Five Proofs

of the Existence of God

Philosopher Edward Feser has a new book out in which he puts forth five arguments for the existence of God. These are not the “Five Ways” of Aquinas so it might be refreshing to discuss one or all of these. At the very least this OP may introduce readers to arguments for the existence of God which they had previously been unaware of.

The five proofs are:

  • The Aristotelian Proof
  • The Neo-Platonic Proof
  • The Augustinian Proof
  • The Thomistic Proof
  • The Rationalist Proof

: The Aristotelian Proof

Chapter 1 defends what I call the Aristotelian proof of the existence of God. It begins with the fact that there is real change in the world, analyzes change as the actualization of potential, and argues that no potential could be actualized at all unless there is something which can actualize without itself being actualized—a “purely actual actualizer” or Unmoved Mover, as Aristotle characterized God. Aristotle developed an argument of this sort in book 8 of his Physics and book 12 of his Metaphysics. Later Aristotelians such as Maimonides and Aquinas developed their own versions—the first of Aquinas’ Five Ways being one statement of such an argument. These earlier writers expressed the argument in terms of archaic scientific notions such as the movement of the heavenly spheres, but as modern Aristotelians have shown, the essential kernel of the argument in no way depends on this outdated husk. Chapter 1 aims to present the core idea of the argument as it might be developed by an Aristotle, Maimonides, or Aquinas were they writing today.

: The Neo-Platonic Proof

Chapter 2 defends what I call the Neo-Platonic proof of God’s existence. It begins with the fact that the things of our experience are in various ways composite or made up of parts, and argues that the ultimate cause of such things can only be something which is absolutely simple or noncomposite, what Plotinus called “the One”. The core idea of such an argument can be found in Plotinus’ Enneads, and Aquinas gave expression to it as well. Indeed, the notion of divine simplicity is absolutely central to the classical theist conception of God, though strangely neglected by contemporary writers on natural theology, theists no less than atheists. Among the aims of this book is to help restore it to its proper place.

: The Augustinian Proof

Chapter 3 defends an Augustinian proof of God’s existence. It begins by arguing that universals (redness, humanness, triangularity, etc.), propositions, possibilities, and other abstract objects are in some sense real, but rejects Plato’s conception of such objects as existing in a “third realm” distinct from any mind and distinct from the world of particular things. The only possible ultimate ground of these objects, the argument concludes, is a divine intellect—the mind of God. This idea too has its roots in Neo-Platonic thought, was central to Saint Augustine’s understanding of God, and was defended by Leibniz as well. This book puts forward a more detailed and systematic statement of the argument than (as far as I know) has been attempted before.

: The Thomistic Proof

Chapter 4 defends the Thomistic proof of God’s existence. It begins by arguing that for any of the contingent things of our experience, there is a real distinction between its essence (what the thing is) and its existence (the fact that it is). It then argues that nothing in which there is such a real distinction could exist even for an instant unless caused to exist by something in which there is no such distinction, something the very essence of which just is existence, and which can therefore impart existence without having to receive it—an uncaused cause of the existence of things. Aquinas presented an argument of this sort in his little book On Being and Essence, and many Thomists have regarded it as the paradigmatically Thomistic argument for God’s existence.

: The Rationalist Proof

Chapter 5 defends a rationalist proof of the existence of God. The proof begins with a defense of the principle of sufficient reason (PSR), according to which everything is intelligible or has an explanation for why it exists and has the attributes it has. It then argues that there cannot be an explanation of the existence of any of the contingent things of our experience unless there is a necessary being, the existence of which is explained by its own nature. This sort of argument is famously associated with Leibniz, but the version of it I defend departs from Leibniz in several ways and interprets the key ideas in an Aristotelian-Thomistic way. (Hence, while it is definitely “rationalist” insofar as it is committed to a version of PSR and to the thesis that the world is intelligible through and through, it is not “rationalist” in other common senses of that term. For example, it is in no way committed to the doctrine of innate ideas or other aspects of the epistemology associated with continental rationalist philosophers like Descartes, Spinoza, and Leibniz. And its interpretation of PSR differs in key respects from theirs.)

For whatever reason I’m starting my reading with the rationalist proof. Because, you know, everyone here is always so rational. 🙂

332 thoughts on “Five Proofs

  1. Kantian Naturalist: Wait a minute — are you saying that it’s Scholastic doctrine that God has no essence at all? I thought the doctrine was the God is that being whose essence is His existence.

