The Grounding Problem and Presentist Explanations (2011; penultimate Draft to appear in Synthese) [Abstract] Opponents of presentism have often argued that the presentist has difficulty in accounting for what makes (presently) true past-tensed propositions (TptP) true in a way that is compatible with her metaphysical view of time and reality. The problem is quite general and concerns not only strong truth-maker principles, but also the requirement that truth be grounded in reality. In order to meet the challenge, presentists have proposed many peculiar present aspects of the world as grounds for truths concerning the past, such as uninstantiated haecceities, Meinongian non-existents, ersatz times, and dispositional and distributional properties. The main problem with all such solutions is that any explanation of what grounds a TptP that involves the past is eo ipso a better explanation than any that involves only the present. Thus, the quest for an account of grounding for TptP that is compatible with the presentist ontology and ideology is doomed to be explanatorily deficient with respect to eternalism. In a recent article, Ben Caplan and David Sanson have claimed that presentists should change their strategy and, rather than seeking for exotic grounds for TptP, should adopt a more liberal view of explanation. That is, they should allow themselves to resort to "past directed" explanations, even if they do not accept the past in their ontology and ideology. I argue that such a proposal is not compatible with the tenet that there is a substantial distinction between the ideology of such a version of presentism and that of eternalism. Therefore, the presentist cannot endorse such "deflationist" explanations as an easy way out to the problem of the grounding of TptP. 1 Stating the Grounding Problem The central tenet of any presentist theory is that (P) Only the present is real The usual intended reading of (P) entails two claims. The first - which is the typical construal of the position - is ontological, i.e. it concerns what exists: (Op) Only presently existing entities exist The second is ideological, i.e. it concerns what properties and relations are instantiated by what exists: (Ip) The only properties and relations that things instantiate are presently instantiated properties and relations 1 The grounding problem1 for the presentist is that of providing a ground for (presently) true pasttensed propositions (TptP) that is compatible with both her central tenet and the claim that truth supervenes on being: (BSP) Truth supervenes on things and the properties and relations that they instantiate Note that the notion of grounding at issue here is quite weak. In particular, it does not depend on some strong truth-maker principle, such that for each truth there must be a particular entity that stands in the truthmaking relation to that truth. The only requirement that (BSP) makes is that truth be grounded in reality2. Given that the central tenet of presentism implies two distinct theses, the grounding problem, too, splits into two: (i) the ontological problem of accounting for truths concerning no longer existing entities, and (ii) the ideological problem of accounting for truths concerning properties that are no longer instantiated (by possibly presently existing entities)3. In what follows, I will concentrate only on the ideological problem. In a recent article, Caplan and Sanson4 illustrate the problem with an example. Let us suppose that pale Arnold goes to the beach and gets a tan. It is then true to claim now (1) Arnold was pale However, if the truth of (1) supervenes on the properties that Arnold instantiates, and if – according to (Ip) – those are only the properties that Arnold presently instantiates, what properties can ever do the job? The ordinary qualitative properties that Arnold now instantiates are certainly not suitable for this (he is tanned!). The presentist's answer is that Arnold, along with present-tensed properties such as that of being tanned (his "ordinary" properties), presently possesses also many past-tensed properties, such as that of having been pale5. As Caplan and Sanson correctly see, if the only point at issue were the supervenience of truth, such properties would suffice. However, by claiming that the presentist has difficulty in providing a ground for the truth of TptP, her opponent is pointing out that the presentist lacks a satisfying explanation of truthmaking for such propositions. Consider the explanation that the presentist provides for the truth of (1), on the ground that it supervenes on the fact that Arnold instantiates having been pale: (Ex1) (1) is true because Arnold instantiates having been pale 2 1 See Crisp 2007, Davidson 2003, Keller 2004, and Markosian 2004. 2 I thank an anonymous referee of this Journal for pushed me to stress that. 3 A related problem is that of accounting for truths about "cross-temporal" claims, i.e. about the relation(s) that present objects have with entities in the past. 4 Caplan and Sanson 2010; see also Tallant 2009 for an analogous stance towards the ontological problem. 5 This is not the only answer to be found in the literature. Presentists have appealed to dispositional (Parson 2005) and distributional properties (Cameron, 2010) in order to restrict the range of truthmakers for past-tensed truths in the present (and have appealed to uninstantiated haecceities, and/or Meinongian non-existents, in order to solve the analogous ontological problem). However, I agree with Caplan and Sanson (2010) that all these presentist solutions share the same problem of providing unsatisfactory explanations of truthmaking, because I agree with them that (Ex2) is a better explanation than (Ex1). Thus, confining my discussion to the "Lucretian" solution (as it is sometimes called; see Bigelow 1996) will not affect my point. Besides, I am not considering here non-serious ontological presentism, i.e. forms of presentism according to which an entity can exemplify a property even at a time when it does not exist (see Craig 2000, 2003 and the critique in Bourne 2005). I find the arguments in Bergmann 1996 and 1999, to the effect that presentism entails serious presentism, convincing (but see the objections in Hudson 1997). Although (Ex1) is not devoid of explanatory force, there is a better candidate: (Ex2) (1) is true because Arnold instantiated being pale Whereas (Ex1) "points" to the present, (Ex2) "points" to the past6, which is exactly what is expected of an explanation of what makes a TptP true. (Ex1) can be said to be indirectly about the past only