Bonaventure's Critique of Thomas Aquinas

Étienne Gilson declared in 1959, “The long and short of it is simply that, in matters of theology, one cannot be right against Saint Thomas Aquinas.”[1] That so chauvinistic a statement could have been made by so irenic a thinker as Gilson gives a fair measure of just how mightily Aquinas towered over mid-twentieth century Catholic thought. Following Aeterni Patris (1879), which called for the Church “to restore the golden wisdom of St. Thomas” (§31), Thomism became the de facto (if not de jure) philosophical and even theological orthodoxy in many Catholic orders and institutions, not least through the notorious shibboleths of the “24 Thomistic Theses” published by Pope Pius X in 1907. The aim of this document was to ensure conformity on the part of philosophers and theologians to key Thomistic principles, some of them relatively obscure (“The principle of individuation . . . is matter designated by quantity” [§11]), but others touching on central theological questions: “We do not perceive by an immediate intuition that God exists, nor do we prove it a priori” (§22).

The twenty-second Thomistic thesis elaborated Pope Pius IX’s earlier condemnation of “ontologism,” namely the teaching—associated in the nineteenth century with the anti-Kantian Vincenzo Gioberti—that “that being, which we understand in all things and without which we understand nothing, is the divine being.”[2] Pius X highlights two distinct but related issues which are implicated in “ontologism.” First, must we in some sense already know God in order to know anything else? And second, does the conceptual link between God and “being” somehow permit us to reason a priori to his existence, even if we bracket the existence of creation itself? The classic version of this “ontological” argument for God’s existence was developed by Anselm of Canterbury in his Proslogion, on the basis of Augustine’s suggested definition of God as “he…than whom nothing better and greater can be.”[3]

Aquinas rejected both of these positions, motivated in each case by his adherence to what Philip Cary has called his “rather empiricistic version of Aristotle’s epistemology,” according to which “the universal forms that the human mind understands are intelligible species abstracted from sensible things, and hence are created things, not the uncreated Ideas in God.”[4] For Aquinas, all we can know directly are creatures, by way of the intelligible “forms” which our minds mine from the likenesses they impart to us in sensation.[5] The first aspect of them with which our intellect becomes acquainted is “being,” to be sure, but created being, the “common” or “universal existent (ens commune, ens universale) which is variously instantiated in every finite particular.[6] If that is so, it follows that all knowledge of God begins from the knowledge of creatures, as in the famous “five ways” to God with which his Summa Theologiae opens.[7]

A Cordial Rivalry

What is most curious about the Thomistic triumphalism canvassed above is that, in his own lifetime, Aquinas’s efforts to baptize Aristotle met with fierce criticism from contemporaries such as Bonaventure of Bagnoregio, who warned Aquinas that he was selling his Augustinian birthright for a mess of Peripatetic pottage. For seven remarkable years, from 1252-1257, Bonaventure lived and worked with Aquinas, as they taught theology together at the University of Paris. The two were almost exact contemporaries, with Bonaventure roughly four years Aquinas’s senior. This was a meeting of minds on the order of Aristotle’s studies with Plato, or Hegel’s period as the roommate of Hölderlin and Schelling when they were seminarians at Tübingen. The great debates that unfolded between Bonaventure and Aquinas during and after this period are not so well known as the development of German Idealism, much less as Plato’s and Aristotle’s mutual influences, but they are no less rich, and ought to be better known than they are at present by students of scholastic philosophy and theology in particular.

However friendly Bonaventure and Aquinas might have been in the refectory (and later tradition has been quick to embellish the meager contemporary evidence of their mutual affection), their works, both from the 1250’s and following, reflect a number of deep disagreements. They parted ways over how to receive and interpret the prior theological tradition, notably the “Augustinian” inheritance that descended through Anselm and the Victorines. They also disagreed about how to respond to the day’s most important intellectual developments, as in the rise of a kind of anti-Christian “Aristotelian fundamentalism,” inspired in particular by the Arab Aristotelian commentator Ibn Rushd (a.k.a., Averroës), who maintained that God has no knowledge of particulars, and that all humans share a single intellect.

