## Wednesday, April 05, 2006

### Unchanging Time and the Infinite Past

You sometimes hear people argue that there couldn't be an infinite past, or else the present couldn't have been "reached" yet. But this is a bad argument. Alejandro succinctly explains:
Time being infinite in the negative direction just means that for every instant t there is a previous instant t’. It doesn’t imply that anything has to “do” an infinite task.

As I noted in that same comments thread: it does not take time for "now" to be reached, any more than it takes distance for “here” to be reached. We may posit an infinite space without supposing anything to cross it. Similarly, we may posit an infinite temporal dimension without supposing anything (the “moving ‘now’”?) to have traversed that.

The problem lies in conceiving of "the passage of time" as being a kind of movement. We imagine the present-marker "starting" at the beginning of time, and moving forward into the future. But this picture belies a deep incoherence. It takes a second dimension - time - to move along some dimension. (Think of a graph plotting the change in y-axial distance against the x-axis of time.) But what is the present-marker moving through, as we track its changing temporal location? It can't be moving through the first-order timeline, since that is rather what it is moving along. We need to posit another temporal dimension, a 'meta-time', in which it can traverse first-order 'time'. This leads to infinite regress, and an absurd commitment to infinitely many temporal dimensions.

We must conclude that there is no present-marker, or "moving 'now'". All times are on an equal ontological footing, the same way that all distances are. 'Now' is no more a privileged time (or "one true present") than 'here' is a privileged location or "one true place". The significance is merely indexical. Now is the time I'm at, and here is the place. But there are other places and times, no less real and existing than my own.

To avoid regress, we must recognize that time exists atemporally. Each moment stands in temporal relations (e.g. "before" or "after") to other moments, and indexically represents itself as 'present'. And that's just how it is, eternally. The moments themselves don't change. Rather, "change" is merely the fact of one moment differing from those which stand in the 'before' relation to it.

Besides which, even if they were possible, any external changes to time itself could have no impact on our experiences. At this moment in April, I have memories of March, which I conceive of as "last month". But if God were to rewind time, to “replay” the universe backwards, we couldn't tell the difference! God would see April first, but what he would see is me with my memories of March (and of course no memory of the "future" moments which God had previously shifted the present-marker from). He would later see those memories form, back in March. But the order in which God views things, from "outside time" (so to speak), cannot affect the experiences we have within our chronology.

Consider the movie Memento, where the viewed chronology is all jumbled up. The first scene we see is the last event to occur within the movie's chronology. As the movie progresses, we get to see earlier events. The fact that our external view is jumbled up doesn't affect the true chronology of events internal to the movie. Those events stand in 'before' and 'after' relations simply in themselves, quite independently of our viewing the movie.

The idea of the "moving 'now'" or present-marker is like the external movie projector. It highlights a sequence of moments, one after the other. But it needn't show those moments in the correct sequence (as represented internally by those moments themselves). So even if there could be a "moving 'now'", it would be strictly irrelevant to the proper chronology of things. April occurs after March, no matter what order the moving 'now' might happen to show them in. The 'now' could move backwards through time, but it would make no difference -- either to our experiences, or to the first-order temporal facts.

Since it makes no difference anyway, we clearly don't need the moving 'now' at all, any more than a set of movie frames needs a projector in order for there to be facts about the movie's chronology. It is enough for the frames, or moments, to exist. They internally represent their own chronology. No external highlighting is needed.

We could imagine a movie with infinitely many frames. Perhaps we couldn't watch it from start to finish, just like a moving 'now' couldn't traverse an infinite past to reach the present. (Aside: this might actually be possible via hyper-acceleration, however!) But in neither case is such external highlighting necessary. Each frame/moment exists, and represents itself as 'present', and as 'after' other moments. And that's all we need. It's perfectly coherent to recognize that there could be a moment -- perhaps this one -- to which infinitely many other moments stand in the 'before' relation. That is, we could have an infinite past.

Categories:

1. I agree with you that to imagine the present as "moving" into the future is a deeply flawed way to concieve time. But I'm not sure if the mistake Jonathan was making (the argument that the present cannot have been "reached" if time is infinite in the negative direction) can be pinned down to this image you criticize here. They seem to me to be two related but independent mistakes.

