Presentists believe that only present things exist. Their theories, at first glance, seem to offer many admirable features: a simple ontology, and a meaningful, objective status for key temporal phenomena, such as the present moment and the passage of time. So intuitive is this theory that, as John Bigelow puts it, presentism was “believed by everyone...until at least the nineteenth century” (1996, p. 35). Yet, in the last 200 years presentism has been beset by criticisms from both physicists and metaphysicians. One of the most significant criticisms is that presentists cannot provide an acceptable system of truthmaking. If there is no past, how can there still be truths about the past? In this paper, I introduce a new theory of presentism, which addresses this problem in a novel way: by simply denying that there are any truths about the past. While prima facie an unintuitive position, I will argue that a sensible presentist philosophy of this kind can be described, so long as it is accompanied by an appropriate system of physics. I will also indicate at certain points that adopting presentism could allow us to understand fundamental physics in new, more intuitive ways. By the end of the paper, I hope to not only show that hard presentism is a defensible theory of time, but also that it could offer a number of advantages to the physicist and the philosopher alike.
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See Baia (2012) for a formal layout of this supervenience principle.
The objection also applies to true statements about the future, but whether there are any such truths has been in dispute ever since Aristotle’s famous sea battle in De Interpretatione. It will be most instructive here to focus on the past. Note also that I will throughout this paper assume that statements are the bearers of truth-value, but the arguments I make would be equally applicable to true beliefs, true propositions, etc.
Caplan and Sanson (2011, p. 202) discuss how these problems with explanation affect other sorts of upstanding presentism, too.
I will discuss in Sect. 5.1 whether the everyday present might be sufficient to ground some broad, indeterminate truths about the past; for example <There was a past>.
Properties like <Being a universe where Ceasar crossed the Rubicon>, held presently by the universe itself. This position has roots among the Greek stoics, see Bigelow (1996).
Properties like <Being Ceasar>, also known as haecceities. This property comes into existence when Ceasar does, but then lingers afterwards, continuing to haunt the universe to this day. See Ingram (2016).
This objection is covered in detail by Baron (2013a).
Dolev (2010) claims that some upstanding approaches lead to a problematic “double meaning” of truth, if present truths satisfy the aboutness principle, but past truths do not.
For a summary, see Baia (2012).
See Baron (2015) for an overview of this version of nefarious presentism.
Meinongian metaphysics is the position that objects can have some sort of being, without existing. Criticisms of that general metaphysics will apply to the presentist case. For a defence, see Paolini Paoletti (2016).
If “made true” means that truths bear grounding relations, then it is concerning that those relations do not have any relata, other than truths themselves. See Baron (2013b).
Leininger (2015) makes a similar point using a “One Instant Test”. If God created the universe as it exists now, out of nothing, then it would contain the same proxies that the upstanding presentist advocates for, or the same brute facts that the nefarious presentist advocates for. But there should not be any past truths, in this one-instant universe!
See Asay and Baron (2014), who also claim that nefarious presentism cannot account for past negative existentials, such as <There have been no unicorns>.
Miller (2017), for example, argues that these non-presentist dynamic theories of time face an even harder challenge in accounting for truthmaking than presentism does.
In Sect. 5.1 I will consider whether the hard presentist might believe in a small number of indeterminate past truths, grounded by the physical present. I still consider that position to fall within the purview of hard presentism, since it would still involve there being far fewer past truths than we might intuitively believe in. This distinction should not matter a great deal anyway, since this will prove to be an unconvincing alternative.
Norton (2010), for example, acknowledges that describing passage can be difficult, but cautions against using this as a reason to disregard passage as unreal.
The metaphysical status of these laws is a controversial topic. Certainly, the hard presentist cannot understand laws in terms of relationships between events at different times. As I discuss in Sect. 4.2, the hard presentist may simply have to treat passage as primitive, and then ground the laws in that primitive passage. I will not address this issue any further in this paper, but for a summary, and a modern critique of laws, see Filomeno (2019).
But how can we make sense of this state, S, if no S exists? I think it may be useful to adopt the terminology of Barbour (1999, ch. 2) who talks of each time (in this case, the present) as containing a time capsule, an intrinsic representation as of things occuring before and after that time. Ismael (2002) questions why Barbour does not simply believe in one time capsule, one existing moment in time. In a manner of speaking, this is exactly what the hard presentist believes in. While the present might be understood, alongside passage, as representing events that could in theory occur at nonpresent times, this does not imply that nonpresent events exist, or that there are truths about them.
Some readers might wonder whether the fact that S could in theory have evolved into the present might make it true that S could have happened in the past—which seems to be a truth about the past. Grounding indeterminate past truths in the present still leads to problems of the kind discussed in Sect. 2.1, however. I will address this issue further in Sect. 5.1.
See Barnes and Cameron (2008) for several arguments suggesting that nonpresent truths are quite distinct from determinism, bivalence, or even the existence of nonpresent things.
See McCall (2009) for a quantum theory example.
The original work on this interpretation was quite explicit on this point, with Bohm himself describing quantum systems as “determined by definite laws, analogous to (but not identical with) the classical equations of motion” (1952, p. 166). While there has been some discussion of indeterministic versions of the Bohmian interpretation, it is generally regarded as an advantage of the Bohmian approach that it can avoid any notion of indeterminacy. Callender (2007, pp. 359–361) discusses some of the options available here.
