By JOHN BRUNGARDT, Ph.D.

John F. X. Knasas, Thomistic Existentialism & Cosmological Reasoning. Washington, DC: Catholic University of America Press, 2019. 329 pp.; hardback, $65.00, ISBN: 9780813231853 (link)

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“St. Thomas reconciles intelligence and mystery at the heart of being, at the heart of existence. And by this means he sets free our intellect; he returns it to its own nature in returning it to its object.” – Jacques Maritain (1948, p. 224)

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Avicenna recounts that, in his attempt to understand the Metaphysics, he reread the text some “forty times and consequently memorized it.” (Gutas 2014, p. 16) Yet he still could not grasp Aristotle’s meaning. He began to despair of ever understanding the book, until he found a copy of al-Farabi’s On the Purposes of the Metaphysics, which was the golden key that unlocked the Stagirite’s mind for Avicenna.

In Thomistic Existentialism & Cosmological Reasoning, Dr. John F. X. Knasas, Professor Emeritus at the University of St. Thomas in Houston, proposes his own golden key for unlocking the depths of Aquinas’s various arguments for the existence of God:

Among younger scholars of Aquinas there is some renewed interest in the De Ente reasoning and the notion of esse that it contains. By illustrating the value of Aquinas’s understanding of the thing’s existence as a sui generis actus or attribute of its own for classical cosmological reasoning, I hope to contribute to this momentum by reopening a path of Thomistic interpretation that flourished in the 1950s—Thomistic Existentialism. (Knasas 2019, p. 5; below, “TECR” with page numbers)

To that end, Knasas proposes as means an explanation of “the De Ente reasoning,” the twenty lines of Latin text (see Leon.48.377:127–146) in the fourth chapter of St. Thomas Aquinas’s On Being and Essence (De Ente et Essentia). Having argued for the distinction between essence and existence, and that there can be only one being whose essence is existence, St. Thomas continues with the following:

Everything that pertains to a thing, however, either is caused by the principles of its own nature, as risibility in man, or else comes from some extrinsic principle, as light in the air from the influence of the sun. Now, it cannot be that existence itself is caused by the very form or quiddity of the thing (I mean as by an efficient cause), because then the thing would be its own cause, and the thing would produce itself in existence, which is impossible. Therefore, everything the existence of which is other than its own nature has existence from another. And since everything that is through another is reduced to that which is through itself as to a first cause, there is something that is the cause of existence in all things in that this thing is existence only. Otherwise, we would have to go to infinity in causes, for everything that is not existence alone has a cause of its existence, as was said above. It is clear, therefore, that the intelligences are form and existence and have existence from the first being, which is existence alone, and this is the first cause, which is God. (source translation slightly modified)

Many of the book’s themes, interpretations, and arguments presented in the explanation of the above lines of St. Thomas are ones Knasas has developed throughout his career (The Preface to Thomistic Metaphysics in 1990, his 2003 Being and Some Twentieth-Century Thomists, as well as many articles). Indeed, much of the book’s first part consists in republications. Yet these are marshaled together along with other, new materials as parts in a new whole. Taking into consideration Knasas’s hope of inspiring a younger generation of scholars, I note that the book is not suitable as a primer on the debates about Thomistic existentialism since the mid-20th century. Yet that is not its aim. Rather, it is highly suitable for more advanced students of Thomistic philosophy or those similarly and seriously interested in the textual intricacies and natural theological importance of actus essendi in Aquinas’s thought.

In the following review-essay, I explore in some detail Knasas’s argumentation and some of its consequences. First, I will look at some of the background to the issues regarding the contemporary Thomistic schools of thought so as to set forth what is at stake in the debate (§1). Then, I consider the scope and overall argumentative structure of the work (§2). Following that, the next several sections will examine the details of Knasas’s book (§§3–5). I then discuss its consequences and their criticisms, as well as further questions (§§6–7). Knasas’s latest articulation of Thomistic existentialism ought to awaken some Thomists from various dogmatic slumbers for various reasons. Indeed, it has helped me to see more clearly what is at stake in taking both Thomistic metaphysics and Thomistic natural philosophy seriously as speculative habitus, not merely as historical studies, and the challenges such clarity reveals.

1. What Is At Stake

The general school of Thomism which Knasas’s book seeks to defend, existentialist Thomism, arose from the work of Thomists such as Jacques Maritain (e.g., see Existence and the Existent), Etienne Gilson (e.g., Being and Some Philosophers), Joseph Owens (e.g., An Elementary Christian Metaphysics), and their students. One scholar summarizes this approach as follows:

Thus, according to Existential Thomism, although Aristotle’s metaphysics is a metaphysics of Being as Being, for him “Being” is nothing more than substance actualized by essential form. For Aquinas, by contrast, metaphysics is about “Being as Being” in the sense of esse, “to be,” actus essendi, “existential act.” God is Pure Act, the One Who Is, and creatures must be understood as participants in that “to be.” Our knowledge of this “to be,” moreover, cannot be intuitive or conceptual, but must be through an existential judgment that asserts real existence but leaves the plenitude of “Being as such” as a mystery that transcends adequate conceptualization. (Ashley 2006, p. 50)

That is, in contrast to the proffered interpretation of Aristotle, in which the analysis of “being” terminates in act and potency, the Thomistic existentialist analysis of being proceeds further to a real distinction between essence and existence (esse, the act of existence). However, since this is a thesis common to all Thomists, what makes the existentialist approach different, apart from a matter of emphasis?

Ashley’s summary is helpful in this respect, that from it one can begin to see why debates about the nature of metaphysics so frequently characterize the discussion between Thomistic existentialists and their interlocutors. Some of the main fault lines here regard the meaning of “being as being,” how the mind becomes aware of or discovers this notion, and whether finding answers to such questions requires the philosophy of nature prior to metaphysics, and how all three of these affect the possibility and structure of proofs for the existence of God.

Thus, St. Thomas will often say that being is that which falls first into the intellect, but at the same time being as such is the subject-matter of metaphysics, which part of speculative philosophy is the last to be learned, and to which falls the philosophical contemplation of God. Within this latter contemplative order, the previously discovered or realized notion of being (ratio entis) is a necessary condition for elaborating an account of the Divine Names; whether or to what degree actus essendi as an aspect of the notion of being is sufficient in this realm is part of the debate. How does one explain our ability to grasp being as such? What is grasped when we do so, and when? How does this help us to achieve the intellectual habit of metaphysics, that is, as a “science” to use the old terminology, a habitus specifically different from natural philosophy, the study of changeable being (and thus, not being as such)? How are these grounds for metaphysics to be self-referentially defended by one’s account of the possibility of human knowledge? Clearly, therefore, the stakes are high.

Knasas, a student of Joseph Owens, recognizes this. Thomistic Existentialism & Cosmological Reasoning takes Knasas’s version of Thomistic existentialism to the limit to work out the logically demanded interpretation of St. Thomas’s viae to God, given the elements of Knasas’s view of the act of existence as the fundamental, non-formal act of being, as opposed to the fundamental but formal act of being, a view defended by others, including the so-called “Aristotelian Thomists” who emphasize the essential priority of natural philosophy to metaphysics, among other points. In a previous book, Knasas highlighted the debate between these Thomistic schools of thought:

[T]o know any commonality is not automatically to know its definition, or fundamental description. Hence, to intellect being, the ratio entis, is not automatically to know how it should be defined. As Gilson shows in Being and Some Philosophers, throughout the history of philosophy thinkers have disagreed on how fundamentally to understand being. The same is true of the Neo-Thomists. For great lengths of philosophizing, if not exclusively, the Aristotelian Thomists, like those of the River Forest Dominicans: for example James Weisheipl, William Wallace, Vincent Smith, and Benedict Ashley, will insist on a definition in terms of formal act. On the other hand, Existential Thomists such as Etienne Gilson and Jacques Maritain, without denying formal act, will insist upon a definition in terms of non-formal existential act. True to their epistemology of transcendental concepts, neither of these Neo-Thomist camps [the Aristotelian and the Existentialist Thomists] believe that their differing definitions of being could both be right. Taken as fundamental descriptions, one has to be correct and the other incorrect. Among their scattered and reduced disciples, the debate continues. (Knasas 2003, p. 9–10)

Here, then, is how the emphasis of existentialist Thomism yields a real divide of opinion: is being to be most formally understood in terms of a formal act or some further, non-formal existential act that the competing interpretation cannot reach? If the latter, what does this imply about the science of metaphysics or its approach, as natural theology, to the existence of God? While Knasas’s book addresses these questions, its focus is especially the second.

