Sunday, June 6, 2010

God and possible worlds

Brandon Watson (here) and James Chastek (here, here, here, and here) offer some helpful reflections on the notion of “possible worlds,” which is put to so much work in contemporary analytic metaphysics. And dubious work, from an Aristotelian-Thomistic (A-T) point of view. A common procedure is to characterize the essence of a thing as the set of properties it has in every possible world, a necessary truth as one that is true in every possible world, and so forth. For A-T, this gets things backwards. It is the essence of a thing that determines what will be true of it in every possible world, not what is true of it in every world that determines its essence. In general, it is incoherent to define modal notions like necessity and possibility in terms of possible worlds, since the notion of a “possible” world itself presupposes modality.

Moreover, as A-T uses the term, a “property” is not part of the essence of a thing, but a feature that flows from its essence. Simply noting that a thing has some feature in every possible world ignores this distinction, and is for that reason too an inadequate way to characterize a thing’s essence. For example, rationality and the capacity to learn languages are both features human beings have in every possible world (if you want to put it that way), but the latter capacity presupposes rationality and is therefore less fundamental than it. While rationality is part of our essence, then, the capacity to learn languages is not, but is rather a “property” – something proper to us in that derives necessarily from our essence. “Property” as used by contemporary philosophers ignores this distinction, and is applied indiscriminately to what is part of a thing's essence, to what is not part of its essence but is nevertheless “proper” to a thing, and to what is neither part of a thing’s essence nor proper to it but merely some contingent feature it has (e.g. the fact that such-and-such a human being was born in Los Angeles or has a blog).

(But might some human being not lose his rationality or capacity to learn languages due to brain damage or the like? Doesn’t that mean the former is not really part of his essence and the latter not really a property? No, that doesn’t follow at all, because to be impeded in the exercise of a power does not entail that one doesn’t have it. From an A-T point of view, every single human being – including one in a so-called “persistent vegetative state” – necessarily has rationality, the capacity to learn languages, etc. Terri Schiavo was a severely damaged rational animal, not a non-rational animal; a human fetus is a rational animal that has not yet been fully formed, not a non-rational animal; and so forth. Restore Terri Schiavo to perfect health and you get someone who can once again exercise her rationality. Restore a rose bush or a dog to perfect health and you still have something that can never exercise reason. Let a human fetus develop fully and you get something that can exercise rationality. Let a rose bush or a dog develop fully and you never get something that can exercise rationality. Thus it is erroneous – not to mention absurd and morally obscene – to compare the likes of Terri Schiavo or a human fetus to a plant or a non-human animal. And thus does bad metaphysics lead to the rationalization of grave immorality, even murder. But I digress.)

It is also often said that for God to be a necessary being is for Him to exist in every possible world. This too is at least very misleading. It leaves the impression that there are these things called “possible worlds” that have some kind of reality apart from God, and it turns out – what do you know! – that God happens to exist in every one of them, right alongside numbers, universals, and other necessarily existing abstract objects. To be sure, since possible worlds other than the actual one are themselves mere abstractions (unless you are David Lewis), they would not exist as concrete entities that God has not created. But the “possible worlds” account of God’s necessity nevertheless insinuates that that necessity is grounded in something other than God Himself – that what is possible or necessary in general is to be determined independently of God, with God’s own necessity in turn defined by reference to these independent criteria. For A-T, this is completely muddled. The reason God is necessary is that He is Pure Act or Subsistent Being Itself, not because He “exists in every possible world.” And since God just is Being Itself – rather than “a being” among other beings, existing in one possible world or in all – all possibilities and necessities whatsoever are themselves grounded in the divine nature, rather than in anything in any way independent of God.

Keep in mind that A-T eschews Platonism and takes a moderate realist approach according to which universals exist only in their instantiations or in an intellect which contemplates them. There is no realm of abstract objects à la Plato’s Forms. What, then, of uninstantiated universals, things that don’t exist but could have? What grounds their possibility? The A-T position is that all universals pre-exist as ideas in the divine intellect. Instantiated universals are those ideas that serve as archetypes for the things God creates, uninstantiated universals are the ones that do not. If we think of a possible but non-actual world on the model of an uninstantiated universal, then possible but non-actual worlds are just the ones which exist as ideas in the divine intellect which God has not used as archetypes in creating.