Aquinas was an enthusiastic Aristotelian, and sought above all to show that Averroists such as Siger of Brabant were everywhere misreading “the Philosopher.” Bonaventure also knew Aristotle well and everywhere draws on him respectfully and creatively. Nonetheless, he was a purer Augustinian than Aquinas, and rejected not only the Averroists’ radical views, but also Aquinas’s more moderate Aristotelian empiricism. For instance, Bonaventure expressly denies that the mind is a “blank slate”: “One asks whether all knowledge is from the senses. We must say that it is not, for the soul knows God and itself and whatever is within it without the assistance of the exterior senses.”[8] Consequently, he also defended both of the key claims rejected in the twenty-second Thomistic thesis, insisting, with Augustine, that we do indeed “perceive by a pure intuition that God exists” (this is often called his theory of “divine illumination”), and with Anselm, that we do indeed “prove it a priori.”

Divine Illumination: God as the Mind’s First Object

In fact, Bonaventure beautifully links these two concerns in the fifth chapter of his masterwork, the Mind’s Journey to God (Itinerarium Mentis in Deum). In this short text, which offers a meditation on God’s self-identification as “he who is (qui est)” (Exodus 3:15), Bonaventure insists that “what first falls in the intellect is . . . the divine being” (illuminationism), from which it follows that “it is impossible for him to be thought not to be” (the ontological argument).[9] Bonaventure begins this discussion by exploring the implications of naming God “who is,” seeing in it the infinite fullness and perfection which is presupposed to the knowledge of any and every finite reality. The intellect, he argues, first knows Being, which is identical with God:

So, being is what falls first in the intellect (quod primo cadit in intellectu), and that being which is pure act. But this is not particular being, which is restricted being, because that is mixed with potency, nor analogous being, because that has actuality in the minimal degree, since it minimally exists. And so it remains that that being [which falls first in the intellect] is the divine being.[10]

This might seem quite abstract, but with a bit of unpacking, it offers a rich and coherent account of human knowing, grounded in two plausible premises. The first is that the most fundamental object of our knowledge is always being. If I see someone approaching from a great distance, I first simply observe that there’s something coming (being “falls first into the intellect”), and only later that it’s a living thing, a human, and finally, my friend William. So far, Bonaventure and Aquinas are on the same page: “Our intellect naturally knows the existent (ens),” Aquinas writes, which he later specifies as “the universal existent (ens universale).”[11] (Ens is the present participle of the verb esse, “being” as opposed to uninflected “to be.”)

But being, as Aristotle tells us, is said in many ways. Bonaventure’s second premise specifies that the first object of our intellect must be “pure act” rather than “restricted” or “analogous being,” the latter being his equivalent of Aquinas’s “universal existent”—analogous being is being insofar as it is predicated “analogously” of each of Aristotelian categories (a cat exists in one way, the blackness of its fur in another, etc.).[12] This priority of “pure act” in our knowledge follows from an intuitive account of actuality as that which we must first understand in order to understand “potency”: I can only be potentially sitting if I’m actually in some other state, e.g., standing up or lying down. So too, our knowledge of imperfect, limited realities cannot be (logically) prior to our knowledge of perfect, unrestricted being: “privations and defects,” as Bonaventure argues earlier in the Itinerarium, “can only be known through positive attributes (positiones) . . . How could the intellect know that this being is a defective and incomplete entity, if it had no knowledge of a being without any defect?”[13]

At first and indeed second glance, the teaching of Itinerarium 3.3 or especially 5.3 looks a lot like the so-called “ontologism” we considered above, i.e., the view that “that being, which we understand in all things and without which we understand nothing, is the divine being.” So much like it, in fact, that the nineteenth-century editors of the still-standard Quaracchi edition of Bonaventure’s works were moved to describe Itinerarium 5.3, somewhat theatrically, as “those words, which have been to many a stone of offense (lapis offensionis).”[14]

The Quaracchi editors essentially seek to save Bonaventure from Pius IX’s condemnation by reversing his actual position. They propose that, for Bonaventure, “being itself . . . is not apprehended in its purity and distinction by the human intellect in its first act, but only most imperfectly in that shadow of the most common being.”[15] Here, we are told that the intellect first apprehends “common being” (what Bonaventure calls “analogous being”), which is precisely what he denies. Bonaventure does of course distinguish “analogous” from “divine being,” but only by way of denying that the former can be the ultimate foundation for our acts of knowing.

