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From International Philosophical Quarterly, 23:3, September 1983, 251-265.  For the reasons Felt provides here I reject Lonergan’s Molinism as expressed  here (at 9.20.7 Corollary V [from Lonergan's Insight, Chapter XIX, Section 9]).  Also, at the end of the second section of this essay, Felt shows the relevance of the unintelligibility of fully determinate possible worlds to the problem of evil, to which this site has devoted much space.


Impossible Worlds

James W. Felt, S.J.


No philosophic thicket has grown so profusely in the past twenty years as that of “possible worlds.” None perhaps is so tangled.  I propose not so much to untangle it as to cut much of it away.  For whatever the purely logical or formal advantages of the notion (and I have nothing to say about that), it is entirely misguided to invoke “possible worlds” to make sense out of the real world.  For, I shall argue, “possible worlds,” as usually understood, are metaphysical monstrosities: they are inconsistent with metaphysical principles which do in fact obtain, hence are metaphysically, if not quite logically, impossible.

Let me identify a little more closely some of the shrubbery I propose to excise.  Leibniz’s “possible worlds” provide the classic case, and it has been argued lately (as well as long ago) that there cannot be any “best” of all possible worlds any more than there can be a greatest integer.1   I shall argue, however, that there are no possible worlds at all, at least none of metaphysical interest.

Interest in Leibniz’s notion of possible worlds mushroomed lately because it seems to provide modal logic with a semantics, a theoretical account of the conditions under which formulae of a system are true.  Thus Kripke and others have developed a paraphrase roughly to the effect that a statement of the form, “It is necessary that p,” is true if and only if p is true in all possible worlds; a statement of the form, “It is possible that p” is true if and only if p is true in at least one possible world.  A vigorous and complex controversy has ensued over the meaning and philosophic respectability of the very notion of possible worlds. Positions range from sheer “possibilism”—for example that of David K. Lewis who maintains an infinity of worlds, all equally real, the possible as well as the actual—to various forms of “actualism,” which holds that all references to possible worlds must reduce to references to elements of the actual world (for instance, Nicholas Rescher and Robert Merrihew Adams).

Let us take a closer look at what Lewis means by “possible worlds.”  He writes:

I believe that there are possible worlds other than the one we happen to inhabit.  If an argument is wanted, it is this.  It is uncontroversially true that things might be otherwise than they are.  I believe, and so do you, that things could have been different in countless ways.  But what does this mean? Ordinary language permits the paraphrase: there are many ways things could have been besides the way they actually are.  On the face of it, this sentence is an existential quantifi-cation.  It says that there exist many entities of a certain description, to wit “ways things could have been.”  I believe that things could have been different in countless ways; I believe permissible paraphrases of what I believe; taking the paraphrase at its face value, I therefore believe in the existence of entities that might be called “ways things could have been.”  I prefer to call them “possible worlds.”2

What distinction is there, then, between possible worlds and the actual world? Lewis replies:

If asked what sort of thing [possible worlds] are, I cannot give the kind of reply my questioner probably expects: that is, a proposal to reduce possible worlds to something else.

I can only ask him to admit that he knows what sort of thing our actual world is, and then explain that other worlds are more things of that sort, differing not in kind but only in what goes on at them.  Our actual world is only one world among others.  We call it alone actual not because it differs in kind from all the rest but because it is the world we inhabit.  The inhabitants of other worlds may truly call their own worlds actual, if they mean by “actual” what we do; for the meaning we give to “actual” is such that it refers at any world i to that world i itself.  “Actual” is indexical, like “I” or “here,” or “now”; it depends for its reference on the circumstances of utterance, to wit the world where the utterance is located.3

I shall, on the contrary, contend that in general there are no “ways things could have been,” even though my position is not deterministic.  Thus even an actualist like Rescher, who wishes to root the possible in the actual, errs when he grants that there are “as yet unrealized possibilities that await us in the future” as well as “the possible albeit unrealized doings of actual things such as my possible attendance at the film I failed to see last night.”4

The shadow of Parmenides seems to lie over these discussions.  For whether with Lewis one takes possible worlds to be as real as the actual, or one tries to replace them solely by the actual, the upshot seems the same: all is reduced to a planar understanding of what it means to be.  In these controversies the anti-Parmenidean (Aristotelian) notion of potentiality, as an intrinsic character of the actual, has tended to be supplanted by possibilities (in the plural), Lewis’s “ways things could have been,” purely formal and discrete patterns.  The dynamism of potentiality has been exchanged for a dust of homeless forms.

What I propose to do is the following: (1) set up some metaphysical (or cosmological) principles descriptive of the ultimate structure of the experienced world; (2) use these principles to evaluate the modern theories of Lewis and Rescher, and the classical theories of Molina and Leibniz, noting the import of these principles, especially as related to the problem of God and evil; (3) finally, come to grips with a fundamental objection against the whole contention of this essay.5


1. Some Metaphysical (Cosmological) Principles

In fashioning the few principles we should need in order to examine the notion of possible worlds, I have in mind Alfred North Whitehead’s description of speculative philosophy:

Speculative Philosophy is the endeavour to frame a coherent, logical, necessary system of general ideas in terms of which every element of our experience can be interpreted.  By this notion of “interpretation” I mean that everything of which we are conscious, as enjoyed, perceived, willed, or thought, shall have the character of a particular instance of the general scheme.6

The sense which Whitehead here gives to the word “necessary” is delicate but crucial:

The adequacy of the scheme over every item [of experience] does not mean adequacy over such items as happen to have been considered.  It means that the texture of observed experience, as illustrating the philosophic scheme, is such that all related experience must exhibit the same texture. Thus the philosophic scheme should be “necessary,” in the sense of bearing in itself its own warrant of universality throughout all experience, provided that we confine ourselves to that which communicates with immediate matter of fact. . . .

