- Thomistic Existentialism and Cosmological Reasoning by John F. X. Knasas
This study offers an interpretation of Aquinas’s philosophical contribution to demonstrations of God’s existence by reviewing the argument of De ente et essentia and its significance as a version of a cosmological argument. Its larger agenda is to defend Thomistic “realism” and specifically a distinctive “existentialist” approach to Thomism. Its targets of criticism therefore include other Thomists as well as early modern and analytic thinkers.
The first half of the book (part 1: “Aquinas’s De ente Reasoning and the Cosmological Argument”) argues that Aquinas’s understanding of existence as actus essendi allows for a version of a cosmological argument that is immune to Kant’s critique of Leibniz’s “remarkably shallow” (3) understanding of existence. The first chapter reviews Leibniz’s cosmological reasoning and Kant’s critique thereof, and prepares the way for considering existence not as a “determinate property” (granting some insight to Kant) but as an “act or perfection of a thing” (as in Aquinas). Chapter 2 reviews the De ente proof, focusing on the notion of esse and giving particular attention to how esse is grasped by the second operation of the intellect. Chapter 3 reviews neo-Thomist interpretations of the De ente proof, engaging Gilson and Maurer, Wippel and MacDonald, Dewan and Calahan. Chapter 4 continues to highlight the importance of actus essendi by engaging “Analytic Thomist” treatments of De ente (including those offered by Peter Geach, Brian Davies, and Anthony Kenny). Chapter 5 considers some non-Thomist objections to De ente’s cosmological reasoning (including those from Kant and analytic philosophers and ending with Heideggerian objections to “ontotheology”).
The second half of the book (part 2: “The De ente Reasoning and Aquinas’s Proofs for God”) argues that Aquinas’s use of this notion of actus essendi in the De ente argument sheds light on what his cosmological arguments—any arguments from existing effects to God as their cause, including all the viae one finds in the Summae and elsewhere—are meant to demonstrate. Chapter 6, “Aquinas’s Metaphysics and Our Knowledge of God’s Existence,” is primarily [End Page 168] concerned with arguing that natural philosophy cannot prove the existence of God, advancing the interpretation in the rest of part 2 that the other less explicitly metaphysical viae are still examples of “De Ente reasoning in different guises” (173). Chapter 7, “A More Robust Version of the De Ente Reasoning,” continues the argument that the reasoning of De ente, insofar as it explicitly draws on the proper object of metaphysics (ens inquantum ens), must be integrated into any proofs for the existence of God. This is followed by three chapters interpreting the more commonly discussed other proofs in light of De ente reasoning: on viae in the Summa contra gentiles (chap. 8); in the Summa theologiae and the Compendium theologiae (chap. 9); and “other possible viae” in the commentary on the Sentences (I Sent., d. 3; II Sent., d. 1, q. 1, a. 1), De potentia (q. 3, a. 5), the prologue to the John commentary, and chapter 15 of the first part of the Summa contra gentiles (chap. 10). Rounding out the second half of the book, chapter 11 (“Questions and Replies”), responds to some questions raised by Knasas’s interpretation: Why would Aquinas “camouflage” metaphysical principles in other versions of a cosmological argument? Why does Aquinas ask about the distinction of essence and existence in God after formulating other versions? And are less explicitly metaphysical cosmological proofs still only comprehensible to metaphysically advanced philosophers?
As Knasas reminds us throughout the volume, and in a short concluding chapter, one of the goals of his interpretation is to display and defend a philosophical approach named in the first half of his title: Existential Thomism or “Thomistic Existentialism,” characterized by its particular emphasis on being as actus essendi, an act that is distinct from that which it actualizes, the substance which in itself is...