To see what I mean, imagine an (possibly) inmortal being moving with constant speed in an homogeneous space. If the being has short-term memory, he can wonder: "Have I existed and been moving forever, or has my motion started somewhere?" And he may reason that if he has been moving forever, he has traversed an infinite distance to get "here"; but an infinite distance cannot be traversed, so his motion must have had a beginning.

This being is not falling into the fallacy you criticize in this post, because he is literally and truly moving. But I think he is commiting the same kind of fallacy Jonathan commits, and his reasoning is not valid. This shows the "an infinite past cannot be traversed" fallcy to be somewhat independent of the "time as a moving now" fallacy.

The being's reasoning fails because an infinite distance can be traversed -if it is done in an infinite time. (Also in a finite time with hyperacceleration, but even with infinite time there is no contradiction). And even if the "moving now" view of time could be articulated coherently, the "speed of time" could not be other than "one second per second", and so the "now" could have traversed the infinite past because it would have had an correspondingly infinite amount of "meta-time" or whatever you call it to do it; there is no need for hyperacceleration there.

2. I think I remember trying to explain this to you...
anyway... good post !

alejandro,

"The being's reasoning fails because an infinite distance can be traversed -if it is done in an infinite time."
I like Richard's explination better because there is some value in sidestepping the unresolvable equasion where you start talking about infinite distances being traversed in infinite time when this is not really required.

3. Richard, Alejandro simply defines (in the quote you cited) what "time being infinite in the negative direction" means. But definitions are not arguments or refutations of arguments. His comment pays no mind to the implications of what it states, and since it simply defines what "time being infinite in the negative direction" means, I don't blame it for that. But it doesn't argue for the possibility of that supposition, and it isn't a refutation of anything. (Defining moral relativism doesn't refute moral objectivism).

Your comments, Richard, (at least those in the first three paragraphs of your entry) presuppose a B-Theory of time, and since that's a completely different discussion it's simply a red herring in regards to the traversal of infinite past time discussion (as Alejandro also seems to suggest in his comments). Also you appear to assume that space and time are identical in nature, which is not a position that everybody holds.

From the assumption that there is no "moving now," it doesn't follow that all times are equally existent. Presentism solves the problem just as well.

Moreover, assuming a B-theory of time doesn't avoid the problem you raised; in fact, it runs right into it. In B-theory there is a present-marker, namely, the phenomenological now, even though it lacks any ontological distinction from other times. The problem is this: In order for there to be a present-marker in the manner in which you were using the term—that is, one that moves along a certain dimension or line—the other parts of that line must be existent, just as in the B-theory of time. (Again, presentism avoids this issue.) And B-theorists do speak of the present; they just don't make an ontological distinction there as presentists do. Presentists avoid this problem because in presentism only the present (and not the entire line) exists. So the B-theory of time is, in fact, the exact problem which you raise, not the solution.

4. Don Jr, if someone claims that an infinite past is impossible or contradictory based on a wrong definition of it, and I provide the correct definition and note that it is obviously self-consistent, then I have indeed refuted the claim.

You may answer that I have not proved the definition to be self-consistent. True, I haven't because I thought that was obvious: it is analogous to what means for the negative numbers to extend to negative infinity. So it can't give rise to a contradiction, quite independently of whether an A or a B theory of time is correct, whether the present "moves" or not, or all those discussions, which I agree are a red herring with respect to Jonathan's original argument. And I don't see what further argument for the possibility could I make.

By the way, there might seem to be a contradiction between my comment quoted by Richard and my comment on this thread, in which I seem to say that the traveller would be in fact doing an infinite task and taking an infinite time to do it. There is really no contradiction because what I meant now by that is simply that: 1) for every t, the traveller moves at the same speed v, 2) for every t, there is a previous t'. There is still no "infinite task to be completed" in the sense Jonathan was thinking. This also answers to Genius: I am not really dividing two infinities. My point was simply that both space and time could be infinite in that example (in the sense of infinity that I defined in the quote Richard makes) and without any need for hyper-acceleration.

5. Alejandro - that's a fascinating example you mention in your first comment. I still want to say that there are connections between the two issues, but perhaps not such strict ones as I'd assumed.

