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spheres, but as modern Aristotelians have shown, the essential kernel of the argument in no way depends on this outdated husk.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. Erik: And how do you determine what the actual explanation is?

    That’s exactly my question. It seems to me that there are many cases where we don’t know. And that’s a deep philosophical problem I won’t pretend I have solved. And I don’t see how you or Feser have either.

    So now you are not even happy with actual explanations, instead you want correct explanations. What is the relevant distinction between them? Is there any?

    There isn’t, I was using those words synonymously.

    According to PSR, the sufficient explanation, insofar as relevant to a given fact, *is* the actual correct explanation for it according to the best of our ability

    Under that interpretation you can’t meaningfully distinguish between all sorts of magical fairies, ghosts, wizards and so on. Merely sufficient explanations can be made up for all sorts of things with all sorts of ad-hoc reasoning.

    You mean brute facts look as good to you as PSR? Okay, now I know who I am talking to.

    I don’t se brute fact vs PSR as a valid dichotomy. Like KN I take the PSR as a sort of methodological ideal. We (always should) seek explanation, but we have no right to think there will always be one. And we should not rest content with mere sufficient explanations.

  2. Rumraket: Like KN I take the PSR as a sort of methodological ideal.

    This explains why you challenge it only half-heartedly, incoherently. You know that there is really no meaningful life without PSR. Given this, I don’t need to defend it. No need to defend it when there is no proper challenge.

  3. Erik: This explains why you challenge it only half-heartedly, incoherently.

    Nothing I say is incoherent or half-hearted.

    You know that there is really no meaningful life without PSR.

    That doesn’t even make sense. My ability to find meaning in my life has nothing to do with the PSR. Whether there is an explanation for everything has no bearing on what I take to be meaningful in or of my life.

  4. Rumraket: My ability to find meaning in my life has nothing to do with the PSR.

    Which is why your challenge to it is coherent and effective only in your own mind. In reality, it is not a meaningful challenge, because it addresses only a corollary. Half-heartedly.

  5. dazz,

    Can a necessary being not be a brute fact?

    The claim is that the necessary being explains itself, and is therefore not a brute fact and not an exception to the PSR.

  6. keiths:
    dazz,

    The claim is that the necessary being explains itself, and is therefore not a brute fact and not an exception to the PSR.

    I know, it just doesn’t make any sense to me. “It explains itself” explains nothing in my book

  7. Besides being wrong about what constitutes a genuine explanation, Feser is also making a fallacious argument from consequences here. He’s basically saying “If the PSR isn’t true, then there are brute facts, and any explanations resting on them aren’t real explanations. That’s terrible. Therefore the PSR is true.”

    That’s bad reasoning.

  8. keiths:
    Besides being wrong about what constitutes a genuine explanation, Feser is also making a fallacious argument from consequences here.He’s basically saying “If the PSR isn’t true, then there are brute facts, and any explanations resting on them aren’treal explanations.That’s terrible.Therefore the PSR is true.”

    That’s bad reasoning.

    Yeah, we must always assume God is at the end of the causal or explanatory chain or else or else we know nothing at all. What a joke.
    Ironically this line of reasoning seems to make their followers incredibly prone to obsessing with unexplained events, or rejecting valid explanations: why bother with human evolution when you can end the regress by positing special creation a few thousand years ago?

  9. Hi everyone,

    I feel there’s an important point that’s being missed here, in the discussion about PSR. For Scholastics, PSR is not a principle about facts, but about beings. Whereas for Leibniz, PSR means that every fact and every true proposition must have an explanation – and for Leibniz, that means logical entailment – for Scholastics, facts are abstracted by the mind from the real world, and are not things that need to be explained as such: rather, it is real objects that need to be explained. Moreover, on the Scholastic understanding, explanation need not mean logical entailment.