To be sure, it is only those ideas that do not imply a contradiction that can serve as archetypes in creation – even God cannot make a round square. But the reason is that what God creates are beings, and a “round square” is not any kind of being at all. (Cf. Summa Theologiae I.23.3) A possible being is a possible being, something which “participates” in Being Itself (in the A-T sense rather than the Platonic one – see my discussion of the Fourth Way in Aquinas). Hence, again, possibility is grounded in God (qua Being Itself) rather than in anything outside Him.

As the “participation” language indicates, for A-T anything other than God that exists or might exist is an imitation of God. In creation, that which is unlimited and perfect in God comes to exist in a limited and imperfect way in the natural order. (Recall the doctrine of divine simplicity, as Thomists understand it: Attributes that are distinct in us are analogous to what in God is one.) The divine ideas according to which God creates are therefore to be understood as the divine intellect’s grasp of the diverse ways in which the divine essence might be imitated in a limited and imperfect fashion by created things. As the Scholastic writer Henri Renard sums it up:

From all eternity God contemplating His essence, which is the actuality of all perfection, sees the possibility of limited imitations of that supreme perfection. Thus, from an eternity He conceives the possible essences; consequently, these essences are said to be eternal, immutable, and necessary. The formal realization of the possibles, then, is in the divine intellect. The foundation, however, for this cognition is the essence of God as imitable, for the essence of God is the source of all reality, of all possibles, of all beings. (The Philosophy of Being, p. 112)

Or, as John McCormick puts it:

[I]f anything at all besides God is possible, it is because it can imitate in a finite way some infinite perfection of God. God’s essence as imitable in a finite way in created things is, therefore, the ultimate foundation of the possibles and the final reason why things are possible at all… God’s essence is therefore the Exemplar and Prototype of all reality. (Scholastic Metaphysics, Part I, p. 55)

And just to be ecumenical, let’s also quote a philosopher outside the A-T tradition, albeit one who was influenced by it – the greatest of the moderns, G. W. Leibniz:

It is farther true that in God there is not only the source of existences but also that of essences, in so far as they are real, that is to say, the source of what is real in the possible. For the understanding of God is the region of eternal truths or of the ideas on which they depend, and without Him there would be nothing real in the possibilities of things, and not only would there be nothing in existence, but nothing would even be possible…

For if there is a reality in essences or possibilities, or rather in eternal truths, this reality must needs be founded in something existing and actual, and consequently in the existence of the necessary Being, in whom essence involves existence, or in whom to be possible is to be actual. (Monadology 43-44)

As this last passage indicates, if we agree that some non-actual entities are possible, that any possibility must be grounded in something actual, and that nothing less than what is Pure Act can ultimately be the ground in question, then we have in the notion of possible but non-actual beings the basis of an argument for God’s existence. Or at least some philosophers who would ground all possibilities in the divine nature have thought so (though others have held instead that God’s existence must first be established separately, and then appealed to as an explanation of possibility).

Necessary truths too, for both A-T and Leibniz, are grounded in the divine nature. For suppose we agree that there are such truths – the truths of mathematics, for example – but also that the moderate realist is correct to hold that there are no abstract objects à la Platonism. Such truths have to be grounded in something actual, but it cannot be either the material world or any finite intellect, since neither is necessary. Only that which is infinite, purely actual can do the grounding. What we have here, though, is essentially the “argument from eternal truths” defended by the likes of St. Augustine and Leibniz, which deserves a post of its own, and will get it when I get the chance. Suffice it for now to note that for A-T, as for your more formidable non-A-T writers, necessity no less than possibility must be grounded in God – so that to ground God’s necessity in something other than Him is to get things backwards, and certainly to get them wrong.

I've got your further reading right here:

P. Coffey, Ontology, chapter III

Gyula Klima, “Contemporary ‘Essentialism’ versus Aristotelian Essentialism” (from John Haldane, ed., Mind, Metaphysics, and Value in the Thomistic and Analytic Traditions)

David Oderberg, Real Essentialism, sections 1.1 and 6.2 (only some of which is online, I’m afraid)


  1. Great post Ed. Even when I disagree--a rare occurrence--I come away learning something new. Two request: I would love to read your thoughts on the New Natural Law Theory and would you republish your post on philosophy and polemics? The link from Bill Vallicella is defunct.

