Sunday, October 6, 2013

Time passes

by Brad Dowden

The essence of nowness runs like fire along the fuse of time.*

Time passes. It flows. Or so they say. Great philosophers say this.

But they are mistaken.

Fluids flow, but time flows only in a metaphorical sense. This is the sense in which future events somehow move constantly closer to our Now, while past events recede ever farther into the past, just like when a runner who approaches us, then passes us by, and then recedes. We all experience this flow, but only in the sense that we all experience optical illusions.

Physicists sometimes speak of time flowing in another sense. This is the sense in which change is continuous rather than discrete. In this sense, time may flow, but this isn’t the sense of “flow” that philosophers are usually talking about.

Physicists sometimes carelessly speak of time flowing when what they mean is that time has an arrow, a direction from the past to the future. In this sense time definitely does flow, but again this isn’t the sense of “flow” that philosophers are usually talking about.

In the sense of “flow” that too many philosophers do promote, I believe they are confusing time existing with time flowing. Here is why. Things change, so time exists. But that change doesn’t itself change; so, it’s a mistake to say the change “flows.” Let me explain this a little more. Time is what clocks measure. Time is a measure of change that puts dates on events, and tells us how long an event lasts, and says which events happen before which other events. That isn’t the same thing as the flow of time. When things change we say, “Time flows on,” or “Time stops for no one,” but these are inaccurate, poetic remarks. The changes are a sign of time existing, not time changing. When you experience change from eggs to omelets, or change from here to there, you are experiencing time itself, not a passage of time, nor a passage of the passage.

If you can place a date on an event and say it occurred, say, on Tuesday, then that same event doesn’t flow into Wednesday and then on into Thursday. It’s always an event that occurred last Tuesday. So, it is a mis-description of events to say they flow from the present into the past, yet that is what too many philosophers do say.

If time passes, what does it pass? Maybe you want to say it passes us. Hmm. Does it pass our childhood just as fast as it passes us now? Probably it passes at the same rate. OK, let’s assume it does pass at that rate. But what rate would that be? It would have to be a rate of one second per second. But that’s silly. One second divided by one second is the number one. That’s not a coherent rate.

I recommend saying the flow is subjectively real but not objectively real. The mistaken belief that time flows is due to our being misled by careless speech about time (“Time stops for no one”), but it is also due to some objective feature of our brains that makes us “feel” as if time is flowing. I suspect this objective feature is partly our having different perceptions at different times and partly our anticipating experiences before remembering those experiences.

Half the philosophers of time would accept my argument above; the other half believe the flow of time is necessary for “a literal and complete account of Everything That Is So,” to quote from last week’s posting by Professor Pyne. Half of us are mistaken. Which side of this fence are you on–the side that says time is dynamic and flows, or the side that says time is static and doesn’t flow?


Brad Dowden
Professor
Department of Philosophy
Sacramento State

*George Santayana, in The Realms of Being.

18 comments:

  1. Brad, I have two simple-minded questions/thoughts.

    I am interested in your claim that the flow of time is like an optical illusion. Is that really a good comparison given the discreteness of optical illusions, i.e., the fact that they occur in specific predictable situations and can be explained against the background of typically veridical visual experience? Or is the experience of the flow of time more like the constant illusion that color is an objective property of objects rather than a relation between us and the light that they reflect?

    Also, I am wondering whether our tendency to speak of the flow of time might be better explained as the result of a poorly chosen reference frame, in much the same way we once spoke of the movement of the heavens on the assumption that the earth is stationary. In other words, we experience time passing by like a river, but the truth is that we are moving through it. If that were the case, it seems to me that there would have to be a reason given for why one reference frame is really objectively more correct than another. For example, to do this with respect to space, we need to talk about why there really is a fact of the matter concerning which of two objects are accelerating.

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  2. Randy, I agree with you that it can be misleading to say the flow of time is like an optical illusion. In too many ways it is not like an optical illusion. I picked that term just to have a flowery way of saying that we are misled by our experiences when we interpret them as time’s flowing or passing.

