Bringing in Edward Feser’s Five Proofs of the Existence of God

Edward Feser’s Five Proofs of the Existence of God* (San Francisco: Ignatius Press, 2017) has been out for a few weeks now, though I received my copy, ordered in June, just a few days ago. The book commands serious reading and serious reading is slow reading. I am therefore quite early on in my reading and reflecting upon the book. Even so, I do have some comments on the book I would like to offer, the first of which is that the book is extraordinarily well organized: Feser tells you in advance and clearly what he will do, does it, and then, periodically and helpfully, sums up where the argument stands, telling you what he thinks the book has done.

Second, the book spells out a version of classical Aristotelian metaphysics or, more specifically, of the natural theology that the Aristotelian tradition thinks that that metaphysics includes. This metaphysics adheres to a resolute rationalism, according to which the real is intrinsically rational or, better, intelligible. It upholds, then, among other principles, the principle of non-contradiction, according to which no being can both be and not be, in any one respect and at any one time, and the principle of excluded middle, according to which all beings must either be or not be, in any one respect and at any one time.

In Five Proofs, to be sure, Feser does not so much set forth or defend such principles as he thinks and argues in accordance with them. But he does set forth and defend the theses that are specific to and indeed define any specifically Aristotelian version of rationalism, those of the theory of actual being and potential being, in short, of act and potency, and the distinction between them. Thus the characterization (pp. 18, 19, etc.) of change as “the actualization of a potential.”

Third, the book’s perspective is thoroughly and straightforwardly Aristotelian in upholding in addition the thesis that philosophy, more specifically, metaphysics, and, more specifically still, natural theology are, not just speculative theories, but demonstrative sciences. That is, it is held, within them there are to be found arguments that are not only valid and sound, arguments, but indeed also demonstrative or apodictic arguments, in a word, proofs. And thus the book’s primary claim, that natural theology can prove the existence of God in, as its title tells us, [at least] five ways. As Feser puts it (p. 15):

A long line of thinkers, from the beginnings of Western thought down to the present day—Aristotelians, Neo-Platonists, Thomists and other Scholastics, early modern rationalists, and philosophers of some other schools too, whether pagans, Jews, Christians, Muslims, or philosophical theists—have affirmed that God’s existence can be rationally demonstrated by purely philosophical arguments. The aim of this book is to show that they were right, that what long was the mainstream position in Western thought out to be the mainstream position again.

I have for decades now, since undergraduate days, understood full well that the Aristotelian tradition has viewed the philosophical disciplines as, at least in principle, philosophical sciences and at least some of the classical arguments for the existence of God as demonstrative arguments. Still, when I read the above passage of Feser, I found myself, on the one hand, enjoying a refreshed appreciation of just what those views are, and, on the other, a determination to put his claim to the test: that is, I found myself committed to the task of determining which of the theses advanced in his book are supported by arguments both explicit and valid, sound, and demonstrative, most particularly those theses immediately involved in the purported proofs of the existence of God.

And that led me to see more clearly than before what one of the primary aims of my ongoing series of posts devoted to the reading of and reflecting upon Aquinas’s Commentary on Aristotle’s Metaphysics has been, that of determining which of the theses, if any, of the Aristotelian metaphysics have been actually proven by Aquinas in the Commentary; this in turn is a purpose subordinated to that of determining which of the theses, if any, of the theses of, finally, metaphysics are supported by arguments both explicit and valid, sound, and demonstrative, most particularly those theses immediately involved in the purported proofs of the existence of God.

It is in line with these aims that although, in my posts of July 16, 2017, and August 19, 2017, the “Aquinas’s Argument That One Science Must “Rule” the Others. A Critical Assessment” and “Aquinas’s Argument That Wisdom Is the Ruler of the Other Sciences. A Critical Assessment,” respectively, I found two central arguments of the first paragraph of Aquinas’s “Prologue” to his commentary to be both valid, in that, if their premises true, their conclusion has to be true, I did not find it to be evident that they are also sound. That is, though it is evident in both cases that that the arguments are valid, it is not evident that, in addition, their premises, and therefore also their conclusions, are all true. Much less, I will add now, is it evident that they are demonstrative.

Let me close by noting that, along with other works by Feser, his Five Proofs will serve as a constant companion as I work my way through Aquinas’s commentary on Aristotle’s Metaphysics. That, it seems to me, is reason enough for me to identify this introduction to Feser’s work as the seventh in the series of posts dedicated to the sustained reading of and commentary upon Aquinas’s.