Notice, however, that the condemnation does not distinguish between what we might call implicit and explicit understanding. Bonaventure’s position, at least as it is sketched in Itinerarium 5.3, expressly denies that God is the mind’s first explicit object, while affirming that we are always in some sense already acquainted with God in all our acts of knowing, just as some acquaintance with light is presupposed to, even if not explicitly thematized in, every act of vision:

Remarkable is the blindness of the intellect, which does not consider that which it knows first and without which it can know nothing. But as the eye, intent on various differences of colors, does not see the light by which it sees other things, or if it sees, does not notice it, so too the eye of our mind, intent on particular and universal beings, nonetheless does not notice being itself, beyond every genus, although it occurs first to the mind.[16]

His point is that we cannot help but be acquainted with the reality of God, who is the uninflected “to be” from which every particular borrows its being, even if we subsume that infinite reality under any number of mistaken descriptions. If “understand (intelligere)” is susceptible of interpretation in either an explicit or implicit sense, then perhaps we might take Pius IX’s condemnation of “ontologism” as applying, in the first instance, to explicit understanding. In that case, Pius would prove to have condemned a position which Bonaventure in fact criticizes himself in his Disputed Questions on the Knowledge of Christ q. 4, to which we can now turn. 

Three Theories of Illumination

The Itinerarium is an immensely compressed work, at points almost telegraphic in its economy of expression. As David Bentley Hart once said of Robert Jenson’s prose, you have the sense that if you dropped Bonaventure’s sentences, they might explode. Nonetheless, we find a more expansive treatment of the mind’s pre-theoretical acquaintance with the LORD in the long fourth question of the Disputed Questions on the Knowledge of Christ (ca. 1254), which asks, “Whether whatever is known by us with certainty is known in the eternal principles (rationes aeternae)?”[17] (“Ratio aeterna” is Bonaventure’s favorite expression for the “divine ideas,” the exemplars subsisting in the divine intellect, in and through which God knows and creates. “Ratio” is a nightmarishly ticklish term to translate; depending on the context, “reason, nature, account, principle,” or “aspect” are all good English equivalents.)

Bonaventure distinguishes among three possible ways of affirming this proposition: first, that we only know the divine ideas; second, that the divine ideas are the ultimate cause but not the object of our knowledge; and third, that we know the divine ideas confusedly and indistinctly in and through our knowledge of particular beings. Strikingly, the same threefold scheme appears both in Aquinas’s discussion of the “abstracting” intellect in the Commentary on the Sentences,[18] and in the somewhat later Exposition of Boethius’s “On the Trinity.”[19]

In the latter work, he takes up this scheme in considering whether God is the first object known by the intellect,[20] a question quite close to the presenting issue in Itinerarium 5.3, on which the Exposition might well be dependent, or vice versa. In truth, “literary dependence” is almost certainly too bloodless a notion to be adequate here; we should probably instead imagine a series of heated lunchtime debates between Bonaventure and Aquinas, with each then gradually and serially drafting his own preferred account of the proceedings.

The first position Bonaventure identifies maintains “that the evidence of the eternal light contributes to certain knowledge as the entire and sole basis for knowledge.”[21] For this approach, the only objects of human knowledge are the perfectly intelligible principles of every creature, which are identical with God the Word; all knowledge is thus knowledge of the divine essence. This view was (so to speak) too hot for Bonaventure to handle, since it assimilates all knowledge to the beatific vision, in which the blessed directly see the Word, and in him, see all creatures, actual and possible.[22] He insists that any account of human knowledge must keep our acquaintance with creatures at the center; otherwise, it would not explain our knowing so much as explain it away.

By contrast, the second approach that Bonaventure considers is much too cold, an Aristotelian naturalism according to which “the eternal reason necessarily contributes to certain knowledge by way of its influence, so that the knower, in knowing, does not attain to the eternal reason, but to only to its influence.”[23] The “influence” in view here is at least analogous to the position maintained by Aquinas, nicely summarized in the Exposition of “On the Trinity,” where he writes, “The human mind is divinely illumined by a natural light, according to the Psalm: The light of your face is sealed upon us, Lord,” insofar as “it has in itself the means for making things actually intelligible, namely the agent intellect,” i.e., the mind’s form-miner.[24]

He puts the point more clearly yet in the Summa Theologiae: “We must say that the human intellect knows all things in the eternal reasons, by participation in which we know all things. For the intellectual light which is in us, is nothing other than a certain participated likeness of the uncreated light, in which the eternal reasons are contained.”[25] It would have been more accurate of Aquinas to say that, on his view, we know all things, not in the eternal reasons themselves, but rather in a created likeness of those reasons.