    Readers may ask why, if the Scholastic version of PSR is not concerned with facts, Feser is so concerned to show that there are no “brute facts.” The reason is that if there are “brute facts,” then the ontological realities which they correspond to are also “brute”: in other words, some things “just are,” and that’s all we can say. That is why Feser describes the regress of explanations which he is concerned with as a nomological regress rather than a logical regress: “The notion of an explanatory nomological regress terminating in a brute fact seems, when carefully examined, as incoherent as the notion of an effect being produced by an instrument that is not the instrument of anything.” (Scholastic Metaphysics, 2014, editiones scholasticae, p. 145)

    Another point worth making is that PSR need not even be formulated with reference to explanations. Feser writes:

    …[W]hile PSR is typically formulated in terms of intelligibility or explanation – which are epistemological or logical, rather than metaphysical notions – it need not be so formulated. As Jacques Maritain notes, PSR can be formulated as the principle that “whatever is, has that whereby it is” (1939, p. 99). This makes no explicit or implicit reference to the intellect’s operations – as talk of intelligibility and explanation do – but it has the generality of the more usual formulations of PSR, which PC [the principle of causality] lacks. Actualizations of potency, contingent things, and changes and beginnings of existence have that whereby they are, namely their causes; and that which is uncaused insofar as it is pure actuality or subsistent being itself also has that whereby it is, namely its own nature. (Scholastic Metaphysics, 2014, editiones scholasticae, p. 139)

    Later, however, Feser explains why PSR can be recast as the principle that every being is intelligible (i.e. has an adequate explanation):

    Being and truth are convertible in the sense that they are the same thing considered under different aspects. Being is reality considered in itself, truth is reality considered in relation to an intellect which grasps it. In other words, truth is just being considered as intelligible. Now if every being is in this sense true – and that this is Aquinas’ own view is uncontroversial – then it follows that every being is intelligible. And that is just what PSR says. (Scholastic Metaphysics, 2014, editiones scholasticae, p. 139)

    I hope this clears up a few misunderstandings on the part of readers.

  10. keiths: KN is not asserting the existence of brute facts here.

    If there are no actual brute facts then there is no good reason to reject the PSR.

    KN needs to explain the possibility of brute facts, not merely assert it.

  11. keiths,

    You ask:

    If a wife asks her husband how the bumper got dented, and the husband says “I wasn’t paying enough attention and I backed into a light post,” do you really think the wife is entitled to say “That’s not an explanation. You haven’t explained the pattern of neural firings that led to your lapse of attention, and you haven’t explained the laws of physics”?

    No. What you overlook, however, is that the husband’s lack of attention still requires an explanation of some sort. Now suppose the husband were to say to his wife, “I wasn’t paying enough attention and I backed into a light post,” and his wife were to ask, “Why weren’t you paying attention?”, and the husband replied, “I just wasn’t. That’s all.” I think the wife would be entitled to say: that’s not an explanation.

    If, on the other hand, the husband replied, “I don’t know, but I think it’s because I’m getting older, and my brain isn’t functioning the way it used to,” or “I was momentarily distracted by a billboard featuring Eva Herzigova” (which apparently has caused car crashes in real life), then I think that would suffice to answer his wife’s question.

    Keep in mind, however, that PSR isn’t just a principle about states of affairs. It is, even more, a principle about beings. The wife didn’t ask for an explanation for the existence of any being, however; she was merely concerned with explaining the car crash. In that case, I’d say that the two explanations I proposed go far enough, in answering her question, and they don’t stop at any “brute facts,” either, so I don’t see a problem here.

  12. Erik:

    Well, I thought you knew better than to just go by what Torley says. I thought you knew what PSR actually is, without any need for anyone to quote it for you. But now you still refuse to know better even after quoting.

    I’m quite familiar with the PSR from years of studying Spinoza, Leibniz, and Kant. I don’t need Feser or Torley to tell me what it is or isn’t. I’ve been quite clear on this from the very beginning of our conversation: I understand the principle of sufficient reason as the a priori claim that every fact must have an explanation. If that’s what you intend to defend, we can continue. If you have a different version of the PSR, I’d like to know what that is.

    Note: since the PSR has the status of an a priori principle, it is equivalent to “necessarily, every fact has an explanation”. Hence the negation of the PSR is “possibly, not every fact has an explanation”. In other words, the negation of the PSR entails the possibility of brute facts.

    Let’s take “facts” to be true claims, where a claim is true if (1) the claim is embedded within a conceptual framework consisting of both formal and (if relevant) material inferences and (2) the use of that conceptual framework allows for reliable tracking and classifying of real patterns.