2. The Scope and Overall Argumentative Structure

Knasas frames his inquiry in Thomistic Existentialism & Cosmological Reasoning with Leibniz’s “classical” (defined as pre-Kantian) cosmological question and proof of God’s existence (TECR, 1–2; see also 9–30 and 311–14). Since Leibniz’s conception of existence is “remarkably shallow” (2), Thomistic existentialism must provide the necessary depth. However, the motivation that structures the book is the fact that “the most persistent critics of Existential Thomism are other Thomists” (3). The most important criticism, says Knasas, is that the claimed centrality of esse in Aquinas’ metaphysics fails to appear in the most central Thomistic viae to God—such as the Five Ways in the Summa Theologiae or their variants in other texts—thus undermining the claim.

To answer this criticism, Knasas advances two arguments he claims are new: first, that Thomistic existentialism must defend its interpretation of the Thomistic viae by defending the view that traveling all such viae belong properly to the metaphysician; second, that the De Ente reasoning has two versions, the stated reasoning in the text and a more robust version: “To deal with the apparent absence of the metaphysics of esse in Aquinas’s viae, Existential Thomism needs to acknowledge a more robust version of the De Ente reasoning” (4–5). This would explain how Thomistic Existentialism can borrow from other arguments for the existence of God without losing its existentialist character.

The book has two parts. The first part (chs. 1–5) argues “that Aquinas’s De Ente reasoning possesses sufficient logic to be a proof for a first cause of existence” (173), and thus lays the groundwork for elaborating the two arguments answering the critics of Thomistic existentialism in the work’s second part (chs. 6–11). Knasas’s concern in the second part is “more historical” yet not without philosophical implications: “Aquinas’s proofs for God are in fact the De Ente reasoning in different guises” (173). Once Knasas’s argumentation has run its course, then, the De Ente reasoning is no longer “camouflaged in the viae” (4), for “Aquinas is not intending to camouflage his reasoning” but merely show it in various venues or in different garb (292–93). Indeed, the second part of the book could be seen as a reply, and more, to Oliva Blanchette’s remark that “no one else [besides Knasas] is willing to say that the argument in De Ente et Essentia is a proof like those in either one of the Summae” (2004, p. 152).

3. The Essence of the De Ente Reasoning

The main lines of these two arcs of argumentation are as follows. Chapter 1 examines Leibniz’s cosmological arguments for the existence of God from the world’s contingency and their famous criticism by Kant, who claimed that being or existence is not a predicate. Since, as mentioned above, Leibniz’s conception of existence is “remarkably shallow” (2; see 14–15, 25–26), it requires rethinking. Knasas maintains that existence can be a predicate, that Thomistic versions of cosmological reasoning ought not rely upon a principle of sufficient reason, and that encountering the Leibnizian arguments “forces us to begin thinking through what we mean by the thing’s existence” (29) and to seek “a more carefully wrought understanding of existence” (30).

3.1. The two key elements, in Chapter 2

Chapter 2 presents the De Ente reasoning which contains the essentials of that more carefully constructed understanding (most of the chapter is taken from Knasas 2014). The remaining chapters of Part I defend Knasas’s interpretation against various objections, both interpretive and philosophical. The interpretative and philosophical claims of Chapter 2  involve two key elements that function as the logical sine qua non of the entire book. These elements are presented and then defended against alternate interpretations, after which Knasas considers how the passage of the De Ente in question provides an argument for the ultimate cause of esse, thus completing the exposition of the twenty lines of De Ente, ch. 4, as an argument for God’s existence. 

The two key elements, then, deserve comment. The first: Knasas emphasizes that the De Ente reasoning is not content with a “factual” reading of existence. That is, “Aquinas insists that the fact-sense [of the thing’s existence] be deepened to include the act in virtue of which the thing is a fact. A thing is a fact in virtue of its actus essendi.” (36) The question, then, is exactly how to understand actus essendi. Knasas’s answer is as follows:

In respect to the substance rendered a being by composition with esse, esse is prior (prius), first (primus), most profound (profundius) and most intimate (magis intimum). Esse is the core around which the thing revolves. It is like the hole of a doughnut. Just as the hole is outside the doughnut yet “inside” the doughnut, so too esse is an act distinct from the thing but for all its distinctness esse is most intrinsic to the thing. (36)

This analogy—repeated on 37–38 and 309, and see also the book’s cover-art, an illustration of ST, Ia, q. 44, a. 2—is to illustrate Knasas’s key claim that actus essendi is, in a way, both “outside” and “inside” the thing. Actus essendi is both prior and posterior to the essence of which it is the act, albeit in different respects. This tracks the ability of esse to ground both the essential and accidental predication of “being” (37–38), and this “dual status of esse as both accidental and essential is guaranteed to drive analytical minds mad.” (38) Yet it is a maddening feature that Knasas must use to ground both versions of the De Ente reasoning in the second part of the book (see remarks on 104, 174, 216, and 288).

The second element is Knasas’s interpretation of Aquinas on the duplex operatio intellectus, the first and second operations of the intellect, understanding and judgment. With this, Knasas explains the basis for the understanding of esse as just indicated. To do so, he proposes a “phenomenology” about the intellectual acts in question in the texts of Aquinas describing them. The first operation is defined by the absolute consideration of an essence (42). This “absolute consideration” of an essence is an “intention-free” (44) grasp of the essence of a thing insofar as that essence is existence neutral. For the same essence is found existing in things or in the senses or in the knowing intellect (see 50–51; also 143–49 and 300–301), and so it cannot be necessary that essence exist in one mode or other. It is existence neutral.

Consider some examples provided by Knasas, in this case in the context of a discussion applying his view of existence-neutral essence and esse to modality (what is possible in view of some active or passive power, or what is possible simply speaking, or absolutely):

Considered as such the absolutely possible leads to some curious subject areas. Two examples are the annihilation of the cosmos and/or spiritual creatures. Insofar as each is existence-neutral, then absolutely speaking their non-esse is possible. . . . Likewise, I could say that a cup of coffee at two thousand degrees Fahrenheit is absolutely possible as such. The coffee is temperature neutral and so is not opposed to any temperature. But from the viewpoint of passive potency such coffee would never exist. Existing at that temperature would vaporize the coffee. (64)

The coffee analogy percolates throughout the book (51, 54, 92, 312). In these places, the analogy is to clarify that just as coffee is temperature neutral, so also is essence existence neutral. Now, how coffee is to some degree indifferent to temperature within a given range, or, to say it differently, that coffee is apt for a range of temperatures, does illustrate Knasas’s point. However, we should consider the example of ‘temperature neutral coffee’ for a moment.