    You said, “we experience time passing by like a river, but the truth is that we are moving through it.” I doubt that we are moving through it. There is no reference frame in which time passes, so a correct selection of frame is not key for this issue.

    Proponents of time’s passage think like this. They won’t say last Tuesday flows into last Wednesday, but they will say we are moving through time because we are getting farther away in time from last Tuesday in the sense that our "now" recedes from last Tuesday.

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  3. Ok, I think I follow that. Would you be willing to say some more about the confused notion of flow and the mischief that it causes? Is it just that when a philosopher interprets a statement like "Time is passing" realistically s/he mistakenly legitimizes a request for a theory of time that explains this phenomenon as a real feature of the universe?

    Also, I am curious about where you stand regarding the ontological status of time. I am thinking, specifically, of Kant's claim that it is an innate a priori intuition, not a feature of reality itself. Are you fundamentally a realist or an instrumentalist about time?

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    1. The mischief that belief in time’s flow causes is of several kinds. One kind is that it gets people to confuse physical time with psychological time and thus think that the following is an interesting question, “Could time pass more slowly on Friday afternoons?” Physical time, the time that clocks measure, won’t pass more slowly on Friday afternoons, but psychological time might. Psychological time is our awareness of physical time.

      A second kind of mischief occurs when it encourages people to accept McTaggart’s A-theory of time as opposed to his B-theory. The A-theory comprises two theses: (1) Time is constituted by an A-series in which an event’s being in the past and its degree of pastness are two properties that are intrinsic to the event itself; these properties are not relations to us or to our now. Similarly, an event’s being in the present or in the future is an intrinsic property of the event. (2) The second thesis of the A-theory is that time actually flows. The B-theory disagrees with both of these theses. It implies that there is no objective distinction between past, present and future, and that time does not actually flow (or at least that it does not actually flow in the sense of flow used by the B-theory).

      Randy, your other question is about the ontological status of time. I wouldn’t accept Kant’s clever claim that time is an innate a priori intuition that structures all possible conscious experience. I believe physical time is an objective, mind-independent feature of the world. It would exist even if no conscious beings had ever evolved. Kant would disagree. I have a completely convincing argument I could give you that Kant is mistaken.

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    2. Kant, wrong?
      OK, this might be a bit confused, so maybe I'll be asking for clarification. I'm curious about the argument against Kant, Brad, largely because it seems to me that time, as you indicate in your post, is an artifact of change. Does that not imply a perspective? That is, time as a phenomenon is an experience of change, which 'flow' inaccurately describes. What I mean is, for there to be something other than this now, this now, this now, this now... there must be a something from the point of view of which now is bracketed by before and after, no? Or, are you saying that flow is inaccurate as a description because time is not phenomenal at all, there is no point-of-viewness to it. If the latter, then in what sense is there a present to which future and past are relative? You said that physical (I'll take this to mean objective -- at least not subjective or psychological) time is measured by a clock, but what is it that the clock does in the measuring? Tick, tick, tick, tick, a hand passes numbers on a circular scale or a crystal vibrates. A frame of reference is necessary in which to designate tick1 as now, but tick2 as now, rendering tick 1 in the past, and anticipating tick3 in the future. How does this make sense absent a point of view or experience?

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    3. Where there is change there is time. Time is a product of change or a measure of change; I’m not sure what you mean by saying it is an “artifact of change.” If artifacts are humanly-made, then I’d say time is not an artifact of change but clocks are. The kind of time that clocks are designed to measure is called physical time, and it existed long before humans existed.

      I don’t agree with you that “time as a phenomenon is an experience of change” if that implies time doesn’t exist without experience of change. Physical time is not an experience; it is more of a structure of all possible events. It exists without EXPERIENCE of change.

      You ask me whether I believe, “time is not phenomenal at all, there is no point-of-viewness to it.” Psychological time is necessarily phenomenal; it requires human awareness and a point of view. Physical time doesn’t. Physical time is CAPABLE of being observed, sensed, or known; but it exists without being observed, sensed, or known.