This doctrine of necessity in universality means that there is an essence to the universe which forbids relationships beyond itself, as a violation of its rationality.  Speculative philosophy seeks that essence.7

The test of such a speculative system must be found in its power and scope, in the way it draws out fundamental insights (including pre-philosophical ones) into rational connection and balance.

For a philosophic scheme ultimately reposes on principles describing our experience of the world which suggest themselves with a kind of direct immediacy confirmed by careful reflection.  David Lewis almost suggests as much when he writes: “One comes to philosophy already endowed with a stock of opinions.  It is not the business of philosophy either to undermine or to justify these preexisting opinions, to any great extent, but only to try to discover ways of expanding them into an orderly system.”8

We must, with Henri Bergson, carefully distinguish between the intuitions (properly understood) which ground our metaphysics and the conceptual terms by which we attempt to articulate and communicate them.  Concepts are like intellectual snapshots which, however numerous and exact, never capture process any more than stroboscopic photos of a bird in flight capture flying.  No speculative scheme ever quite succeeds in articulating experience.  The principles I am about to suggest, then, are imperfect, conceptual expressions of what I find, after reflection, to be fundamental features of the experienced world.  The (perhaps infelicitous) names I give to the principles are mainly my own, but I am indebted to the thought of Bergson, Whitehead, and Charles Hartshorne for the evidence with which these principles recommend themselves to me.  And since they do not form a whole metaphysical system but only a fragment of a cosmology, I believe they are consistent also with the metaphysics of St. Thomas Aquinas.  To me, at least, they gain their credibility both from their intrinsic obviousness and from the more compelling description they afford of the adventure of human experience.

Principle 1: The Principle of Determinateness: That settled actuality (past actuality, whether immediate or remote) is wholly determinate and particular. To preclude sophisticated difficulties possibly arising from the principle of quantum indeterminacy, I provisionally, for the sake of this study, restrict discussion to the realm of ordinary perception.9

Examples: (1) Gone with the Wind, as completed, comprises a particular set of words arranged in a determinate order.  In this it differs from a novel envisioned or in the process of being written.  (2) Brahms’ Fourth Symphony is a particular set of notes determinately arranged.  (I am here referring, of course, to the symphony taken as a formal pattern, a pattern displayed in the score; I am not speaking of a performing of the symphony.)  (3) The way you last passed through a doorway (whether right foot first or left, and so on).

Principle 2: The Principle of Process (or of Determination): That dynamic actuality (or existing actuality or concrete process) is, or at any rate involves, a process of determination whereby from the indeterminateness of potentiality there is educed the determinateness of settled actuality.  This is a process of actualizing the determinate from the limited indeterminateness given in the present for the immediate future.

Examples: (1) The writing of Gone with the Wind.  (2) The composing of Brahms’ Fourth Symphony.  (3) Your walking through a doorway.  (4) Your driving a dune buggy on the beach.  The sea on your right and the sheer palisades on your left set restrictions on the range of possibility for your driving; so also do the steering radius of the buggy, your speed, and other factors.  Within that range of possibility, however, it is your act of driving (steering, etc.) which forms determinate tracks in the sand behind you, tracks which, prior to your driving, had no definition, were simply not there.

One may notice a strong similarity between Principle 2 and the hylomorphic account of substantial change.  That change is a process of “educing” from the potentiality of the matter a form not previously “there.” In that theory, of course, in animal generation a specifically similar form is in the agents (parents); so also, in the case of artifacts, in the intention of the agent.10 Furthermore it can be argued, though I shall not do so here, that Principle 2 in effect requires that the dynamic actuality which is present process cannot be instantaneous, but embodies, within a temporal thickness, a unique co-presence of the immediate past, the present, and the immediate future.

Principle 3: Agency alone educes the particular determinateness of settled actuality from the indeterminateness of Possibility.  (In this paper I am using “agency” broadly, to mean causal activity, whether conscious and intentional or not.)  Apart from such agency, therefore, there are not possibilities but Possibility.  When considering different possibilities for acting, however, one has already supplied the (intentional) agency whereby these possibilities enjoy their distinctness.

Corollary 1: Particular possibilities, particular ways of being, do not temporally precede actuality, whether settled or dynamic.  This is a specification of Bergson’s somewhat less guarded principle that the possible does not precede the real.

Examples: (1) Gone with the Wind was not a possibility before Margaret Mitchell conceived it.  This is not to say that it was impossible, given the existence and the health of the author.  It means rather that, prior to its conception (and I am granting, for the sake of simplicity, that the novel existed in some real sense when it had been well conceived by Mitchell), there was no “it” to refer to. It was Mitchell’s creative act which produced the determinateness of concepts and words which constitutes the novel.  Mitchell invented it, she did not find it lying around among a preexisting collection of “possibles.”

(2) The formal pattern of notes which is Brahms’ Fourth Symphony (to be more precise: which is the directions for, or the character of, the performing of Brahms’ Fourth) had no existence in the temporal world before Brahms conceived it.  It was therefore not around to be “possible.”