That is, we should test ourselves in our thinking about essence and possibility at such an absolute level. When treating of possibility and impossibility, James Ross distinguishes between deficient conceptions, where something is revealed as impossible because the terms employed do not have a reference, and defective conceptions, where an impossibility is indicated because “its semantic content requires conflicting real necessities; . . . atomless water is impossible because of what atoms are and what water is.” (Ross 2008, p. 41) ‘Temperature neutral coffee’ is at least a deficient conception. More, if what is “absolutely impossible should be determined on the basis of an incompatibility of terms” (TECR, 64–65), then “temperature neutral coffee” seems to imply a defective conception insofar as liquidity as a state is defined by a matter’s temperature. Trying to truthfully understand “temperature neutral coffee” is like trying to truthfully understand “atomless water.” So, there is a significant difference between saying that coffee as such is temperature neutral and thus “not opposed to any temperature” and that coffee as such is apt to a natural range of temperatures. In one way, some things surely are neutral to other things in the way that Knasas requires to make his analogy work. However, the point is whether such neutrality can still obtain at the high level of generality Knasas requires, between essence and existence. (I return to this in §6.)

The second operation is what grasps the esse of the thing (44). As it is later succinctly summarized: “Judgment adds esse to what is totally existence-neutral.” (289) That is, the twofold operation of the intellect grounds the proto-abstraction of existentially neutral essences from a given individual in the first operation, thus making room for the precise realization and role of the existential act by the second operation. As Knasas observes, the astonishing feature of the first is that “it amounts to doing the prima facie oxymoronic task of considering what in itself is nothing” (53), namely, the existence-neutral essence of the individual drawn from “the rich context of the data” of sensed material objects (44). Yet, as the oft-debated line famously reads, the second operation respicit esse rei—“looks at . . . the existence of the thing” (39)—and thus the intellect “moves from the thing as existence-neutral to the thing as really existing.” (54) Both are required to properly see how esse is that “addition to the individual that renders the individual a fact or existent.” (54) This is the esse that is both an attribute of the thing and its existential core (see also 124 and fn. 41).

3.2. Knasas’s defense of his interpretation

The explanation of the De Ente’s compressed cosmological reasoning, on Knasas’s interpretation, requires both of these elements. Chapters 3 through 5 defend Knasas’s interpretation and, along the way, elaborate some points of detail. The sequence of objections and replies Knasas presents is as relentless as it is broad. Chapter 3 is a defense against various “Neo-Thomist” alternatives; Chapter 4 considers difficulties raised by analytic Thomists and others; Chapter 5 features objections against cosmological reasoning more generally.

In Chapter 3, Knasas counters claims that the De Ente passage does not present a via to God (contra Etienne Gilson and Armand Maurer), engages in the debate over how the real distinction between essence and existence is established in the passage or whether presupposed (contra John Wippel, Scott MacDonald, Lawrence Dewan, and John Cahalan), and addresses texts of Aquinas that speak of form or essence as the cause of esse. Chapter 4 argues against analytic Thomists’s troubles, among others, and sees Knasas engaging with Peter Geach, Brian Davies, and Anthony Kenny. Chapter 5 features six objections: 1) whether existence can be an attribute, featuring another appearance by Kant with a large cast of guest stars; 2) Knasas’s defense of the sense realism required to motivate the grasp of esse as distinct from existentially-neutral essences; 3) whether the scope of explanation in the De Ente reasoning requires appeal to the principle of sufficient reason or starts with the world as a whole (it does not, unlike the Leibnizian counterpart); 4) whether arguing against the possibility of an infinite regress is required by the core De Ente reasoning (it is not); 5) a brief consideration of the problem of evil; and 6) a brief consideration of Heideggerian onto-theological objections.

Much in these replies is insightful for any student of St. Thomas. Since the second half of the book features many intramural school debates, however, it is worth noting the last objection just mentioned from Chapter 3. “Some think,” Knasas writes, “that the priority of esse is contradicted by other texts that speak of forma as a cause of esse.” (99) No one is named. However, from his later critique of Geach and references there—see 108, fn. 10, and 95, fn. 60—views like those held by Geach, Davies, or Ralph McInerny seem to be meant. After citing various texts where Aquinas speaks about the essence as a cause of existence, Knasas derives his resolution to the dilemma by returning to his interpretation of the duplex operatio intellectus, “truly the mental furnace in which Aquinas hammers out his basic metaphysical ideas.” (102) 

He turns to a passage in St. Thomas’s commentary on the Metaphysics, Book IV, lect. 2, where Aquinas is commenting on an argument that “being” and “one” are convertible. Avicenna’s account of “being” and “one” undermine this convertibility by claiming that “the terms being and one do not signify a thing’s substance but something added to it. He said this of being because, in the case of anything that derives its existence from something else, the existence of such a thing must differ from its substance or essence.” (n. 556 [unum et ens non significant substantiam rei, sed significant aliquid additum. Et de ente quidem hoc dicebat, quia in qualibet re quae habet esse ab alio, aliud est esse rei, et substantia sive essentia eius]) Aquinas presents his own view in n. 558:

Even though a thing’s existence is other than its essence, it should not be understood to be something added to its essence after the manner of an accident, but something established, as it were, by the principles of the essence. Hence the term being, which is applied to a thing by reason of its very existence, designates the same thing as the term which is applied to it by reason of its essence. [Esse enim rei quamvis sit aliud ab eius essentia, non tamen est intelligendum quod sit aliquod superadditum ad modum accidentis, sed quasi constituitur per principia essentiae. Et ideo hoc nomen ens quod imponitur ab ipso esse, significat idem cum nomine quod imponitur ab ipsa essentia.] (St. Thomas, In Meta., IV, lect. 2, n. 558; Rowan translation)

If McInerny is indeed one of the “some” included in this section, then we should look at his interpretation of this text:

Ens is imposed to signify from esse; the thing is denominated a being from its existence. However, although esse is other than essence it is not another nature but the very actuality of the essence, an actuality which is as it were constituted by the principles of the essence. . . . [Unlike accidental denomination,] when a thing is called ens, it is denominated from the actuality of what it is. The thing is what is denominated and since the id a quo is not an accidental nature the thing is not denominated ens through some added nature. That is why ens like unum is predicated in quid of that of which it is said. (McInerny 1986 [1959], 224–25)

For McInerny, as for Knasas, the problem here is how to avoid the result—were esse something superadded in the mode of a categorical accident, as Avicenna contends—that ens and unum would turn out to be non-convertible terms, given that it is substance which is most of all a being (see ibid., 216–24). Nor, McInerny contends, could one ever say that “being is what exists” is an essential predication; it would always be accidental to the ratio entis that “being exists.” But this is an essential predication because a being (ens) is so called from the very actuality of its essence.

A solution like McInerny’s, however, is too Averroistic for Knasas (see TECR, p. 34 and fn. 5), because it does not sufficiently separate the essence from its act of existence. For Knasas, by contrast, Aquinas distinguishes between a substance and a being to a sufficient degree that a different solution suggests itself (see 100–101, interpreting SCG II.54, a text later brought up against McInerny for similar reasons at 308–309). That is, esse as the act of a substance is the act of the constitutive principles of that substance’s essence, and thus “essence . . . is a total and complete potency” (102; see also 309: “as thoroughly existence-neutral, the subject of esse is an absolute passive potency for the esse”).

For either McInerny or Knasas, one would then reason as follows: essence as potency would limit existence as act, explaining how form is a cause of esse qua subject; further, standing to each other as potency to act, essence and existence compose a true unity, preserving the convertibility of ens and unum. Yet the “routes” to this solution differ as indicated earlier: McInerny emphasizes that even existence is a formal act, whereas Knasas’s view employs esse as a non-formal existential act.