because what past-tensed properties things presently instantiate depends on what presenttensed properties were instantiated: (Ex3) Arnold instantiates having been pale because he instantiated being pale Thus, the "indirect" explanatory force that (Ex1) has is derived from its relation to (Ex2). Caplan and Sanson conclude that (Ex2) is the proper explanation of the truth of (1) and that the presentists should endorse it. Of course, the explanans in (Ex2) points beyond what (Ip) allows. Thus, the explanans in (Ex2), differently from that of (Ex1), cannot be taken to express what the truth of (1) supervenes on: (Ex2) does not correspond, in any sense, to a grounding relation. Yet this does not mean that the presentist must reject (BSP)7. Rather, she should reject the implication from (BSP) and (Ip) to (EP1) An explanation of truth-making must point only to things and the properties and relations that they instantiate By rejecting (EP1), the presentist claims that irreducible hypothetical explanations, which point beyond what she admits as real, are legitimate explanations of truth-making. They are legitimate because they do not commit to strange kinds of "hypothetical" properties or facts, but only to the use of a primitive tensed language. In what follows, I argue that rejecting (EP1) is not compatible with maintaining that the distinction between presentism and eternalism is substantial and not merely verbal. In general, I do not think that the sceptical position to the effect that presentism and eternalism are not genuine metaphysical alternatives is true or even remotely plausible. I will not directly argue for the anti-sceptical view here, but will take for granted that the most common varieties of presentism are clearly distinguishable from eternalism (with respect both to the ontological side and the ideological side)8. What I will argue for is that a certain version of presentism - namely that version of presentism that implies a rejection of (EP1) - is incompatible with an anti-sceptical stance with respect to the ideological distinction between presentism and eternalism. Further, given that it makes no sense to defend a position if you are sceptical as to the distinction between it and the alleged opposite view, that version of presentism has to be rejected as ideologically indistinguishable form eternalism. Therefore, my argument, far from being against the anti-sceptical tenet that there is a genuine distinction between the two positions, actually assumes such a tenet as one of its premisses. 3 6 I am here talking only loosely about the utterance of tensed statements "pointing" to the present and to the past, because for the present purpose I do not need to spell out the idea in detail. However, it can be given a precise characterization, as in Fine 2005 (where he speaks of "target" and "topic"). 7 As Kierland & Monton 2007 and Merricks 2007 argue. 8 For a defence of a genuine distinction between the two position, see Sider 2006, which concentrates on the ontological side of the debate. However, an analogous defence can be formulated with respect to the ideological side. 2 Presentism, Eternalism and Scepticism Lately, sceptics have mounted attacks on the idea that the distinction between presentism and eternalism is a genuine metaphysical distinction. These sceptics have been concerned mainly with the ontological theses of both sides, but clearly, the ideological issue also lies within the scope of their critiques. The sceptics' arguments allegedly provide us with reasons to think that the two parties to the dispute (the presentist and the eternalist) are not in disagreement; hence, the debate between them is not substantial9. I do not think that the arguments of the sceptics are compelling or convincing. However, they cannot simply be dismissed as irrelevant; hence, their challenge must be met, and it is not trivial that every version of presentism and eternalism meets it satisfactorily. As is often the case with respect to sceptical doubts, a clear characterization of the distinction at issue reduces the appeal of the sceptical hypothesis. This is so in the present case, too. Many parties to the dispute think similarly. Ted Sider, for instance, has argued at length against the sceptical hypothesis, and I follow his defence of anti-scepticism. He defines a merely verbal dispute as follows: "To say that an apparent dispute over sentence p is merely verbal is to say that the disputants do not mean the same thing by the sentence p, and that what one says by uttering p is consistent with what the other says by uttering non p"10. Conversely, there is genuine disagreement between two parties to a debate on a sentence p if both parties understand p in the same way and one party but not the other is willing to give assent to p. In order to argue that the debate between the presentist and the eternalist is merely verbal, the sceptic aims at showing that the two parties systematically misunderstand each other when they argue for their positions. That is, according to the sceptics, there is no claim embodying the philosophical view of either, which both understand in the same way, and to which one but not the other is willing to assent. Their views are compatible, as a little reflection shows, but their deluded state to the effect that they are in disagreement prevents them from seeing it. From that, it follows that there is no theoretical question that they both understand in the same way, and to which they give possible different and incompatible answers. I do not think that the sceptic's tenet can be maintained in general. Indeed, there are ways to make perfectly clear the distinction between presentism and eternalism, with respect both to the ontological side of the dispute and the ideological side of the dispute. Typically, both the eternalist and the presentist agree that (P) and (E) are incompatible with one another, but the presentist assents to (P) and rejects (E), while the eternalist assents to (E) and rejects (P). (P) Only the present is real (E) The past (and the future) are as real as the present However, that does not mean that every position that identifies itself with the core theses of presentism is thereby able to meet the challenge of the sceptic and distinguish itself clearly form eternalism. In what follows, I argue that a certain "deflationist" variety of presentism fails to meet 4 9 See Savitt 2006, Dorato 2006, Meyer 2005, and Callender ms. I take it as a triviality that if two parties to a debate are not in disagreement, then they are engaged in a merely verbal dispute, and thus the debate between them is not substantial. I also assume here that the sceptics are considering the two philosophical views of presentism and eternalism from the outside, rather than considering whether or not each of the presentist and eternalist can state within her framework the distinction between herself and her rival. 