  2. Best critique of the new natural law theory, I believe, is Hittingers.

  3. I've noticed a difference set of vocabularly often used to describe the way in which a universal relates to a concrete particular. Can you shed some light on the metaphysical presuppositions behind these terms (if there are any such pressumptions):

    1. exemplication/instantiation
    2. inherence

    It seems that Platonists use (1) more often whereas A-T theorists use (2) more often. But I noticed you used (1) in your post.

  4. Does it really make any sense to speak of "possible worlds" in connection with God? If his creative power is infinite and is fully actualized, does it not follow that he brings every conceivable existent into being?

    If not, then God would appear to be in some kind of process where he deliberates on which realities to create. (You have several followers on your blog who would love to get into that) Whatever he wills comes into being, whatever he does not is not a "possible world" it is an "impossible world."--it can never come into being under any circumstances.

    Yet that brings on further difficulties. There are worlds he "could" create, but chooses not to instantiate. He thus limits his power for all eternity and it no longer makes any sense to speak of him as omnipotent.

    Of course Aquinas addresses such questions and his view is that God does not create necessarily, but by an act of divine will. Yet if God is not in some kind of time frame, such a claim is not coherent. If God's power is fully and completely actualized in all of eternity, where do his "acts of will" come in if they also are fully realized and without change in his very being?

    While Aquinas insists on God's divine simplicity, he then spends page upon page dissecting it into a myriad of properties, many of which are replete with the anthropomorphisms he severely criticizes at other points.

    Aquinas notes that God "acts immediately by his essence" yet then often presents the notions that God "wants," "plans," and "desires."

  5. JT: Yet that brings on further difficulties. There are worlds he "could" create, but chooses not to instantiate. He thus limits his power for all eternity and it no longer makes any sense to speak of him as omnipotent.

    I don't follow your logic here. If I have the power to build a table, does that power go away if I'm not constantly building tables?

    Why does a power have to be used to be a power?

  6. Probably the most charitable thing that could be said about David Lewis is that his ontology of possibilia provides unfettered descriptive powers vis-a-vis modal properties. In this respect it is similar to modern physical theories, which allow for the quantification of natural phenomena, albeit in a manner that doesn't really explain anything.

    I once wrote a paper in which I pegged Lewis as "cubist." He decomposes his material, disposes of it in separate planes, and pieces it back together to form a collage. It is a descriptive rather than a depictive metaphysics: just as modern, and just as meaningless, as the painting genre from which the metaphor was taken.

    An additional metaphor that sprang to mind (one I eschewed employing in deference to scholarly standards), was that Lewis adhered to a "baggy sweatpants" ontology; that is, one that gave him unlimited mobility and comfort, as well as the ability to fart in any general direction he pleases.

    Some things, it is said, are best left in impossible worlds.

  7. Ed,

    Pardon the off-topic post. But, I was wonder if you ever read this piece by Stanley Fish, and if you plan on posting a blog entry about it sometime.

    Normally I wouldn't suppose you'd be interested in such commentary, but this article seems to mesh beautifully with the theme of TLS.

  8. Hi Daniel,

    The brief answer to your question is that the power you speak of is potential power, not actual power.

    For Aquinas God is Pure Act, with no hint of Potency, which includes his infinite power. As a young Dominican with a bare introduction to Thomism, I was fascinated by the concept of God as Pure Act and wrote the following syllogism and presented it to one of my Dominican professors:

    God can create whatever is coherently conceivable.

    God's infinite power is fully actualized, never potential.

    Therefore, God creates whatever is coherently conceivable.

    Of course I was told that I was absolutely wrong and directed to various sources in Aquinas' writing where he insists that God creates freely through acts of the Divine Will, not by necessity of his nature. I would soon find out that the "Divine Simplicity" was far more complicated than I could have ever imagined.