Don Jr. - I don't see how presentism helps. So we say that movie frames only exist while they're being shown in the projector. (Perhaps each frame pops into existence, ex nihilo, when it's their turn to be shown; and promptly disintegrates immediately afterwards.) That doesn't change the fact that the external order of viewing is utterly irrelevant to the temporal relations represented within a frame. Again, when watching Memento, we see the latest events first, even if the later frames (of earlier events) haven't popped into existence yet.

Everyone agrees that past moments did exist, and that future ones will do so, and that suffices to construct a timeline -- the "first-order temporal dimension" discussed in the post. There are still internal facts about the movie's (universe's) chronology that aren't affected by external viewings of it. That remains true even if frames (moments) only exist during presentation.

6. Of course, Alejandro, you are correct in the case that someone is not aware of what "infinite past time" entails. That's fairly obvious. I was assuming, though, that the concept was (correctly) understood by those discussing it. But yes; I agree with your point.

As an aside, I wasn't objecting to anything you had said Alejandro. I admitted that there was nothing wrong with the statement of yours on which I commented. I just thought that Richard had attempted to use it to refute what he thought to be a "bad argument." If that was the case (though I'm not sure that it was), then I object to that usage of your statement, not the statement itself.

Richard, I'm not sure about the analogy you gave in your last comment. I couldn't square it properly in my mind with presentism, and I'm not quite sure what your point was either, so I can't really comment on it. (I've been studying most of the day for an upcoming test, so please forgive the lack of sharpness I have remaining—not that I ever started with much.) But, regardless of that, my comments were merely an attempt to show that the B-theory of time does not solve the problem which you initially raised and, in fact, that it (the B-theory) is an exact model of that problem. In regards to the issue you initially raised, presentism avoids that problem completely. (Indeed, if I am correct that the B-theory of time is guilty of the problem you initially raised, and guilty in the manner in which I conveyed in an earlier comment, then presentism can't possibly be guilty of that problem as well.)

7. This is an old point; Thomas Aquinas pointed out something like it in exactly this context in the thirteenth century, and he was just clarifying a point that had already been made by Muslim Aristotelians. I'm not convinced, though, that it has anything to do, one way or another, with A-theory or B-theory. (I've gone on record denying that there is any clear way to make a distinction between A-theory and B-theory, so that's perhaps unsurprising.)

I'm also not convinced that the traversal in the objection is supposed to be an infinite traversal by time, rather than a traversal by the world as measured by infinite time. (Neither way saves the argument, I think, but the latter seems much less straw-mannish; and in that way of understanding the problem, I think Don Jr. is right that your analysis is just "an exact model of the problem".)

8. While I was reading this post, a connection occurred to me.

Brian Greene writes in The Fabric of the Cosmos that the idea of a "moving light", highlighting moments in sequence so that each one briefly becomes the "now", is unsupported: physicists have found nothing in the laws of physics that corresponds to such a moving light. But it's not just a matter of this idea being unsupported by evidence. In fact, this idea is actually contradicted by the evidence, specifically the evidence of Einstein's special relativity.

The main idea behind special relativity is that there is no one, universal time. On the contrary, observers on relative motion will disagree on which events are simultaneous, and there is no way, even in principle, to declare one of them right and the other wrong. (Gedankenexperiment: A moving train car has two photon detectors set up at either end of the car. Equidistant between them is a device that, when activated, emits a pair of photons, one in each direction. While the car is in motion, the device is activated. According to observers on the train, the photon detectors go off simultaneously; according to observers watching from the platform, the detector near the front of the train car goes off first. Neither is more right or more wrong than the other; it's all a matter of perspective.)

One of the more interesting implications of this is that observers separated by a great distance, even if they are moving at ordinary speeds, will disagree dramatically on which events are simultaneous - which means they will disagree on what does or does not exist at a given moment. For example, according to the equations of special relativity, if an observer 10 billion light-years from Earth walks away from us at 10 miles per hour, his list of "things that exist now" will encompass events that, from a stationary observer's perspective on Earth, lie 150 years in the future.

In this sense, presentism is false. There is not one unique present that's the same for everyone; Richard is correct when he says that all moments must exist timelessly, and that the notion of "present" is merely indexical. That is exactly what special relativity says.