Until next time.


* You may easily purchase a copy of Five Proofs through, by simply clicking on the following:

** Thomas Aquinas, Commentary on the Metaphysics of Aristotle. Translated and introduced by John P. Rowan (Revised edition; Notre Dame, Indiana: Dumb Ox Books, 1995 [1961])

This edition of Aquinas’s text is serving as the text at hand in the present series of readings and comments. It is available online, at:

If you prefer to do your reading in hard copy, you may easily purchase a copy of the work through, by simply clicking on the following:

About Rchard E. Hennessey

See above, "About the Author/Editor."
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9 Responses to Bringing in Edward Feser’s Five Proofs of the Existence of God

  1. David Murphy says:

    Hello Richard, I appreciate these first thoughts of yours about Feser’s new book. I have read some of his others, but not yet this one.

    From what I know of Feser’s writing and speaking, I would expect him to maintain that the Aristotelian tradition gives Thomism the materials for demonstrative proofs of God’s existence, and of a number of properties of the god of classical theism. I remain unconvinced that Thomism as a system can legitimately claim to offer proofs that are demonstrations when it makes heavy use of analogical predication. Aristotle is explicit, as I understand him, that “pros hen” predication is a kind of equivocal predication. And Thomistic analogical predication is a kind of pros hen predication manqué, as I understand it, since we do not know the primary analogate when it’s God, though we do know it when it’s “surgical” or the like. Thomistic analogical predication is not a kind of Aristotelian analogy by which C is to D as A is to B. In the case of “God talk,” since we do not know the valence of “good” when predicated of God, a proof that relies on stepping from “there is a creature such that it is F” to “God is F” will not be demonstrative. There is an equivocation on F.

    The above is one problem I have with Thomism. Am I wrong, and if so, where?
    I’d say more in response to your above post, but if it turns out that you agree with my thoughts about analogical predication, we may be in agreement that it is not evident that Thomistic proofs are demonstrative. Aristotle after all insists that terms must be predicated univocally in a demonstration that yields episteme.
    (And does any position in natural theology really count as ‘episteme’ in any strong sense?)

    • I blush, well, nearly, to admit that it has been a very long time since I have given any serious thought to the theory of analogy, so I am not prepared at present to offer you anything but a few off-the-cuff remarks, from which I will refrain. But you should know that Feser places a great deal of importance on analogy. He tells us early on (p. 14) that his (nearly 80 pages long) sixth chapter, “The Nature of God and of His Relationship to the World”:

      “…begins with exposition and defense of three key background principles: the principle of proportionate causality, according to which whatever is an effect must in some sense preexist in its total cause; the principle of agere sequitur esse, according to which the way a thing behaves or operates follows from what it is; and the Thomistic account of the analogical use of language.”

      And the book’s index points to ten or so different places in which the topics of analogy and the analogical use of language are mentioned or treated. So it may well be the case that, as I mover through the book, I will come up with a few things that at least I think I might have to say.

      You raise your questions in relation to natural theology. But, and here comes my first thought, it is not only in relation to natural theology that analogy comes up: it comes up in the assignment of being to, not just “primary substances,’ but also to “accidents.” So, one might go on to ask whether any position in metaphysics really counts as ‘episteme’ in any strong sense.

  2. David Murphy says:

    My understanding is that in these discussions, there are two types of analogical predication. One is fundamental to Aristotle’s whole philosophy of nature, sc. proportional analogy, C is to D as A is to B vel sim. Ari comes to conclusions about nature’s ways and structures through analogical reasoning; e.g. a fish’s spine is to a fish what a squid’s “pounce” is to a squid and what a mammal’s bones are to the mammal (AnPo 98a20-23).
    Thomas’ analogical predication of names of God, on the other hand, seems akin to Aristotle’s “pros hen” predication, as I suggested above. E.g. the primary analogate of “healthy” is the healthy organism. We understand health, so we understand what it means to say an organism is healthy. When we call urine healthy, we do so because it is an indicator of the organism’s state of health. When we call a medicinal drink healthy, it’s because it helps produce health in the organism. The latter two predications are parasitic on the primary one and can’t be understood without an understanding of what it means to be a healthy organism.
    In a demonstration in which one combines premises about organisms with premises about urine or drinks, there is great danger of equivocation, since obviously the “being” differs in these cases. Properties can belong to organisms that cannot belong to liquids, and so on. from “if it’s healthy, its bodily humors are in right balance”, it won’t follow that the “bodily humors” of urine or medicine are in the right balance. This may be a lousy example of an equivocation, but I think you get the idea. Aquinas is very fond of “healthy” as a predicate that gets predicated analogically. I think it’s a case of Ari’s “focal meaning” topic, though Aquinas calls it ‘analogy.’
    Feser is quite explicit about how this Thomistic kind of analogy works. I haven’t read whether he shows that it does not entail equivocation. Aquinas himself insists that it occupies a third place, i.e. not univocal predication and not equivocal. Aristotle insists that a demonstration cannot make use of equivocation (e.g. AnPo 77a5-9).
    So I’m eager to hear your take on how successfully Feser defends Thomistic analogical predication. As I recall, too, Aquinas gets it from Pseudo-Dionysius, maybe also Augustine, though I’m not sure about the latter as an influence on predication.