    The criteria for admitting a claim as true depend on the rules of the conceptual framework: the rules for admitting a claim as true in logic or mathematics stipulate what it is for a claim to be provable, with non-proven claims inadmissible (though of course interesting). In the empirical sciences, we don’t require provablity but rather testability as the criterion of truth or warranted assertion.

    Let’s take “explanations” now as models of underlying processes that generate observable patterns that in turn are described by true claims. For example, it is a fact that the Earth and other planets orbit the Sun. The laws of orbital mechanics, themselves embedded in Newtonian mechanics, explain why this fact holds. And general relativity, in turn, is a model of the underlying causal processes (how mass distorts space-time) such that the inverse square law is a good approximation of what is going on, as long as the masses involved are not too huge or going too fast.

    Given these concepts, the question “could there be brute facts?” is the question “could there be true claims that aren’t embedded within some larger model?”

    Nonsense because “empirical inquiry” is not all inquiry there is. Nonsense because Torley (certainly Aristotle, St Augustine, Leibniz, etc) was not talking about “empirical inquiry”. Nonsense because PSR is not limited to empirical inquiry nor primarily about it. You should really, really know better. We are philosophy guys here.

    Torley claimed — quoting from Feser — that the reason why we should accept the PSR is because we can’t do science without it. And science is empirical inquiry. Leibniz certainly thought that the PSR was the principle that made science different from mere trial-and-error.

    Nonsense because, at best, all you mean here is something like “we currently have no explanation” for some empirical phenomenon. This is indecisive to assert brute facts, because you need a philosophical principle or a logical reason to convert this epistemological uncertainty into a metaphysical existent called brute fact. Bring it on.

    No, because (1) “brute fact” is itself an epistemological concept, not a metaphysical one and (2) I am asserting the possibility of brute facts, not the assertion of the existence of brute facts. Again, my point is that (2) is not threat to science, which means that the denial of PSR is no threat to science.

  13. vjtorley,

    I understand pretty well what it is to explain a fact. I have no idea what it is to explain a being as distinct from explaining a fact about that being.

  14. Hi Kantian Naturalist,

    You write:

    But let us be clear: one is not blocking the way of inquiry simply by raising the logical possibility of brute facts, unexplained explainers. This is because it would still require the process of inquiry to determine if any particular fact is brute or not. And since it is always possible that we can be mistaken in which facts are brute and which ones are not, inquiry as a self-correcting process can even lead us to explore explanations for supposedly brute facts. What is taken to be a brute fact by one generation of inquirers can be a topic for inquiry and explanation by the next generation.

    On this basis, I conclude that the possibility of brute facts does not undermine the process of inquiry. But since the denial of the PSR amounts only to the possibility of brute facts, and the possibility of brute facts does not undermine the process of inquiry, then inquiry cannot depend on the PSR.

    You argue that merely saying that there might be brute facts does not prevent us from investigating a particular state of affairs S; hence the process of scientific inquiry is not threatened. But it’s simply not good enough to say that your hypothetical supposition (of the possibility of brute facts) does not prevent scientists from investigating S. What if scientists get lazy and decide not to bother investigating S, after all? They might say to one another: “Investigating whether S has an explanation or not is bound to take lots of time and money. Why don’t we just take S as a given, instead, and treat it as a brute fact?” PSR is the only principle that can put a stop to such intellectually lazy behavior, by telling scientists: you must investigate S and never give up, or you’re not doing your job.

    While I’m about it, I’d like to ask you a question: what would it take to convince you that some state of affairs S was a brute fact, and why do you think that would be a rational inference in the hypothetical situation you are envisaging?

  15. Hi Kantian Naturalist,

    You write:

    I understand pretty well what it is to explain a fact. I have no idea what it is to explain a being as distinct from explaining a fact about that being.

    Personally, I tend to think of explanations as relating to states of affairs rather than facts – for example, what explains the mysterious Tunguska event of 1908? Probably it was the air burst of a meteoroid. But states of affairs don’t always have to be events. Meteoroids themselves are beings, whose existence surely requires an astronomical explanation, too.

    But if you prefer to envisage explanations in terms of facts, you might like to consider it this way. Not all facts are facts about some being, because not all facts describe the properties of some being. There are some existential facts which simply assert the existence of beings of a certain kind – e.g. “Carnivorous plants exist.” If you can explain facts like these, then you have thereby explained the existence of a certain kind of being.