Bonaventure has two main objections to this view. First, it fails as an interpretation of Augustine, who was insistent “that the mind in certain cognition has to be regulated by immutable and eternal rules, not as through the habit of his mind, but as through those things which are above him, in the eternal truth.”[26] Lydia Schuhmacher, among others, has offered a vigorous contemporary defense of the view that Aquinas was a truer Augustinian than Bonaventure in his theory of knowledge.[27]

It would take us too far afield to rebut this thesis; I will simply recommend Steve Marrone’s The Light of Thy Countenance: Science and Knowledge of God in the Thirteenth Century as a salutary alternative, and help myself to his critical appraisal of Schuhmacher’s project: “I find her description of the so-called Franciscan current . . . as well as its purported Avicennian foundations, almost entirely unrecognizable, at moments incoherent.” Bonaventure is in fact right to see deep continuity between his and Augustine’s theories of knowledge, as he copiously documents with quotations from On the Teacher, On True Religion, On the Freedom of the Will, On the Trinity, and On the City of God.[28] For instance, Augustine writes in On the Trinity, “We behold, then, by the sight of the mind, in that eternal truth from which all things temporal are made, the form according to which we are, and according to which we do anything by true and right reason, either in ourselves, or in things corporeal.”[29]

And second, if God’s role in human knowing occurs only at the level of our dispositions to formulate reason’s first principles, then “God can no more be called the giver of wisdom than the fertilizer of the earth, nor should knowledge be said to come from him more so than wealth.”[30] I suspect that Bonaventure was responding here to a comment from Aquinas’s Sentences commentary: “As every natural work is in God as in the one containing it (in continente), including walking and the like, so also the knowledge of the truth is in the Holy Spirit, who works in the intellect and conserves it.”[31] For Bonaventure too, all natural powers are “supernatural” in the sense of contingently receiving their being and structure from God. But the mystery of intellect constitutes a distinct spring through which supernature penetrates nature; for him, as for David Bentley Hart, “we can approach nature only across the interval of the supernatural.”[32]

Bonaventure instead seeks a middle way between “nothing-but-God” illuminationism and Aristotelian empiricism. On this view, “Certain knowledge necessarily requires an eternal principle (ratio) to regulate it and serve as its moving principle (ratio), not indeed as alone in all its brightness, but along with the created principle (ratio), and partly seen together with (contuita) it by us.”[33] This is why he says, in the Itinerarium, that God’s being is “contuita” in knowing finite being—the proper object of human knowing remains the creature, but the light which irradiates it shines forth from that creature’s infinite source, which is in known in and through our act of knowing the particular.[34]

Bonaventure takes it that we can only know necessary truths in particular if, along with creatures themselves, we also “contuit” the eternal archetypes which they express. “Things exist in their own genus, and also in the mind and in the eternal principle (aeterna ratione),” he notes. “But their being is not entirely immutable in the first and second modes, but only in the third, namely as they exist in the eternal Word. And so it remains that nothing can make things to be perfectly intelligible unless Christ is present, the Son of God and our teacher.”[35]

We know, for example, that a triangle’s interior angles sum to 180 degrees. But this knowledge cannot arise from the inked paper that composes a particular instance of a triangle, since its sides only approximate the rational relations in which triangularity consists, and its existence is a passing vapor compared with the eternal necessity which shines through it. What then does one know, in knowing a triangle as a triangle, if not a distant echo or pale reflection of what the Father knows in knowing triangularity as one of the words which subsist in his Word?

Aquinas, after criticizing the “nothing-but-God” illuminationism which Bonaventure also rejects, sketches a weaker position which is strikingly similar to Bonaventure’s own: “Others said that the divine essence is not the first thing known by us who are on the way, but rather the influence of its light, and in this respect God is the first thing which is known by us.”[36] However, Aquinas seems to think that this position commits us to saying that explicit knowledge of God is the first object of the intellect. Consider how he formulates an objection to his own position, in terms strikingly reminiscent of Itinerarium 5.4:

For that in which we know all things and through which we judge all the things we know, is the first thing known by us, just as light is known by the eye prior to those things which are seen through light, and the intellect’s principles are known prior to its conclusions. But all things are known in the first truth, and through it we judge all things, as Augustine says in his On the Trinity and On True Religion. Therefore, the first truth, namely God, is that which is first known by us.[37]

The illustration of this claim with the trope of light strikes a distinctively Bonaventurian note, since he explains how God can be the first known (implicitly) and yet not adverted to (explicitly) with the same simile: “As the eye, intent on various differences of colors, does not see the light by which it sees other things, or if it sees, does not notice it, so too the eye of our mind.”[38]

Aquinas’s response to this objection strengthens the allusion further. He first proposes (implausibly) that, for Augustine, “uncreated truth itself is not the proximate principle by which we know and judge, but [we say it is] because we know and judge through the light which is impressed on us and which is its likeness.”[39] (Aquinas is as keen to construe his account of Aristotelian abstraction as still a form of Augustinian illumination as Bonaventure is to incorporate the extractive agent intellect within his overarching illuminationism.)