This point is illuminated by asking whether “Brahms’ Fifth Symphony” was possible before Brahms died.  (I am assuming that Brahms wrote only four symphonies.)  The question turns out to be illegitimate, for we have no Brahms’ Fifth Symphony to talk about.  We may inquire about a fifth symphony but not about the Fifth Symphony.  There is no Brahms” Fifth Symphony which was or is possible for the precise reason that there never was an actual Fifth Symphony.

Bergson was right, then, in maintaining that the “possible” (understood determinately) arises only simultaneously with the real. The “possible” in that sense is just the character of the real (whether past or present)—in Lewis’s phrase, “the way things are.” But then the “possible” is by no means identical with “Possibility” or “potentiality” (see Corollary 2 below)

I should clarify these distinctions.  I take “possibilities” (or “possibles”) to be Lewis’s “ways things are,” formal patterns of being.  “Possibility” (especially with a capital p) I take to be either the total, unitary, but structured fabric of possibilities, or else the range available for real possibilities in a particular case, this range being governed by the determinate character of the settled past in its relation to Possibility as a whole.  “Potentiality,” however, is the power, the potentia, residing within the real, of becoming determinate, of realizing itself, in some particular new way within the given range of possibility.

(3) In your dune buggy on the beach you have a literal width of possibility of where you can drive (that is, between the sea and the palisades), but it is the driving itself which creates the determinate tracks in the sand.  They do not lie out there ahead of you, waiting to be selected.  Yet the model suited to most current discussion would rather be that of a railroad engine entering a switchyard.  All the tracks are there ahead of time, and the activity of throwing switches merely determines which track the engine winds up on.

(4) The door frame constitutes a certain width of possibility for how you can comport yourself in leaving the room.  But precisely how you do walk out acquires determinateness precisely by your act of walking out.

(5) More strikingly: I have in the past pondered my own death (and probably you have your own), wondering how far it lies in the future and what its circumstances will be.  But on the above principles such speculation is meaningless.  There is no such thing ahead of time as “my death,” taken in the implied full determinateness.  This denies neither that I shall die nor that the passage of events gradually narrows the range of indeterminacy.  It asserts, however, that the precise character (and time) of my death will be determined only by, and simultaneously with, my dying.

Bergson was right, I think, in claiming that we habitually treat time as if it were a kind of space.  We think of our death as lying out ahead of us in time just as we might think of a boulder as lying on the road around the bend.  But to do this is to destroy time (as he also claimed), for it supposes that the future is already determined.

Corollary 2: The link between Actuality and Possibility lies not in possibilities but in potentiality. This potentiality is grounded in the actuality of the settled past and in the dynamic actuality of present process.  Thus the new actual is always growing out of the womb of the potential, but the potential is itself rooted in and structured by past actuality.

The actualists are therefore right in denying an independence to the possible.  On the other hand, to be potentially is really a way to be, even though it is not to be actually.  And this of course is just what Aristotle said in response to Parmenides, who conceived of only one way of being, being in actuality.

Charles Hartshorne has eloquently summarized a position similar to the one I have been attempting to sketch:

Only the past alone is fully determinate, the future is to be determined within the limits of causal possibility.  These limits are just the determinateness of the past as capable of being superseded by some kinds of successors but not by other logically conceivable kinds . . .

[T]he togetherness of actuality and possibility can only be in actuality.  Indeed the possibility of the future is the same as the actuality of the past and present, in their character as destined to be included in some richer total reality.  The potentiality of an event is just the actuality of its predecessors.11


2. Some Impossible “Possible Worlds”

(1) The “possible worlds” of David Lewis. According to the above principles, Lewis’s “possible worlds” are metaphysically impossible, for he assumes them to be completely determinate cosmic histories, yet does not furnish the agents by which to effect the determinateness.

Lewis, of course, will not be impressed by this objection.  For he maintains, as we have seen, that the agents or causes in all his possible worlds are equally real, and that the term “actual,” by which we think to differentiate our world from other possible worlds, is purely indexical, so that the inhabitants of other possible worlds have an equal right to call their own worlds “actual.”

There are, in effect, two assumptions operative in such a position: (1) that it makes sense to talk about “the inhabitants of other possible worlds,” and (2) that the purely indexical use of “actual” is adequate. Both of these assumptions have been challenged by Robert C. Stalnaker.12  As against the first, he challenges the innocence of passing from “ways things could have been” to “possible worlds,” the “things” that could have been otherwise.  It would be comparable to confuse “the ways people act” with “people.”13  If, then, as I would press the argument, Lewis takes his “ways things could have been” in a sense comparable to “the ways people act” as distinguished from the “people,” then he has no agents to account for the diversity of the “ways.” If on the other hand he has shifted from talking about the “ways” to talking about the “things” exemplifying the “ways,” I should like to know with what justification.

