A Problem for Actualism About Possible Worlds Author(S): Alan Mcmichael Source: the Philosophical Review, Vol
Total Page:16
File Type:pdf, Size:1020Kb
Philosophical Review A Problem for Actualism About Possible Worlds Author(s): Alan McMichael Source: The Philosophical Review, Vol. 92, No. 1 (Jan., 1983), pp. 49-66 Published by: Duke University Press on behalf of Philosophical Review Stable URL: http://www.jstor.org/stable/2184521 Accessed: 09-02-2017 14:56 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/2184521?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms Philosophical Review, Duke University Press are collaborating with JSTOR to digitize, preserve and extend access to The Philosophical Review This content downloaded from 128.195.69.222 on Thu, 09 Feb 2017 14:56:26 UTC All use subject to http://about.jstor.org/terms The Philosophical Review, XCII, No. 1 (January 1983) A PROBLEM FOR ACTUALISM ABOUT POSSIBLE WORLDS Alan McMichael I. INTRODUCTION T he notion of a possible world has many uses in the formal philosophy of language. Its primary use, of course, is in the interpretation of sentences about necessity and possibility. A prop- osition is necessary if and only if it is true in all possible worlds; possible if and only if true in some possible world. One advantage of the possible worlds interpretation is its extensionality. The inten- sional notions of necessity and possibility are replaced by quan- tifiers over possible worlds. The language in which these quan- tifiers appear, sometimes called "world theory," can be given an ordinary Tarski semantics. A second advantage of the possible worlds interpretation is purely heuristic. It just seems to help our modal thinking to imagine other possible worlds. However, the nature of possible worlds is the subject of a familiar controversy, the dispute between actualism and possibilism. One common position in this controversy, which I shall call atomistic actualism, seems to me the most plausible. Nevertheless, I shall show that it is open to serious objection. It fails to provide an adequate interpretation for certain modal sentences, assuming that we adopt standard rules of interpretation. Thus we must either reject atom- istic actualism, even though, as I shall argue in the next section, the alternatives are not attractive, or reject the standard semantics, despite its practical successes. II. POSSIBILISM AND ACTUALISM' According to the possibilists, possible worlds are concrete en- tities. In this respect, they are like the concrete universe which we 'The possibilism-actualism distinction should not be confused with the possibilism-modalism distinction. A possibilist in the sense of the second distinction is a person who believes that necessity and possibility are ana- lyzable in terms of quantification over some kind of entities. Whether he or she is a possibilist in the first sense depends on whether those entities are taken to be actually existing or merely possible. 49 This content downloaded from 128.195.69.222 on Thu, 09 Feb 2017 14:56:26 UTC All use subject to http://about.jstor.org/terms ALAN MCMICHAEL inhabit. For the possibilist, this concrete universe is the actual world. (In saying that possible worlds are concrete, the possibilist is not saying that they are made of actual concrete things. Many worlds contain nonactual concrete things, such as individual dragons and unicorns.) According to the possibilism of David Lewis, this world's actuality is a merely relative matter.2 This world is indeed actual with re- spect to itself, but every other world is actual with respect to itself. So all worlds are on an ontological par. This postulation of on- tological parity, while perhaps it can be consistently maintained, is prima facie absurd. The apparent absurdity may not be sufficient reason for dropping Lewis' theory altogether, but it is enough reason to prefer a consistent alternative. A second form of possibilism takes the notion of actuality to be absolute. Thus this world is distinguished from others by the non- relative property of actuality. In the most plausible version of this view, the property of actuality is taken to be simple and irreduci- ble.3 Another-way to put the view is to say that all possible worlds have being, but only this world has existence or actuality. Many phi- losophers have found this two-tiered Meinongian ontology quite incomprehensible. I am inclined to reject it also, provided that some actualist alternative can be found. Actualists who believe in possible worlds view them as existing abstract entities. The actual world is not actual merely in the sense that it exists-all possible worlds exist-but rather in the sense that this concrete universe corresponds to it. Robert Stalnaker is an actualist who gives serious consideration to the view that possible worlds are irreducible abstract entities.4 He suggests that the term 'world' is in fact misleading: there is only one world, this one. However, there are many 'ways the world 2Lewis, Counterfactuals (Harvard University Press, 1973), 84-91. 