    That was the start of a slow process which eventually led me to leave the Order, the Church, and belief in any deity as well. I've been following Dr. Feser's blog after reading TLS. I actually agree with much of what he says in terms of the failures of modern philosophy (and I despise the "New Atheists" as much as he does), though I didn't find his presentations of three of Aquinas' proofs for God to be any more compelling than when I studied them in my youth. However, I remain open to the possibility of being convinced otherwise. The search continues.

  9. "God can create whatever is coherently conceivable.

    God's infinite power is fully actualized, never potential.

    Therefore, God creates whatever is coherently conceivable."

    Good question.

  10. JT: God can create whatever is coherently conceivable.

    God's infinite power is fully actualized, never potential.

    Therefore, God creates whatever is coherently conceivable.

    "Pure act", to me, doesn't mean "always in act". What it means (again - to me - and keep in mind I have no theological or philosophical training) is that nothing outside of God is necessary for God's power to be actualized.

    Potential power must be actualized by something outside itself (if I understand the concept correctly). God requires nothing outside himself in order to act.

    I've probably muddled that considerably and I'd appreciate your comments (and the comments of others as well.)

  11. JT: God can create whatever is coherently conceivable.

    Thinking about this some more...

    This statement implies that God has infinite potential - that He "can create" is a statement of potential. But such potential is not actualized by another, so God would seem to be pure act and pure potential.

    I'm not sure how this all works within the act/potency distinction.

    It's really too bad this forum isn't more active. Threads just lie there with unanswered questions that no one notices. Maybe if there was a sidebar on the main page with recent post activity?

  12. @JT,

    It seems to me that your argument, while interesting, falls down when we look at the use of the verb 'can' in the major premise.

    If we use 'can' in an univocal sense, this would imply that God is in potency with respect to some external thing, which contradicts minor premise.

    if we use 'can' in an analogous sense, without further analysis of what God's 'can'-analogue means, it isn't apparent that the conclusion follows from the premises.


  13. It is the essence of a thing that determines what will be true of it in every possible world, not what is true of it in every world that determines its essence. In general, it is incoherent to define modal notions like necessity and possibility in terms of possible worlds, since the notion of a “possible” world itself presupposes modality.

    Well, it is certainly not incoherent for non-reductionists to do so, even if it is mistaken finally. For reductionists (Lewis, Sider, but lots of others) we needn't talk of non-reducible possible worlds. We can talk about the worlds that exist. Every world exists at every world for Lewis (for Plantinga too, for that matter). To say that p is possible is just to say that p is true at one of those worlds. Nothing remotely circular there.

    No one denies that the essence of an object (including its individual essence) determines what is true of it in various worlds (setting aside the non-essentialists, including Lewis). What possible world talk does is tell us what it means to say that something is essentially E. It tells us nothing about explanatory priority.

    Possible worlds are indispensible for the semantics of modal talk, whatever metaphysical views one might have. Much of this post seems keen on drawing conclusions about the viability of possible world semantics from deep Thomistic metaphysical assumptions. But this is a mistake. There is nothing about possible worlds that precludes the Thomistic view that God is the source of all possiblity (see Brian Leftow's, God and Necessity, forthcoming in OUP, or see much of the recent work by Hugh McCann, both of whom take this metaphysical line on possible worlds). It's coherent to take possible worlds as metaphysically dependent on God's will, etc. I find the Thomistic view wildly over-reaching and beyond credibility on this score. Both Leftow and McCann, highly sympathetic to the Thomistic position, are clear-headed about the difficulty of making good sense of Thomisic modality. But these issues have nothing to do with whether we accept or like possible worlds talk.

  14. Dr. Feser,

    Thanks for the post! I'm new to your blog and actually came to this piece by a link from your most recent entry on the ontological argument.

    With regard to the "archetypes" of which you speak, or ideas in the divine intellect, how do you square this understanding of the grounding of essences with the possibility of trans-species evolution? Or do you accept the latter? (I personally am not sure I do, but that's another story)

    Do you see a number of discrete divine ideas that account for each successive species or essence (I am using the two interchangably for convenience at the moment) along the trajecotry of the evolutionary line? This would seem to imply the somewhat awkward conclusion that at some point, an animal would be born to a parent of a different species from itself.