Stalnaker also counters the adequacy of Lewis’s purely indexical use of “actuality.”  It assumes that there is a kind of absolute view, even-handed or indifferent to all worlds, and that the inhabitants of any world are equally entitled to refer to their own world as “actual.”  Stalnaker replies:

The mistake in this [Lewis’s] reasoning, I think, is in the assumption that the absolute standpoint is a neutral one, distinct from the view from within any possible world.  The problem is avoided when one recognizes that the standpoint of the actual world is the absolute standpoint, and that it is part of the concept of actuality that this should be so.14

The Parmenidean flavor of a position like Lewis’s is echoed in another modern criticism:

Lewis wants to understand what sort of being possibilities have.  Things, as he says, might be otherwise than they are.  Or rather, more accurately, things might have been otherwise than they are.  The possibility existed that things be one of several different ways, but they turned out to be only this way.  Lewis fastens on the “ways,” but in doing so, he loses all the possibilities.  He claims that these “ways” have just the same sort of being as this one way things turned out.  But if this one way is actual, then all the other ways must be actual.  The universe on this picture is a superworld of pure actuality.  To say that a possibility exists is just to say that somewhere an actuality exists.  This is clear from the definition of possibility as truth in a world.  On this view of worlds, the only way to be true in a world is to actually obtain there.  On this theory, then, possibility reduces to actuality—somewhere else.15

(2) Nicholas Rescher’s mind-dependent possibilities.  Moving from the “possibilist” toward the “actualist” end of the spectrum, Nicholas Rescher claims that unactualized possibilities are mind-dependent:

Possibilistic claims have their principal point where the contrast between the actually real and the hypothetically possible prevails, and where the domain of what is or what does happen is to be augmented by that of what can be or what might happen.  Now the items of this second, hypothetical sphere clearly cannot just “objectively be” the case.  It is my central thesis that by the very nature of hypothetical possibilities they cannot exist as such, but must be thought of: They must be hypothesized, or imagined, or assumed, or something of this sort.16

Now this is surely a step in the right direction, and is consistent with Principle 3 above.  But Rescher’s position proves nonetheless untenable.  In his preliminary remarks to the above essay he asserts: “There are as yet unrealized possibilities that await us in the future.  And there are the possible albeit unrealized doings of actual things such as my possible attendance at the film I failed to see last night.”17  What, we must ask, is the agency by reason of which these plural possibilities enjoy their determinateness?  According to Rescher’s central thesis it would seem that each of these possibilities must meticulously be thought of, imagined, or hypothesized by a rational mind.  But this is, in the context, hardly plausible.  Rescher seems to be thinking of more possibilities than he has minds actually thinking of them.  And indeed he does quickly make a substantial qualification:

We are not saying that to be a possible (but unactualized) state of affairs requires that this state must actually be conceived (or entertained, hypothesized, and so on)—so as in fact to stand in relation to some specific mind.  Rather, what we are saying is that possible, albeit unrealized, states of affairs or things obtain an ontological footing, that is, they can be said to “exist” in some appropriately qualified way only insofar as it lies within the generic province of minds to conceive (or to entertain, hypothesize, and so on) them.18

But if this absolves Rescher’s theory from an unreasonable multiplicity of busily hypothesizing minds, it aggravates the problem of accounting for the apparent distinctness of the hypothetical possibilities themselves.  Rescher is in fact forced to oscillate between saying that hypothetical possibilities must be conceived19 and that they must be conceivable.20  But by the principles worked out above, these two stances are crucially distinct and one can’t have it both ways.

At the heart of the problem lies Rescher’s claim that potentiality itself is purely mind-dependent.  To the objection that an acorn has in itself a potentiality to grow into an oak, Rescher replies: “Regardless of the status of the acorn as being independent of the existence of the mind, and whatever the acorn in fact does, the strictly modal aspect of what it may or may not do is not and cannot be an aspect of objective reality.”  Are we driven, then, he asks, to a “possibility-idealism,” so that if there were no rational minds “there would be no unreal possibilities”?  Yes, he answers; if rational minds were abolished, “the domain of unrealized, albeit possible, things would also have to vanish.”21

The ease with which Rescher has shifted from speaking of potentiality to possibilities betrays the fundamental inadequacy of his position.  By Corollary 2, one cannot give an account of the relation between the real and the possible without recognizing potentiality as an essential, distinct, and mind-independent ingredient of the actual.

(3) Reflective aside.  At this point we are in a position to take a harder look at the root issues here at stake.  Running like Ariadne’s thread through the writings of Lewis and many others lies the unexamined assumption that there exist multitudinous, discrete “ways things could have been” even though there are no real causes responsible for the determinateness of that presumed plurality.  Hand and glove with this assumption is the tendency to substitute possibilities for potentiality.  Experientially we find ourselves within an actual world which in its ongoing process is constantly achieving its determinateness by the activity of real causes synthesizing settled determinateness out of a range of real Possibility (not out of possibilities).  With Lewis, however, we may incautiously move from recognizing that things could be otherwise (recognizing potentiality) to positing discrete ways in which they could be otherwise (thus confusing potentiality with possibilities).  With Lewis, too, we may even move to passing from these discrete ways of things to things which are assumed to exemplify the ways—to possible worlds indistinguishable, except indexically, from the actual.

According to the principles defended in this essay these discrete “possible worlds” are metaphysical monstrosities, just as square circles are logical monstrosities (Meinong notwithstanding).  For the determinateness of the actual, as distinguished from the circumscribed indeterminateness of the possible, is achieved precisely and only by the activity of real agents.  Whereas there are actual entities which continuously found the potentiality in which the actual world weaves itself, the only actual causes we have which can account for the supposed determinateness of any one of these hypothetical states of affairs (possible worlds) is we ourselves in our thinking of them.  (In this Rescher has a point.)

Even so, to what extent do we succeed in defining a possible world by thinking about it?  If we take our principles seriously, its only definition will be what we explicitly give it.  Inevitably we begin with imaginative material drawn from our own experience; to that extent any possible world resembles the actual world.  But if we should try to construct it wholly by creative conceptualization, we find ourselves completely unequal to the infinite task of definition.  Our conceptualized possible world will be almost infinitely vague and indeterminate compared to the actual world.

