Introduction
The paper to which Ross Cameron respondsFootnote 1 aims to adumbrate three challenges facing the classical theistic conception of God arising from modal realism and to point to the kind of commitments a theist must embrace if she is also to endorse modal realism. The first of the challenges is the tension between the analysis of necessity furnished by modal realism and the classical theistic understanding of God as a necessary being and as outside space and time. While I do not propose that the theist faces a strict dilemma, I argue that the theist must choose between two unpalatable options. First, divine necessity can be explained by understanding God to be an abstract entity. However, this is undermotivated, given the nominalistic underpinnings of modal realism. Alternatively, the theist could embrace the second option: that there is a God at the actual world and He has a counterpart at every other world. Then, though, the theist needs to embrace a highly revisionary understanding of God.
Cameron succeeds in identifying two ways in which the theist can coherently maintain that the necessity of divine existence be expressed with the framework of modal realism. Indeed, far from there being a serious tension between modal realism and theism, Cameron points out that the theist need only attend to arguments already provided by David Lewis to account for divine necessity – arguments which, of course, Lewis himself did not put to such a use.
The first way is to follow David Lewis on the different ways in which an entity can be said to exist at or in relation to a world. While God is not wholly in any world nor partly in any world by having a part that is wholly in it, God does exist from the standpoint of a world.Footnote 2 Indeed, in just the way a pure set – for example, the numbers – exists from the standpoint of all worlds so does God. Cameron argues that, since Lewis did not see modal realism as a means for, or as entailing, the nominalistic reduction of all abstracta, there is no principled reason why the modal theist realist should not avail himself of this explanation of divine necessity. It should only be ruled out if one took modal realism as being necessarily cashed out in strictly nominalistic terms. Given the commitment of Lewisian realism to sets and Lewis's neutrality on universals there is no reason to regard modal realism in that way.
The second way is to understand God as existing at every world. That is, God enjoys trans-world identity. Because of the problem posed by accidental intrinsic properties Lewis rejects the ‘leading of double lives’ notion of (literal) trans-world identity. That means that among the things which cannot enjoy trans-world identity are ‘ourselves, and other things that we ordinarily name, or class under predicates, or quantify over’ (210). While Lewis rules out overlap for anything that has accidental intrinsic properties, God has His intrinsic properties essentially. In this respect God is just like a universal. If there are universals, then Lewis recognizes that he needs to qualify his rejection of trans-world identity. Following the approach taken with respect to universals the theist can regard God as being wholly present as a part of every world.
While Cameron shows the theist what she must say, I shall suggest that the price remains a dubiously high one. Let me explain.
The abstract God
I shall begin with an excuse, or perhaps a plea. At one point what I say in my paper is at best misleading and over-compressed and at worst false (since I know what I meant to express, I believe that I am guilty of the former). This is the claim that ‘realism about possible worlds as spatio-temporally closed and complete domains [as “large possible individuals”] provides (arguably) a framework whereby those traditional inhabitants of an abstract realm such as properties and numbers can be explained without commitment to any kind of Platonism.’Footnote 3 At least in the hands of David Lewis modal realism did not seek reductively to analyse away all abstracta; indeed, as already noted, there is a commitment to sets.
Modal realism is, though, Occamist in its motivation. While it is fecund in the number of entities allowed, it is parsimonious in the kinds of entities it admits into existence. Lewis has a Quinean approach to the ontological inventory. The reality of some kind of entity is tied to its indispensability in our best explanatory picture.Footnote 4 The motivation for modal realism is to deliver a reductive account of modality, an account of the closeness relation between worlds which is central to discussion of counterfactuals and ‘ideologically’ economical accounts of propositions and properties. This can be achieved through the combination of possible worlds (maximal mereological sums of individuals, each world itself being a (very) large individual) and set theory. The spirit of modal realism is an austerely nominalistic one. All we need are concrete individuals and sets to attain a huge explanatory gain (and perhaps universals, but I leave that discussion to one side).
The difficulty for the theist with the first way suggested by Cameron is to explain the motivation for introducing another kind of abstract entity. There is nothing incoherent in the claim that God exists like a pure set from the standpoint of every world. Yet it is not clear why the modal realist would need to appeal to divine existence in quantifying over a world or worlds. Of course, this is just what the theist must do if God is to be understood as necessary. Now, though, it is the prior commitment to divine existence which is determining the ontological inventory. Perhaps this is an entirely acceptable price for the theist. It is, though, ad hoc when set against the reasons for admitting concrete individuals and sets into our ontology.
The trans-world God
Universals are ‘the things, if such there be, that are wholly present as non-spatiotemporal parts in each of the things that instantiate some perfectly natural property’ (67). I take it that Cameron should not be regarded as saying that God be understood as being a universal. It is unclear what particulars would have God as a non-spatio-temporal, recurrent part. Presumably the theist can hold that God is present in everything. What, though, is being instantiated in every thing? It is also doubtful that the classical theistic conception of God could be stretched to regard divine existence as that of a universal. If the divine nature is not instantiated, then there would be the particular difficulty in characterizing God as an uninstantiated universal.
God should be understood as a single, particular entity essentially possessed of the great-making properties and, lacking any accidental intrinsic properties, as enjoying trans-world identity. The second part of challenge set out in the original paper is specifically directed at the conception of God as being in space-time. So, such an entity must be part of every world – perhaps like universals a non-spatio-temporal part that is somehow present in a world. If it is granted that God is part of a world, then should the inhabitants of that world count God as a worldmate? Lewis observes that ‘if two things are part of the same world, then I call them worldmates. A world is the mereological sum of all the possible individuals that are parts of it, and so are worldmates of one another … things are worldmates iff they are spatiotemporally related’ (69–71).
With God as a worldmate at every world it will turn out that the meaning of ‘actual’ is more complex than the modal realist had realized. Recall that ‘actual’ functions as an indexical term, picking out the world of its utterer. Now, it had seemed that ‘actual’ has a univocal meaning for worldmates. For, being a worldmate entailed that we all share a location – namely we are all at the very same world. From God's perspective all worlds are actual since he is in every world. Imagine that there is a special demonstrative ‘wthat’ which points all at once, so to speak, at the contents of one's world. When I employ it I pick out the totality of everything at my world. When my worldmate, God, employs it, He picks out the totality of everything at every world. Whereas the modal realist began by defining ‘actual’ in terms of the location of the speaker, its meaning shifts depending on the identity of the speaker.
Once again, there is a response on the part of the theist. There is no shift in the meaning of ‘actual’. Instead, there is just a special case in which it picks out all rather than some worlds because of the trans-world identity of the utterer. Still, there remains the worry that the existence of God as a worldmate at every world makes it true that all worlds are actual from the perspective of any world. Now, if a world is actual for one of my worldmates, then should we not regard it as actual for me? On Lewis's account we must answer ‘Yes’ and, in doing so, preserve the relativity of actuality. That is, ‘every world is actual at itself, and thereby all worlds are on a par. This is not to say that all worlds are actual – there's no world at which that is true, any more than there's ever a time when all times are present’ (93). The introduction of God as present at every world complicates matters. The theist modal realist must revise her understanding of actuality.