    I hope that helps.

  16. vjtorley:
    They might say to one another: “Investigating whether S has an explanation or not is bound to take lots of time and money. Why don’t we just take S as a given, instead, and treat it as a brute fact?” PSR is the only principle that can put a stop to such intellectually lazy behavior, by telling scientists: you must investigate S and never give up, or you’re not doing your job.

    Or they might say: “Why don’t we stop the investigation here, since we have no resources to spare? I don’t want to lose my house and go bankrupt.”

  17. Kantian Naturalist: Note: since the PSR has the status of an a priori principle, it is equivalent to “necessarily, every fact has an explanation”.

    Referring to the OP:

    The Aristotelian proof begins with facts about the world.
    The Neo-Platonic proof begins with facts about the world.
    The Augustinian proof begins with facts about the world.
    The Thomistic proof begins with facts about the world.

    About the PSR Feser writes:

    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.)

    What on earth would lead you to believe that in the case of the PSR Feser is treating it as an a priori principle?

  18. Mung: KN: “I understand the principle of sufficient reason as the a priori claim that every fact must have an explanation. If that’s what you intend to defend, we can continue. If you have a different version of the PSR, I’d like to know what that is.”

    Mung: see here for starters

    Yeah, it says “1. The principle of sufficient reason (PSR) holds that there is an explanation for the existence of anything that does exist and for its having the attributes it has.”

    I don’t see a particularly meaningful distinction between what KN said and what Feser defines it as. At least from those two it is not clear to me whether they have any relevant differences for the purposes of this discussion.

  19. Mung: What on earth would lead you to believe that in the case of the PSR Feser is treating it as an a priori principle?

    Because if it’s not a priori then it’s a posteriori, and if it’s a posteriori then it’s really just an empirical generalization based on induction. Hardly the right sort of premise to serve as proof that God exists.

  20. vjtorley,

    I was going over this in my head earlier while running errands. I think that what counts as an explanation (and also what counts as a good explanation) will vary according to different domains of inquiry.

    For example, if someone wants an explanation of why there’s no largest prime, the explanation would consist of being shown how the proof works. But proof, while a fascinating concept, is restricted to wholly a priori domains, like logic and mathematics.*

    By contrast, in most of the sciences, explanations consist of models of causal processes — e.g. an explanation of the Tunguska explosion would consist of different models of causal processes, evaluated for likelihood based on available evidence.

    I would distinguish explanations from justifications, however. There’s a difference between explaining — giving a model of a process that explains by virtue of showing how some observable regularity is embedded in some larger pattern — and justifying — giving reasons why someone ought to do (or believe) or not do (or believe), or why they are blameless for having done (or believed) what they did or do.

    (In one sense, this question whether the PSR is about explanations or about justifications is one of the major fault-lines between Spinoza and Leibniz.)

    * Whether metaphysics is a priori is precisely what’s controversial here.

  21. Kantian Naturalist:

    I was going over this in my head earlier while running errands. I think that what counts as an explanation (and also what counts as a good explanation) will vary according to different domains of inquiry.

    Um. Let’s see if I have this right (probably not). A “brute fact” is one for which there simply is no explanation. There may be one or more proposed explanations, but by definition these must be incorrect. And of course we can’t be talking about facts for which there is no explanation YET, which implies that there IS one, which simply has yet to be found. A brute fact has none.

    So the question is, can a “brute fact” meeting this criterion actually exist? And as I understand this, the PSR says no, it can’t. My problem is, I can’t see how this could be knowable. It’s like “the greatest good for the greatest number”. We can take the nominative position that it exists, while conceding that we could not possibly recognize it even if we stumbled on it.

    Presumably, a brute fact might be “explained” by some model which proves to be solidly predictive and coherent with other good models (reality as we know it), because our incorrect proposed explanation comes close enough. In which case, why bother with the whole issue at all?

  22. Hi Kantian Naturalist,

    I’ve been pondering the question of whether PSR is analytic or synthetic, and a priori or a posteriori. I’m not altogether clear as to whether a Thomist would say it’s analytic or synthetic, but I’m sure he/she would insist that it’s a posteriori.