3This second form of possibilism is usually adopted as a view about all possible objects, rather than merely about all possible worlds. See, for example, the theory of possibles contained in Terence Parson's Nonexistent Objects (Yale University Press, 1980). Meinong, and possibly Leibniz, held similar views. 4Stalnaker, "Possible Worlds," Nous 10 (1976), 65-75. Stalnaker does not explicitly endorse this view, but he does defend it against objections. I am grateful for his comments on this matter, in which he points out that his main theses are (a) that actualism does not require a reduction of possible worlds and (b) that reduction of propositions to possible worlds has certain advantages over the reverse reduction of possible worlds to propositions. 50 This content downloaded from 128.195.69.222 on Thu, 09 Feb 2017 14:56:26 UTC All use subject to http://about.jstor.org/terms A PROBLEM FOR ACTUALISM ABOUT POSSIBLE WORLDS might have been' or 'world-states,' and they are what we mean by the term 'possible worlds.' These world-states are abstract entities distinct from this concrete universe. We might think of them as specially determinate properties. One of the world-states is actual in the sense that it is exemplified by our concrete world. This world state is 'the way the world is.' None of the other world-states is exemplified. Thus the notion of actuality does not remain unex- plained, as it does in the absolutist form of possibilism, because in construing worlds as a kind of property, the actuality-nonactuality distinction collapses into the exemplification-nonexemplification distinction. On the view in question, possible worlds are basic properties. They are not properties that might be reduced to simpler proper- ties, or to properties and relations. This particular aspect of the view is one I find unattractive. The decision to treat possible worlds as basic clashes with all commonly accepted patterns of reduction. Reduction proceeds from tables and chairs to atoms, not vice versa. Since this world contains tables and chairs as parts, it too is com- plex. But since the state of this world, the way the world is, must somehow encode the complex interrelations of this world's parts, it also is complex, a complex of properties and relations. Finally, just as the state of this world is complex, so too are the other world- states. Alvin Plantinga is an actualist who takes worlds to be complex states-of-affairs.5 A state-of-affairs is a proposition-like entity. Exam- ples are Karpov's being world chess champion and Plantinga's having climbed Mount Everest. The former state-of-affairs obtains, the latter does not. Both states-of-affairs, however, are possible. That is, each is such that it could have obtained. Not every possible state-of- affairs is a world, only those that are maximal. A state-of-affairs S is maximal if and only if for any state-of-affairs S', either it is impossi- ble for S to obtain and S' not to obtain, or it is impossible for both S and S' to obtain. That is, S is maximal if and only if for any state-of- affairs S', S either includes S', or S precludes S'. Speaking loosely, a maximal state-of-affairs is one which is completely determinate.6 A 5Plantinga, The Nature of Necessity (Oxford University Press, 1974), IV. 1. 6This is only loosely correct because a maximal possible state-of-affairs may include a state-of-affairs of something being F without including, for any individual X, the state-of-affairs of X's being F. The importance of this point will become clear in the next section. 51 This content downloaded from 128.195.69.222 on Thu, 09 Feb 2017 14:56:26 UTC All use subject to http://about.jstor.org/terms ALAN MCMICHAEL possible world is a state-of-affairs which is both maximal and possi- ble. Although all these worlds exist, just one of them is actual in the sense that it obtains. Thus the distinction between actuality and nonactuality is merely the distinction between obtaining and not obtaining. As in Stalnaker's theory, worlds, being abstract objects, exhibit a duality which accounts for the distinction. There are two other actualist theories which are very similar to Plantinga's.