10 Sider 2009: 385. the challenge with respect to the ideological side11. It is, as far as ideology is concerned, indistinguishable from eternalism, so it has to be rejected as a genuine form of presentism. Note that even a non-sceptic can (and often does) claim that the presentist and the eternalist understand ordinary tensed claims differently, or at least that they have different theories of the semantics of tensed statements. Consider the ontological aspect of the disagreement between the two positions. While the eternalist can give the truth conditions of (2) in terms of quantification over past objects12, as in (2e), the presentist has to resort to irreducible tensed operators, which she does not take to commit her to the existence of past objects, as in (2p) (2) There were dinosaurs (2e) There are dinosaurs, located in the past (i.e., at some moment earlier) (2p) WAS: There are dinosaurs However, the two different understandings of ordinary tensed sentences reflect a substantial disagreement in the protagonists' philosophical theories13. That is, although they read (2) differently, they do understand (2e) and (2p) in the same way, the first as committing and the second as not committing to the existence of dinosaurs, and they disagree about their evaluation. In particular, they disagree on the truth of (2e). The sceptic challenges the ontological difference between presentism and eternalism by claiming that there is a systematic misunderstanding of the quantificational apparatus that is used in the debate: it is always possible to translate in a truth-preserving way (and, indeed, even "meaningpreserving way" according to the sceptic) a sentence that quantifies on past entities (which can be accepted only by the eternalist) into a sentence that is free of this commitment, and vice versa. Thus, (2e) and (2p) are understood differently by the two parties, and what the eternalist states with (2e) is compatible with what the presentist states with (2p). The anti-sceptic argues that there is no systematic misunderstanding in the presentist and eternalist use of quantifiers14. When the presentist affirms (Op) and the eternalist denies it, they both understand existence in a sense that they maintain to be fundamental. Thus, the disagreement between the sceptics and the anti-sceptics can be summarized as a disagreement about the thesis of the ontological difference between presentism and eternalism: The ontological difference: there is a sense of fundamental existence, and both the presentist and the eternalist understand it, and they disagree on the truth of claims about the existence (in this sense) of past entities 5 11 There is also an ontological version of that position, and I argue elsewhere that that variety of presentism is unable to meet the corresponding ontological sceptical challenge. 12 Often, the eternalist provides truth-conditions by quantifying over temporal parts of objects instantiating properties simpliciter. That does not change my main argument, but accommodating it would require some reformulation. I thank an anonymous referee for having pointed out that to me. 13 See, for instance, Sider 1999. 14 According to Sider, such a "translation scheme" is actually not always truth-preserving, as is shown by claims about the existence of a set that contains a computer and a dinosaur. Moreover, tense operators do not have the same inferential role as quantifiers over past and future times; hence, they make no ontological commitments. Along with the scepticism about ontology, there is an analogous claim about ideology. The sceptic claims that the presentist and the eternalist systematically talk past each other, not only in their claims about existence, but also when they talk about "how things were in the past". Of course, the anti-sceptics may be happy to concede that the two parties understand differently, or at least assign different semantic treatment to, a sentence such as (1). The eternalist will give truth conditions for (1) in terms of the properties that Arnold instantiates at moments preceding that of the utterance, as in (1e), while the presentist gives truth conditions in terms of primitive tense operators, as in (1p) (1) Arnold was pale (1e) At some past moment (i.e. before that of the utterance), Arnold is pale (1p) WAS: Arnold is pale However, according to the anti-sceptics, those two understandings are not compatible with one another, because they reflect a deeper disagreement as to how reality is. Recall the ideological tenet of presentism: (Ip) The only properties and relations that things instantiate are presently instantiated properties and relations How is the first 'instantiate' in this tenet to be understood? If it is to be understood as being in the present tense, (Ip) turns to be a triviality that the eternalist need not deny. If, on the other hand, it is to be understood as the disjunction 'instantiates now, or instantiated, or will instantiate', (Ip) would be blatantly false, and thus rejected by the presentist too15. The sceptic argues that there are no other senses in which 'instantiate' can be read in the presentist's and eternalist's claims. Therefore, her hypothesis of mutual misunderstanding is justified. The anti-sceptic claims that 'instantiate' in (Ip) has to be understood in a fundamental sense, which both protagonists understand. The core of the ideological disagreement between the presentist and the eternalist can be stated as follows: The ideological difference: there is a fundamental notion of instantiation, which both parties understand in the same way, and such that they disagree about the properties and relations that things instantiate (in this sense) In particular, whereas the presentist upholds (Ip), the eternalist denies it, and upholds instead: (Ie) Things instantiate (in the fundamental sense) the properties that they presently instantiate, those that they did instantiate, and those that they will instantiate16 Therefore, (1e) and (1p) are incompatible because (1e) implies that Arnold instantiates (in the fundamental sense) the properties that he instantiated, while (1p) does not. In other terms, the 6 15 This reasoning reflects an analogous argument concerning the ontological claim of presentism. See Crisp 2007; and Lombard 1999 and Meyer 2005 