9. Ebonmuse, William Lane Craig talks about that issue in much detail in his Time and Eternity. He also discusses it in an article, "God and Real Time," but not as fully, I think, as in his book.

10. Yeah, I've a separate post on Presentism and Relativity which discusses the interesting argument Ebonmuse mentions.

Brandon, thanks for the pointer, I wasn't aware of the issue's pedigree.

Don Jr., could you explain what presentism is and how it avoids the problem? My understanding was that it is simply the claim that only the present time (the time highlighted by the moving 'now') really exists. This seems to be exactly the idea of a 'moving time' that I was arguing against! You say that other times need to "be existent" for the problem to arise, but that isn't so, as the analogy of the presentist movie clip (where only the currently presented frame exists) illustrates.

I'm not sure what you mean by "the phenomenological now", or why you think I'm committed to any such thing. I hold that I'm conscious of 'now' in much the same way that I'm conscious of 'here'. There's no one present-marker. Every single moment has its own internal, indexical, self-representation of being 'now'. And there are no external markers. So I don't think your comments apply to me at all.

11. Excellent to see physics in philosophy !

12. Hah, I've been beaten to the punch! It just goes to show I need to do a lot more reading of your archives, I suppose.

Incidentally, does anyone know when the 28th Philosophers' Carnival will be up? It seems a bit late.

13. Ebonmuse, I don't know if you think that because someone has argued the position you initially held, then that position must be right; nevertheless, I'd suggest you at least scan Craig's article in order to see a defense of presentism against the relativity issue you raised, whether you ultimately agree with it or not.

Assuming a B-theory of time doesn't avoid the problem you raised; in fact, it runs right into it. In B-theory there is a present-marker, namely, the phenomenological now, even though it lacks any ontological distinction from other times. The problem is this: In order for there to be a present-marker in the manner in which you were using the term—that is, one that moves along a certain dimension or line—the other parts of that line must be existent, just as in the B-theory of time. (Again, presentism avoids this issue.) And B-theorists do speak of the present; they just don't make an ontological distinction there as presentists do. Presentists avoid this problem because in presentism only the present (and not the entire line) exists. So the B-theory of time is, in fact, the exact problem which you raise, not the solution.

The phenomenological now (not sure if that's an "official" term) is simply the now we experience, which, on your theory, is responsible for the illusion of the passage of time.

On presentism, the now doesn't move. The now exists, and is all that exists. You are right when you say that on presentism the present time is all that exists. You are wrong, in my opinion, when you assume that that indicates a "moving now" (that is basically, if not exactly, the hybrid A-B theory of time that McTaggart attacked in his "The Unreality of Time," which presentism avoids as well).

Again, your initial argument, not subsequent modifications, is what I was objecting to. In your initial argument you said that there could be no "present-marker," where this present-marker was assumed to be starting at the beginning of time and moving forward along some dimension or line of time. Presentism is not guilty of this because on presentism only the now exists, not the entire line. So they're can't possibly be a present-marker in the sense that you were using the term. There can be a present, sure—that's obvious. But there is only the present on presentism; it doesn't mark anything along a line. If, however, you're going to say that presentism remains guilty simply because it has a "history" of time (that is, that it can speak of the past and the future or before and after), even though there is no actually existing line of time, then pretty much all theories of time will be subject to your complaint.

You say, in regards to your B-theorist version of time, "Every single moment has its own internal, indexical, self-representation of being 'now'. And there are no external markers." Sure, that avoids the problem of a present-marker in the sense that you were using the term, but then that just becomes an implausible view of time that has innumerable issues elsewhere. For example, it's not clear if that theory could explain how a single entity experiences all these equally existent nows. And, even if it could solve that problem, it's not clear how it could explain the illusion of the passage of time (if they're all equally existent, with no external influence, then why do we seem to experience them in succession?). Basically, the theory just seems to be completely adverse to, and without explanation for, our phenomenological experience of time. But at least it would avoid the "present-marker" issue at hand.