    A proposition is analytic if the predicate concept is contained within the subject concept. But this is precisely what Feser appears to say in the following quote:

    Being and truth are convertible in the sense that they are the same thing considered under different aspects. Being is reality considered in itself, truth is reality considered in relation to an intellect which grasps it. In other words, truth is just being considered as intelligible. Now if every being is in this sense true – and that this is Aquinas’ own view is uncontroversial – then it follows that every being is intelligible. And that is just what PSR says. (Scholastic Metaphysics, 2014, editiones scholasticae, p. 139)

    On the other hand, Feser also says on the same page:

    As with PC, though, Scholastic philosophers take PSR to be more certain than a mere empirical hypothesis can be. Indeed, like PC [the principle of causality]
    it is often regarded as self-evident. This does not entail that it is universally assented to, or that it can be known to be true from an analysis of the concepts or the terms in which it is formulated. The idea is rather that, as Garrigou-Lagrange writes, “though it cannot be directly demonstrated, it can be indirectly demonstrated by the indirect method of proof known as reductio ad absurdum (1939, p. 181). Garrigou-Lagrange’s way of trying to show this is to argue that to deny PSR entails denying PNC [the principle of non-contradiction] as well – though this strategy does not seem more promising than the attempt to derive PC from PNC.

    However, there are ways of carrying out a reductio other than by arguing that PSR entails directly denying PNC itself. One can argue that anyone who denies PSR would, if he is consistent, also have to deny other things he would not deny or even could not coherently deny… Denying PSR, Pruss notes, entails radical skepticism about perception…

    …To reject PSR is to undermine the possibility of any rational inquiry. (Scholastic Metaphysics, 2014, editiones scholasticae, pp. 143, 144)

    In the above passage, Feser appears to be asserting that denial of PSR is not self-contradictory (which means that PSR isn’t analytic, but synthetic), but that denial of PSR undermines the possibility of rational thought.

    So I’ll say that it looks like Feser regards PSR as a synthetic proposition, but that if you have the right concept of being (as Scholastic philosophers do) then PSR will be analytic.

    What about a priori vs. a posteriori?

    I don’t think a Thomist could claim that PSR is knowable a priori, independent of all experience, since for Thomists, PSR relates to beings rather than facts. And we need experience to tell us that there are beings.

    However, the fact that PSR is a posteriori does not make it a mere sense datum. It takes a being with an intellect to grasp it.

    My two cents.

  23. Kantian Naturalist: Note: since the PSR has the status of an a priori principle, it is equivalent to “necessarily, every fact has an explanation”. Hence the negation of the PSR is “possibly, not every fact has an explanation”. In other words, the negation of the PSR entails the possibility of brute facts.

    There has always been a deep problem with what you take an a priori principle to be. You seem to be thinking you can state them and negate them as you please, as if they had no entailments to the rest of epistemology and metaphysics.

    Kantian Naturalist: In the empirical sciences, we don’t require provablity but rather testability as the criterion of truth or warranted assertion.

    And how do you do that with an a priori principle? What makes you bring it up when we are talking about an a priori principle? Why should scientific considerations have priority over the philosophical?

    Clearly, either we are not talking (only) about the empirical realm (because we are talking about a philosophical principle) or we are not talking about a priori principles in your abstract sense, but about philosophical principles that have entailments, including entailments to (the philosophy of) science. Either way, we cannot start with nor be bound by the requirements of the empirical sciences.

  24. Erik: Which is why your challenge to it is coherent and effective only in your own mind. In reality, it is not a meaningful challenge, because it addresses only a corollary. Half-heartedly.

    So ridiculous.

    Maybe get a job making unpleasant fortune cookies.

  25. Rumraket: Yeah that doesn’t make much sense to me either.

    I am required to explain why there is another car in my garage. I explain that a friend of mine is visiting and it is his car, he drove it here and parked in my garage. I am now required to explain why my friend drove here and parked in my garage. I invited him over and he had time off.

    You could ask more questions about why my friend would accept the invitation and so on. I give an account of that to my best understanding. Sooner or later, I hit somewhere where I no longer know the reasons why things are, or happen, the way they are/do. I have not explained everything there is to know about why there is another car in my garage, but it would be rather silly to say that I have not explained anything at all. I have in fact explained a lot.