In this respect it is worth paying attention to the difference between the definite and indefinite articles.  A year before the battle one might have talked about a battle at Gettysburg but one could not have talked about the Battle of Gettysburg.  The latter achieved its determinateness, about which we are now in some position to speak, precisely by the battling of the actual soldiers.  Similarly, an admiral in peacetime might dreamily think of a sea battle tomorrow (especially if he is a Walter Mitty); an admiral in World War II might reasonably plan for the sea battle tomorrow (say, at Midway), if actual circumstances have made the inevitability and partial character of the battle clear.  Even so, however, the battle viewed in prospect is not identical with “the Battle of Midway,” and at least part of the difference lies in the complete determinateness effected by the actual battling.  (Otherwise the admiral would infallibly know whether he would win on the morrow.)

Is then actuality to be identified with determinateness, as I may seem to have implied?  Charles Hartshorne seems to think so.  If one is to go along with Leibniz, he says, one “must admit that a possible world is as definite and complex as the corresponding actual one.”  This is quite correct.  But then Hartshorne goes too far.  He adds that such an admission “reduces the distinction between possible and actual to nullity.  Value is in definiteness, and definiteness is “the soul of actuality.”  Were possibility equally definite it would be redundant to actualize it.”22

There are two things wrong with this assertion.  In the first place, mutual implication constitutes logical equivalence but does not entail logical or metaphysical identity.  In the system of Thomas Aquinas, for instance, although every (finite) act of existence (esse) requires its actual form, and every actual form requires its esse, the form is nonetheless not identical with the esse.  Similarly, for Whitehead although determinateness implies real agency, and real agency always produces determinateness, it is not the case that the agency is the determinateness. Secondly, it cannot be that “value is in definiteness, and definiteness is ‘the soul of actuality.’” For Hartshorne himself grants that “[o]nly the past alone is fully determinate,” as we saw in our first quotation from him.  But then he would have to grant here that value resides only in the past rather than in the present.  With Whitehead, however, I maintain that value is preeminently found in the contrast experienced by the actual entity in its present subjectivity; what has subjectively perished, the settled past, has value only insofar as it is relived in the subjectivity of its successors.  If we equate determinateness with actuality we neglect the heart of reality (which is durée for Bergson, creative process for Whitehead, esse for Thomas), and once again risk confusing potentiality with possibilities and actuality with sterile forms.

(4) The “middle knowledge” theory of Luis de Molina.  So far we have concentrated on “pure” possibilities, “ways things could have been.”  What about conditional possibilities, “ways things would have been (or would be)” in certain circumstances? And under which consideration (or both?) do we best situate our assessment of Leibniz’s “possible worlds”?  It is illuminating first to look at a simpler and earlier view, one with which Leibniz was perfectly familiar: the scientia media theory of the sixteenth century Jesuit theologian, Luis de Molina.  This theory finds contemporary expression, as we shall see, in the position taken by Alvin Plantinga concerning God and evil.23

Molina took for granted, as did his contemporaries, that God infallibly knows both all possibles, everything that can or could be (this was called “knowledge of simple intelligence”), and all reals, everything that is, was, or will be (“knowledge of vision”).  But, it was held, God’s knowledge cannot be passively acquired, cannot be spectator knowledge, because in that case He would be acted upon and in some way perfected by the creature.  No, God’s infallible knowledge must be grounded directly in the divine creative decrees themselves.  But then how can we reconcile the infallibility of this knowledge, based on a divine decree ontologically prior to the event, with the freedom of the creature’s decision?  It would seem that we must give up either the inerrancy of God’s knowledge or the freedom of the creature.

Molina was unwilling to give up either, and proposed the following way out of the dilemma.  He posited yet a third kind of divine knowledge, a sort of intermediate knowledge (a “scientia media”) falling between knowledge of simple intelligence and knowledge of vision.  Through it God knows infallibly what any free agent would determinately do, and do freely, in any hypothetical situation regardless of whether the agent is ever in that situation.  The particular object of this middle knowledge is that one of two possible contradictory acts that a free agent would perform if certain conditions were fulfilled. Molina referred to this object as the “contingent future”; later the term “futurible” was coined.  The complete set of futuribles, then, is the complete set of “would’s” as distinguished from “could’s” or “will be’s.”

Armed with this simple but ingenious idea, Molina proposed the following account.  In virtue of this middle knowledge God knows (eternally and infallibly) precisely what a human being, say Adam, would do (and do freely) if placed in a certain precise situation.  This situation includes very specially the exact amount of divine help (“actual grace”) extended to him.  Thus, by virtue of this middle knowledge God knows that Adam and Eve, say, would sin if placed in the situation described in Genesis, and He knows this irrespective of (“prior” to) His decision to place them in just that situation.  But then if, for inscrutable reasons of his own, God couples this hypothetical knowledge with an absolute decree that this situation in fact should come about, the middle or hypothetical knowledge becomes knowledge of vision, of what infallibly must occur.  Thus God infallibly knows the sin of Adam and Eve antecedent to, or at any rate ontologically prior to, their historical sinning.  Yet this knowledge in no way forces them to sin, for that they would sin in such a situation depends on them in their freedom, not on God.

Molina’s theory thus stands or falls on the coherence of the notion of futuribles.  But according to our principles futuribles are metaphysically monstrous: they posit the determinate outcome of a free agent’s acting while excluding the acting!  Thus, futuribles are metaphysically inconsistent fictions which cannot form an object of anyone’s knowledge, not even God’s.