As a consequence of his reading, Knasas maintains that Aquinas “navigates between both Avicenna and Averroes in virtue of his existence-neutral understanding of essence in the essence/esse distinction. . . . Essence as abstraction ad quodlibet esse makes intelligible Aquinas’s position against both Averroes and Avicenna.” (103) Indeed, it does more than make Knasas’s reading of Aquinas position intelligible, “It is crucial philosophically. The consideration of a thing as existence-neutral is the sine qua non for judgment going on to grasp the esse rei as profundius and magis intimum.” (311)

Hence the central role of the two elements from Chapter 2, noted above. They are emphasized again at the close of Chapter 3 (104–105), for the reason that the priority of esse grounds the “short” version of the De Ente reasoning to God’s existence, while the quasi-causality of esse by form or essence as subject of esse grounds the “longer” version of the De Ente reasoning, for “any conditions for the presence of form in matter become conditions for the esse.” (104) 

4. Constructing the Longer, More Robust De Ente Reasoning

The first two chapters of Part II’s defense of the presence of the De Ente reasoning in other of Aquinas’s proofs for God’s existence aim to accomplish the following. First, Knasas argues in Chapter 6 that, according to Aquinas, only metaphysics can prove the existence of God. Chapter 7, following upon the two ways in which esse is considered in relation to essence (as either prior or posterior), Knasas explains the “longer” form of the De Ente reasoning which arises from the second way of considering esse. Together, these chapters are the foundation interpreting the other Thomistic viae to God as various guises or venues for the De Ente reasoning (chs. 8–11).

Analogous to Chapter 2, then, Chapters 6 and 7 defend the key ideas that Knasas requires so that the argument of Part II might have any purchase. This is illustrated by a comment early in Chapter 8:

But there will be no turning back from my earlier conclusion that Aquinas would be schizophrenic to write viae intended to be philosophically cogent apart from the textually verifiable thesis that the philosopher proves God’s existence in metaphysics. Moreover, doing otherwise would make the viae purely arguments of natural philosophy. That approach would commit Aquinas to the heretical position of proving the eternity of the world and of motion, and it would confine the reasoning to the material universe as Aquinas admits at ST I, q. 44, a. 2. (217)

The first sentence of the above refers to Chapter 6, and a key condition of the cogency of the “more robust” De Ente reasoning from Chapter 7 is described in the remainder.

Chapter 6, then, claims the proofs for God’s existence as an absolute Thomistic metaphysical right. Knasas marshals his evidence from across St. Thomas’s texts, providing the following helpful summary:

First, at In de Trin., q. 5, a. 4, co., Aquinas has the philosopher reaching both God and the separate substances only (nisi prout) in metaphysics. Second, at the beginning of his Summa contra Gentiles, Aquinas reserves knowledge of God’s existence to the last part of philosophy—metaphysics. Third, at ST I, q. 44, a. 2, co., Aquinas understands matter/form reasoning as getting the philosopher to a celestial body only. The philosopher proceeds further, not by extending natural philosophy reasoning, but by grasping the esse of the sensible thing—ens inquantum ens. Fourth, at SCG I.20, the argument for the immateriality of the mover of the celestial spheres from the eternity of motion begins from the “supposition” of the eternity of motion. But in natural philosophy the eternity of motion is a strict conclusion. Aquinas’s suppositional way of speaking indicates a metaphysics already in place. Fifth, In II Phys. Aquinas assigns the consideration of a wholly unmoved mover to metaphysics. A remark of Aquinas from the De Anima commentary, while he is speaking of “separate substances,” repeats this assignment. Sixth, as far as I can tell, Aquinas never explicitly claims that the science of physics proves God’s existence as he so claimed for metaphysics. Texts for the former claim are ambiguous and hence only apparent. (185–86)

Many of these texts are well known to familiars of this debate. On the last claim, for instance, one might think of the famous passage in Aquinas’s commentary on Aristotle’s claim in Metaphysics, Book VI, lect. 1, at n. 1170 that “if there is no substance other than those which exist in the way that natural substances do, with which the philosophy of nature deals, the philosophy of nature will be the first science. But if there is some immobile substance, this will be prior to natural substance, and therefore the philosophy which considers this kind of substance, will be first philosophy.” (Rowan translation; see TECR 184, and fn. 20, where Knasas helpfully points out an error in Ralph McInerny’s reedition of this translation, where the last line incorrectly reads “therefore the philosophy of nature, which considers this kind of substance, will be first philosophy.”)

While Knasas admits that this text “might be” saying that “natural philosophy proves God’s existence or even gets to the immaterial substance” he finds it too ambiguous and indecisive a text, and chooses to interpret it in light of clearer texts. Yet in a question such as this, the textual ought to be subordinated to the philosophical; thus, one scholar notes that “natural philosophy concerns itself with an immaterial, immobile prime mover under its aspect of a mover, and nothing else.” (Johnson 1991, p. 105) This way of attempting to solve the debate, philosophically speaking, claims that natural philosophy attains to the existence of God not the to prejudice of metaphysics, insofar as what is attained by one ratio (or “aspect”) does not obviate the need for other rationes that are more adequate. I return to this issue briefly in §7, below.

Chapter 7 then articulates the longer or more robust version of the De Ente reasoning. It is in this chapter that Knasas backs up his claim that natural philosophy on its own is doomed to heresy. The main function of the chapter, however, is to distinguish the two versions of the De Ente reasoning by focusing on the longer one.

The first or shorter route to God “is basically the original De Ente reasoning,” as Knasas later summarizes (216). That is, one can focus on any given existent and, considering the priority of esse to that existent, one can run the argumentation to a single subsistent cause of esse. Earlier, Knasas quotes Maritain approvingly to illustrate this: “Let us but grant to a bit of moss or the smallest ant its due nature as an ontological reality, and we can no longer escape the terrifying hand that made us.” (153; quoting Maritain in Degrees of Knowledge)

The second, longer, or more robust version of the De Ente reasoning presented schematically in Chapter 7 is described as follows:

If the focus is esse’s character as the act of some nature, then a much longer path through the metaphysically appropriated reflections of the natural philosopher opens. At each point of the second path, however, the priority of some esse is waiting to be focused upon. Hence, the metaphysician need not walk the entire length of the second path to its conclusion of esse subsistens as the transfixing final cause of the separate intellectual substance that moves the first physical cause. (216; and see also 104, 174, 276–77, and 288)

The robust version, then, is meant to map “the intelligible topography” (215) for all other viae by both borrowing from natural philosophy and certain metaphysical excursions. But the shorter route (the priority of esse to its subject) is always standing ready in the background.

To plot that map, Knasas’s textual theodolite fixes upon the three stages of philosophical inquiry found in ST, Ia, q. 44, a. 2, c. (from a materialist notion of being, to being as existing in composite substances, to being as being). What the metaphysician can borrow from the natural philosopher are the lines of reasoning found in causal explorations of the second stage. 

Here, Knasas looks to argumentation, like that of the De Principiis Naturae, ch. 3, that defends the necessity of agent causes of the coming into being of composite substances (192–96). This sequence of agent causes initiates the more robust path. Some Thomists, to their detriment, focus solely upon the “vertical” causality of simultaneous agents (Vincent E. Smith, Benedict Ashley, and John Quinn; see 196–99). The key here, Knasas argues, is to see the problem of a threatening horizontal regress of agent causes eternally back through time (193; more on this below). The impossibility of a horizontal regress of physical agents to explain itself forces the natural philosopher “to move vertically to a nongenerable body in whose continuous motion the eternal series of generations takes place.” (194; see also 231) That is, natural philosophy in its general mode can prove the existence of, but not empirically identify, some physical primum mobile (195–96), and that is where it stops. This concludes the second stage of ST, Ia, q. 44, a. 2. (Note: This conclusion of the natural philosopher would not prevent him, Knasas maintains, from going on to conclude that such a first moved mover is eternal and thus motion is eternal.)

