The Passage of Time
Introduction…
When we consider the passage of time, we can investigate two different sets of relations or properties: relations of ‘earlier than’, ‘simultaneous with’, and ‘later than’ (e/s/l relations), and properties of past, present, and future (p/pr/f properties). Evidently, e/s/l relations are different from p/pf/f properties; for instance, knowledge of all e/s/l relations doesn’t amount to knowledge of what moment or event in time is “present”. That is, even if you know the order in which a sequence of events unfolds, you won’t be able to tell me which event in the sequence is currently present, or how far in the past a particular event is.
A-theory and B-theory, the two predominant theories of time, deal with e/s/l relations and p/pr/f properties in distinct ways. The crucial distinction between A- and B-theory concerns the status of p/pr/f properties (also called ‘tensed facts’). For example, a B-theorist would respond to our first paragraph, in which the existence of a “present” moment is implied, by saying this is simply not the case. So, according to the B-theorist, given a set of e/s/l relations, there is indeed no way to know which event is objectively “present” in the sequence, but this is simply because there is nothing objective to know. While the B-theorist denies the (objective) existence of tensed facts, the A-theorist affirms their existence.
…and the Aim of this Essay
In my view, the dismissal of the following questions (and similar ones): “Which event is present”, “What is the present”, “How does time pass”, as essentially incoherent, is unfounded. I will offer some reasons to support this contention later on in the paper. Rather than “dismiss the question” of the present, and of time’s passage, I think we ought to look further into the curious nature of time. It is indeed mysterious to consider that time passes. After all, when it “passes”, where does it go? How can we think that events in the distant past once were truly present, when they’re now only vaguely present in memory?
B-theory, by definition, is incapable of answering these questions since it assumes the present doesn’t really exist. However, as I will argue later, we needn’t proceed on that assumption. I myself cannot provide answers to the aforementioned questions here. But that is alright, for my main goal in raising this line of thought is to stipulate that a) we are not rationally required to dismiss such lines of inquiry as confused or incoherent and b) by extension, we may then want to favor A-theory.
So, onto the main point of this particular paper…
It is, in part, the fact that we experience certain events as present that I’ll offer a broad defense of A-theory. Again, this broad defense has the goal of (beyond the scope of this paper) encouraging further inquiry into time’s mysterious passage, and its phenomenological nature.
A-Theory and the Passage of Time
First, I will offer an overview of a few different versions of A-theory. Presentism, one such version, says that for an event of thing to move from past, to present, to future, is for it to “come into existence and go out of existence”. Presentists claim only present “events, individuals, and times—assuming times are sums or collections of simultaneous events” exist[1]
Two other versions of A-theory support the intuition that past and future have some reality: the moving spotlight and growing block theories. The moving spotlight theory is an eternalist view of time[2] which further stipulates that the present is metaphysically privileged. For time to pass, then, is for a kind of special spotlight to move and “illuminate” one time (the present) and not others (the past and future).
On the other hand, the growing block theory says that the past and present exist and that there’s something special about the present, but the future doesn’t exist. Instead, the passage of time is like a growing block onto which new time-slices are added. The present, therefore, is special because it is on the cutting edge—there is, briefly, no time after it.
Problems with A-Theory
A-theory faces a number of problems. McTaggart claims, for instance, that the A-series[3] is necessary for real change, and thus real time, to exist. He argues that the A-series cannot exist, and therefore time isn’t real. He says that no event can be past, present, and future—yet all events are past, present, and future. We might counter that they’re past, present, and future across different points in time, not at one point in time. However, the problem McTaggart raises seems to be about privilege. Consider an event that from our perspective turns out to be past: from the perspective of that event it’s present, yet from the distant past, it’s future. These relations are symmetrical, and so what reason is there to privilege one perspective over the other? And then, what reason to believe in real distinctions between past, present, and future?
Something is wrong with McTaggart’s argument. Indeed, we might respond to McTaggart similarly to how Samuel Johnson responded to Berkeley’s denial of material objects—by kicking a rock and saying, “I refute it thus!” Well, perhaps a better approach is to consider this: we needn’t immediately compare our reference frame to McTaggart’s and then struggle to explain why the present is privileged. Rather, we can look into something to which we have direct phenomenological access: our own conscious experience. I’m conscious and experiencing my own consciousness, right now, in this moment. I existed yesterday, last Tuesday, and years before, but I’m not conscious as my past self or in the past. I’m only ever in the here and now, though I have memories of the past, and I’m moving forward in time. My direct experience conveniently privileges the present. Of course, this example makes assumptions about personal identity and temporal persistence, but we can respond to McTaggart’s argument itself without immediately facing those questions.
However, A-theory faces another challenge: the notion of time moving with respect to time (i.e., with respect to itself). Positing hyper-time doesn’t seem promising, but instead seems to induce a vicious infinity. The question is why time, for the A-theorist, is represented on two dimensions. For instance, at T1 it’s 12am, at T2 it’s 2am, at T3, 4am, and so forth. To posit hyper-time is to suggest another dimension of time, and problems arise when we try to stipulate that there is also an objective present of hyper-time. One possible response is to say that if hyper-time exists, it does not move. We might then wonder what motivates one to postulate an A-theory of ordinary time and a B-theory of hyper-time. We could claim there is a realm that is eternal and timeless—I think we should go so far as to say outside of time. Then, we are not claiming there are two dimensions of time, but rather an eternal dimension and a temporal one.