    Or do is the use of the term "divine idea" limited in that it it suggestes discrete "ideas" where there is in reality only continuity? But doesn't this destroy the whole concept of "essence" and put us in a Hegelian of historicist metaphysic?

    If you have already pursued this question I would be happy to be directed to your prior posts (or books).


    Michael Hickman

  15. I agree with Mike Almeida. I don't see anything wrong with possible worlds talk.

  16. Possible worlds are indispensible for the semantics of modal talk

    I'm glad someone else said this, because I was beginning to wonder... I mean, can we have even have formal modal logic without the notion of possible worlds?

  17. Am I right in saying that David Lewis's Modal Concretism is completely incompatible with Classical Theism (since A) Necessity is grounded in God and B) There cannot be more than one God because he is identical with his existence and absolutely simple, and this is obviously in conflict with each of Lewis's "worlds" being casually disconnected)?

  18. I'm not sure Lewis's view is incompatible with theism. There is no reason to take worlds to be brute facts. It might be that God actualized every world in which he exists: viz. every world simpliciter, if you like. Further, though individuals are 'world bound' on Lewis's view, this does not entail that God is not a necessary being. Having necessary existence as an essential property is perfectly compatible with being world-bound. Further, we can drop the world-bounded assumption, and have worlds overlap with respect to God. You might even get the idea that the space of possibility is determined by God, 'thought up' by God, as Leftow always says. So you can get what you want here, I think.

  19. Ed,

    I’m not a professional philosopher, so have mercy on me. But I do try to keep up as best I can, and it seems to me that when someone says God is necessary “because” God exists in all possible worlds, the “because” here expresses an ‘epistemological’ priority within the constraints of a particular argument for God’s existence and not any kind of causal or—I’m expressing this poorly, forgive me—existential priority, as if God’s existing in every possible world is something God derives his necessity from. I don’t think any analytic (theist) philosopher thinks the latter or would disagree with you that the proper order, in terms of existence as such, is better expressed by saying God exists in every possible world because God is necessary. I’ve only ever found the reverse expression helpful as a way to help people come to terms with the possibility of God’s existence (ala Hartshorne’s version of the ontological argument, for example), that is, if I can’t consistently conceive of a possible world in which God does not exist (and philosophers as different as Hartshorne and DBH would agree such a world is not really conceivable), THEN (there’s the epistemological ‘because’) I’m bound to concede God’s (necessary) actuality. But the logic of the argument doesn’t constitute the necessity in question; it just reveals it to be the case. So it's rather to be expected that it runs in the opposite direction.

    Or I might be entirely misunderstanding your concern.


  20. I know this comment of mine is unusually late, for it to be even considered as apart of the ongoing discussion unfolding in the response section of this particular post of Edward's blog (hopefully someone will see or respond to it, most notably, the person ["JH"] to whom it's directed), but I have only recently come across this blog site, and so otherwise would have been impossible ... Yet, to the point.


    you ask if God is " Pure Act ", yet has not willed or, does not will, into existence every 'coherently conceivable thing'; does that not mean God has or does not actualize his full power in creation, and therefore is not fully actual or actualized? To answer this question, which most definitely is not a problem to resolve, simply requires one to understand the true significance of the term " Act ".

    God is " Pure Act ", for two reasons: (1) God is 'pure act' not because he WILLS into existence ALL conceivables (although he can, if he so chose to), yet because he KNOWS (without any potential increase or decrease in his knowledge) of ALL conceivably existing things. Thus God's knowledge is Purely Actual, such that there's never a potential increase or decrease in it; for it's fully realized; no matter if he may not willfully actualize (ergo, creation is a consequence of God's free choice, and not metaphysical or logical necessity) all things he knows as possible (TzimTzum).

    (2) God is 'pure act' becasue no force from without, or outside to him, is required to, let alone can, actualize any of his states and-or potentialities (such as his acts of creation). This not being the case for any finite existent; for example, a person has the potential to be, if they're not actually so, hydrated, but they cannot of their-self actualize this effect, and therefore require a thing external to their-self, namely, water, to actualize this potentiality of theirs; only for an infinite existent, namely God.