But he then tries to explode the light-analogy in a way that makes his concern with the Itinerarium all the clearer: “Nor, however, is it necessary that the very light which is impressed on us be the first thing known by us . . . It needn’t be known except in the knowables themselves, just as light needn’t be seen first by the eye, except in illuminated color.”[40] This is precisely Bonaventure’s analogy, now reversed: it is not the light that is seen first, so that the color may be seen; rather, the color is seen first, and the light only by way of the color.

But Aquinas is only able to rebut Bonaventure’s illuminationism by misconstruing it. Bonaventure does not maintain that God is known first with any clarity or distinctness; here below, we see only through a glass darkly. Nonetheless, Bonaventure stands firmly within the long Platonist tradition in insisting that timeless truths must refer to a timeless order, which undergirds and so renders intelligible our experience of time’s ceaseless flux.

The Ontological Argument

Like the twenty-second Thomistic thesis, Bonaventure connects his illuminationism directly with Anselm’s a priori proof of God’s existence: “If ‘God’ names primary, eternal, simplest, most actual, most perfect being, it is impossible for him to be thought not to be, nor to be except one alone.”[41] Here again, however, the Itinerarium’s compression begs to be unpacked—why does recognizing God as most actual and most perfect being commit us to denying the very possibility of thinking him not to exist? The first of Bonaventure’s Disputed Questions on the Mystery of the Trinity offers an extensive defense of Anselm’s ontological argument, which compares favorably with Aquinas’s dismissive reading of Anselm.

Though no one pointed this out explicitly until Norman Malcolm in the mid-twentieth century, Bonaventure and Aquinas alike seem to have recognized that Anselm in fact developed two distinct versions of the ontological argument.[42] Malcolm distinguishes them as follows: Anselm’s “first ontological proof [in Pros. 2] uses the principle that a thing is greater if it exists than if it does not exist. His second proof [in Pros. 3] employs the different principle that a thing is greater if it necessarily exists than if it does not necessarily exist.” Bonaventure and Aquinas both seem to have implicitly distinguished Anselm’s proofs along the lines Malcolm suggested: each of them considers both proofs as separate arguments for God’s existence, Bonaventure in the aforementioned Disputed Questions and Aquinas in the Summa contra Gentiles.

To the extent that anyone today is aware of Anselm’s ontological argument, however, they typically know only its first formulation: this is the only version of the argument criticized by Aquinas in the Summa Theologiae, beginning from the premise that “what exists in the intellect and in the actual world (et in intellectu et in re) is greater than what exists only in the intellect.”[43] Later still, Descartes defended a version of this argument as well, with the consequence that it alone has come to represent “the ontological argument” in the minds of many of its defenders and detractors (e.g., Immanuel Kant) alike.

Here, however, I want instead to consider Bonaventure’s defense of Anselm’s second ontological argument, from the premise that perfect being includes necessary existence, which is more directly relevant to his argument in the Itinerarium that we all immediately and necessarily intuit God’s existence. In the first Disputed Question on the Mystery of the Trinity, Bonaventure writes,  “God is that than which nothing greater can be thought; but what is such that it cannot be thought not to be, more truly is, than what cannot be thought not to be: therefore, if God is that than which nothing greater can be thought, then God cannot be thought not to be.”[44] In the Summa contra Gentiles, Aquinas offers a second formulation of the ontological argument along the same lines, e.g., “Something greater than God could be thought, if he could be thought not to be.”[45] Both of these arguments descend from Anselm’s second proof in Proslogion 3:

Something can be thought to be which cannot be thought not to be, which is greater than what can be thought not to be. So, if that than which a greater cannot be thought can be thought not to be, that very thing than which a greater cannot be thought is not that than which a greater cannot be thought, which is not fitting. So then, there truly is something than which a greater cannot be thought, which is such that it cannot be thought not to be.

