Abstract
How is the debate between presentism and eternalism to be characterized? It is usual to suggest that this debate about time is analogous to the debate between the actualist and the possibilist about modality. I think that this suggestion is right. In what follows I pursue the analogy more strictly than is usual and offer a characterization of what is at the core of the dispute between presentists and eternalists that may be immune to worries often raised about the substantiality of the debate. I suggest that the debate be characterized in Lewisean terms and define positions I call *Lewisean* eternalism and anti-*Lewisean*’ presentism (analogous to Lewisean possibilism and anti-Lewisean actualism). I explain some advantages of the proposal and discuss some objections. I conclude that pursuing the analogy strictly offers the prospect of giving clear sense to a controversy which otherwise seems to many deeply obscure.
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Notes
Matters are not straightforward, as Sider acknowledges. Most obviously, because neither the eternalist nor the presentist need accept the existence of sets. But Sider argues, even if they do not he has still identified a locus of disagreement between them since the eternalist will assent to, and the presentist will dissent from, the conditional statement ‘If there were sets, there would/would sometime be a set containing a computer and a dinosaur’.
For those who cannot wait: refined actualism is the thesis that (2Act) below is both true and consistent with the possibility of concrete things other than those there actually are.
Here ‘concrete’ may be understood as ‘bearing spatiotemporal relations’.
Lewis considers other characterizations; what is crucial for him is just that he can characterize the worldmate relation in non-modal terms.
One can be a possibilist without being a Lewisean possibilist. It suffices to hold that, for some reading of ‘F’ as a predicate of concrete things, the possible but non-actual existence of Fs entails the existence of non-actual entities which are possible Fs. Lewis just adds that the possible Fs are Fs. But my claim is that the presentist/eternalist debate is illuminatingly compared to that between the anti-Lewisean actualist and the Lewisean possibilist. It is consistent with this that Lewis’s development of possibilism is just one variety, and indeed, that it is a wholly wrong-headed one (perhaps resulting from seeing too great an analogy between the modal and temporal cases). Of course the non-Lewisean possibilist must also say in what the non-actuality of the non-actual entities which are possible Fs consists. (Why are the non-actual entities which are possible talking donkeys non-actual? Not because they are not talking donkeys—nor am I.) He may do so, for example, by saying that they lack, contingently, spatio-temporal properties (rather than, as Lewis does, spatio-temporal relatedness to us). This answer also satisfies the desideratum that the notion of the non-actual is explained in non-modal terms.
A kind of pre-Lewisean modal realism can be envisaged which maintains that possible worlds are maximal summations of concrete entities linked by the worldmate relation, and that ‘actual’ is an indexical denoting us and all our worldmates, but does not include any non-modal clarification of the worldmate relation, and, specifically does not give any non-modal necessary condition of things being parts of the same world. A defender of this pre-Lewisean position would still be in disagreement with common-sense, and would not be a merely ersatz modal realist, since he would insist that the merely possible existence of talking donkeys entailed the existence of talking donkeys, and so would accept the existence of talking donkeys. But he would not have the resources the real Lewis has to defend himself against the charge of embracing an analytic falsehood, that is, to explain why it is not merely analytic that all donkeys are our worldmates (namely, because it is not merely analytic that all donkeys are spatiotemporally related to us and spatiotemporal relatedness is a necessary condition of belonging to the same world) and so not merely contradictory to conjoin the claim that there are talking donkeys with the claim that there are not actually any talking donkeys. This pre-Lewisean modal realism would be, as it were, merely the form of a genuine modal realism. Mutatis mutandis, eternalism without any non-temporal cashing out of simultaneity or the notion of the present, of the kind considered below, is merely the form of a genuine eternalism, standing to what I call immediately below *Lewisean* eternalism as pre-Lewisean modal realism stands to genuine modal realism.
Here ‘concrete’ may be understood as ‘bearing spatial relations’.
To avoid having anti-*Lewisean* presentism entail anti-Lewisean actualism (though we might want this entailment) we can say instead ‘Everything concrete that is spatiotemporally related to me is spatially related to me’ or neutrally ‘Everything concrete that is actual is spatially related to me’. The definition of eternalism will then need to be similarly revised.
Just as, in the statement of Lewisean possibilism, the reference of ‘I’ must be taken to be to a ‘world bound’ (or what Lewis himself (1986: 214) calls a ‘possible’) individual, i.e., one all of whose parts are spatiotemporally related, so, in the statement of *Lewisean* eternalism, the reference of ‘I’ must be taken to be to a ‘temporally bound’ individual, i.e., one all of whose parts are spatially related. The notion of parthood employed here in both explications is that of classical mereology.
I note here the reason for the scare (star) quotes round *Lewisean*: Lewis himself appears to conceive presentism, at least in On The Plurality of Worlds, as the obviously false thesis I have called Megarian presentism (1986: 204). It is his second discussed solution to the problem of temporary intrinsics, which he dismisses as incredible, since no man believes he has no past. (There is another interpretation of Lewis’s discussion here, viz., that he is thinking of presentism as analogous to anti-Lewisean actualism, but, unlike anti-Lewisean actualism itself, does not consider it even worthy of refutation. If this interpretation is correct I can drop the scare quotes.).