    I’d appreciate an answer to this (addressed to Torley).

  2. Pedant: I’d appreciate an answer to this (addressed to Torley).

    Same here. It seems to boil down to the whole “God explains herself” motto

  3. Erik: It is indeed silly. For a guy with a history of hating categories, it’s silly how KN insists on strict category in this case, while (1) clearly having a bias against anything called a priori and (2) probably having a peculiar definition of a priori in mind.

    My ‘history of hating categories’ exists only in your imagination. What happened was, I asked you what you meant by ‘categories’, because different philosophers have used that concept in different ways and have adopted different theories.

    After much back-and-forth, we finally realized that the differences between our views are (1) I regard categories as structures of thought, but not as structures of reality; (2) I regard categories as historically variable, not fixed.

    If you want to go on and say that I “hate” categories because I have a different view of them than you do, well, be my guest.

    PSR stems from antiquity and medieval scholasticism, when people didn’t think in terms of a priori and a posteriori.

    The terms first appear in a Latin translation of Euclid, and the 14th-century logician Albert of Saxony wrote about them.

    They often had philosophy and science mixed up too.

    Isn’t that a good reason to draw a distinction that they didn’t make?

    This might give one reasons to be very suspicious of PSR and to reject it altogether (which most people do here off the bat) or to assume that it has applications and entailments all over the place (which is what I hold). But it gives no reason to look at it through the prism of Kantian categories without any argument.

    I’m not even relying on Kant’s views about the PSR (though I do think he was right that the PSR is a regulative principle about human reason, or what Peirce calls a rule of hope). I wasn’t even relying on the details of Kant’s views about the a priori and the a posteriori, which I would not defend in all respects.

    I was simply saying that there is an important distinction to be made between them, and that whether we treat the PSR as a priori or as a posteriori makes a difference as to what reasons we might have for accepting it or rejecting it.

  4. keiths,

    And while inquiry pursues fundamental explanations, it does not depend on them. Partial explanations suffice.

    Partial explanations may indeed suffice in most everyday situations, but they presuppose the possibility of complete and fundamental explanations.

    Pedant and Kantian Naturalist:

    Wait a minute — are you saying that it’s Scholastic doctrine that God has no essence at all? I thought the doctrine was the God is that being whose essence is His existence.

    That is indeed the Scholastic doctrine. But God’s essence is unbounded, unlike that of finite creatures. God has no “outline,” if you like; and that is precisely what makes God distinct from everything else. “No outline” does not mean “no essence”; it simply means an absence of constraints, because on the traditional view, God is not just His own existence; rather, God is Pure Existence.

  5. vjtorley:..they presuppose the possibility of complete and fundamental explanations.

    Although it is human nature to make such assumptions (hence the mutifaceted religious edifice we have today) they, as we are all in fact in that same boat, are groundless! 🙂

  6. Vincent,

    Partial explanations may indeed suffice in most everyday situations, but they presuppose the possibility of complete and fundamental explanations.

    How so?

    There’s nothing inconsistent about the idea of partial explanations that, if expanded, would ultimately rest on brute facts.

    Suppose I give you a detailed meteorological explanation of how snow rollers form. In what way does my explanation presuppose that the mass of the electron is not a brute fact?

  7. vjtorley: But God’s essence is unbounded, unlike that of finite creatures. God has no “outline,” if you like; and that is precisely what makes God distinct from everything else. “No outline” does not mean “no essence”; it simply means an absence of constraints, because on the traditional view, God is not just His own existence; rather, God is Pure Existence.

    If I’m understanding the terms correctly, does that mean that God has an essence but no ‘form’? Are we supposed to think about ‘form’ in terms of conditions or constraints on activity? So that God has no form because He is unconditioned or unconstrained in His activity?

  8. Kantian Naturalist: My ‘history of hating categories’ exists only in your imagination. What happened was, I asked you what you meant by ‘categories’, because different philosophers have used that concept in different ways and have adopted different theories.

    Since this is so, don’t assume your categories to be right or even applicable without careful consideration.

    Erik: They often had philosophy and science mixed up too.

    Kantian Naturalist: Isn’t that a good reason to draw a distinction that they didn’t make?

    Isn’t that a good reason to consider first if any particular distinction is even applicable? They surely distinguished hierarchies all the way in everything, something that you reject. You prefer other inapplicable distinctions, thus distorting your own understanding of how they reasoned.