for a sceptical reading. See also the debate on defining presentism between Ludlow 2004 and Crisp 2004a, 2004b. 16 Of course, the eternalist has to deal with McTaggart's problem somehow here, by endorsing either a tenseless theory of time or some form of non-standard tense realism. Moreover, (Ie) can be read as saying that temporal parts that exist at different times instantiate properties. eternalist is allowed to point to past instantiation of properties, while the presentist is not; she can only point to the present, and the properties that things now instantiate. The sceptic maintains that there is no sense of fundamental instantiation that we can actually grasp, or at the very least holds that the presentist and the eternalist are, as a matter of fact, using different senses of 'instantiate'. Indeed, we can always translate, in a truth-preserving way, eternalist "direct" talk about the past into presentist talk about the properties that things presently instantiate, in order to make their claims compatible with each other. Indeed, according to the sceptic, the translations are meaningpreserving, even if the parties to the dispute would reject them as good translations in any sense17. If the sceptic is right, presentism and eternalism, contrary to what the participants to the debate think, are indiscernible from each other, at least as far as their ideology is concerned, because there is no claim that both understand in the same way and evaluate differently. Thus, for the anti-sceptics, it is crucial to maintain that each time the presentist and the eternalist disagree about an ideological claim, they share the same notion of fundamental instantiation and understand claims such as (1e) and (1p) in the same way while disagreeing about their truth values. The same goes for any theoretical question about whose answer they take themselves to disagree. If a version of presentism (or eternalism) does not rely on such a notion of instantiation to distinguish itself from its rival, then the difference between this version of presentism and eternalism becomes very shallow. Indeed, if the distinction between the tensed language of the presentist and the tenseless language of the eternalist does not imply that the presentist and the eternalist disagree on which properties are instantiated (in the fundamental sense), the difference between such a version of presentism and eternalism is merely a matter of verbal labels. In what follows, I will consider only the implication of rejecting (EP1) on the grounds of the ideological indiscernibility of presentism and eternalism. My polemical target is not the distinction between presentism and eternalism in general, but the distinction between any "deflationist" version of presentism that rejects (EP1) and eternalism. Usual forms of presentism imply (EP1) or some analogous claim, and thus they differ in the way they explain what makes true claims about the past, such as (1), true. This makes the distinction between (Ip) and (Ie) substantial. By claiming (Ip) and (Ie), respectively, the presentist and eternalist are not merely using different labels to name the same thing, because the explanation of truth-making for true past-tensed sentences we provide depends on whether we endorse (Ip) or (Ie). For the very same reason, any version of presentism that rejects (EP1) cannot be defended against the sceptical arguments. Of course, even a version of presentism that rejects (EP1) may still differ from eternalism with respect to ontology. Further work is required to show that the ontological challenge of the sceptic raises analogous problems for the presentist who rejects (EP1). I will not address such problems in this paper; it is, in any case, bad enough for the anti-sceptical presentist if the version of presentism that she endorses (the one rejecting EP1) turns out to be ideologically indiscernible from eternalism. 3 Ideological scepticism Let us see what the sceptic's arguments are for doubting the difference in ideology between presentism and eternalism. The sceptic, in order to provide evidence for the claim that the parties do not understand each other, argues that qualifications such as 'real' or 'fundamental' possess no clear meaning. By claiming that only the present is real, while the past is not real, the presentist is quite obviously not to be taken as denying that there ever were past things and that they ever did 7 17 They are "hostile" translations; see Sider 2009: 13-4. instantiate properties and relations. Presentism is not the thesis that there has not been anything up to the present and that the whole universe was created (together with all our memories and alleged traces of the past) just a moment ago. Neither does it imply the claim made by some occasionalists that the world is, at every moment, destroyed by God and recreated anew18. The sceptic finds it difficult to grasp a notion of reality (fundamental existence and instantiation) that could make (P) and (E) substantial theses over which disagreement arises, or at least she finds difficult to believe that the presentist and the eternalist use such a notion in stating (P) and (E), respectively19. As it is used in the debate, the qualifications 'real' and 'fundamental' do not seem to possess a contrast class; hence, the sceptic concludes, they have no clear meaning. If she is right, we have reason to think that the disputants think that they understand themselves and each other when they disagree on matters of fundamental existence or instantiation, whereas in fact they are not only understanding the same sentences differently, but are actually saying the same thing (or at least compatible things) by using different sentences. As is the case with every sceptical hypothesis, the hypothesis that the presentist and the eternalist misunderstand each other when they argue for their (respective) positions cannot actually be disproven. Yet, I maintain that the anti-sceptic can provide reasons for not taking the sceptical hypothesis seriously and that hence, the sceptic is wrong; presentism and eternalism are substantially distinct metaphysical positions. Firstly, philosophers who are experts concerning the notions of (existence and) instantiation do take themselves to disagree on the truth-values of claims such as (Ip) and (Ie). Of course, this fact does not by itself rule out the logical possibility that even the experts (even after much discussion), still misunderstand each other. However, the prima facie evidence is that, in debating, philosophers who are experts in these matters understand the central points at