After the end of the second stage, a “web of reflections” (205) is now available to the Thomistic Existentialist metaphysician. This third stage could consider the first moved mover and the priority of its esse and return to the De Ente reasoning (201). Or, the metaphysician could consider agent cause of the first moved mover, which must be a non-bodily agent, and how the priority of esse is found in the cognition and volition of such a soul or intelligence/angel (201–205). Or, the consideration of the esse of accidents or motion can provide another version of the more robust path (205–215). These latter two are the ways in which the various viae to God camouflage the De Ente reasoning at greater length.

Here we should pause for comment on some details of this longer route. Knasas’s construction of this longer path for the De Ente reasoning requires both (a) an already-in-place metaphysics and (b) separation of metaphysics from the limitations of natural philosophy. The limitations of natural philosophy, Knasas claims, are not only that it cannot discuss the existence of God in any way (Chapter 6). Worse still, “absent metaphysics, the first argument for motion’s eternity is a strict demonstration.” (180) (Here, the “first argument” is Aristotle’s argument in Physics VIII.1 (251a9–b10; see St. Thomas, In Phys., lib. VIII, lect. 2, which argues from the nature of motion itself. The first argument, in short, is that motion must be eternal because any attempt to start motion implies a prior motion and its mobile; the second argument, at 251b10–b29, is from time.)

That is, if there were no separately established metaphysics, then natural philosophy would lead to heresy (see 217). Elsewhere, Knasas calls the natural philosopher’s argument for the eternity of motion “a strict conclusion” (186), a necessary conclusion (195), “a necessary plateau in physical reasoning to a first mover” (197, and see 259); the natural philosopher grasps motion’s eternity “not just as a possibility but as a fact” (198), a result endorsed “necessarily” (201), a result he “cannot avoid” (222, see also 265), a “strict demonstration” or argument “with demonstrative status” (234) as long as the argument is run sans an already-in-place metaphysics of esse. This is the reason, Knasas continues to insist, that the threat of a horizontal regress of agent causes must be dealt with. Aquinas can see this supposed demonstration of the natural philosopher as a supposition because of an independent metaphysical insight, namely the possibility of an agent cause of existence rather than mere becoming (see 232–36). 

Absent from this analysis, however, is an interesting comment of St. Thomas’ on a peculiar capacity of the arguments from motion and from time in the Physics. Having just referred to these very arguments of Aristotle’s, he says:

But if one rightly considers the arguments posited here, the truth of the faith cannot be attacked efficaciously by arguments of such a sort. For arguments of this sort are effective in proving that motion did not begin by way of nature, as posited by some. [Sed si quis recte rationes hic positas consideret, huiusmodi rationibus veritas fidei efficaciter impugnari non potest. Sunt enim huiusmodi rationes efficaces ad probandum quod motus non inceperit per viam naturae, sicut ab aliquibus ponebatur.] (In Phys., lib. VIII, lect. 2, Leon.2.371, n. 17, my translation; see Rowan ed. n. 987)

St. Thomas does go on to discuss what is focused on by Knasas, namely of a creative cause of being as such (nn. 987–88). However, before that, the comment just quoted is making an additional point about Aristotle’s arguments (rationes hic positas or huiusmodi rationes). One might read the rationes hic positas as the arguments about to be given by St. Thomas concerning creation. Still, to keep the continuity of meaning, the “arguments of such a sort” that might seem to impugn the faith are the ones that St. Thomas asks the reader to “rightly consider,” and just after that, to consider these given individual illations (singulas illationes) of Aristotle. That is, the logic of Aristotle’s arguments need closer inspection.

St. Thomas did this for the argument from time in n. 983 (Leon.2.370, n. 13). In short, Aristotle’s argument begs the question. Aristotle assumes that every “now” is a middle (see 251b20), that is, every now is an intermediate, both a beginning and an end, and so there must be time before any now, and consequently the subject of time, i.e., something in motion. So, motion is eternal by this composition of now’s. However, it is not of the nature of a point or a now to be a middle, St. Thomas argues, and so the eternity of time or motion does not follow from such an argument any more than it would follow “that every line is infinite because every point is a beginning and an end.” (Rowan translation, n. 983) This exposition of the weakness of the argument from a logical point of view shows that more than a metaphysical critique is possible.

Likewise, a logical critique of the argument attempting to prove the eternity of motion from the nature of motion itself is possible. This would complete the Thomistic case qua philosophical refutation insofar as it would show where the opposing view reasons poorly, and not merely how its conclusion can be opposed by different grounds (for to refute a conclusion is not to refute an argument). Consequently, I add that an analogous logical fallacy is present in the argument from motion, namely, a fallacy of composition by imagining that any given substance must necessarily be a “middle” between a generating predecessor and a generated successor. Just as it does not follow that every line is infinite upon the premise that every point is a beginning and an end, so also it does not follow that time is infinite from the premise that every “now” of time is a beginning and an end, and so also it does not follow that motion is infinite from the premise that every motion belongs to a “middle” mover. The fallacy of composition in each case leads to begging the question.

Seeing that there is a fallacy of composition is enough to undermine demonstrative confidence in both Aristotelian arguments. Note how this coheres with the metaphysical argument propounding the opposing case. Were there no logical fallacy of composition here, creation with a beginning in time would be absolutely impossible, like undoing yesterday or making an irrational man, since such a creative act would violate the purportedly “intermediate” nature of substances. Thus, one can correctly add the a metaphysical argument allows us to see the possibility of a beginning of time, but the logical analysis suffices to see that the argument itself does not work.

So, while metaphysics is needed to explain in a positive way the type of causation that is prior to that of natural causes, only logic is required to see that these natural philosophical arguments do not conclude with necessity. This avoids the excessively brutal result that a philosopher who subjectively does not know of metaphysics would somehow inexorably reach a strictly demonstrated conclusion that is also false, for that is a contradiction in terms, as a strict demonstration must reach a true conclusion from true premises (see Posterior Analytics, I.2, 71b20–24). Such a natural philosopher might falsely take it to be true. His logician-friend objects, we might imagine: “Yet you cannot explain motion as such by more motion temporally prior to it, for this is question begging.” The natural philosopher, realizing his logical mistake, would be unable, qua natural philosopher, to give any positive alternative, yet the failure of the demonstrations he was trying to construct would indicate to him in a negative way “that motion did not begin by way of nature” as St. Thomas says (n. 987). He would be left wondering how exactly motion does exist, and thus begin his search for a knowledge beyond physics, which is what Knasas’s analysis requires as a result anyways.

5. Aquinas’s One and Many Ways to God

Chapters 8–11 present Knasas’s interpretation of St. Thomas’s various proofs for God’s existence in light of the reasoning of Chapters 6 and 7. The argumentation here, while detailed, is well prepared by the “intelligible topography” mapped out in Chapter 7. Knasas considers the via in both Summa contra Gentiles (Chapter 8) and Summa Theologiae and the Compendium (Chapter 9), as well as various other texts (from the Scriptum, the De Potentia, and those in the prologue to Super Ioannem; see Chapter 10). The challenge here consists “in discerning which path and/or which combination of paths is being mapped out in any particular via,” that is, the shorter or the longer path (217). Knasas answers with close textual analyses of the viae. Some viae can be read along both paths, others are merely the short path or the long path in disguise.

For instance, the first proof from motion in the Summa contra Gentiles or the Prima Via of the Summa Theologiae can be read according to either path, depending upon at which point in the argumentation the priority of the esse to its subject is considered (220–21, 253–54). One could focus more immediately upon the priority of esse to the “first mover” that the argument reaches in the Summa contra Gentiles, or one could take the longer path and work through, by process of elimination, all possible lower, qualifiedly first movers, like outermost sphere souls or angels. The Secunda Via does not use the longer path (259), while the Tertia Via can be read as taking either the more direct or the more metaphysically circuitous route (263–64). But these are just some of the cases. Unwrapping each via, Knasas finds underneath either the shorter or the longer variants of the same De Ente reasoning based upon judgmentally grasped esse of existentially neutral essences.