      You ask, “What is it that the clock does in the measuring?” My answer is that it counts the ticks. No human counter or conscious counter need be involved.

      You say “A frame of reference is necessary in which to designate tick1 as now.” I agree with you. Let’s talk more about reference frames. As physicists use the term, it may best to think of a reference frame as just a mathematical coordinate system; x for distance this way, y for distance that way, z for distance there, t for time, and this event [say, the birth of Jesus Christ] at coordinate location <0,0,0,0>. How long an event lasts can be different in different reference frames. It absolutely must be different if the two frames are moving relative to each other. This result is a theorem in Einstein’s special theory of relativity.

      What is necessary for designating tick1 instead of tick2 as now is some conscious being that can be aware of time. Whether the year 1900 is in the future depends on whether we are asking Kant or Professor Bellon.

      We haven’t yet talked about REASONS to believe Kant is wrong about the ontology of time.

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  4. Isn't the best account of the illusion of passage William James's 'Specious Present'?
    I observe a ball roll across the floor. That is, I don't see the ball at place 1 at time 1, place 2 at time 2, place 3 at time 3...
    I see it move from place to place.

    That is, my experienced present has a duration which the real present - on any account of time - lacks.

    My capacity to observe the motion of the ball is only for very short intervals of time. If the ball keeps rolling, then for earlier segments of its rolling, I'm remembering it move, not observing it move.

    On no account of time (at least one that has a reasonable chance of being right) does our experience of the Specious Present represent anything real.

    Is it reasonable to suppose that our cognitive illusion about passage derives from this perceptual illusion of the Specious Present?

    BTW, Brad who are some current philosophers who accept the myth of passage?

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    1. William James’ account could be better if it didn’t confuse physical time with psychological time. Physical time is what clocks measure; psychological time is our awareness of physical time. James is right that our awareness of the present isn’t instantaneous like the physicist’s instant; there is a so-called specious present we are conscious of that lasts longer. But inserting the word “real” by calling it “the real present – on any account of time” is unfair. There is nothing unreal about the physicists instantaneous present, the present that lasts for zero seconds. To call it unreal is to assume that psychological time is real but physical time is not.

      When you ask for names of current philosophers who accept the myth of passage I assume you mean you want the names of philosophers who would say passage is NOT a myth. The leaders here are William Lane Craig and Quentin Smith.

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  5. That is precisely the point I was making:
    That the idea that of time's passage may derive from our perceptual experience of the Specious Present.

    That we experience a Specious Present is a psychological fact about our experience of the world, not a fact about time.

    But in real time the present is as it were a 'point' - no temporal extension.

    I was asking whether you thought that our conceptual illusion of 'passage' may be explained by our perceptual illusion of the Specious Present.

    Thanks for the information about current believers in the myth of passage. I thought that 'myth of passage' had become a term of art.

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    1. Tom, yes I agree with you that “the idea that of time's passage may derive from our perceptual experience of the Specious Present.” But I would prefer to say “derive in part.” There is probably much more to why we tend to believe in time’s passage than just our perceptual experience of the specious present.

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  6. Brad, I actually am interested in what you think is the best argument against the Kantian perspective on time. Regarding space, the standard argument against Kant's view is that we've since discovered that real space has properties that our conscious experience of it does not, a discovery that is not even possible on Kant's view, since for him all scientific inquiry occurs on this side of the grid.

    I also wonder how we know that what we call psychological time is our experience of real time. For example,we say that color is how we experience EMR at certain wavelengths, but that's because we have a well developed causal theory about how that works. It doesn't seem like we have a causal theory about how real time gives rise to the subjective experience of time, or even how it could. During any particular interval I suppose I have a subjective sense of how much time has actually elapsed. But is the amount of time that has actually elapsed really what is giving rise to that feeling? Or are we always just somehow simulating time without having any direct contact with it?











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    1. Randy. Yes, that is how we know Kant is incorrect about space. But I’d put less emphasis on “conscious experience,” and instead say that we have tested and accepted an empirical theory, the general theory of relativity, which implies that the geometry of space is non-Euclidean contra Kant who said space MUST be Euclidean.

