Taken together, these various considerations leave the at-at theory looking a good deal more credible. If we find it natural to hold that motion makes for intrinsic differences, this is not surprising: our perceptual experiences of motion are in fact intrinsically different from our experience of motionless objects. In clarifying the situation it is helpful to distinguish two forms or modes of motion: phenomenal and non-phenomenal (or “P-motion” and “NP-motion” respectively), where the former refers solely to motion as it features in our immediate experience—i.e., the intrinsically dynamic motion to be found the experiential realm—and the latter refers to motion in its purely physical (non-experiential) form, as a feature of objects-as-they-are-in-themselves. If the at-at theory were intended to be providing an exhaustive account of motion in all of its forms, P-motion as well as NP-motion, then it would clearly be inadequate; but its proponents only intend it to be an account of NP-motion, and as an account of motion in this form it may well be entirely adequate.
We are now in a stronger position to address this question: Does intrinsically dynamic motion exist in our universe? In one respect, the answer is obviously “yes”. It is not a feature of mobile material objects such as footballs, cars and planets—these possess only NP-motion, which adequately characterized by the at-at theory—but it evidently exists in our own experience, and (very probably) the experience of other conscious subjects (e.g., non-human animals). Provided we adopt the stance of taking experience seriously—as I am currently proposing that we do—then since experience is just as real as anything feature of concrete reality, the same applies to the phenomenal features associated with P-motion: they too are as real as any other property or feature.
So far so good, but a further pertinent question is more difficult to answer: Is P-motion a physical phenomenon? The answer this question depends on the relationship between the phenomenal and the material. There may be nothing approaching agreement on precise relationship between consciousness and the physical world, even among non-reductionists about the phenomenal, but there are only two main options. If some form of dualism is true—whether substance dualism or property dualism—then since experience is non-physical, so too is P-motion. In this case, P-motion will be a part of our wider universe, i.e. the sum total of what exists, both material and immaterial, but it won’t be part of the physical universe. If, on the other hand, some form of materialism is true, then experience itself is a physical phenomenon, and so P-motion will also be physical in nature. For those who take experience seriously, the relevant form of materialism is one which accepts experience is real and irreducible, but also takes it to be entirely physical in nature. Materialists of this persuasion make room for the phenomenal by holding that there is more to the physical realm than is recognized by current physical theories in general, and current physics in particular. More specifically, they maintain that some parts of the physical world possess intrinsic natures that are (partly or wholly) experiential in nature. Which parts of the physical world are thus endowed? Perhaps the neural processes in mammalian brains with which we are already (partially) familiar, or perhaps some yet-to-be discovered physical fields that are generated by the neural processes in mammalian brains—there are no doubt other possibilities, for as most would agree, there is much about the physical world that we have yet to discover. We can call this position on the matter-consciousness relationship phenomenalized materialism, for obvious reasons.
If the claims of the phenomenalized materialists turns out to be true, then both P- and NP-motion are real ingredients of the physical world. NP-motion exists where it seems: wherever moving material bodies are to be found. P-motion is (probably) rather more localized: motion in this intrinsically dynamic form exists only within the brains of those conscious subjects who are perceiving (or imagining, or dreaming) bodies in NP-motion.5 But both forms of motion are fully real, and fully physical, phenomena.
§4 The Reality of Passage
The preceding considerations have a broader significance, for what goes for experienced movement applies more generally: to temporal passage, at least as it features in our experience.
Echoing the distinction between P- and NP-motion, we can distinguish between experiential and metaphysicalpassage, or “E-passage” and “M-passage” respectively. By the latter I intend to refer to the various metaphysical accounts of temporal passage which apply the universe as a whole; the main contenders here are Presentism, the Growing Block and the Moving Spotlight conceptions (in their various particular guises). As for E-passage, I take this to refer to all those dynamic aspects of our immediate experience that are, or could easily be taken to be, suggestive of passage—those features of our experience which give rise to, or nurture, the notion that time itself has an active, flowing character which space does not. Experiences which feature P-movement play a prominent role here: think of what it is like to watch the countryside stream by from the window of a speeding train, or to see the walls of a corridor slide by as you walk along it, or your surroundings blend into a blur as you quickly turn your head. As the world flows by (or seems to), doesn’t it also seem as though we ourselves are smoothly and steadily sliding into the future? But it would be a mistake to suppose that experiences have to feature P-movements to have a dynamic or flowing qualities which are the mark of E-passage. Most forms of auditory experience share this feature: think of what it is like to hear a succession of notes, or just a single note continuing on (and on …): doesn’t each brief phase seem to flow smoothly into the next? The same applies, if less obviously, to much of our bodily experience: think of the way a severe pain just continues on without pause or interruption—other bodily sensations have a similar quality—we might call it immanent flow—albeit in a lower register. Other forms of “inner” experience also occur in a stream-like way: think of the manner in one’s inner soliloquy unfolds over time, with one thought (or memory-image, or imagined scene) being experienced as giving way to the next. From a phenomenological perspective we may well seem to live out our conscious lives from the midst of a “sphere” (or “horizon” or “arena”) of personal present awareness, as Valberg (2007) and Johnston (2010), have recently suggested, but it is crucial to recognize that the contents of this sphere or arena are not static: they are undergoing continuous passage, as they flow out of the present into the past. E-passage is a ubiquitous feature of our conscious lives.6