    Well said.

  26. vjtorley: for Scholastics, facts are abstracted by the mind from the real world, and are not things that need to be explained as such: rather, it is real objects that need to be explained.

    vjtorley: Keep in mind, however, that PSR isn’t just a principle about states of affairs. It is, even more, a principle about beings. The wife didn’t ask for an explanation for the existence of any being, however; she was merely concerned with explaining the car crash.

    vjtorley: I hope this clears up a few misunderstandings on the part of readers.

    It doesn’t for me. What’s a “real being”? (Forgive me, but I can’t help thinking here about Pinocchio wanting to be a “real boy.”)

    Also, I think the “for Leibniz, all entailment is logical” is controversial. Broad’s book has him holding the scholastic view according to which entailments are “analytic” (can’t remember what Russell said about this). But for at least a generation, that view has been heavily contested (not that Feser cares about recent philosophy).

  27. Kantian Naturalist: Because if it’s not a priori then it’s a posteriori, and if it’s a posteriori then it’s really just an empirical generalization based on induction. Hardly the right sort of premise to serve as proof that God exists.

    And yet, each of the arguments of Aquanas’s Five Ways do exactly that. Each of them begins from facts known from observation. So Thomist philosophers would disagree with you. And that’s my point. You need to read Feser as a Thomist not as a Kantian. No offense.

  28. vjtorley,

    Interesting!

    As I see it, the PSR has got to be synthetic a priori.

    It can’t be analytic because its negation is not a logical contradiction (as Feser points out). But I think it cannot be a posteriori because its epistemic status doesn’t depend on observations.

    This is a subtle point because we need to distinguish epistemic status from psychological status. How we acquire knowledge is one thing (psychology); what justifies that knowledge is something else (epistemology).

    When I teach this stuff to my students, the most common objection I get is “but 2+2=4 is a posteriori, because we were taught in school — here are two apples, and here are another two apples, and now there are four apples”. But while my students are obviously right that we learn to add by performing concrete operations on physical things, that doesn’t make arithmetic a posteriori. The a priori status of arithmetic is due to how the claims of arithmetic are justified, not to how they are acquired or applied. (As I point out to my students, one can indeed prove that 2+2=4, if one assumes set theory and the Peano axioms!)

    I mention all this because I disagree with how Torley put a point above: that the PSR can’t be a priori because it assumes that there are beings, and we learn that there are beings through sense-experience. Apriority isn’t about how we acquire knowledge but about justification. Since the epistemic status of the PSR doesn’t depend on induction over observations — it’s not like “all swans are white” — it’s got to be a priori.

    Now, this raises the rather deeper question: how can synthetic a priori principles be justified? Since they can’t be justified on the basis on sense-experience, what basis is there for their justification?

    I find Feser’s reasoning here to be suggestive but flawed. His argument is that acceptance of the PSR is necessary for there to be rational inquiry at all.

    Let’s call this the pragmatic argument for the PSR: if one is committed to rational inquiry at all, then one ought to accept the principle of sufficient reason. Put otherwise: if one is going to be involved in trying to figure stuff out — solve problems, build models, test theories, etc. — then one must accept that every being is fully intelligible. If one didn’t accept that every being is fully intelligible, then one could not engage in any rational inquiry at all.

    Now, is this correct? I do not think it is. I think there is a serious lacuna between the pragmatic version of the PSR and the rationalist version of the PSR, and the pragmatic argument for the PSR only works for the first version of it. But it’s the second version that Feser requires for his proof that God exists.

    Recall Peirce’s pragmatic version of the PSR:

    every fact of a general or orderly nature calls for an explanation; and logic forbids us to assume in regard to any given fact of that sort that it is of its own nature absolutely inexplicable. This is what Kant calls a regulative principle, that is to say, an intellectual hope. The sole immediate purpose of thinking is to render things intelligible; and to think and yet in that very act to think a thing unintelligible is a self-stultification. … True, there may be facts that will never get explained; but that any given fact is of the number, is what experience can never give us reason to think; far less can it show that any fact is of its own nature unintelligible. We must therefore be guided by the rule of hope, and consequently we must reject every philosophy or general conception of the universe, which could ever lead to the conclusion that any given general fact is an ultimate one. We must look forward to the explanation, not of all things, but of any given thing whatever. (“A Guess at the Riddle”, 1888)

    The “rule of hope” here is: always look for explanations! There may be facts that can’t be explained, but keep on trying to explain them, since you never know whether any given fact has an explanation or not, and you won’t find it if you give up!