(5) The “possible worlds” of Leibniz.  Leibniz conceived God to have infallible knowledge, apart from (antecedent to, as it were) His creative decree, of all possible “worlds,” of all possible cosmic histories in their complete detail.  In accordance with the Principles of Sufficient Reason and of Perfection God naturally chooses to create that world in which the most perfection is realized.  Any other supposition is absurd.  However paradoxical it may seem to our limited minds, then, this world, with all its evil, must contain on balance the greatest possible amount of perfection.

We have already seen that the very conceivability of a “best” possible world has been challenged by both classical and contemporary thinkers.  But on our principles there are simply no possible worlds at all for God to choose from.  This may best be seen by comparing Leibniz’s theory with that of Molina.

Molina’s principal work, Concordia Liberi Arbitrii cum Gratiae Donis, Divina Praescientia, Providentia, Praedestinatione et Reprobatione (1588)—Molina was not shy—was familiar to Leibniz, who summarizes it in his Essais de Théodicée, Première Partie, pars. 39–40.24  Having reviewed some of the points of controversy between the Molinists and their adversaries, Leibniz proceeds to align himself exactly with Molina (as he says explicitly in par. 43) in accepting the notion of futuribles (Leibniz calls them “conditional futures” or “contingent futures”).  He writes:

. . . [I]t will suffice if I explain how I think that there is truth on both sides.  To that end I come to my principle of an infinity of possible worlds represented within the object of the divine intelligence, where all conditional futures must be contained. . . . Thus we have a principle of certain knowledge about contingent futures, whether they actually occur or whether they [only] ought to occur in a certain situation.  For within the domain of the possibles, they are represented as they are, that is, as free contingents. . . . And although it should be true and possible that contingent futures which consist in the free actions of rational creatures should have been entirely independent of the divine decrees and of external causes, it would be possible to foresee them: for God would see them just as they are in the domain of the possibles, prior to his deciding to admit them to existence.25

Leibniz’s “possible worlds,” then, more clearly than those of Lewis, are worlds of “would’s” as well as of “could’s.”  The determinateness in these worlds is not merely a matter of “ways things could be,” taken abstractly, but also of “ways agents would freely act” in specific situations.  Yet insofar as these worlds are only “possible,” the agents are only hypothetical, and hypothetical agents are just not agents.

Leibniz’s “possible worlds” are thus subject to the same fatal criticism as Molina’s “futuribles.”  Like Molina, Leibniz tries to have it both ways: God is supposed to know the determinate outcome of an agent’s free action, but without the acting of the agent.  Yet it is only the acting that could produce the determinateness!

But, you might object, is God not capable of conceiving any number of possible cosmic histories, and do these not qualify to be called “possible worlds”?  Indeed, is this not the traditional doctrine, defended by St. Thomas Aquinas when he asserts that God’s knowledge extends not only to all that is ever actual but to that which is merely possible?26

God forbid that I forbid God from conceiving as possibilities any number of such hypothetical world-histories, or you from calling them “possible worlds” if you wish!  But on the principles defended above, I contend that any such “possible world” is sterile in its relationship to the actual world; it is a pure fancy, metaphysically inconsequential.  For instance, it cannot possibly serve in the function Leibniz assigned it, for there is no way in which it can pass from purely hypothetical to actual without robbing human agents of their freedom!

I mean that, for a purely hypothetical but completely determinate world-history, God is the necessary and sufficient agent effecting that determinateness.  If, for example, it includes a free agent P who is conceived as deliberately doing act q at time t, it is solely God who provides the determinateness for that conceived scenario.  If now Leibniz’s God is to say, “Let that world be!” then to God must be attributed all the determinateness of the events, including P’s doing q at t.  No, says Leibniz: ontologically prior to His creative decree, God knew what P would freely do at t; it is just that God decrees to let that world exist.  But what P is conceived to do at t cannot be attributed to P as to its author apart from P’s actual acting at t.  Hence as long as the situation is purely hypothetical, the only determinant of what P is conceived to do at t is God Himself conceiving it.  Thus God, not P, is the determinant of q in that kind of “possible world.”

If therefore one were to assert with Leibniz that there is some way in which such a divinely conceived and completely determinate hypothetical cosmic history could, by divine fiat, become actual, nothing would remain of human free agency, nor, I am afraid, could God be acquitted of responsibility for the moral evil in the world, since on that supposition God would be the determinant of every event.

Unless therefore God is to appropriate to Himself all the determining process in the world, there are no possible worlds available for Him to choose from in creating an actual world.  God cannot know the detailed and determinate course of world events apart from His decree that there be a world, for apart from that decree there are no finite agents to determine that course of events.

This conclusion shows that it is not playing metaphysical parlor games to take a stand on the ontological status of possible worlds, for that directly bears on the problem of reconciling the existence of God with that of evil in the world.  If the principles adopted above are accurate, it is simply not the case that God knew, as it were ahead of time, what evils would occur in this world and then went ahead and created it anyway.  Yet that is the implicit attitude underlying the common question, “Why did God choose a world with so much evil in it?” If God had available for his choice an infinity of possible worlds, it is difficult indeed not to think that He chose badly. 27


3. Metaphysics and Logic: A Crucial Objection

I face, finally, a crucial objection to the procedure and the conclusions of this argument, an objection which has perhaps already occurred to the reader. Someone might protest: “Despite your intentions, you have not in fact taken seriously the notion of ‘possible worlds,’ and your principles, even if they were to be granted, systematically neglect an infinity of them.  For your principles, besides being unprovable, apply, if they apply at all, to this actual universe.  But there is nothing logically contradictory about denying any or all of them.  Hence it is logically possible for other worlds (universes) to exist, exemplifying different metaphysical principles, and they precisely constitute an indefinite multiplicity of possible worlds untouched by your overzealous exorcism.”