issue in the same way. Thus, it would not be rational to take such a logical possibility seriously. If asked what (existing) entities satisfy a certain condition, the presentist and the eternalist understand in the same way the notion of existence that is at issue, and give (possibly incompatible) answers. More importantly in the present context, if they are asked in virtue of what properties that things instantiate a certain condition obtains, they both understand the sense of instantiation at issue in the same way and do not equivocate when giving their (possibly incompatible) answers. This is a minimal (necessary) condition for there to be a genuine debate, and if such a condition is lacking in a certain variety of presentism (or eternalism, for that matters), the sceptic can reasonably claim that her further arguments make the point against that variety of presentism. Indeed, if a presentist defends the idea that a certain theoretical issue requires different interpretations of the meaning of the terms in question, and that the presentist can answer in terms that do not imply the very same notion of instantiation endorsed by the eternalist in her answer (or vice versa), she allows legitimate suspicion that she is misunderstanding her rivals, and that, with respect to the version of presentism that she endorses, the sceptic is right. Suppose there is no agreement on whether a theoretical question requires an answer in terms that imply fundamental instantiation. Then the thesis that what the two parties to the dispute claim is reciprocally compatible looks much more plausible, because everything that the eternalist is allowed to say in terms that imply fundamental instantiation can be reformulated by any presentist who refuses to construe the theoretical question in the same way as the eternalist in terms that do not imply it. Hence, it can be advanced as a legitimate answer to the very same question. 8 18 As an anonymous referee pointed out to me, not all forms of occasionalism entail this theory of destruction and recreation. A world populated by substances that do not possess any causal power but are able to endure in time would be an occasionalist world. 19 See Savitt 2006, Dorato 2006, Callander ms, and Dolev 2008. Again, the sceptic is not right overall on the distinction between presentism and eternalism: the presentist and the eternalist do disagree on whether there are, in the fundamental sense, past objects and whether they instantiate (in the fundamental sense) properties and relations. However, a presentist who allows herself to change the sense of a theoretical issue is taking her position (i.e. the variety of presentism that she endorses) very close to a verbal variant of eternalism, and eliciting thereby the sceptic's suspicion that the debate in that case is not substantial. In light of the foregoing, I propose the following constraint on any genuine presentist or eternalist position: (ASC) An anti-sceptical stance toward the ideological difference between presentism and eternalism is not compatible with construing a theoretical question, which the opponent understands in terms of fundamental instantiation, in terms that do not require the answer to imply fundamental instantiation From this constraint, it follows that any version of presentism that (a) denies (EP1), and (b) maintains that in the matter of grounding what is explained by the eternalist in terms of the fundamental instantiation of some property can be explained by her in terms that do not imply the fundamental instantiation of some relevant property, fails to be compatible with anti-scepticism. Therefore, given that the presentist (as the eternalist) has to defend anti-scepticism on pain of collapsing the distinction between the position that she is defending and that of her rival, she cannot deny (EP1), as Caplan and Sanson suggest that presentists should do. Note that for the eternalist, the grounding problem is trivial. As a consequence of accepting (Ie), the eternalist has no qualms about accepting (Ex2) as the correct explanation of the truth of (1)20. Is the presentist equally at ease with such an answer, as Caplan and Sanson claim? Apparently no, because there is a simple argument from (Ex2) against presentism: (SA) If (Ex2) is the correct explanation of the truth of (1), then things instantiate properties in the past too; that is, presentism is false In reply, the presentist may resort to past tense operators and spell out (Ex2) as (Ex2'). (Ex2') (1) is true because WAS (Arnold instantiates being pale) Note that the presentist is not compelled to endorse some non-fundamental sense of instantiation, and that she can construe 'instantiates' in (Ex2') in terms of fundamental instantiation - viz. she can maintain that the notion of instantiation that shows up in (Ex2') is the very same that shows up in (Ex1) and (Ex3)21. However, by construing (Ex2) as (Ex2') the presentist does not escape the charge of infringing (ASC), because claims about fundamental instantiation when embedded in a past tense operator do not entail that the property (or relation) at issue is fundamentally instantiated. Thus, even if the notion of instantiation used in (Ex2') is fundamental instantiation, i.e. the way in which a presentist who rejects (EP1) construes (Ex2), this does not entail that Arnold instantiates being pale. It would run counter to the purpose of the primitively tensed talk of the 9 20 Of course, eternalists may have problems with the tense showing up in (Ex2), in the case that they are also tenseless theorists. Yet a tenseless version of (Ex2) can easily be constructed: (1) is true because Arnold, at a time preceding that of the utterance of (1), instantiates being pale. Obviously, (Ex2) can be, and often is, interpreted in terms of temporal parts too. 21 I thank an anonymous referee of this Journal for having pointed that out to me. presentist to maintain otherwise. This is good news for the anti-sceptics, because otherwise the eternalist and the presentist would agree on the matter of fundamental instantiation, and indeed (Ex2) and (Ex2') would just be graphical variants of each other. However, it means that neither (Ex2) nor (Ex2') is available as an explanation for the presentist, because accepting either of them would, for the presentist, be to equivocate on the issue at stake. Further, given that the presentist can propose (Ex2) or (Ex2') as an explanation only if she denies (EP1), it follows that if the presentist denies (EP1), she can no longer distinguish her "deflationist" position from the eternalist's (at least as far as