    I do think that an acceptance of the principle of sufficient reason in the Peircean version is indeed a pragmatic presupposition of rational inquiry. One can’t be engaged in the activity of rational inquiry without being committed to the search for explanations.

    But notice that the Peircean ‘rule of hope’ version of the PSR (which he also calls by the Kantian term, a ‘regulative principle’) is not the same as the rationalist version. On the rationalist version, we know a priori that every being is fully intelligible. That is to say: we know already that everything already has an explanation, and we just have to find it. There is not even the possibility that some things can’t be explained.

    In short: what Feser needs is an argument for the rationalist PSR, but what he gives us is an argument for the pragmatic PSR.

  29. Hi walto,

    You might want to fix the indentation in the second, fourth and fifth paragraphs of your last post.

    Just for the record: Feser himself doesn’t say that for Leibniz, all entailment is logical entailment. Instead, on page 140 of his Scholastic Metaphysics he quotes from a philosopher named Peter Weigel, who writes: “As Leibniz presents the principle, every fact and every true proposition – at least every true contingent proposition – must have an explanation. What is sufficient reason furthermore assures the truth of what it explains… Hence Leibniz’s rendition has a logical cast to it, whereas Aquinas is not fishing for reasons for every logically contingent proposition.” (Aquinas on Simplicity, 2008, New York: Peter Lang, pp. 128-129)

    It was this passage which I paraphrased in a comment above, as follows: “for Leibniz, PSR means that every fact and every true proposition must have an explanation – and for Leibniz, that means logical entailment…” I have no idea whether Feser would agree with this way of putting it or not.

    Anyway, I’d like to thank you for pointing out that Leibniz’s own views on entailment may not be as clear-cut as some of his detractors believe.

    Re your other question, “What is a real being?”, Feser would answer that a real being – I’m talking about contingent beings here – is a compound of essence and existence. (Here’s a rough analogy, which I alone take responsibility for: think of essence as being like a casting mold and existence as the molten liquid which is poured into it. Essence is what limits a thing’s manner of existence, giving it form but at the same time preventing it from realizing certain perfections that characterize other forms.) An imaginary being, on the other hand, is just an essence without any existence: the casting mold without the liquid, if you like. It’s an empty husk: a set of limitations without any thing to be limited by them.

    God, the Necessary Being, is just Pure Existence, without any limitations, like a molten liquid without any mold to confine it within the bounds of some form. God’s form, so to speak, is to have no form.

    The foregoing analysis assumes that there is a real distinction (and not just a logical one) between a thing’s essence and its existence, as Thomists maintain. Feser provides several arguments for this position in his book.

    I hope that answers some of your questions. Cheers.

  30. vjtorley: God, the Necessary Being, is just Pure Existence, without any limitations, like a molten liquid without any mold to confine it within the bounds of some form. God’s form, so to speak, is to have no form.

    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.

  31. Kantian Naturalist: But I think it cannot be a posteriori because its epistemic status doesn’t depend on observations.

    This is probably silly, but if one holds the PSR must be held true for rational inquiry to be possible, I don’t see how one could also hold that it’s a posteriori principle arrived at by induction: how could the first occurrence of rational inquiry be possible? with no past experience of rational inquiry there’s nothing to derive the PSR from inductively, so no PSR, no rational inquiry

  32. dazz: This is probably silly, but if one holds the PSR must be held true for rational inquiry to be possible, I don’t see how one could also hold that it’s a posteriori principle arrived at by induction: how could the first occurrence of rational inquiry be possible? with no past experience of rational inquiry there’s nothing to derive the PSR from inductively, so no PSR, no rational inquiry

    You’re right, which is precisely why it can’t be based on induction — and that’s why I disagreed with Torley that the PSR could be a posteriori.

