Modal Fictionalism

Questions about necessity (or what has to be, or what cannot be otherwise) and possibility (or what can be, or what could be otherwise) are questions about modality. Fictionalism is an approach to theoretical matters in a given area which treats the claims in that area as being in some sense analogous to fictional claims: claims we do not literally accept at face value, but which we nevertheless think serve some useful function. However, despite its name, “Modal Fictionalism” in its usual manifestations is not primarily fictionalism about claims of necessity and possibility, but rather a fictionalist approach to claims about possible worlds. (For instance, modal fictionalism is not normally fictionalist about the claim that “it is possible that there be a species of tail-less kangaroo”, but rather about the claim that “there is a possible world in which there is a species of tail-less kangaroo”.) The practice of taking possible worlds to be merely convenient fictions, or of treating talk about possible worlds as being useful without being literally correct, is quite common in philosophical circles. It is only recently, however, that philosophers have seriously examined the implications of taking possible worlds to be merely fictional objects, like Sherlock Holmes or a frictionless surface.
Theories employing possible worlds terminology have been found to be very useful in philosophy, e.g. when engaging in thought experiments; distinguishing various claims in metaphysics, or in the philosophy of language, mind, knowledge or ethics; and in areas other than philosophy, like linguistics, modal logic, and probability theory. Many have found the status of these worlds and their contents to be puzzling, to say the least. What are they? Where, if anywhere, are they supposed to be? How are we supposed to discover facts about them? Isn't it extravagant to believe that just because a situation is possible, it must in some sense exist? Modal fictionalists take theories committed to the existence of possible worlds, merely hypothetical situations, non-actual but possible objects etc. to be strictly and literally false, and so they avoid the problems of believing in possible worlds. Nevertheless, they claim, they can enjoy the benefits of using these seemingly problematic theories.
Modal fictionalism should be of interest to those concerned with the metaphysics of modality, since theories committed to the literal existence of possible worlds (and, even more worryingly, the literal existence of merely possible objects ‘contained’ in these worlds) come at a cost, both to economy and to many people's intuitions. But it is, or should be, of wider interest as well, since it is one of the most discussed applications of a fictionalist treatment of abstract objects, along with mathematical fictionalism. Lessons learned in the case of modal fictionalism can hopefully be applied to other areas in which we may wish to evade literal theoretical commitments.
I shall begin by discussing the motivation for modal fictionalism, and distinguishing some of its varieties. Next, I shall seek to put fictionalism in a slightly broader theoretical context, by discussing its connections with instrumentalism and eliminativism, and by discussing what connection there might be between “fictionalism” and treatments of paradigmatic fictions. I shall then discuss the debate about the “Brock/Rosen objection” and a problem raised by Bob Hale, both of which turn on technical problems concerning modal claims about the status of the modal fiction. Finally, in section 4, other concerns about modal fictionalism will be discussed.

[size=30]1. Types of Modal Fictionalism

Modal fictionalists often focus on the claim that possible worlds are merely fictional entities, and apparent commitment to possible worlds is to be explained in the same sort of way that apparent commitment to ideal gases or frictionless surfaces is to be explained. Rosen 1990 and others have formulated modal fictionalism as a theory that takes talk of possible worlds to be on a par with talk about paradigmatically fictional objects, e.g., Sherlock Holmes (“There is a (non-actual) possible world at which there are blue swans” is to be understood on the model of “There is a brilliant detective at 221b Baker Street”, in Rosen's example). This goes with an at least partial account of how we are to treat paradigmatically fictional claims: that they are, literally and strictly speaking, false. The literal truth, according to modal fictionalists, is that there are no merely possible worlds (or merely possible situations, or outcomes), and there are no merely possible objects. Strictly and literally speaking, there is no sculpture that I spent this morning making, though there could have been. When the flipped coin comes down heads, there is strictly speaking no outcome of that very throw in which it comes down tails.
What is literally true, however, is that according to the modal fiction, or according to the fiction of possible worlds there is a (merely possible) sculpture I could have spent this morning making, and there is an (unactualised) outcome of the toss in which the coin came down tails. What is said in talk about merely possible worlds and merely possible objects is generally literally false, but the slightly more longwinded talk about what is true according to the fiction of possible worlds is literally true. One might think (as Hinckfuss 1993 does) that talk about possible worlds is (or should be) governed by implicit presuppositions known to be false so that what is said in the language of possible worlds does not commit one to the existence of possible worlds, but only to some more economical proposition: something of the kind “if there were possible worlds of such-and-such a sort, then …”, or “given the presupposition that there are possible worlds, …”. Or you might have some other account of the functioning of talk about possible worlds: Nolt 1986 suggests we should take typical “possibilistic discourse” to be a game of make-believe (Nolt 1986, p. 440), and while Nolt does not tell us specifically what theory of make-believe he has in mind, there are many theories of make-believe (most famously Walton 1990) that might be employed by a modal fictionalist to explain the behaviour of our typical utterances about possible worlds. Stephen Yablo (Yablo 1996) is one person who employs Walton's theory in his fictionalism (or, as he prefers in Yablo 2001, figuralism) about possible worlds.
The main benefit which a fictional approach to possible worlds offers is, of course, the advantage of using the language of possible worlds, without the stiff ontological cost of literal commitment to such worlds. It is an especially tempting account of merely possible objects (like blue swans, or dragons, or the Holy New Zealand Empire): even those who accept some abstractionist account of possible worlds (see van Inwagen 1986) might well be reluctant to accept the literal existence of their contents. After all, it is often thought that the distinguishing mark of merelypossible objects is that they do not actually exist.
Central to fictionalist treatments of possible worlds are biconditionals connecting truths about necessity and possibility, on the one hand, and the contents of the modal fiction, on the other. Central biconditionals will be all the instances of the following schemas (where P expresses a proposition):
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اقتباس :: Possibly P iff according to the fiction of possible worlds, P is true at some possible world.
Necessarily P iff according to the fiction of possible worlds, P is true at all possible worlds.

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Either schema will be adequate to yield the other, given the standard inter-definition of possibility and necessity, provided enough logical machinery is available for reasoning within the scope of the “according to the fiction” operator. As a matter of fact, the above is a simplification, since, according to Rosen (1990, p. 335), what is true according to the fiction of possible worlds may be only a proposition connected with P: the paraphrase of P into the language of possible worlds. In general, for Rosen, this will be the analysis of P in Lewis's theory of possible worlds. Rosen states the form of the fictionalist biconditionals at its most general as:
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اقتباس :: P iff according to PW, P*.

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where “PW” is the fiction of possible worlds, P is any proposition, and P* is its possible-worlds “paraphrase” (Rosen 1990, p. 335). In simple cases the above biconditionals will do as they are: for example,
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اقتباس :: Possibly, pigs fly iff according to the fiction of possible worlds (or according to PW), at some possible world, pigs fly.

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In less straightforward cases, however, the proposition expressed by P* may have to differ from that expressed by P.[1] Fictionalists may also employ other biconditionals when constructing their fiction — one example is a biconditional to ensure that every proposition that is (really) true is according to the fiction true in the actual world.[2] A modal fiction may require more contents than those yielded by such biconditionals: what other contents the fiction of possible worlds might contain is an important question, and one unsurprisingly which different modal fictionalists will answer differently.[/size]

Modal Fictionalism

[size=30]1. Types of Modal Fictionalism

Modal Fictionalism :: تعاليق

Modal Fictionalism