Is this objection as fatal as it sounds or is it, as Socrates would say, only a wind-egg?  I frankly doubt that I shall persuade anyone who is sympathetic to this objection; nevertheless I think it mistaken.

For I deny what the objection presupposes, that logic enjoys precedence over metaphysics.  Is it really the case that there is a paramount logical order in which various metaphysical structures are included as so many sub-areas in a Venn diagram? Or is the logical order rather a reflection of the structure of the real (whether one calls the real, “being,” or “process,” or “becoming”)?  If the latter, then insofar as one has in fact laid hold of some of the ultimate principles of the real, they are no longer negotiable. To repeat Whitehead’s earlier remark: “This doctrine of necessity in universality means that there is an essence to the universe which forbids relationships beyond itself, as a violation of its rationality. Speculative philosophy seeks that essence.”28

Everything here hinges on the relation one acknowledges between metaphysics and logic.  To argue this carefully, even if one could agree on the meaning of “metaphysics” and “logic,” would require, to say the least, an essay in itself and I shall not attempt that here.  I do however venture the following interconnected assertions:

(1) Whether the logical order is viewed as an abstract character of the in-some-way-extramental real, or as a reflection of the structure of thought, the logically possible inheres in and depends upon the real, not the other way around.  This is already an implication of Principles 2 and 3, and Corollary 1.  In that sense, the principles I have defended claim for themselves a certain autonomy.  That they are unprovable is true but not a criticism, for the same is true of any conceivable metaphysical principles as well as of any other genuinely basic assumptions necessarily underlying thought.  The only interesting question is whether they are in fact true.

(2) That if they are true they are true for this universe and no other, is also correct but again not necessarily a criticism.  For it may be doubted (and I do doubt it) that it makes any sense to hypothesize other worlds in which metaphysical principles true for this world are violated.  Let “X” stand for some world which obeys different metaphysical laws from ours. Then the assertion: “X is a possible world” is arguably an inconsistent proposition, either internally or at least in its being asserted (or both).  For the “is” in that proposition is not a pure copula but has existential import.  Either in the content of the proposition itself, or at least in the context of its being asserted by a thinker in this world, the character of the “is” is inevitably structured by the metaphysics of this real world.  And that, I think, is why Stalnaker was correct above (part 2, section (1)), in criticizing Lewis’s theory of actuality for tacitly assuming that there is an absolute standpoint, independent of the actual world, from which to view possible worlds.  Rather, he says, “the standpoint of the actual world is the absolute standpoint, and . . . it is part of the concept of actuality that this should be so.”29

(3) Similarly, even the objector must grant that he (or she) as well as the rest of us must perforce follow the laws of thought which obtain in this world, even when trying to speculate about metaphysically oddball worlds.  There is simply no other way for us to think if we are to think at all.  But can such thought really get us into possible worlds which disobey the metaphysics of our own?  Or is it rather that we haven’t escaped our own metaphysical structure at all, any more than (as Kant I think observed) we can imagine two universes?  If we have not, then the metaphysical structure of this world provides a touchstone for evaluating the sense or nonsense of proposed possible worlds.

(4) At the beginning of this essay I disclaimed having anything to say about “the purely logical or formal advantages” of the notion of “possible worlds.”  I suppose that what I have just been saying casts doubt on whether there is room at all for a purely logical, metaphysically innocuous, way of speculating about “possible worlds.”  I am unable at present to resolve this issue.  Nevertheless, since it is the metaphysical, not the logical, problem of “possible worlds” in which I am interested, I see no reason to approach it by assuming a pre-eminence of logic over metaphysics.

(5) Finally, it is worth noting that the objection draws much of its apparent strength from the seeming arbitrariness, hence replaceability, of the principles which I have set down.  But is one really free to make substitutions?  The picture changes considerably when these principles, which are only fragments of a cosmology, are set into the context of a complete metaphysical system.  As I have said, I think those principles are compatible with the philosophies of Whitehead, Bergson, Hartshorne, and even Thomas Aquinas.  Let us see what happens when we embody them in the metaphysical systems of Whitehead and of Aquinas.

For Whitehead, the metaphysical structure of reality is constituted by God in his “primordial nature.”  Insofar as our principles are true, they must form part of that constitution.  Now this constitution of a metaphysical structure, of the ways things can be related to one another, of an ultimate ground of possibility for the process of the universe, is unique. It is an Ur-act which is “free” in two respects: (1) it is bounded by no outside restraints; (2) it is self-constituting, self-creating.  It is just the ultimate reason why the process of the universe is ordered as it is, and there is no reason beyond the ultimate reason.  To ask for such a reason would be to make a category mistake.  Further, this ultimate structure of possibility countenances, by its very nature, no alternative.  It is the absolute structure for the universe, and insofar as we succeed in discerning some of its features, they have a kind of absolute status as well.  This is the ground for the privileged status of the actual as over against the merely possible.

