it should treat Aquinas as an unavoidable conversation partner in the history of Christian thought. And like anyone else from Christian tradition, Aquinas is to be read generously yet critically in light of the “Scripture alone” principle—which the Protestant Reformation recovered for the whole church.

3. There are many ambivalences and serious problems in the Thomist system.

Aquinas’s thought has a myriad of brilliant insights, but the Thomist system, which includes his metaphysics and epistemology, contains tendencies and trajectories that can lead to structural theological flaws.

In The Cambridge Companion to the Summa Theologiae, Christoph Schwöbel points to Adolf von Harnack’s insights that “Thomas’s account of grace remains constantly ambivalent. On the one hand it looks back to Augustine, on the other hand, it points forward to the dissolution which Augustinianism would undergo in the fourteenth century. … Thomas intends to insist on the sole efficacy of divine grace; but the way in which he develops this theme already points in the opposite direction.”

Aquinas’s thought is pervaded with an ontological optimism that translates into epistemological optimism (stressing the positive role of reason), moral optimism (underlining the role of virtues as human habits), and, in the post–Vatican II interpretation, soteriological optimism (all humanity participates in one way or another in the mystery of salvation).

From this point of view, one cannot easily separate Aquinas’s classical theism (and its implications for Trinitarian theology and Christology) from his soteriology, ecclesiology, sacramentology, Mariology, and devotional life. The latter components of his thought are all argued in terms of the former, so it is incongruous to consider the latter flawed and the former sound. All of Aquinas’s theological constructs are formed and shaped around the same parameters, which incorporate Scripture but are not ultimately submitted to it.

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In other words, Aquinas’s thought is part of a larger integrated system that needs to be appreciated as such and appropriated eclectically, but not unquestioningly.

4. Roman Catholicism is the full outcome of Aquinas’s theology and legacy.

The Roman Catholic Church has long held Aquinas as its vital intellectual champion, the most thoughtful, profound, and comprehensive voice of Roman Catholic thought. The Church of Rome has long appropriated Aquinas as the Catholic theologian par excellence.

Canonized by Pope John XXII in 1323, only 50 years after his death, Aquinas was proclaimed a Doctor of the Church by Pius V in 1567 for being the Roman theologian whose thought was seen to have defeated the Protestant Reformation.

In the 20th century, the Second Vatican Council (1962–65) established that Aquinas should be the supreme guide in theological studies leading to the ordination of priests. Pope Paul VI (Lumen Ecclesiae, 1974) and then John Paul II (Fides et Ratio, 1998) expressed a deferential appreciation by identifying Aquinas “as a master of thought and a model of the right way to do theology.”

Aquinas laid the foundations for the theological framework typical of Roman Catholicism, including their belief in a fundamental interdependence between nature and grace (sometimes referred to as “natural theology”), which most Protestants find highly problematic from a biblical perspective. Evangelical theology has always been grounded in the historical-redemptive motif found in Scripture: creation, sin, and redemption, however formulated.

Aquinas is acknowledged as the authority behind many nonbiblical developments in medieval and modern Roman Catholicism, from the Council of Trent to Vatican I and II. These distorting departures from the biblical faith exist in critical areas of Catholic soteriology, ecclesiology, sacramentology, and devotions. While Aquinas has a high view of the Bible, it falls far short of the scriptural standards reinstated by the Protestant Reformation.

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When engaging with Aquinas, it would be foolish to throw the baby out with the bathwater. Yet evangelical Thomists cannot ignore the fact that Rome regards him as the quintessential founder of Roman Catholic theology, in all its divergence from Protestant thought.

5. Evangelicals should neither be infatuated with Aquinas nor disparaging of him, but exercise maturity.

Today’s renewed evangelical appeal to Aquinas’s metaphysics and epistemology is not occurring in a vacuum. In our current cultural climate, Aquinas primarily symbolizes a return to the “great tradition” of premodern Western philosophy, a retrenching of evangelical modernity in Christian antiquity.

In some sectors of evangelical theology, the thought of keeping classic thinkers like Plato and Aristotle integrated into our biblical worldview produces an anxiety-relieving effect. In a world that is suspicious of metanarratives, Aquinas’s theology holds apologetic appeal for its claim to harmoniously combine faith and reason and to challenge skepticism with the rationality of faith.

However, the remedy may be worse than the problem, especially if it leads to an infatuation with Aquinas and an uncritical idealization of his thought.

For one, there has been a recent trend of evangelicals converting to Roman Catholicism, in part because of an attraction to Aquinas’s intellectual density and spiritual depth. In many cases, conversion begins with an affirmation of his metaphysics and ethics, which eventually leads to a full embrace of his theology. Upon further study, such individuals become convinced that Aquinas’s thought could not be split into disconnected pieces, and their conversion to Roman Catholicism follows.

Perhaps, as Barrett points out, it is unfair to see this potential for conversion as a universal caution—that it is untrue to say that Aquinas is “the gateway to Roman Catholicism.” But, at the same time, one should not be naive about the attraction many find in Aquinas’s theological vision and how it can often be an appetizer for the “full package” of Roman Catholicism.

Yet a disparaging attitude toward Aquinas is equally problematic. Aquinas belongs to a pre-Reformation age when the Western church had not yet committed itself to what Rome would officially endorse at the Council of Trent and later. Although he is behind much of what Roman Catholicism would transform into an anti-Protestant stance, he is still part of a more “fluid” time in church history that requires reading with both spiritual empathy and critical discernment.

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We should read Aquinas like Peter Lombard, Bonaventure, Duns Scotus, and other medieval theologians, who benefited from Aquinas’s insights and lessons yet raised issues wherever his system departed from Scripture.

We must neither fear Aquinas nor elevate him as an absolute standard for Christian orthodoxy—neither dismissively rejecting nor naively embracing his system of thought. Evangelical theology must seek a realistic reading of Aquinas, submitted to Scripture’s supreme authority and in the service of the gospel.

This piece has been adapted from Engaging with Thomas Aquinas: An Evangelical Approach at the permission of Inter-Varsity Press.

Leonardo De Chirico is the director of the Reformanda Initiative in Rome, pastor of Breccia di Roma, lecturer in historical theology at Istituto di Formazione Evangelica e Documentazione (Padua) and the author of several books including Same Words, Different Worlds: Do Roman Catholics and Evangelicals Believe the Same Gospel? and the newly published Engaging with Thomas Aquinas: An Evangelical Approach.