issues of ideology are concerned, but that is bad enough). In other terms, if the "deflationist" presentist claims that she is not impressed by (SA), because by accepting (Ex2) as the correct explanation she is not compelled to maintain that Arnold instantiates properties in the past as well, the sceptical hypothesis to the effect that the disputants understand the term 'instantiation' differently here is justified. On the one hand, due to the fact that the "deflationist" presentist rejects (Ie), she does not mean by talking about the properties that Arnold instantiated to imply that Arnold instantiates them in the fundamental sense of instantiation. On the other hand, if she nonetheless endorses (Ex2) as an explanation, she provides a warrant for the sceptics to maintain that her version of presentism and eternalism are, at least as far as their ideology is concerned, indiscernible. To put the point more explicitly, consider the theoretical question (Q), elicited by the idea that truth requires grounding. (Q) In virtue of what properties that things (in particular, Arnold) instantiate is (1) true? The eternalist has a very simple answer: in virtue of being pale, which is a property that Arnold instantiated (viz. instantiates at some previous instant). The presentist cannot give this simple answer, unless she understands 'instantiate' in (Q) not as implying fundamental instantiation, because Arnold does not instantiate in the fundamental sense being pale (although in some version of presentism he does instantiate having been pale). The "deflationist" presentist denies (EP1) and insists that when asking for explanation of truthmaking we should read (Q) as (Q') In virtue of what properties that things (in particular, Arnold) either instantiate or did instantiate or will instantiate is (1) true? Note that the eternalists have no qualms about reading (Q) as (Q') because, according to them, pasttensed instantiation does imply fundamental instantiation. Yet this is not the case for the presentist, who construes (Q) as (Q') precisely in order to do away with implications of fundamental instantiation in her explanatory talk22. If a presentist maintains that a theoretical question that is construed by the eternalist in terms that imply fundamental instantiation has to be read as not implying fundamental instantiation, then it is no longer clear that someone who endorses presentism in that form and the eternalist share a notion of fundamental instantiation. Indeed, this is exactly the kind of equivocation that the sceptic is pointing to when she maintains that there is no intelligible 10 22 It is easy to demonstrate that, given the presentist assumption on tenses, (Q') does not require an answer that implies that Arnold instantiates in the fundamental sense the property in question. There are formally acceptable answers to (Q') such that Arnold instantiated (or will instantiate) certain properties (and the the correct answer is of this kind). Given that, on the presentist reading of tenses, the proposition that Arnold instantiated (or will instantiate) certain properties does not imply that Arnold instantiates in the fundamental sense the properties in question, it follows that an answer to (Q') is not committing to fundamental instantiation. I thank an anonymous referee for having pushed me to make this passage more explicit. sense of fundamental instantiation that both parties understand or at least use, and thus no clear ground for disagreement between the two: where else should their disagreement on the matter of fundamental instantiation show up if not in disputing theoretical issues, such as what grounds TptP? If the deflationist presentist allows "non-serious" talk to do serious metaphysical work, such as explaining truth, the sceptic if justified in claiming that the distinction between her and her opponent's view is merely verbal, and that their positions are compatible at the end of the day. Thus, if the presentist and the eternalist do not abide by (ASC) they will lose any ground for disagreement. Note that appealing to the idea of temporally qualifying instantiation will not help the presentist here. Consider the ontological distinction again. The eternalist qualifies fundamental existence only in the sense that she maintains that objects can occupy temporal locations other than the present, just as much as they can occupy different spatial locations. Although the eternalist is not committed to an overall similarity between space and time, she does take the analogy here seriously: as far as existence is concerned, "points" in time and "points" in space are on a par23. The same cannot go for the presentist. According to her, what existed is not what exists (in the fundamental sense) at a non-present temporal location: what existed does not exist at all (in the fundamental sense). If she were to construe her tensed past and future talk as committing to fundamental existence, the sceptic would be right in claiming that presentism and eternalism are only verbal variants of the same theory 24. It is not just that we can translate every truth of the eternalist into a presentist counterpart once we make clear the ontological commitment of the two parties (i.e. what they take to exist in the fundamental sense); rather, it will turn out that they are not, in fact, disagreeing. Any version of presentism that implies this ontological indistinguishability should be thereby rejected, because ontological anti-scepticism is an essential methodological premiss of both presentism and eternalism. The same goes for instantiation. The eternalist qualifies fundamental instantiation only in the sense that she maintains that objects can instantiate (in the fundamental sense) different properties at different temporal locations. The same cannot go for the presentist. According to her, the properties that an entity instantiated are not instantiated in the fundamental sense. If she were to claim the contrary, the sceptics would be right: nothing of what the presentists claim about fundamental instantiation in the past would contradict what the eternalist maintains about fundamental instantiation in the past. Indeed, the difference between the ideology of the presentist and that of the eternalist would be merely verbal. Of course, there may be further differences in the way temporal qualification is understood by the presentist and the eternalist, even in such a case, and even limiting our attention to the ideological side of the issue. For instance, the eternalist would normally understand it as being at bottom tenseless, whereas the presentist understands it as being at bottom tensed. However, not all eternalists are tenseless theorists; therefore, the difference between the tensed view and tenseless view would not be always a difference between the presentist and the eternalist. In addition, and more to the point, what counts here is whether or not the presentist's tensed qualification of instantiation implies fundamental instantiation. If it does, the sceptic is 11 23 I am not claiming that the eternalist is committed to a substantivist view or space and time (or space-time); that is why I put scare quotes around 'points'. The "points" here can be just what would be contained in them if substantivism were true. See Mellor 1998 for an eternalist who does not take the analogy between space and time to hold across the board. 