Online research in philosophy

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.

Modal realism -- Time, space, world -- Existence -- Actuality -- Modal realism and modal tense -- Transworld individuals and their identity -- Existensionalism -- Impossibility -- Proposition and relief -- Fictional worlds -- Epistemology.

According to Lewis's modal realism, all ways the world could be are represented by possible worlds, and all possible worlds represent some way the world could be. That there are just the right possible worlds to represent all and only the ways the world could be is to be guaranteed by the principle of recombination. Lewis sketches the principle (put roughly: anything can co-exist with anything else), but does not spell out a precise version that generates just the right possibilities. David Efird and Tom Stoneham have offered a principle that aims to do just that.In this paper, we argue that Efird's and Stoneham's principle of recombination is not successful – it fails to generate the right possibilities – but we also suggest ways that their account might be improved to solve the problem we raise. We also argue against Efird's and Stoneham's claim that the correct principle of recombination demonstrates the possibility of nothing concrete – it is true that their principle of recombination has models consistent with the existence of an empty world, but we only get the possibility of nothing if mereologically null individuals are possible. The Lewisian should only think mereologically null individuals are possible if he or she has some independent reason for believing in the possibility of an empty world, so the principle of recombination provides no new evidence for that possibility. We draw some morals from this for the correct way to formulate the principle of recombination.

This article argues for two related theses. First, it defends a general thesis: any kind of necessity, including metaphysical necessity, can only be known a priori. Second, however, it also argues that the sort of a priori involved in modal metaphysical knowledge is not related to imagination or any sort of so-called epistemic possibility. Imagination is neither a proof of possibility nor a limit to necessity. Rather, modal metaphysical knowledge is built on intuition of philosophical categories and the structures they form.

According to the zombie conceivability argument, phenomenal zombies are conceivable, and hence possible, and hence physicalism is false. Critics of the conceivability argument have responded by denying either that zombies are conceivable or that they are possible. Much of the controversy hinges on how to establish and understand what is conceivable, what is possible, and the link between the two—matters that are at least as obscure and controversial as whether consciousness is physical. Because of this, the debate over physicalism is unlikely to be resolved by thinking about zombies—or at least, zombies as discussed by philosophers to date.



In this paper, I explore an alternative strategy against the zombie conceivability argument. I accept the possibility of zombies and ask whether that possibility is accessible (in the sense of ‘accessible’ used in possible world semantics) to our world. It turns out that the question of whether zombie worlds are accessible to our world is equivalent to the question of whether physicalism is true. By assuming that zombie worlds are accessible to our world, supporters of the zombie conceivability argument beg the question against physicalists. I will then consider what happens if a supporter of the zombie conceivability argument should insist that zombie worlds are accessible to our world. I will argue that the same ingredients used in the zombie conceivability argument—whatever they might be—can be used to construct an argument to the opposite conclusion. If that is correct, we reach a stalemate between physicalism and property dualism: while the possibility of some zombies entails property dualism, the possibility of other creatures entails physicalism. Since these two possibilities are inconsistent, one of them is not genuine. To resolve this stalemate, we need more than thought experiments.

This thesis examines the alethic modal concepts of possibility and necessity. It is argued that one cannot do justice to all our modal talk without possible worlds, i.e., complete ways that a cosmos might have been. I argue that not all of the proposed applications of possible worlds succeed but enough remain to give one good theoretical reason to posit them. The two central problems now are: (1) What feature of reality makes correct alethic modal claims true and (2) What are possible worlds?

I propose a different way of thinking about metaphysical and physical necessity: namely that the fundamental notion of necessity is what would ordinarily be called "truth in all physically possible worlds" – a notion which includes the standard physical necessities and the metaphysical ones as well; I suggest that the latter are marked off not as a stricter kind of necessity but by their epistemic status. One result of this reconceptualization is that the Descartes-Kripke argument against naturalism need no longer trouble us. I end by relating the difference between my view and the standard view to the question, whether there could have been a different world than ours.

Possibility offers a new analysis of the metaphysical concepts of possibility and necessity, one that does not rely on any sort of "possible worlds." The analysis proceeds from an account of the notion of a physical object and from the positing of properties and relations. It is motivated by considerations about how we actually speak of and think of objects. Michael Jubien discusses several closely related topics, including different purported varieties of possible worlds, the doctrine of "essentialism," natural kind terms and alleged examples of necessity a posteriori. The book also offers a new theory of the functioning of proper names, both actual and fictional, and the discussion of natural kind terms and necessity a posteriori depends in part on this theory.

Some argue that theories of universals should incorporate structural universals, in order to allow for the metaphysical possibility of worlds of 'infinite descending complexity' ('onion worlds'). I argue that the possibility of such worlds does not establish the need for structural universals. So long as we admit the metaphysical possibility of emergent universals, there is an attractive alternative description of such cases.

It is commonly supposed that metaphysical modal claims are to be evaluated with respect to a single domain of possible worlds: a claim is metaphysically necessary just in case it is true in every possible world, and metaphysically possible just in case it is true in some possible world. We argue that the standard understanding is incorrect; rather, whether a given claim is metaphysically necessary or possible is relative to which world is indicatively actual. We motivate our view by attention to discussions in Salmon 1989 and Fine 2005, in which various data are taken to support rejecting the transitivity of accessibility (Salmon) and modal monism (Fine); we argue that relativized metaphysical modality can accommodate these data compatible with both standard modal logic(s) and modal monism. Noting an analogy with two-dimensional semantics, we argue that metaphysical modality has a complex structure, reflecting what is counterfactually possible, relative to each indicatively actual world. In arguing for the need for relativization, we are broadly on the same side as Crossley and Humberstone (1977) and Davies and Humberstone (1979); our contribution here is, first, to offer distinctively metaphysical reasons for relativization, and second, to show that relativization can be incorporated in ways minimally departing from standard modal logic(s).