    Kantian Naturalist: I’m not even relying on Kant’s views about the PSR (though I do think he was right that the PSR is a regulative principle about human reason, or what Peirce calls a rule of hope).

    The parentheses completely prove my point. And I was not accusing you of employing Kant’s views of the PSR, but imposing Kantian “a priori” on the PSR without careful consideration. Consider for example this bit from Stanford website https://plato.stanford.edu/entries/sufficient-reason/

    When Leibniz insists that every truth or fact requires a sufficient reason, what does he mean by “sufficient reason?” In some texts he suggests that sufficient reason is an “a priori proof”. This should not be understood in Kantian terms as a proof that doesn’t require any input from sense experience. Rather, Leibniz uses the term “a priori” in its original pre-Kantian meaning, which means an argument from causes to effects. An a priori proof is a proof that reflects the causal order.

  9. Hi Kantian Naturalist,

    That’s an interesting way of putting it, but I guess it’s about right.

    Hi keiths,

    Suppose I give you a detailed meteorological explanation of how snow rollers form. In what way does my explanation presuppose that the mass of the electron is not a brute fact?

    Snow rollers are “a very rare phenomenon where snowballs form naturally by a very strong wind blowing across a flat, snowcovered field when the snow is easily compacted (snow temperature near 32 degrees F).” Electrons don’t figure in the explanation, so your question is a little unfair. However, suppose someone were to ask, “And what makes the wind blow?”, only to be told, “It just does, that’s all.” I think we would all agree that the foregoing explanation would then be unsatisfactory.

    Here’s an easy way to see my point. Consider the question that New Atheists most love to ask ID proponents: “Who designed the Designer?” And think of how these atheists typically respond when they’re told: “No-one.” The atheists’ dissatisfaction, I would submit, stems from the answer sounding too much like an inexplicable “brute fact.”

  10. Vincent,

    Electrons don’t figure in the explanation, so your question is a little unfair.

    They do figure in a fuller explanation. The properties of snow (and hence of snow rollers) very much depend on the behavior of electrons, and the behavior of electrons is affected by their mass. If that mass turns out to be a brute fact, no problem. The explanation of snow rollers still works.

    As I said above, there’s nothing inconsistent about the idea of partial explanations that, if expanded, would ultimately rest on brute facts, such as (possibly) the mass of the electron.

    Your claim doesn’t fly:

    Partial explanations may indeed suffice in most everyday situations, but they presuppose the possibility of complete and fundamental explanations.

    The PSR is not a prerequisite for inquiry.

  11. Vincent,

    Consider the question that New Atheists most love to ask ID proponents: “Who designed the Designer?” And think of how these atheists typically respond when they’re told: “No-one.” The atheists’ dissatisfaction, I would submit, stems from the answer sounding too much like an inexplicable “brute fact.”

    Speaking for myself, the problem isn’t with that “explanation” being presented as a brute fact. It lies elsewhere.

    There are really two kinds of “brute fact”, which I’ll call “epistemic brute facts” and “ontological brute facts”. Ontological brute facts truly have no deeper explanation; they just are. Epistemic brute facts may have a deeper explanation, but if they do, we don’t know it yet.

    Our explanations come to a halt at either kind of brute fact, at least until we discover that the brute fact is merely epistemic, not ontological, by finding a deeper explanation for it. Yet science and other forms of rational inquiry proceed apace. They simply do not depend on the absence of brute facts, either epistemic or ontological. And since the PSR merely asserts that ontological brute facts don’t exist, inquiry doesn’t depend on the PSR.

  12. Vincent,

    Do you agree that your claim below is incorrect, as I’ve explained above?

    Partial explanations may indeed suffice in most everyday situations, but they presuppose the possibility of complete and fundamental explanations.

  13. Hi keiths,

    I think your distinction between an epistemic and an ontological “brute fact” is a valid one, but I reject your definition of an ontological “brute fact” as faulty. You define it as something which truly has no deeper explanation. By your definition, God would then be an ontological “brute fact.” Feser would reject this assertion, however, as he sees God as self-explanatory, whereas an ontological “brute fact” is not just a state of affairs having no deeper explanation, but rather, a state of affairs no explanation at all. That is why it makes no sense.

    As to whether scientific inquiry presupposes PSR, I’ve already conceded that Kantian Naturalist makes a persuasive argument that it need not do so. What I continue to maintain, however, is that the existence of an ontological “brute fact” is incompatible with its being genuinely explanatory of anything in the real world.

    And if the existence of snow rollers did turn out to depend on the mass of the electron, I think it would be fair to demand an explanation of that, too.