The second part concludes by answering various questions that still remain about this way of reading the many viae as one. Here are the first two: Why didn’t Aquinas just clearly present the other viae while openly averting to the De Ente reasoning? If the De Ente reasoning, which includes already the simplicity of subsistent esse, is behind all the viae, why does Aquinas treat the identity of essence and existence of God as a separate question in the Summae?

Taking the success of Chapter 6–10 as a given, Knasas answers that Aquinas’s own reasons for writing in this way may never be known (291). However, the answers to the first two questions are that Aquinas’s theological genre is the reason for presenting multiple guises of the De Ente argument—292: “Hence, while a philosopher might be content to deal with the an sit of God by giving the De Ente proof, a theologian in fidelity to his vocation might want to multiply the arguments so that where one fails another works”—as well as separating the question of God’s existence and His simplicity (295). The commanding interpretive lens fashioned by the De Ente reasoning, then, allows Knasas to conclude overall that Aquinas offers a novel and superior path of cosmological reasoning to the existence of God.

6. Knasas and Some 21st-Century Thomistic Critics

I now wish to discuss two points. The first involves two critiques of Knasas’s positions raised by other Thomists, and then a question for readers of the book to consider, especially Thomists concerned with Thomistic natural philosophy.

6.1. John Wippel and the subject of metaphysics

The first point concerns the sine qua non of Knasas’s argumentation as a whole, and this must be considered in light of previous criticisms of his interpretation of Thomistic metaphysics. In a section of Chapter 6 not mentioned above, Knasas argues that assigning knowledge of God, angels, rational souls, and sensitive souls to metaphysics does not result in the circular scenario where metaphysics proves the existence of its own subject matter (186–188; Knasas had previously argued that the activity of sensation is property of metaphysics, not natural philosophy, see 183). He proposes that the traditional degrees of abstraction, the cognitive removals from matter and motion that distinguish the speculative sciences, need not be understood as an initial condition for the sciences. That is, one need only realize the proper degree of abstraction somewhere during the development of the science (186, and see 189). To initiate metaphysical inquiry, Knasas maintains that the analysis of the activity of sensation is sufficient:

Furthermore, because . . . sensation is not one of the instances of change under the subject matter of natural philosophy, then we have a multiplicity not covered by ens mobile. The multiplicity of the real and the cognitional is covered by a wider sense of ens. This wider sense is sufficiently distinct from ens mobile. Another object of science is offered. How separateness from matter is realized in a third way different from physics and mathematics should be left to the unfolding of the science. And initial requirement to rise to a third degree of abstraction is a red herring for understanding Aquinas’s approach to metaphysics. (187)

This is a long-held view of Knasas’s (developed from the work of Joseph Owens, see Knasas 2003, pp. 65–70 and its reference to Knasas 1990), and defended again as recently as 2019 in an essay that presents a bolstered defense of the view (see Cullen and Harkins, eds., The Discovery of Being and Thomas Aquinas: Philosophical and Theological Perspectives, a collection of conference papers first presented in 2011, but published just after the book under review here). The metaphysician, Knasas maintains, presuming the realization that broadens the ratio entis by attending to the multiplicity of real and cognitional being thanks to sensation, looks to habens esse, which is “what the metaphysician first works out concerning the subject matter of the science.” (TECR, p. 189)

John F. Wippel would disagree. In his essay in the Cullen and Harkins volume (see pp. 38–41), Wippel critiques the earlier versions of Knasas’s view. It is unclear that the latest iteration escapes Wippel’s criticism. In short, Wippel appeals first to St. Thomas’s approving adoption of the Aristotelian structure of a demonstrative science, including the prerequisite that no science can demonstrate the existence and nature of its subject, but rather must presuppose that knowledge. Wippel also argues that Knasas’s view about the subject of metaphysics is contradicted by St. Thomas in the prooemium to his commentary on the Metaphysics, where Aquinas says that the whole science of metaphysics has as its subject what is known to be separate from matter secundum esse et secundum rationem, namely, what is attained through the abstraction also called separatio. 

In short, Wippel reads Aquinas as requiring an initial integrity of or fullness to one’s grasp of the subject matter of metaphysics, and concludes that “Knasas’s proposal should not be regarded as a defensible interpretation of Aquinas’s understanding of our discovery of the subject of metaphysics.” (Ibid., 41) This would seem to exclude that, broadly speaking, a dialectical investigation characterized as metaphysical in its subject-matter suffices as grounds for saying that one is “doing” metaphysics. One might be reasoning metaphysically in some broad sense, but not in the mode of a scientific habit of metaphysics. Knasas’s proposal, by contrast, is that being as habens esse is that with which the metaphysician initiates his science, only later fully realizing the immaterial account of ens commune. So, his approach, if it is to escape Wippel’s more formal reading, seems to require that “metaphysician” here be taken less strictly.

6.2. Which essence is brought into being by actus essendi?

Even if this is a satisfactory escape from Wippel’s critique, or if there is some other one, Knasas’s approach to the subject-matter of metaphysics requires as its sine qua non his interpretation of Aquinas’s twofold operation of the intellect. The first operation, drawing from the data of sensation, attains in its absolute consideration the existential neutrality of essence, to which the second operation integrates the esse of the being: “Judgment adds esse to what is totally existence-neutral.” (289) It is Knasas’s view of cognitive realism that is the foundation here of his account of essence: “The only way in which something real could also cognitionally exist is by being of itself existence-neutral.” (301)

However, other Thomist scholars cast doubt on this understanding of essence as adequate to the task of understanding being. For instance, Gaven Kerr (2019, pp. 151–52) calls Knasas’s view of essence “too Avicennian to be Thomistic” (Knasas would of course disagree, see TECR, 310). Kerr argues that: “For Thomas the essence exists either in the thing or in the mind, it has no third state of being independent of these two. . . . Knasas maintains that there is some third state that essence can be in and which abstracts from all esse, including mental existence, thereby making it existence neutral; I myself cannot fathom what this could be unless it is some Meinongian state.” (Kerr 2019, p. 152) Instead, Kerr understands essence absolutely considered to be akin to a second intention (see Kerr 2015, p. 13 fn. 9). Again, Knasas disagrees:

[Kerr] argues that the absolute consideration of essence is the consideration of a second intention. His reason is that the “consideration” is a consideration of the mind. So, essence is in the mind. Kerr does not mention, however, that Aquinas has absolute consideration abstracting even from esse in anima. So “consideration” in absolute consideration does not mean a second intention existing in the mind. (TECR, p. 53, fn. 41)

Is this reply sufficient to answer Kerr’s critique? Kerr is not alone in finding essence in its absolute consideration an impossible subject for actus essendi. So too does Thomas M. Osborne in a 2017 article, “Which Essence Is Brought into Being by the Existential Act?”, saying: “the essence absolutely considered is an essence to which it makes no sense to attribute existence. The essence that is really distinct from existence is distinct from existence in the way that being in potency is distinct from being in act.” (Osborne 2017, p. 472) I would like to consider Osborne’s argument briefly, whose main target of criticism is Joseph Owens, although Knasas’s position is mentioned in passing (Osborne refers to Knasas’s 2014 article that serves as the majority of Chapters 2–3). Thus, Osborne might help us judge the point of contention between Kerr and Knasas.