We can respond to concerns raised by physics in a similar way. Current physics doesn’t see a distinction between past, present, and future—it doesn’t privilege one reference frame over another. This does not mean there isn’t privilege. Perhaps we’re simply not appealing to a physical distinction when we claim the present is privileged. The relativity of simultaneity introduces a deeper concern, but even then, it concerns appearances in the empirical world. One could, in the vein of Kantian transcendentalism, appeal to something superordinate, something non-empirical that causes observable physical phenomena—maybe something eternal.
B-theory
It’s strange to think about how time might “pass” in B-theory. The passage of time, or perhaps just “change”, consists in having different properties at different times. Events stand only in e/s/l relations; time doesn’t “move with respect to itself”. There really is no past, present, or future—no separate aspect of time apart from the relations in which events stand to one another. B-theory is eternalist in the sense that all e/s/l relations exist.
Problems with B-theory
B-theorists generally liken time to space, but there are dis-analogies. For instance, time has a certain direction (forward, from past to future) while space doesn’t. Temporal motion is constrained unlike spatial motion; similarly, time has unique causal constraints (e.g., no backward causation). Is this enough to undermine B-theory, though? It doesn’t seem like time must be just like space. Naturally, we should expect some differences between them. (And as an aside, the dis-analogies are more of a problem for four-dimensionalism than B-theory itself.)
What I consider a more serious objection to B-theory is its dismissal of, or inability to account for, our lived experience of time. Why do we experience a flow of time? If B-theory is eternalist, why do we move through time at all, and only experience a certain “present”? I have also in mind Arthur Prior’s “Thank goodness that’s over” objection. The four-dimensionalist B-theorist might say that I’m only relieved that my headache is gone because I, as it were, am just one time-slice—one temporal part of a larger four-dimensional space-time object. However, this isn’t a satisfactory response. For one, the question arises of what “privileges” this time slice as the one I’m experiencing (or the one being experienced), now? The four-dimensionalist response, instead of calling off the need for metaphysical privilege of the present, invokes it.
Which to defend?
I don’t think B-theory is completely wrong—insofar as it says e/s/l relations exist and are important—but e/s/l relations don’t provide a full account of time. Our fundamental experience of the world counts in favor of the existence of tensed facts. Experience alone does not confirm A-theory as the “right” account of time, but I think it places a heavy burden on B-theory, and in my view, B-theory doesn’t meet the challenge.
Whichever version of the A-theory we defend, I think its general defense of tensed facts is enough to make B-theory unfavorable insofar as it does not or cannot account for our experience. It’s true our perception of time is subjective, and so it’s difficult to comment on “time itself” outside of experience. But we could also look at our experience of time as indicative of something about time itself. Our experience could arise from something about time itself. Furthermore, whatever our experience is like, it’s true that we’re really having this experience. And so to dismiss it, often by appeal to physics, seems premature, especially when the two need not be mutually exclusive.
One way to think of time might be to consider our experience of time as a secondary or irreducible emergent property—similar to Locke’s idea of primary and secondary properties. I don’t mean the experience of time is “just subjective” or “an illusion”. Rather, I mean there is something real about time that conscious experience picks up on, which may not be discernable by physics, but nonetheless is a property irreducible to B-relations (in other words, a sort of nonreductive property dualism regarding A-properties and B-relations). We could consider this as analogous to space. Things like color, sound, and scent are secondary properties of physical things. They’re not mere illusions, but they are perception-dependent.
And of course, could B-theory allow for conscious experience? We’re conscious in the “present”, right now. But we aren’t yet conscious in the past or the future. If there is no real present, and in fact there are just tenseless relational facts about events, what explains our experience of the present? In other words, physics may not privilege certain events in the world of appearances as “present”, but experience does that that for us, which suggests something about time that underlies and accounts for perception.
A-theory may, then, be preferable because it affirms tensed facts. It’s reasonable (in this case) to appeal to experience and believe in a real distinction between past, present, and future. Thus, it’s reasonable to defend A-theory over B-theory. We might also ask, which is worth believing in? I think A-theory is.
Post-Conclusion Closing Thoughts (because the “conclusion” is never really the Conclusion-with-a-Capital-C)
Of course, the appeal to belief in general and to belief in what is “worth” believing in is a whole separate issue, and indeed this very paper contains a lot of material in a very condensed and simplified format. However, in considering differing motivations underlying A- and B-theory, and the theories’ explicit claims/views, we may begin to see that there is, almost always, much more to most things than there seems. And so two broad responses to almost any given issue, philosophical (e.g., the mind-body problem) or otherwise, are the following: sometimes-premature simplification on the one-hand, and on the other, the introduction of strange, uncharted territory that raises as many questions as it promises to answer. I usually err on the side of the latter.
References
McTaggart, John McTaggart Ellis, 1866-1925, and C. D. (Charlie Dunbar) Broad. The Nature of Existence. 1st pbk. ed. Cambridge: Cambridge University Press, 1988.
Sider, Theodore., John Hawthorne, and Dean W. Zimmerman, eds. Contemporary Debates in Metaphysics. Malden, MA: Blackwell Pub., 2008. Print.
And my own creative imagination
– Ashley Gasdow