For Thomas Aquinas, God, in knowing Himself, thereby knows all the ways in which his essence (which is existence) can be shared.  God is Himself the ground, the reason, why some things are ultimately possible and others not.  This is “antecedent” to any divine decision to create.  Also, God did not, as it were, sit down and decide what the structure of ultimate metaphysical possibility should be (as Descartes would perhaps have allowed Him to do).  He is in his own essence just that structure, or the ground of it.

If that be so, once again there is an ultimate source for the metaphysical structure of the universe which gives to that structure a privileged status.  The laws of being and becoming are not up for grabs, though one may want to toy with them from a purely formalistic point of view.  But that is not to constitute metaphysically respectable possible worlds.30



1 See for instance Bruce R. Reichenbach, “Must God Create the Best Possible World?” International Philosophical Quarterly 19 (1979): 203–212.  And St. Thomas Aquinas affirms that God could always make better things than He did: Summa Theologiae, I, 25, 6.

2 David K. Lewis, Counterfactuals (Cambridge, MA: Harvard Univ. Press, 1973), p. 84.

3 Ibid, pp. 84f.

4 Nicholas Rescher, “The Ontology of the Possible,” in Milton Munitz, ed., Logic and Ontology (New York Univ. Press, 1973), p. 213.  This essay is also reprinted as chap. 8 of Michael J. Loux, ed., The Possible and the Actual (Ithaca: Cornell Univ. Press, 1979).

5 I should like to make my own the words of Bishop Berkeley in the Preface to the first edition of his Treatise Concerning the Principles of Human Knowledge: “What I here make public has, after a long and scrupulous inquiry, seemed to me evidently true and not unuseful to be known. . . . Whether it be so or no, I am content the reader should impartially examine, since I do not think myself any further concerned for the success of what I have written than as it is agreeable to truth.  But to the end this may not suffer I make it my request that the reader suspend his judgment till he has once at least read the whole through with that degree of attention and thought which the subject matter shall seem to deserve” (New York: Liberal Arts Press, 1957, p. 4).

6 In Process and Reality (New York: Macmillan, 1929), p. 4.

7 Ibid., pp. 5f.

8 Counterfactuals, p. 88.

9 To preclude sophisticated difficulties possibly arising from the principle of quantum indeterminacy, I provisionally, for the sake of this study, restrict discussion to the realm of ordinary perception.

10 In that theory, of course, in animal generation a specifically similar form is in the agents (parents); so also, in the case of artifacts, in the intention of the agent.

11 Charles Hartshorne, Creative Synthesis and Scientific Method (LaSalle, IL: Open Court, 1970), pp. 64, 225.  I am obviously indebted to his thought.

12 In “Possible Worlds,” Nous 10 (1976), 65–75; reprinted as chap. 12 of the Loux anthology.

13 Loux volume, p. 227.

14 Ibid., p. 229.

15 Phil Weiss, “Possibility: Three Recent Ontologies,” International Philosophical Quarterly, 20 (1980): 201f.

16 “The Ontology of the Possible,” Munitz Volume (see note 4), p. 214.

17 Ibid., p. 213.

18 Ibid., pp. 216f.

19 Ibid., pp. 214, 218, 220.

20 Ibid., pp. 216, 220.

21 Ibid., p. 219.

22 Charles Hartshorne, Anselm’s Discovery (LaSalle, IL: Open Court, 1964), pp. 189f.

23 For a summary of Molina’s doctrine see the articles “Molinism” and “Futuribles” in the New Catholic Encyclopedia (New York: McGraw-Hill, 1967).

24 In C. I. Gerhardt (ed.), Die philosophischen Schriften von Gottfried Wilhelm Leibniz (Hildesheim: Georg Olms, 1978), VI. Band, pp. 124f.

25 Ibid., par. 42; my emphasis and translation.

26 As for instance in Summa Theologiae, I, 14, 9, c.  In Thomas’ language, that which is purely possible is a ratio or pattern for God’s scientia simplicis intelligentiae, not an exemplar for God’s mind. Cf. ST, 1, 15, 3, ad 2.

27 Difficult, but not impossible.  Leibniz thought God simply must not have had a better choice, and Alvin Plantinga has recently tried to show that this might indeed be the case.  In The Nature of Necessity (Oxford: Clarendon Press, 1974, esp. chap. ix), he ingeniously argues that the existence of God is logically compatible with that of moral evil in the world since it is at least possible that the only possible worlds available for God’s choice are worlds involving moral evil.  Unfortunately for the (literally) triumphant view he takes of this argument, his demonstration hinges on the assumption that it is possible that God knows that every free agent would commit some moral misdeed in any possible world whatsoever.  But it cannot be possible that God knows this, since there is just no such thing as what a purely hypothetical free agent would do!  Plantinga freely grants that to suppose that there is something specific which a hypothetical agent would do in a particular situation is to make an assumption, an assumption he confesses himself unable to prove (p. 180).  But that assumption is just Molinism all over again and must be ruled out.  This affinity between Molina and Plantinga has been pointed out by Robert Merrihew Adams in “Middle Knowledge and the Problem of Evil,” American Philosophical Quarterly, 14 (1977), 109–117.

28 Process and Reality, p. 6.

29 Loux volume, p. 229.

30 I am in the debt of several philosopher friends for helpful criticisms of earlier versions of this essay, especially to Richard J. Blackwell, Daniel O. Dahlstrom, Vincent G. Potter, S.J., and Youree Watson, S.J.


Posted March 26, 2009

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