  33. dazz: This is probably silly, but if one holds the PSR must be held true for rational inquiry to be possible, I don’t see how one could also hold that it’s a posteriori principle arrived at by induction…

    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.

    PSR stems from antiquity and medieval scholasticism, when people didn’t think in terms of a priori and a posteriori. They often had philosophy and science mixed up too. 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.

  34. Mung,

    And yet, each of the arguments of Aquanas’s Five Ways do exactly that. Each of them begins from facts known from observation. So Thomist philosophers would disagree with you. And that’s my point. You need to read Feser as a Thomist not as a Kantian. No offense.

    From a site that has been arguing as if everything has a reason and cause to then deny PSR as reasonable is interesting. We could just argue that life has no reason or cause and call it a day.

  35. Hi Kantian Naturalist,

    I’ve been thinking long and hard about your last post. I agree with your point that apriority isn’t about how we acquire knowledge, but about justification. I was also impressed with your distinction between the pragmatic PSR and the rationalist PSR, as you call it. Briefly, your argument is that Feser must be committed to the claim that we know a priori that every being is fully intelligible, in order for him to rule out even the possibility that some things can’t be explained. After some reflection, I think you are right here.

    That leaves us with the question: are there any arguments Feser puts forward which might justify such a strong claim? As we’ve seen, the argument that PSR is a presupposition of rational inquiry doesn’t warrant the rationalist version of PSR, but merely the pragmatic version.

    I suspect that if pressed, Feser might argue as follows:

    1. If rationalist PSR (to use your term) is false, then we have no a priori grounds for believing that our cognitive faculties “track truth and standards of rational argumentation, rather than leading us to embrace conclusions in a way that has no connection to truth or logic,” as Feser puts it.

    2. If rationalist PSR is false, then it might (logically) be the case that there are no genuine explanations, since (i) everything might ultimately have to be explained in terms of “brute facts” which themselves have no explanation, and (ii) we can know a priori that an explanation which ultimately rests upon an unexplained state of affairs is not a genuine explanation. But this is absurd.

    As I’ve written previously, I don’t think 1. is a knock-down argument, as it assumes we need a priori grounds for believing that our cognitive faculties are reliable. But it seems consistent to hold that while we have no a priori grounds for believing that our cognitive faculties are reliable, we have excellent a posteriori grounds for believing so – namely, the coherence of our scientific knowledge and the success of our scientific predictions. That leaves us with 2.

    Personally, I find myself in agreement with Feser here. Some readers have pointed out that our explanations are typically partial: we never get all the way to the bottom, and we are happy to call a halt to our demand for explanations, long before we reach “rock bottom,” so to speak. I accept that point. But it’s one thing to say that we don’t usually look for ultimate explanations, and quite another thing to say that our explanations would still be genuine even if there were no self-explanatory ultimate explanations. I think Feser’s a priori intuition is correct: an explanation which ultimately rests upon an unexplained state of affairs is not a genuine explanation.

    I’d be interested to hear Professor Feser’s own views, so I might email him, and see if he’d like to comment.

  36. colewd:
    Mung,

    From a site that has been arguing as if everything has a reason and cause to then deny PSR as reasonable is interesting.We could just argue that life has no reason or cause and call it a day.

    You seem confused about this subject as well.

  37. vjtorley: I think Feser’s a priori intuition is correct: an explanation which ultimately rests upon an unexplained state of affairs is not a genuine explanation.

    As I understand KN argument it should be : an explanation which rests upon a possible unexplainable state of affairs is not a genuine explanation.

  38. Vincent,

    2. If rationalist PSR is false, then it might (logically) be the case that there are no genuine explanations, since (i) everything might ultimately have to be explained in terms of “brute facts” which themselves have no explanation, and (ii) we can know a priori that an explanation which ultimately rests upon an unexplained state of affairs is not a genuine explanation. But this is absurd.

    It’s absurd, but only because of the way youve defined “genuine explanation”.

    Explanations don’t need to be fundamental to be “genuine”. You yourself have conceded:

    Some readers have pointed out that our explanations are typically partial: we never get all the way to the bottom, and we are happy to call a halt to our demand for explanations, long before we reach “rock bottom,” so to speak. I accept that point.

    Those explanations are still genuine. They’re just not fundamental.

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

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