The key distinction required to answer his article’s title question, Osborne claims, is between two types of potency, “sometimes called a distinction between objective potency and subjective potency.” (Ibid., p. 474) An objective potency “the capacity of a mere possible to be created,” whereas subjective potency is “the passive capacity in a subject that is already existing.” (Ibid.) The essence that God creates is “in potency” in the first sense (provided, as mentioned above, that such an essence is absolutely possible, i.e., not in itself an impossibility), whereas the essence that receives existence is “in potency” in the second sense. That is, Osborne maintains contra Owens, it is not essence in its absolute consideration that is receptive of existence.

According to Osborne, Owens’ mistake is to follow Suárez’s critique of certain Thomists. Suárez holds, Osborne maintains, that something cannot have a subjective potency without being in some way actual (e.g., matter). This is what Thomists would deny (again, citing matter as an example). However, “Owens rejects earlier Thomistic accounts of Thomas’s distinction between essence and existence in part because he seems to agree with Suarez’s criticism that such Thomists make essence into something that has its own actuality apart from existence.” (Ibid., 475; again, this is something that they would deny—and a contemporary example here would be McInerny’s view, outlined above.) As a consequence, essence only has objective potency to existence, and “on such [a Suarezian] account, this objective potency or logical possibility could perhaps belong to the essence absolutely considered.” This is what Osborne sees Owens as doing:

Owens seems to share Suarez’s non-Thomistic understanding of potency when he writes that “essence as ‘objective potency’ and as ‘receptive potency’ or ‘subjective potency’ coincide. The essence that receives being has no actuality whatsoever prior to the reception of being.” (Ibid., 476; the quotation is from Owens, An Elementary Christian Metaphysics, 139, fn. 20; see also 134–35 and fn. 8)

To bolster his contention, Osborne considers a pair of distinctions concerning essence from the De Ente. The first is that between essence taken with precision versus taken without precision. This is the difference between signifying a human essence with the term “humanity” as opposed to with “man.” The second distinction is the threefold Avicennian distinction also used by Knasas, between essence absolutely considered (abstracting from quolibet esse), essence in the intellect, and essence in singular things. Osborne notes that this use of Avicenna’s distinction is clearest only in early texts of St. Thomas like the De Ente and Quodlibet 8, q. 1, a. 1.

The first distinction, Osborne argues, does signify essence as entering into real composition in a substance, albeit when signified with precision by an abstract term like “humanity” the essence is signified as a part, prescinding from individuating and accidental conditions, while a concrete term like “man” signifies it as a whole, without prescinding from the nonessential. In either case, however, what is signified is the essence subject to real composition with esse in a supposit. Thus, Osborne argues that Owens is mistaken to say that “[T]he essence that is really distinct from the existence is taken non-precisively. Taken precisively, the essence can have existence only in the mind—you cannot say that Socrates or any other individual is humanity.” (Osborne 2017, 480) While it is indeed false that “Socrates is humanity,” Socrates still has humanity as a part of his whole being. That is, both abstract and concrete terms can indicate what enters into the composite being, albeit with different modes of signifying: “The difference is that the concrete term ‘man’ can have personal supposition, meaning that it can take the place of an individual, whereas the abstract ‘humanity’ always indicates an essence or formal part that inheres in such a supposit.” (Ibid., 482)

It is helpful to note the following similarity: the reason Owens gives for what he claims is a mistake (attributing the essence taken with precision to the composite) is that such an essence only exists in the mind. This is the same mistake that Osborne attributes to Owens, but in regard to the other distinction about essence: the essence absolutely considered doesn’t exist except in function of the mind’s consideration. This is because “Insofar as it is absolutely considered, an essence cannot be said to exist or not to exist.” (Ibid., 486) The role of absolute consideration includes, for instance “[making] possible the attribution of the predicate ‘rational’ to humanity apart from the existence of individual humans.” (Ibid., 494–95) It also shows the falsity of statements such as “Man as such is pale.” (Ibid., 486) But the essence absolutely considered is a second-order objective or cognitional reality, arising in function of the real or formal existence of an essence in things or in minds (human, angelic, or the Divine): “An essence exists only in the singular, in created minds, or in God. The essence absolutely considered cannot exist or not exist because it is considered as not existing. It is prior to the essence that is in our understanding, but is posterior to the essence as existing in and in some way identical to the divine mind..” (Ibid., 495)

Osborne’s exegesis further confirms this view by showing that essence as absolutely considered cannot function as the essence required by St. Thomas’s argument concerning composition of essence and existence in simple substances or angels. That is, the proper interpretation of the argument requires that the essence is a real formal part, not the essence as absolutely considered (492–93). Osborne further argues (see ibid., 496–504) that various Christological texts require that the subject of actus essendi is the supposit, formally modulated by the essential nature. This conclusion is summarized, he finds, in the following passage:

For existence pertains to the hypostasis and to the nature: to the hypostasis just as to that which has existence [sicut ad id quod habet esse]; to the nature as that by which it has existence [sicut ad id quo aliquid habet esse]; for the nature is imposed through the mode of a form, which is called being by the fact that by it something is, just as something is white by whiteness, and someone is human by humanity. (Ibid., 503; Osborne’s translation of Summa Theologiae, IIIa, q. 17, a. 2, c.)

That is, the essence that is actualized by actus essendi is that formal part by which a supposit is determined in its nature. As for the essence absolutely considered, “[it] might be said to have potency insofar as it is nonrepugnant and capable of being predicated of an existing individual, but only the essence of an existing individual enters into composition with existence.” (503)

Yet is Osborne’s criticism applicable to Knasas’s position? At first glance it seems that a consideration like Osborne’s bears out in more detail Kerr’s view of the matter. The mind can clearly consider or “take” essence in an absolute sense, but this is not sufficient to say that essence taken in such a way is that by which a being exists, the formal part by which a supposit exists. That is, essence is existentially neutral in this mode of consideration, but it is not existentially apt (a subjective potency). Kerr’s shorter and Osborne’s longer criticisms ought to be taken as follows, then, as maintaining that a view like Knasas’s, an existentially neutral account of essence, makes essence too much like non-being to be a true potency (compare Aristotle’s criticism of the Platonic view of the first underlying in Physics I.8–9). Prioritizing the intellect’s absolute consideration of essence leads to the result of giving an ontological role to an “essence” that is essentially an epistemological actor. That is, while essence absolutely considered is that which explains absolute possibility (TECR, 63–64) and by consequence objective potency, or the predication of essentially eternal truths about natures (“Man is rational”), it does not follow that such an essence is the essence that is a formal part.

If Osborne is right about Owens (that he wrongly collapses the subjective potency of essence into its objective potency, which is epistemologically grounded on essence absolutely considered qua the basis for absolute possibility), and if Knasas’s view implies a similar conflation, this would explain why actus essendi in Knasas’s account is both prior to and posterior to the very same essence in substances. It is prior as the existential “core” of the substance’s essence as objectively potential, and yet posterior to it as its existential “attribute,” constituted by the essence as subjectively potential. By contrast, according to Osborne’s proposal, essence is only a real part of a being in the second sense; the prior sense of essence “exists” only in Kerr’s Meinongian state or in function of some intellect’s consideration. Yet if Osborne’s criticism is sound and applicable to Knasas’s view, the twofold route of the De Ente reasoning founded on the priority and posteriority of esse to essence would require reconsideration. It is a necessary clarification, therefore, to work out the soundness of such a critique in more determinate detail. Can Knasas’s existentially-neutral essence really split the difference between an Averroistic reading of Aquinas (like McInerny’s, above) and the Avicennian error that all Thomists want to avoid (see above, §3.2)?

7. Thomistic Natural Philosophy Today

My second point is to raise a question and a challenge about the position elaborated in Knasas’s book.

7.1. A question about proofs of God’s existence

Recall that the first, shorter version of the De Ente reasoning achieves its goal by considering esse as prior to the existentially neutral essence of which it is the act. The second version considers esse as posterior to that essence and thus is a longer journey because natural philosophical and metaphysical resources must be expended investigating, in various ways, the causal dependencies of the beings which exist in virtue of those essences. For example, the argument to God from motion would consider the essences of agent causes of motion, along with the essence of motion.