24 Indeed, that is why Sider 2006 argues that the presentist quantification does not commit the presentist to the existence of past and future entities, while Dorato 2006 argues, against Sider, that quantifiers are committing even when embedded in tense operators. I side with Sider in the dispute. correct in holding that the presentist and eternalist only think that they disagree, but that there is no substantial difference in what they claim, at least as far as instantiation is concerned. An explanation of the truth of tensed sentences in tensed language would not just be translatable into the eternalist tenseless language, but would also carry the very same "ideological commitment". If, as antisceptics of both sides think, the presentist's tensed qualification of instantiation does not imply fundamental instantiation, then a presentist who insists that (Ex2) is an available explanation to her nonetheless does not see question (Q) as committing her to providing an answer in terms of fundamental instantiation. Again, this would provide support for the sceptical thesis that the parties to the dispute do indeed simply misunderstand each other, and that there is no substantial difference between the version of presentism in question and eternalism. Further, anti-scepticism with respect to the differences in ideology is an essential methodological premiss of presentism, and any version of presentism (such as those that reject (EP1) and clash with (ASP)) that turns out to be indistinguishable from eternalism, should be thereby rejected25. 4 Adequate Explanations The ideological tenet of presentism (Ip) implies that facts about what properties have been instantiated by things are not "part of reality". Thus, when a presentist provides grounds for a TptP, she cannot point to a property that was instantiated by a thing at some time in the past. However, according to Caplan and Sanson, we should not be so demanding when it comes to explanations of truthmaking. As noted above, they do not wish to reject the claim (BSP) that truth supervenes on being, but rather to reject the implication from (BSP) and (Ip) to (EP1) An explanation of truthmaking must point only to things and the properties and relations that they instantiate This principle (EP1) can be seen as the application to presentism of a more general methodological principle concerning any metaphysical view: (EP) If a philosopher holds that certain facts are not part of reality, she should not appeal to such facts when providing explanations I think there is a point in claiming that (EP) may be too demanding in many cases. Helen Beebee and Achille Varzi have (separatedly) argued against it with respect to the existence of "negative events"26. In providing causal explanations, we often resort to negative descriptions in the explanans. For instance, if Johnny's mother advised John to turn off the gas before going out, and John did not turn it off, it is adequate to say (3) There was an explosion because Johnny did not turn off the gas 12 25 A referee has suggested that Caplan and Sanson can strengthen their proposal as follows. Could not a presentist who endorses (Ex2) reject the request to answer (Q) by denying (BSP) altogether? I think this would be in the spirit of the "deflationist" version of presentism (it is a position very similar to the "cheater" version of presentism upheld by Tallant 2009 with respect to the ontological point). However, a presentist who refuses to answer (Q), and understands it in the same way as the eternalist, still has to explain how her version of presentism differs from eternalism. The same problem that arises for Caplan and Sanson's version of presentism would arise also for that version, because no distinction between such a position and eternalism can be framed in terms of a difference in explanation of truth: both endorse (Ex2). 26 More precisely, then, they have argued against the ontological reading of (EP1). See Beebee 2003, Varzi 2008. However, the fact that this explanation is adequate does not imply that there is a non-doing or a failure, which is the cause of the explosion, as (EP) would imply. Neither can we take what Johnny did instead (for example, going for a walk in the park) as the cause of the explosion (for, of course, it is not a walk in the park that caused the explosion). Rather, the cause of the explosion is likely to be some event of combustion that took place in a gas-saturated environment. The reason why (3) works as an explanation is that it is informative about the circumstances in which the causal relation between the combustion event and the explosion took place, and it is informative in a pragmatically relevant way: it tells us something about the responsibility involved in the disaster. Given that Johnny was supposed to turn off the gas before going out, we consider the information conveyed by the explanans in (3), that is, that he did something else instead, relevant for imputing to him responsibility for what happened. More generally, the adequacy of an explanation is often sensitive to many pragmatic factors other than truth. Thus, (3) is an adequate explanation even if, strictly speaking, read as expressing a causal relation between two events, it is false. As Varzi puts it, the "adequacy of a causal explanation does not only depend on the truth of what is said" (Varzi 2008, p. 2-3). Could not the presentist motivate her resorting to (Ex2) as an explanation of the truth of (1) along the same lines? In that case, a presentist would endorse (Ex2) as an explanation without thereby abandoning (ASP). The presentist would agree that (Ex2) is, strictly speaking, false, and that the ontological ground of the present truth of (1) is given by (Ex1). However, (Ex2) is more appropriate as an explanation. This would allow the