What are the issues at stake in the claim that only what is present exists? Is the claim correct?

Submitted for PH373 (The Philosophy of Time) Summer Exam

This essay considers the intuitive appeal of the presentist position that ‘only what is the present exists’, and shows that neither core intuition can persist under scrutiny; specifically, the failure of presentists to provide truthmakers for other times undermines the common-sense appeal, and further suggests that this position is irreconcilable with the dynamical view that ‘what is present changes over time’. Thus, the position generates several commitments which are difficult to maintain, especially in light of modern physics; hence, I argue that presentism is incompatible with relativity theory.

The view that only the present moment exists is called presentism; I shall parse its central claim as “for any entity x, x exists if and only if x is present”. On this view, individuals from the past (say, Caesar) and events in the future (say, a forthcoming eclipse) have ceased to exist, or may yet exist, but they do not. It is a variant of the A-theory of time, which holds that tense is not merely a matter of perspective, but a feature of reality itself.

The position’s primary draw is its intuitive appeal; indeed, Zimmerman has argued that “it is simply part of common sense that the past and future are less real than the present”. After all, take language as it is commonly used: one typically say “dinosaurs no longer exist”, and not (as the eternalist might have it), “dinosaurs exist at a different location to us in the four-dimensional spacetime manifold”. Moreover, our experience of the passage of time seems to be dynamic: the past is unchangeable, the future is open, but we move through time, experiencing successive moments which (at the moment we experience them) are called ‘the present’. Nevertheless, neither of these intuitions can persist under scrutiny, and the position generates several commitments which are difficult to maintain.

One issue with the former motivation is that ordinary language also presumes countless propositions about the past that can be true or false. “Napoleon was a British monarch” is a statement that is understood to be false. On the common sense view, the best explanation for this is simply that there is an entity, Napoleon, with several properties (such as “being Corsican”), which do not include being a British monarch. Thus, one critique of presentism holds that it is unable to provide an adequate account of what makes past- and future-tensed statements true or false.

Several responses are available to the presentist, but none are compelling. One strategy is to suggest that although only present things exist, we can postulate the existence of ‘ersatz times’ that represent how things were or how they will be, and that the truthmaker for past-tensed propositions can be understood with reference to these ersatz times. That is, just as the proposition “Hilary Clinton could have become president” is made true by there being a ‘possible world’ in which she beat Donald Trump to the presidency, “Napoleon was a British monarch” is made true by there being no ersatz past time at which Napoleon was in fact a British monarch. There are other similar responses which appeal to ‘surrogates’ of various kinds for other times, such as ‘past-tensed properties’ (a presently existing object having the property that it was such-and-such) or temporal distributional properties (having the property of being x then y).

But such a reply immediately abandons the “common sense” appeal of presentism, which partly came from the fact that only the present moment seems vivid and really real. Now, suddenly, we must contend with these abstract entities which abstractly represent past and future moments; and as Lisa Leininger has noted, there is no reason to suppose that the ersatz times actually correlate with reality. The only way to “explain” why there is no ersatz past time at which Napoleon was a British monarch is to simply postulate it as a brute fact, at which point one is either simply speaking of the past existing (not an abstract representation of it), or demanding the acceptance of what amounts to a miracle. Leininger’s response applies equally to other surrogate arguments, since if indeed surrogates could exist in a world with only one moment, then no adequate account of their link to actual past events can be provided.

As well as demonstrating that the presentist is unable to solve these ‘truthmaker problems’ (and concomitantly, cannot provide an account of cross-time relations such as “Lincoln was taller than Napoleon”), Leininger advances a positive argument that the presentist finds herself in a contradiction. This is related to the second foregoing reason I suggested presentism has intuitive appeal, that it claims to account for the dynamic ‘flow’ of time. More precisely, as Kristie Miller has put it, “presentism combines an ontological thesis with a dynamical thesis”: the former is that “only the present moment exists”, and the latter is that “the present moves: which moment is the present changes”. But having now shown that presentism has no plausible account of truth-makers for past-tensed propositions, it seems to follow that these theses are incompatible. The dynamical thesis (or ‘change thesis’) holds that at one moment, an object can have some property; but then time passes, and a new moment becomes the present, and at this moment it can have some different property. But this form of words requires that both times exist; if only the present moment exists, and truthmakers for other times aren’t possible, then change is in fact impossible, and the dynamical thesis cannot hold.

But even if there were some other truthmaker for past- and future-tensed propositions that we have failed to consider, considerations from physics show that it cannot be upheld in any case. For one thing, given the disconnect between the time it takes us to perceive our surroundings and for the surroundings to change (for instance, given the time it takes light to reach our eyes), presentism implies that most of what we perceive is not real. Arguably, this is an unimportant objection – the delta is sufficiently small that we can nevertheless navigate the world coherently – it provides an intuition pump for why the notion of objectively privileging one moment over all others is difficult. According to our best understanding of the universe given by the theories of general and special relativity, the same event may happen at different times for different observers; there is no objective moment that we could call ‘the present’.

Therefore, the presentist claim that “only what is present exists” is incorrect, and collapses in every sense. Relativity theory suggests there is no objective moment one could call the present; even if there were, it is difficult to maintain that no other moments exist, since otherwise we would have no basis on which to say that claims about the past can be true or false; and even if that were not so, no plausible account can be given of how which moment is the present changes, and account for our dynamic experience of the passage of time – thus undermining all intuitive, common-sense reasons for believing presentism.

Result

Mark: 76% (Low First), averaged across this and another answer.