  14. Vincent,

    Feser would reject this assertion, however, as he sees God as self-explanatory, whereas an ontological “brute fact” is not just a state of affairs having no deeper explanation, but rather, a state of affairs no explanation at all. That is why it makes no sense.

    It “makes no sense” only if the PSR is true. But that’s the very question we’re debating.

    What I continue to maintain, however, is that the existence of an ontological “brute fact” is incompatible with its being genuinely explanatory of anything in the real world.

    If you believe that, then why not say the same regarding epistemic brute facts? After all, our explanations end at brute facts of either kind, and any of our epistemic brute facts could, in principle, turn out to ontological ones — unless we assume the truth of the PSR, which again is the very issue we are debating.

    And if the existence of snow rollers did turn out to depend on the mass of the electron, I think it would be fair to demand an explanation of that, too.

    Science pursues the question, of course. But it strikes me as ridiculous to claim that the explanation of snow rollers isn’t “genuine” unless we can explain the mass of the electron.

    In fact, it seems to me that by your criterion, no existing scientific explanation is genuine, because they all currently end in brute facts of either the epistemic or ontological kind.

  15. dazz: Can you please elaborate on what it means for something to be self-explanatory?

    I think he means something is immediately obvious to someone who believes it’s immediately obvious. And doesn’t quite grasp that the belief precedes the obviosity.

  16. dazz, to Vincent:

    Can you please elaborate on what it means for something to be self-explanatory?

    Feser writes:

    God’s existence does not lack an explanation. The explanation lies in his own nature as that which is purely actual, simple or noncomposite, and subsistent existence itself. The universe’s existence cannot be explained in terms of its own nature, because it is not purely actual (given that it has potentialities), not simple (given that it has parts), and not subsistent existence itself (since it is as contingent as its parts are).

    Its explanation must therefore be found in something distinct from it. The difference between God and the world then is not that one has an explanation and the other lacks it, but rather that one is self-explanatory while the other is not. And the distinction is not arbitrary, but grounded in the independently motivated distinctions between what is purely actual versus what is a mixture of actual and potential, what is simple versus what is composite, and what is subsistent existence itself versus what has a distinction between its essence and its existence.

    Here are the relevant steps from Feser’s rationalist argument, to be read with a suitable amount of eye-rolling:

    17. So, no contingent thing or series of contingent things can explain why any particular contingent thing persists in existence at any moment; and the only remaining explanation is in terms of a necessary being as its simultaneous cause.

    18. So, there must be at least one necessary being, to explain why any contingent things exist at all and how any particular contingent thing persists in existence at any moment.

    19. A necessary being would have to be purely actual, absolutely simple or noncomposite, and something which just is subsistent existence itself.

    20. But there can in principle be only one thing which is purely actual, absolutely simple or noncomposite, and something which just is subsistent existence itself.

    21. So, there is only one necessary being.

    22. So, it is this same one necessary being which is the explanation of why any contingent things exist at all and which is the cause of every particular contingent thing’s existing at any moment.

    23. So, this necessary being is the cause of everything other than itself.

    24. Something which is purely actual, absolutely simple or non-composite, and something which just is subsistent existence itself must also be immutable, eternal, immaterial, incorporeal, perfect, omnipotent, fully good, intelligent, and omniscient.

    25. So, there is a necessary being which is one, purely actual, absolutely simple, subsistent existence itself, cause of everything other than itself, immutable, eternal, immaterial, incorporeal, perfect, omnipotent, fully good, intelligent, and omniscient.

    26. But for there to be such a thing is for God to exist.

    27. So, God exists.

  17. Thanks guys

    So it’s about “pure actuality” apparently

    An obvious question springs to mind: If God is pure actuality, no potentiality, shouldn’t his natural creation be necessary too? because a God without a creation seems to entail potentiality

  18. dazz,

    An obvious question springs to mind: If God is pure actuality, no potentiality, shouldn’t his natural creation be necessary too? because a God without a creation seems to entail potentiality

    My guess is that Feser would respond by claiming that God is outside of time, so that there is no distinction between “God before creation” and “God after creation.” Thus no potential of God’s was actualized by the creative act. He is timelessly actual, with no unrealized potential.

    A counterargument would be to point out that the actualization of potential need not be seen in strictly temporal terms.