      My argument against Kant’s views on time is multi-faceted. One facet is that Minkowski has shown that space and time are inextricably linked in the sense that spacetime is more fundamental than either time or space. Einstein eventually agreed with Minkowski. If Kant is wrong about space, then he’s surely wrong about time, too. A second fact gives reasons to believe time is mind-independent.

      Any organism’s sense of time is subjective, but the time that is sensed is not. Here is why. Without minds in the world, nothing in the world would be surprising or beautiful or interesting. Can we add that nothing would be in time? No, because if judgments of time were subjective in the way judgments of being interesting vs. not-interesting are subjective, then it would be too miraculous that everyone can so easily agree on the ordering of public events in time. For example, first, Einstein was born, then he went to school, then he died. Everybody agrees that it happened in this order: birth, school, death. No other order. The agreement on time order for so many events is part of the reason that most philosophers and scientists believe physical time is an objective phenomenon that is not dependent on being consciously experienced.

      Another part of the reason to believe time is objective and not an a priori intuition is that our universe has a large number of different processes that bear consistent time relations, or frequency of occurrence relations, to each other. For example, the frequency of rotation of the Earth around its axis is a constant multiple of the frequency of oscillation of a fixed-length pendulum, which in turn is a constant multiple of the half-life of a specific radioactive uranium isotope, which in turn is a multiple of the frequency of a vibrating violin string; the relationship of these oscillators does not change as time goes by (at least not much and not for a long time, and when there is deviation we know how to predict it and compensate for it). The existence of these sorts of relationships makes our system of physical laws much simpler than it otherwise would be, and it makes us more confident that there is something objective we are referring to with the time-variable in those laws. The stability of these relationships over a long time also makes it easy to create clocks. Time can be measured easily because we have access to long-term simple harmonic oscillators that have a regular period or “regular ticking.” This regularity shows up in completely different stable systems when they are disturbed: a ball hanging from a string (a pendulum), a ball hanging from a coiled spring, a planet orbiting the Sun, organ pipes, electric circuits, and atoms in a crystal lattice. Many of these systems make good clocks. The existence of these possibilities for clocks strongly suggests that time is objectively real, and is not merely an aspect of consciousness.

      Although I am a realist rather than an instrumentalist about time, I think the instrumentalists have some good reasons for their views that do give me pause, but I won’t explore them here.

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    2. Brad, thanks, that's all very clear. Would I be missing anything essential about what you are saying above by summarizing it as follows?

      "The best explanation of the order we observe in the world is that the world is in fact ordered. Time is an attribute of order, therefore time is real."

      As you know, one of my primary interests is explanation, so I think it is interesting to note that your argument for the existence of time and Tom's argument for the existence of intentional states are both, in the end, abductive. Part of why it's interesting to me is that abductive reasoning in this way is by no means unproblematic. This is because in science we typically use abduction as a basis for proposing interesting theories, not confirming them. To defeasibly confirm them, the abduced theories typically need to yield new predictions that are also confirmed and make no predictions that are disconfirmed.

      I have always felt at a loss concerning how to evaluate the explanatory significance of appeals to reality. There is obviously something deeply intuitive about it. Why does everybody agree that Tom is in the room. Well, hey, maybe because Tom REALLY IS in the room? That certainly sounds right, and silly to deny, but there is also something meretricious about it. It is different, but has the same facile feeling of philosophical appeals to the true meaning of terms to terminate their arguments.

      One answer to this may simply be that a reality hypothesis does make non trivial predictions, namely our continued broad agreement about such matters. For example, at one point we might have said that the best explanation for the fact that we all agree about the existence of God is that God really does exist. But now we don't agree, so the reality hypothesis has lost a bit of its explanatory power. Alternatively, suppose that everybody but Chris agrees that Tom is in the room. When we propose that the best explanation of our agreement is that Tom really is in the room, that predicts both our continued agreement as well as something that is causing Chris' ignorance, which we often can find. (She is sleeping, she is on drugs, etc.)