The doctrine (or conviction) that time itself passes has several sources, but E-passage, in its various concrete forms, rooted as it is in the most basic sensory and sensational aspects of our conscious lives, is surely among the deepest and most important. When I look at the clock and discover that an hour has passed since I last looked at the clock—and that I now have only two hours until I miss an important deadline whereas earlier I had three—my sense of time’s ineluctable passage is very acute. This sort of time consciousness derives from and depends on memory; if I had no recollection of my earlier observations of the clock (or any other time source) I would not be conscious of time passing in this sort of way. But I needn’t be aware of time’s passing in this sort of way in order to experience E-passage. If an onset of severe amnesia were to render me incapable of making memory-based judgments, provided my experience were otherwise unchanged in quality—provided it continued to exhibit the immanent directed flow that is characteristic of E-passage—my sense that I am moving forward in time, or that time itself (or the world) is flowing by, would also be fundamentally undiminished. 7
I will not try to ascertain here the precise relationship between E-passage and the other factors which may support the doctrine of temporal passage. Even if E-passage is not the single most important of these factors, it is certainly an important factor, and this is all that matters for present purposes. But since E-passage is a phenomenal feature of our experience, we are confronted with the question of the status of E-passage itself: in what manner, or to what extent, is it really a feature of our world? Here our earlier discussion of P-movement is relevant. Given that we are taking experience seriously, E-passage is as real and irreducible as P-movement (or sensations of pain, or experiencings of yellow). If the reality of E-passage is thus secured, its relationship with the wider world depends on the broader issue of the relationship between the experiential and the physical. If some form of dualism is true, then E-passage is part of the wider universe, but is not a feature of the physical world. But if, in contrast, phenomenalized materialism is true, then E-passage—along with all other phenomenal objects and properties—is as much a physical feature of the world as size, mass or charge. In which case, the immanent flow (as I called it) that characterizes of much of our experience is itself an intrinsic feature of those regions of the physical world which constitute the streams of consciousness of ourselves, and other conscious subjects.
This result is potentially of considerable significance. If E-passage is an entirely physical phenomenon, the claim that our physical universe is in reality entirely passage-free cannot be correct. If our universe is of the Block variety then it is certainly the case that no form of M-passage exists—this holds by definition. But given that E-passage certainly exists (we can be as certain of this as we can be certain of anything) then we can safely conclude that our universe contains at least one significant form of passage—that certain regions or parts of it have an inherently dynamic intrinsic nature. And this result holds even if our universe is entirely devoid of any form M-passage. Of course, this is all assuming that phenomenalized materialism, or something like it, is the correct account of the way the phenomenal and the physical are related, and we cannot be sure that it is. But as things currently stand, phenomenalized materialism looks to be at least as promising and plausible as any of the available (non-reductionist) alternatives.
In a recent discussion (forthcoming), L.A. Paul develops a superficially similar, but in reality profoundly different, position to the one I have been outlining here. It is worth bringing the divergences into clear view—not least because they usefully illustrate the difference adopting a strong realism about experience can make. Paul’s argument runs as follows.
The phenomenon of apparent motion shows that the brain can generate dynamic-seeming experiences on the basis of static (or motion-free) perceptual inputs.
This fact is of great use to the Block theorist in explaining why time seems to pass if in reality it doesn’t.
In such cases there isn’t really any “flow or animation in changes that occur across time”, rather one’s brain merely creates the illusion of such flow.
This illusion does not involve the brain’s literally “filling in” the intervals between static stimuli with dynamic phenomenal pigment (as Dennett sometimes puts it), rather “it just gives the impression of being filled in”, i.e. we have a tendency to believeor say that the gaps are filled in, even though they aren’t.8
Inclined as I am to take experience seriously (in a way Paul clearly isn’t), I do not find this strongly reductionist—in fact, eliminativist—approach to temporal experience remotely appealing or plausible. But it is also worth noting that adopting this stance greatly undermines the reconciliation of the Block view with the temporal appearances that Paul is attempting to bring about. We are, in effect, being urged to accept not only that M-passage is unreal, but that the same applies to passage-as-we-experience-it—and hence that our experience is radically different from how it seems (as paradoxical as that sounds). There is thus a substantial difference between the position I have been recommending, and what is being advocated by Paul. I agree that E-passage exists in the realm of appearances, and that to the extent that these appearances misrepresent the (non-dynamic) external physical reality they can in this respect be construed as misleading or illusory. Nonetheless, the appearances in question are nonetheless fully real experientially, and the experiences in question really do possess dynamic characteristics. In this sense, there is nothing in the least illusory about the flux and flow we find in our experience.