However, to the degree that these typical philosophical viae to God become more thorough, perhaps they even become successful, and not merely in virtue of the ratio of “cause of esse.” For esse is not God’s only effect. He causes other things by causing esse, a causal power proper to God (e.g., TECR, 85, 254). Since esse is not a res, it cannot be the case that God “only” causes esse. Rather, God causes beings, and such beings have many other rationes apart from “existing” and so, as such, these are also rationes for effects of God. It seems, then, that the stronger the more robust version of the De Ente reasoning becomes, the more it demands that the metaphysician—and may even the natural philosopher—produce successful arguments for God’s existence, albeit sans the admittedly more adequate ratio of God as subsistent cause of existence.

That is, the ubiquity of the ratio of esse commune when considering the reality of things does not negate the meaning of the other rationes of God’s effects, and consequently neither does it negate the possibility of naming God as cause in virtue of those effects. Might there be, then, many really distinct ways to God’s existence just as there are many divine attributes which are not synonymous? Just as the various names of God signify the same substance, the many demonstrations of God’s existence would demonstrate the same divine substance that is its very existence, albeit under different rationes. The De Ente reasoning would still be the capstone that reveals a central ratio of God, but for all that not the hidden content of all previous viae, for they would each have their own proper rationes for God.

7.2. The challenge of Thomistic natural philosophy

Knasas’s extensive criticisms of the “Aristotelian” or “natural philosophy” Thomists and their approach to God’s existence can be used to shed light on the challenge Thomistic natural philosophy faces today. Any future such Thomist must take into consideration and respond to arguments such as Knasas’s when claiming that Thomistic natural philosophy as a distinct part of speculative philosophy is still possible. Why is this?

Knasas states that the robust De Ente reasoning has metaphysics borrowing from what natural philosophy discovers by hylomorphic analyses of changing being (190), like those found in the Physics. However, as correctly Knasas points out, not all that is contained in the Physics is strict natural philosophy (182). Indeed, even Aristotle notes that Book I do not belong to the natural philosopher as such (185a1–20), and Knasas’s view requires that Book VIII is mixed up with metaphysics. Further, setting out the principles of the science of nature and the basic definitions of those principles (Books II–IV) cannot belong to natural philosophy qua science, for a science accepts the existence of its basic principles (see St. Thomas, In Post. An., lib. I, lect. 18, n. 10). The natural philosopher as such could only clarify their nature in a rational mode that is more dialectical, and thus distinct from a properly demonstrative procedure (this is the second way of proceeding rationabiliter in Super Boetium de Trinitate, q. 6, a. 1, c., ad 1am q.). 

This leaves the full or complete defense of such principles to first philosophy, as St. Thomas teaches in the reply at SBDT, q. 5, a. 1, ad 9. Thus, there is an apparent danger that natural philosophy might lose its useful pedagogical place and preparatory function that Knasas requires. Does it have anything more to give metaphysics?

St. Thomas does lay out a pedagogical role for natural philosophy in that same ad 9um, adding that from sensible things natural philosophy arrives at a knowledge of the first causes. Is this something it offers to metaphysics? If so, on Knasas’s reading, none of those first causes can be God, as natural philosophy Thomists aver, even God known under the ratio of first mover. This possibility seems to be suggested in SBDT, q. 5, a. 2, obj. & ad 3, where the objector argues that natural philosophy in fact considers things that are entirely free of matter (immunis ab omni materia), because natural philosophy considers the first mover. However, Knasas forecloses the suggestion that God is meant here by arguing that the “first mover” Aquinas claims as the terminus of natural philosophical inquiry is the outermost celestial sphere, the first moved mover, which is free of all terrestrial matter (176–77). This is not a new view of Knasas’s. It was first elaborated in the context of an extensive debate with Mark F. Johnson (see Knasas 1988, Johnson 1989, Knasas 1990 and Johnson 1991, and Johnson 1990 and Knasas 1991).

Taking all this into account, the contemporary student of Thomistic natural philosophy faces the following danger. On the one hand, it seems that his beginnings are fully defended only by metaphysics. For this reason, some, like Edward Feser, even make natural philosophy a part or sub-domain of metaphysics, consequently dividing the philosophy of nature as part of metaphysics from the natural sciences. Such a view would seem eliminate Knasas’s requisite, natural philosophy as an independent source from which to borrows for the longer De Ente reasoning. Also, taking this approach, a beginning student may become habituated to thinking only in putatively metaphysical generalities, thinking he is formally doing metaphysics. On the other hand, historically speaking, St. Thomas’s natural philosophy can only instantiate its general, ultimate explanations with falsities (the celestial spheres), and both historically and philosophically, according to Knasas, natural philosophy can only explain motion by terminating its inquiries with a first thing also subject to motion (the physical, first moved mover). So, is contemporary Thomistic natural philosophy tout court now without its own proper, dialectical beginning and its own true end precisely as an integral science, as a speculative habitus of the soul? If so, then students especially face the danger of taking an apparently easy, apparently metaphysical beginning to natural philosophy, while not bothering to search for ultimate explanations in nature that actually meet the requirements of causal explanatory inquiry by integrating Thomism and modern natural science.

By contrast, Thomistic existentialism is unaffected by the demise of the celestial spheres, just as it is untroubled by puzzles over exactly what inertial motion may or may not be (219, fn. 3, and 255). Indeed, because of the “short path” of the De Ente reasoning, it is strictly speaking in no need at all of a natural philosophy and natural science from which to borrow. Knasas’s Thomistic existentialism can avoid all “pessimistic meta-inductions” against the realism from which it begins its cosmological reasoning, for its focus upon the esse prior to any of the essences of any possible concrete cosmology lets it float freely atop the churning undertow of scientific progress that threatens to sweep the Thomistic natural philosopher out to sea. It is cosmological reasoning unwedded to any particular cosmos. What’s more, since the short path of the De Ente reasoning is always available, Thomistic existentialism is strictly speaking in no need of a cosmos at all. Maritain’s ant would suffice (153).

Conclusion

Thomistic Existentialism & Cosmological Reasoning takes Knasas’s version of Thomistic existentialism to the limit to work out the logically demanded interpretation of St. Thomas’s viae to God, given the elements of Knasas’s view of the act of existence as the fundamental, non-formal act of being (see the quote above, in §1). Other Thomists agree about the high stakes of the debate that Knasas’s interpretation is bound to reignite with this book. For instance, Ralph McInerny long ago expressed concern at the overemphasis of the real distinction as a Thomistic metaphysical cure-all: “There are other questions and other answers,” he noted, “and unless they are first dealt with, metaphysics will become either an aesthetic experience or a science more charismatic than acquired” (McInerny, 1986 [1956], p. 172).

Debates such as these, and other questions raised above through the work of seasoned scholars, serve younger students of St. Thomas’s metaphysics—like myself—as salutary admonition to strive to avoid the fate peculiar to young students in precisely this area: “Non attingunt mente, licet ea dicant ore.” (Sententia Ethic., lib. 6, l. 7, n. 16; Leon.47-2.258:191–92) Even though they mouth the words, they don’t quite get it yet. For my part, one of the many benefits of studying Thomistic Existentialism & Cosmological Reasoning has been to waken me from too dogmatic a slumber in some areas and to gain a more nuanced understanding of the debates about the metaphysics of actus essendi among Thomistic schools of thought. Studying it and attempting to engage with it has helped me to sort out what I know from what I do not know, marking out what I have yet to learn. Consequently, I highly recommend the book and further consideration of the questions it raises and the answers it proposes.