presentist to deploy against the sceptic the same arguments of any of the non-deflationist varieties of presentism (e.g. the Lucretian). Note that the explanans in (Ex1) reports the grounding relation according to (the Lucretian version of) presentism correctly: a relation between a present utterance of a TptP and the present instantiation of a past tensed property. On the other hand, (Ex2) is rather misleading for the presentist, because its explanans expresses a relation between a present utterance of a TptP and a past instantiation of a present tense property, which is what the presentist denies. Are there any reasons for the presentist to prefer (Ex2) to (Ex1) as the proper explanation of what makes (1) true? Caplan and Sanson point out that (Ex2) reflects the rather trivial fact that "[w]hen explaining the truth of a proposition about how things were, one needs to appeal, not to how things are, but rather to how things once were"27. However, this is not a pragmatic reason to endorse (Ex2) and dismiss (Ex1). In effect, (Ex2) is not more informative than (Ex1) about certain facts that are somehow related to truthmaking, given a background of certain shared interests (responsibility or anything else). It is more informative, if anything, about grounding. (This is why (Ex3), by linking a past instantiation of a present-tensed property to the present instantiation of a past-tensed property, allows (Ex1) to be informative about grounding too.) It may be argued that my point here depends on what precisely we mean by 'pragmatic reason'. However, for the argument to succeed, the only condition that we need to accept on what constitutes a pragmatic, rather than a theoretical, reason is the following: pragmatic reasons (in the sense required for the Beebee-Varzi strategy to apply) do not essentially involve descriptive adequacy of some fundamental sort. The underlying idea here is that descriptive adequacy to what is fundamental (e.g. what is instantiated in the fundamental sense, or what exists in the fundamental sense of existence) is a peculiar characteristic of metaphysics - typically, a non-pragmatic field. In particular, claiming that "[w]hen explaining the truth of a proposition about how things were, one needs to appeal, not to how things are, but rather to how things once were" amounts to advancing a plausible condition with which every theoretical notion of grounding must comply in order to 13 27 Caplan and Sanson 2010: 38. respect our pretheoretical intuitions about truth. This condition has been (implicitly) used by the eternalist to argue against the presentist: appealing only to the present to explain the truth of propositions about the past clashes with what an explanation of what grounds a truth should be. Unless this claim is acknowledged to have some force, the grounding problem would not even arise. The reason the presentist should prefer (Ex2) to (Ex1), then, is theoretical, and the pragmatic strategy described at the beginning of this paragraph cannot be pursued by the deflationist presentist. Hence, the arguments of the previous section, about the incompatibility of any version of presentism that endorses (Ex1) with an anti-sceptical stance towards the metaphysical distinction between eternalism and presentism, still apply. 5 Conclusions Let us now review what has been achieved in the foregoing. Firstly, I explained that presentism implies both an ontological and an ideological claim, and that there is a grounding problem for TptP with respect to both claims. Then I highlighted how scepticism about the distinction between presentism and eternalism involves both the ideological tenets and the ontological tenets, and I pointed out that the argument to the effect that eternalism and presentism may turn out to be indistinguishable with respect to their ideology must be faced by the presentist. This allowed me to focus on the ideological challenge of the sceptic, and see what constraints have to be met by the presentist in order to withstand it. The sceptic argues that the distinction between presentism and eternalism is spurious because there is no notion of fundamental instantiation that both parties use and agree on when they claim to disagree on a theoretical statement. Equivocation on the matter of fundamental instantiation thus constitutes support for the hypothesis that there is no genuine distinction between the two positions. Yet a lack of agreement on how to read a theoretical question constitutes evidence that there is equivocation; hence, I proposed a constraint to the effect that theoretical questions should be construed unequivocally by both parties. I then argued that a presentist who denies that an explanation of truth-making must point only to things and the properties and relations that they instantiate viz. who denies (EP1) is equivocating on how to understand 'instantiation' and providing support for the sceptic: her construal of presentism (but not presentism in general) is not substantially distinct from eternalism (as far as instantiation is concerned). Finally, let me stress that my arguments do not support scepticism. The gist of the paper can be put as follows: any version of presentism that implies that the notion of fundamental instantiation is not relevant for distinguishing what can and what cannot be used for theoretical work, fails to meet the essential methodological constraint that there must be a substantive distinction between it and its rival(s). The eternalist has a clear stock of theses that involve fundamental instantiation, and she uses them to ground truths about the past. Whoever denies any of them is thereby in genuine disagreement with the eternalist. This is why the sceptic is wrong in maintaining that there is no genuine disagreement between the eternalist and at least some of her rivals. Indeed, many of her rival presentists deny that things instantiate properties in the past and maintain that there are grounds for past truths in present reality. However, if an alleged presentist allows herself to use talk about the past to do theoretical work without thereby endorsing the corresponding claims about instantiation, the sceptic has a point in claiming that her position is nothing but eternalism in disguise28. 14 28 Thanks to Fabrice Correia, Beppe Spolaore, Carlotta Pavese and two anonymous referees for useful comments. Giuliano Torrengo LOGOS University of Barcelona LABONT University of Torino References Bergmann M. (1996) "A New Argument from Actualism to Serious Actualism", Nous 30: 356-9 Bergmann M. 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