    • What strikes me, on the other hand, is that no matter how different, say, a divine attribute might be from that of a human substantial existent (prote ousia), on the one hand, and some attribute of a paramecium or a sub-atomic particle, it remains that they are all three beings of some sort or another and, as such, they cannot both be and not be, in any one respect and at any one time, and they must be or not be, in any one respect and at any one time. That leads me to think, though I am still open to instruction, that there is indeed a science of beings qua beings, i.e., of metaphysics or ontology.

      • David Murphy says:

        I wasn’t thinking that my cavils about analogical predication rule it out that there should be a science of being/s qua being. Gaven Kerr thinks that Aquinas modifies its subject matter from Ari’s “being qua being” to “ens commune.” I can’t pronounce on that.

        I’ve had a deuced difficult time with SCG II.52-55 or so, because it seems to me that Thomas uses “esse” under different senses, sometimes “being/to be” and sometimes “existence/to exist.” I can’t sort that out. Anyway, I shall wait with interest for further installments either about Feser’s book or about Aquinas’ commentary on the Metaphysics.

      • There has long been an argument floating about to the effect that (1) Aristotle’s conception of science requires that its subject be a genus, (2) being, though analogous, is not a genus, and therefore (3) there is no science of being. I ran into it when I was a graduate student in ca. 1970, but I cannot remember who argued which side. A gentleman named Edward Halper worries about it in his Aristotle’s Metaphysics (London and New York: Bloomsbury Publishing, 2012), though without, as I recall, identifying the philosopher(s) raising the issue.

        I very much appreciate your engagement in discussion with me.

  3. David Murphy says:

    I used to know Ed Halper from International Plato Society days but have lost touch since I can’t do much traveling now. Thank you for mentioning his book on the Metaphysics. I shall have to track it down.

    Just to throw out an idea that is not even half-baked (though perhaps others have thoroughly baked it or thrown it out): I have trouble buying Aquinas’ insistence that an act of existence must be added to form plus matter. If the form of a man – or of a statue of a man – is fully actualized in marble or bronze, doesn’t that just mean that the statue (or the marble or bronze man) exists? When the sculptor puts the finishing touches on the statue, we might say that it becomes fully actualized because the form fully organizes/configures the matter. At that point ipso facto, the statue exists. There is no third thing that must be added to the conjunction of form and matter to bring the statue into existence. The act of existence is only distinct from the realized configuration of matter by form “de dicto” not “de re.” But to have a substance, you already have matter configured by form. If the matter is not configured by form, you don’t have a substance. If the matter IS configured by form, you have a substance that exists. Where is the call for this third thing, an “act of existence”?

    So I am having trouble buying Aquinas’ insistence that substance is the potentiality and the act of existence realizes it. I don’t think potential substances have any identity, and therefore, there are no real potential substances. The potential David Murphy Jr. has no identity because there is no matter, so there is no substance the potential David Murphy. Adding an act of existence is just another name for configuring matter fully by form.


    Edward Feser will tell me I simply fail to understand Aquinas. Maybe I’ll screw up my courage and go over to his blog some day. I did order the book. Aargh.

    • If you don’t understand Aquinas, perhaps that is because, on that particular point, he is not comprehensible.

      I’ll have to set your comment aside for a bit, both because I have a class to prepare and because I need to ponder your (or the) difficulty.

      • phil says:

        During the times that Aquinas is not comprehensible, is that because the subject matter is just that hard for us humans to understand (like a hard math problem) or is he not comprehensible since it is gibberish?

        I too had a hard time understanding why one ought to conclude that “existence” is separate from essence and Aquinas’ argument seems, to me, to only make a logical distinction between knowing the definition of X and knowing whether X is part of the state of affairs…

        thanks for your help.

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