Sider (2006: 75) sets up the sceptic’s case (which he rejects) for the merely verbal character of the debate between the presentist and eternalist as follows: ‘Even the presentist agrees that there once existed dinosaurs. So if “exist” in “there exist dinosaurs” means “once existed” everyone agrees that it is true. And even the eternalist agrees that there do not now exist dinosaurs. So if “exist” in ‘there exist dinosaurs’ means “exist now”, then everyone agrees that it is false. Under neither of these two meanings for “exist” can there be controversy… What else could “exist” mean?’ Mutatis mutandis a sceptic about the possibilist/actualist debate could argue as follows: ‘Even the actualist agrees that that there might have existed talking donkeys. So if “exist” in “there exist talking donkeys” means “might have existed” then everyone agrees it is true. And even the possibilist agrees that there do not actually exist talking donkeys. So if “exist” means “actually exist”’ everyone agrees that it is false. Under neither of these meaning for “exist” can there be controversy… What else could “exist” mean?’ In his (2001: 16) Sider endorses the contention I have been emphasizing—that the eternalist/presentist debate is substantive if the possibilist/actualist one is: ‘the idea that presentists and eternalists do not genuinely disagree … leads to denying that … actualists and possibilists genuinely disagree.’
Can one be an eternalist without being a *Lewisean* eternalist? Does it suffice to be an eternalist to hold that, for some reading of ‘F’ as a predicate of concrete things, the past-or-future but non-present existence of Fs entails the existence of non-present entities which are past-or-future Fs—without going on to add that these past-or-future Fs are Fs? This does not seem to me to be in accord with the spirit of eternalism. But someone who nonetheless takes this line still faces the question in what the non-presentness of the non-present entities which are past but not present Fs consists. Why are the non-present entities which are past dinosaurs non-present? He may answer this question in non-temporal terms (analogously to the way the non-Lewisean possibilist answers the corresponding question about the non-actual in note. v) by saying that the non-present is that which lacks, not spatial relatedness to us, but spatiality simpliciter.
As Lewis says: ‘things that are parts of two worlds may be simultaneous or not, they may be in the same or different towns, they may be near or far from one another, in very natural counterpart theoretic senses. But these are not genuine spatiotemporal relations across worlds’ (1986: 71).
It is easier for the eternalist than the possibilist since he can identify ordinary individuals—such as planets, cities and cars—with perdurants. So he can say that two temporally separated events happened in the same place because, for example, they occurred in the back seat of a certain car (whilst acknowledging an equally good sense in which they happened hundreds of miles apart because one happened in Manchester and the other in London). For the reasons Lewis gives, the possibilist cannot identify ordinary individuals with trans-world individuals even though, of course, he does not deny the existence of the latter.
‘I deliver a maxim, which is condemn'd by several metaphysicians, and is esteem'd contrary to the most certain principles of human reason. This maxim is that an object may exist, and yet be no where: and I assert, that this is not only possible, but that the greatest part of beings do and must exist after this manner. An object maybe said to be no where, when its parts are not so situated with respect to each other, as to form any figure or quantity; nor the whole with respect to other bodies so as to answer to our notions of contiguity or distance. Now this is evidently the case with all our perceptions and objects, except those of the sight and feeling.’ (1978: 235–236).
Though given special relativity, of course, on this proposal the present shrinks to a space–time point. On a Newtonian conception of substantival space, complete with the notion of absolute rest, on the other hand, it expands to include everything. In fact, it is hard to see how an eternalist who endorses the Newtonian conception of absolute rest can give any account of the present without employing or presupposing temporal concepts, that is to say, it is hard to see how he can explain in any non-temporal terms what ‘there are dinosaurs existing now’ adds to ‘there are dinosaurs’ (I assume that causal (non-)connectibility by a finitely fast signal is an implicitly temporal notion).
Given special relativity this results in branching within times (cf. Lewis on branching within, versus branching of, worlds (1986: 209) in a world that branches there are events a, b and c such that there is no space–time interval between b and c, but there is an interval between a and b and one between a and c, each of b and c may be in the absolute future of a, but not timelike, spacelike or lightlight separate from each other, so for an observer at a there is no such thing as the future).
Otherwise the debate between the presentist and eternalist remains at the level of the pre-Lewisean (note vi) debate between actualist and possibilist about the existence of donkeys in other worlds, when no non-modal characterisation of worlds or the worldmate relation is available.
References
Crisp, T. (2004). On presentism and triviality. In D. Zimmerman (Ed.), Oxford studies in metaphysics (Vol. 1). Oxford: Oxford University Press.
Hume, D. (1978). A treatise of human nature. In: L. A. Selby Bigge (Ed.), 2nd ed. revised by P. H. Nidditch. Oxford: Clarendon Press.
Lewis, D. (1986). On the plurality of worlds. Oxford: Basil Blackwell.
Sider, T. (2001). Four dimensionalism. Oxford: Oxford University Press.
Sider, T. (2006). Quantifiers and temporal ontology. Mind, 115, 75–97.
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Noonan, H.W. Presentism and Eternalism. Erkenn 78, 219–227 (2013). https://doi.org/10.1007/s10670-011-9303-1
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DOI: https://doi.org/10.1007/s10670-011-9303-1