      I'm not sure you completely addressed my final question, namely whether we know our subjective sense of the flow of time is itself best explained by the objective existence of time. Do you think this can be assimilated to the general problem of explaining qualia? Do you suspect that the flowy feeling of time just arises in the same way as the reddy feeling of tomatoes and the screechy feeling of badly played violins? So that to whatever extent we can meaningfully discuss philosophical zombies and mutants, the flowy feeling of time can be added to the list of things they might experience differently or not at all?

      I suspect time is different somehow. For example, our subjective sense of time seems to be related to our flicker fusion threshold, the rate at which a flickering source of information is perceived as continuous. A drug like LSD may raise or lower the flicker fusion rate with the result that we experience time as speeding up or slowing down. I wonder if this is a framework for understanding the function of the phenomenology of time that we don't quite have for other qualia.





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  7. Randy, you said: Would I [Randy] be missing anything essential about what you [Brad] are saying above by summarizing it as follows?

    "The best explanation of the order we observe in the world is that the world is in fact ordered. Time is an attribute of order, therefore time is real."

    That is a fine summary and gets to the heart of the matter.

    I like your idea that our subjective sense of time such as its giving us a flowy feeling is related to our flicker fusion rate. And it does seem to be a special framework for understanding the function of the phenomenology of time that we don’t have for other subjective senses or qualia (if there are such things as qualia). I am hoping that Matt will step in and tell us whether we should believe in the existence of qualia.

    You said: “Why does everybody agree that Tom is in the room. Well, hey, maybe because Tom REALLY IS in the room? That certainly sounds right, and silly to deny, but there is also something meretricious about it.” I like calling it meretricious. It’s a terrible explanation. Tom’s being in the room is only one part of the explanation of our agreeing that he is in the room. A much better explanation of our agreement will add to the fact of Tom’s being in the room that we are using our eyes, and we all seem to see Tom in the room, and here is how our eyes work…. And notice how likely it is that, with the present lighting in the room, we are seeing accurately rather than inaccurately. And an even better explanation would add that there is a lack of evidence that Tom is NOT in the room. We need to defend our belief that we are not in one of those odd situations where we all agree that Tom is in the room when he really is not.

    Randy, you asked “whether we know our subjective sense of the flow of time is itself best explained by the objective existence of time.” I would say we do not know this.

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  8. Randy, you’re making me think more about the nature of explanation. Here is a reason why I don’t agree with you when you say: “The best explanation of the order we observe in the world is that the world is in fact ordered.” I would say that only one part of the best explanation is that the world is in fact ordered. Here is why.
    Suppose all ten of us in a room agree that Tom is in the room. We all agree because we do not realize we are all looking at a 3D hologram projection of Tom. But in fact Tom actually is in the room, though we are not looking at him. Then it would be a mistake to say, “The best explanation of our agreeing that Tom is in the room is that Tom is in fact in the room.” The best explanation instead should speak about the hologram.

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    1. Randy, I may be confusing two senses of the term “best explanation.” When you say,

      The best explanation of the order we observe in the world is that the world is in fact ordered,

      this would be OK to me if it means that the order we observe in the world is best explained as being caused by the world being ordered that way, but it would not be OK to me if it means that the best way to explain our believing in the order we claim to be observing in the world is that the world is ordered that way.

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  9. Brad, that's a good clarification and I agree completely. My original formulation is definitely a simplification that can be Gettiered in the way you suggest. I like to avoid reference to causation when I talk about explanation because I prefer an account of explanation that would survive even if causes turned out not to be real. But I still agree completely that the claim here should be that the actual existence of order or Tom is just an essential part of the best explanation of the appearance of order or Tom.

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  10. Randy, we are in agreement about this. I, too, am unsure how useful the concept of cause is, but at the level of ordinary practicing physics it is everywhere. For example, the explosion caused the damage, the increase in frequency caused the vibration, and so forth.

    What do you think about time flowing? We can continue this discussion offline if you wish.

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