Frigg and Hoefer (2007) provide a summary of the limited options for GRW theory.
I will not cover all twenty-one of the criticisms discussed by Eagle (2004), but a couple of key examples are listed here.
Or, strictly speaking, from the sensory experience I am having as of seeing porridge-coated dishes in the sink. A person can only presently access information at her own location—from within her own brain—so even our sense experiences are a form of retrodiction. This limitation is discussed further in Sect. 5.1.
The hard presentist can readily explain why our apparent memories are past-oriented: it is simply possible to form mental states representing events that, in general, can be expected to change fairly little as a result of passage. Other more widely-acknowledged explanations, like the entropy-asymmetry of memory formation, could also be relevant. See Barrett and Sober (1992) for a discussion of the relationship between memory and entropy.
Falkenburg and Weinert (2009) summarise some historical perspectives on this issue.
Which, as originally posed by Ghirardi (1985, p. 10), describes systems using “a stochastic behaviour having classical features”.
For a summary of the consistent histories approach, see Griffiths (1984).
I describe passage as a property, but some may prefer to think of objects as undergoing passage; to think of passage as something that is happening rather than as something that is instantiated. The distinction should not matter for the purposes of this toy model.
Though this approach is uncommon, I am not the first to describe quantum systems using the indeterministic motion of classical particles. Ellis and Goswami (2012) present a similar theory built on a growing-block conception of time, while Gao (2017, p. 80) describes classical particles undergoing random, discontinuous “jumps”, even in their time-derivative-independent properties such as position.
The idea that the variable of time is unreal, but change is not, is expressed by Barbour (2009). He describes change occurring to a three-dimensional universe without the need to invoke objective durations of time—exactly what I propose within this presentist toy model.
First introduced by Feynman (1948).
Ontologically, this raises questions about whether the wave function exists in the form of a “pilot wave” or “guiding field”, as original proponents of the theory such as Bell (2004, p. 128) believed. Dürr et al. (1992) give a summary of this historical context. The similarities between the toy model and Bohmian mechanics are worth investigating further, since adopting the position that the wave function only represents the nonexistent past and future of a system might give the Bohmian a stronger justification for rejecting wave function realism.
For an introduction to this problem, see Zurek (1991).
See Galvan (2010) for a summary of this problem.
Introduced by Zeh (1970), who illustrates this separation of states in the EPR paradox.
Of course, each of these answers has faced its share of criticisms, so the measurement problem is by no means a settled issue. I will not look into the details of how each of these answers fare, but for an overview, see Wallace (2007).
This approach mirrors how many Bohmians approach the measurement problem, as outlined by Holland (1993, ch. 8). Problems (B) and (C) vanish if we posit that the outcomes of measurements are determined by corpuscles. Bohmians are criticised by the likes of Zeh (1999) and Brown and Wallace (2005), however, for also positing a global wave function in their theory, creating confusion about whether the corpuscles explain anything about measurement that the wave function does not already explain. The toy model avoids such criticisms, since it does not posit that any wave function exists. Only the corpuscles do, so they alone explain what we see when we perform a measurement.
Noninvasive measurement has also traditionally been included in this definition, but this has recently been called into question—see Hermens and Maroney (2018).
A more precise argument for why wave-like microscopic entities alone are insufficient as a foundation for macroscopic phenomena is outlined by Leggett (2002).
It could be argued that the probabilities associated with ancient macroscopic historical events might be less overwhelming. While every particle might imply something about the big bang, for instance, that implication is sufficiently vague that there may be multiple nontrivial accounts of the big bang that could, in theory, evolve into what exists now.
The audacity! While this is his most famous example, Moore’s most notable essay on the subject (1925) focuses much more on other examples, particularly on examples of past truths. This leads him to claim that time is real, at least in some sense, and that there must be, and we must know, at least some truths about the past.
See Kelly (2005) for criticisms of this kind, and some defences.
For this reason, I am inclined to think that the everyday practical implications of hard presentism are minimal. We already act on the basis of what we think the present is consistent with, not on the basis of known past truths. However, some may still wonder if doing away with “underlying” past truths might have problematic implications for ethics, or law, or our everyday practices in general. I will leave this matter for further work.
Though this claim has been challenged experimentally, see Miller (2019).
Ismael (2015) discusses some of these theories, and puts forward one of her own.
See Miller et al. (2018) for two theories of this kind.
For example, Hartle (2005) takes the time-asymmetry of entropy change, and links it to the perspective of a simplified “robot” mind, an information gathering and utilising system (IGUS). The IGUS model has been picked up by others as a good way to understand this problem, see Ismael (2017). The level of consciousness needed for an observer to perceive passage will depend on the psychological theory in question.
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I would like to thank Dean Rickles, Kristie Miller, and my anonymous reviewers for their helpful comments and feedback. This research was partially supported by an Australian Government Research Training Program Scholarship.
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Dawson, P. Hard presentism. Synthese 198, 8433–8461 (2021). https://doi.org/10.1007/s11229-020-02580-9
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