The key idea here, as Malcolm suggests, is that necessary existence is a distinctive sort of great-making property, and so belongs necessarily to the greatest possible being, whose existence must thus either be impossible or necessary.[46] The idea that necessary or unconditioned existence is a perfection is intuitive—fragile dishes depend on gentle handling, and otherwise identical but unbreakable objects would be greater dishes. So too, ordinary internal combustion engines are constrained by their need for fuel—an otherwise identical engine which could generate its own power without external input would be a greater engine.[47]

By progressive abstraction along these lines, we can form the idea of a being whose existence is absolutely unconditioned, depending on nothing outside itself in any respect. Such a being would be “most perfect” and “most actual,” as Bonaventure suggests in Itinerarium 5.6, since anything which possesses an admixture of potency is necessarily dependent, needing to be moved by something else which is actual in the relevant respects. And, if such a being is possible, it necessarily exists, since by definition its existence depends on nothing other than itself.

Bonaventure considers an objection to this argument: how, the objector wonders, can you say that God’s non-existence cannot be thought? It is obvious that I can assert his non-existence. And if you say that those assertions are false, then you are not saying anything more than can be said for all necessary truths, many of which are plainly dubitable.[48] (An extreme case is Fermat’s Last Theorem, which is apparently necessarily true, but known [rather than believed] to be so only by a few people in the world, and perhaps only by Andrew Wiles.)

This nicely anticipates the objection that Aquinas would lodge against this argument in the Summa Contra Gentiles, where he insists,

That [God] can be thought not to be comes, not from the imperfection or uncertainty of his being, since his being is most manifest in itself, but rather from the weakness of our intellect, which cannot behold him in himself, but [only] from his effects, and so is led to know him by reasoning.[49]

Aquinas’s candor is admirable: we cannot be immediately acquainted with God, he insists, because (as all good Aristotelians know) we can know only what is given to us in sensation; we know God only remotely, by reasoning from his effects.

Bonaventure’s response to this objection is strikingly similar to Malcolm’s interpretation of Anselm’s second ontological argument: it is not that we cannot form the thought, “God does not exist,” but rather that:

His existence is so evident in itself and certain for the knower, that if he would rightly consider it, there is no way for its truth to be removed. For it is a truth most evident and most present, which is absent from no place, no time, no thought, which is not the case with other created truths.[50]

The reason that God cannot coherently be thought not to exist, is that if he exists at all, he exists in such a way that his existence is totally unconditioned by anything else, but rather conditions everything else. It is the uninflected “to be” at the heart of every statement with existential import, and so accompanies every thought, even the thought, “There is no God.” Only the fool can form this thought, because only a fool would contradict himself in his very act of speaking.

Bonaventure gives us good reasons to think that, contrary to the twenty-second Thomistic thesis, we do in fact perceive by an immediate intuition that God exists, and also prove it a priori. He recognized that his arguments on this score were distinctively Platonic in sensibility, and so opposed to the faddish Aristotelianism which was then overtaking the theological academy. He was also insistent, however, that his deepest loyalties were to the Church’s own distinctive intellectual traditions, particularly as he received them from Augustine and Anselm.

In a famous passage from his sermon, “Christ the One Teacher of All,” for instance, Bonaventure exalts Augustine above the Academy and the Lyceum alike: “Thus it seems that among philosophers, to Plato was given discourse on wisdom, but to Aristotle, discourse on knowledge. For the one looked to higher things, but the other principally to lower. But discourse on both, namely wisdom and knowledge, was given to Augustine.”[51]

Ad Mentem Thomae?

Even if you have somehow made it this far without being converted to illuminationism and the truth of the ontological argument, this exercise has a broader value. It illustrates, above all, the importance of reading something other than Aquinas. This is crucial in the first instance because the Common Doctor was wrong about many things. It is even possible—Gilson’s bizarre confidence notwithstanding—to contradict him in matters theological. Bonaventure certainly had no compunction about doing so, and he too is a Doctor of the Church.

But even for Thomists of the strict observance, it is important to recognize those who only know Aquinas do not even know him. To understand Aquinas’s thought—to reason “ad mentem Thomae”—requires recognizing it as a complex and shifting, albeit often implicit, debate with his contemporaries. Only from the perspective of scholastic theology as a whole can we grasp Aquinas’s true, undeniable genius—and his real limitations.