  19. dazz: An obvious question springs to mind: If God is pure actuality, no potentiality, shouldn’t his natural creation be necessary too? because a God without a creation seems to entail potentiality

    I suppose this turns on the question, “could God have chosen not to create the universe?” I’m confused on this question myself.

    Consider: it is often claimed that God created the universe in an act of love. But God is (among other things) pure love. So for God to not have created the universe would have been to not act on His love, and so would have amounted to God not being God.

    Another way of putting the question would be, “does God have free will?” And while it might be tempting to say “yes”, I’m less sure. God isn’t tempted by transgression, so He never has to chose to do the right thing. You might say that His will and His intellect are never at odds. So He never has to make choices of the kind that we fallen creatures do when we are faced with a choice between selfish desire and selfless love.

    Yet it’s precisely in those kinds of cases — when we resist temptation (selfish desire) and do what we know in our hearts to be morally right (acting out of self-less lovingkindness) — that we exemplify the exercise of free will.

    If God has free will, it would have to be in a sense radically different than we do.

    On the other hand, denying that God has free will soon leads to pantheism and other heresies.

  20. keiths: A counterargument would be to point out that the actualization of potential need not be seen in strictly temporal terms.

    Your comment number is 196437. Is all actualization of a potential necessarily temporal?

  21. KN,

    Another way of putting the question would be, “does God have free will?” And while it might be tempting to say “yes”, I’m less sure.

    That kind of talk makes theists nervous, because to say that God lacks free will means that he is limited in a way that mere humans are not.

    Yet by insisting on God’s free will, they also undermine the free will defense against the problem of evil. For if it’s logically possible for a free agent to always choose the good, as God does, then why didn’t God create us to do the same?

  22. keiths: A counterargument would be to point out that the actualization of potential need not be seen in strictly temporal terms.

    Yeah, that’s why I wrote “without a creation” not before one. Not to avoid the time
    counterargument, but because it’s irrelevant to the question of necessity for all I can tell

  23. Kantian Naturalist: I suppose this turns on the question, “could God have chosen not to create the universe?” I’m confused on this question myself.

    Consider: it is often claimed that God created the universe in an act of love. But God is (among other things) pure love. So for God to not have created the universe would have been to not act on His love, and so would have amounted to God not being God.

    Another way of putting the question would be, “does God have free will?” And while it might be tempting to say “yes”, I’m less sure. God isn’t tempted by transgression, so He never has to chose to do the right thing. You might say that His will and His intellect are never at odds. So He never has to make choices of the kind that we fallen creatures do when we are faced with a choice between selfish desire and selfless love.

    Yet it’s precisely in those kinds of cases — when we resist temptation (selfish desire) and do what we know in our hearts to be morally right (acting out of self-less lovingkindness) — that we exemplify the exercise of free will.

    If God has free will, it would have to be in a sense radically different than we do.

    On the other hand, denying that God has free will soon leads to pantheism and other heresies.

    That was awesome

    These arguments for god existence seem to always end up falling face first against some unavoidable special pleading (they all look like the same argument anyway) and leading to the same contradictions.

    Like WLC’s cosmological argument, which relies on God being an effective cause with no material cause of the universe. That one seems to boil down to: God created the universe out of nothing… because he can (yippee!)… but how is that not a pantheistic conception of the universe?

  24. dazz,

    That one seems to boil down to: God created the universe out of nothing… because he can (yippee!)… but how is that not a pantheistic conception of the universe?

    Because it maintains a distinction between the universe (the created) and God (the creator).

  25. dazz,

    Yeah, that’s why I wrote “without a creation” not before one. Not to avoid the time counterargument, but because it’s irrelevant to the question of necessity for all I can tell

    It is relevant.

    1. If God is within time, and the creation is a necessary entity, then the creation must have existed for all time, just like the Son, so that there never was a moment of creation; that is, never a moment when God actualized his potential of being a universe creator.

    2. If God is outside of time, but the actualization of potential is a strictly diachronic phenomenon, then there must have been at least one instant of time in which the universe did not yet exist. But that would mean that the universe is not a necessary entity — at least not within time. So the only out for the theist would be to argue that since God is outside of time, his creative potential is “never” unactualized.

    3. If God is outside of time but there is such a thing as an extratemporal actualization of potential, then the theist would have to explain why God isn’t actualizing a potential of his by (timelessly) instigating the creation, particularly if the decision to create is an exercise of his free will.

  26. KN,

    But God is (among other things) pure love.

    Which is self-contradictory, because to be pure love is to be nothing but love. If God is “pure love”, then he is not those “other things”.

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