14. Presentism requires that the present is always changing. You believe that March used to be objectively present, but now April is instead. That's all the "movement" I need for my arguments. (You deny that March any longer "exists", but that doesn't help you here. I've explained in previous comments how we can construct a timeline, even if you insist that only one point of the line truly exists at any given moment.) You then object that "pretty much all theories of time will be subject to [the] complaint." But static conceptions of time, like that which I advocate in the main post, have no problem here (as you finally admit in your last paragraph). The problem applies to all dynamic theories of time, it's true. But those are precisely what I was trying to argue against.

"if they're all equally existent, with no external influence, then why do we seem to experience them in succession?"

I address this in my discussion of how external influence is utterly superfluous. Our memories are built into the present moment. They aren't sensitive to external orderings, any more than the characters in a movie are sensitive to the fact that we're watching them backwards. What they (we) have access to are the orderings as represented in the internal chronology. So at any given moment, I will have memories of the recent past. What more stands in need of explanation? What more could be explained? Presentism doesn't add anything here, it offers merely the illusion of explanation. Again, my main post showed how its external claims are superfluous to our internal experiences.

(Perhaps there is the locative indexical fact - why am I experiencing this moment rather than some other one? But this is a separate and broader issue. We can just as well ask why am I me and not someone else. The first-personal nature of phenomenal experience is puzzling, but it's no special problem for a static conception of time.)

15. The problem doesn't apply to all dynamic theories of time. It applies to hybrid dynamic-static theories of time, such as the one McTaggart refuted in his "The Unreality of Time." Presentism is not subject to those criticisms though.

I admitted that true static conceptions of time—those which don't try to explain the existence of a phenomenological now, but rather explain it away—are not subject to your complaint. But then, as I said, they just have innumerable issues elsewhere. You addressed the issue (if it can even be considered an issue) of our memory for one instant in time, not of our experience of time in succession, or the illusion of the passage of time. You also left untouched the issue of how one unit, one person, seems to experience all the equally existent "nows" and seems to experience them in succession. If Don-today is the same person (or unit) as Don-yesterday, then why I am not now also experiencing yesterday as if it were today? Basically, you didn't answer the question which you attempted to answer. You didn't explain why we seem to experience time in succession; you simply explained how for one instant in time we could have memories of other instances in time, but that issue was never raised. (And "Why am I experience this moment rather than another?" is not at all the same as "Why am I me and not someone else?" unless you hold to some sort of monism whereby at rock-bottom the "self" must be illusional.)

No offense, but I didn't see you "[explain] in previous comments how we can construct a timeline, even if you [Don Jr.] insist that only one point of the line truly exists at any given moment." Rather, I saw you give some projector analogy that didn't really make any sense, at least to me, or have any relevance to the discussion. Admittingly, it may be that your analogy makes sense but that I'm just not understanding it; however, even if that is the case, your remarks there had to do about ordering and re-ordering time (like in Memento), so I don't even see the relevance to the discussion anyway. Again, I was objecting to your initial use of the "present-marker" criticism, which required that the entire line or dimension of time be existent. Presentism does not fall subject to that criticism. If, however, you want to modify your argument, then I'd have to reconsider my response.

16. Yes, by all means, please do reconsider your response in light of my later clarifications! (There would be little point in my talking to you otherwise!) In actual fact the core of my criticisms does not "require... the entire line or dimension of time to be existent." That's just an assumption you've made, and which I've repeated rebuked. The core of my objection is to the idea of the "one true present" changing over time, which presentism is quite obviously committed to.

The idea of the 'present-marker' is simply that of an ontologically privileged present. (If the name confuses you in this respect, just return to the idea of the "one true present", which I take to be synonymous, and which - again - the presentist is quite obviously committed to.) It doesn't make any claims about the privileges enjoyed by other times on the scale, and particularly whether or not they can be truly said to "exist".

The latter point seems merely terminological in any case - as Brandon might agree - since everyone agrees that all times have existed or will exist at some point, but also that they're no part of this moment in time. The remaining question seems to be whether to restrict our quantifiers to those objects that exist at present, or whether to broaden its scope to include other moments. Perhaps for this reason, presentism is sometimes instead characterized as the view which takes "temporal becoming" seriously. The 13th April isn't yet privileged to be the 'one true present'. (Indeed, it doesn't even "exist" yet.) But it will be, tomorrow. So the present must "move" or change from here to there, or rather now to then, even if you insist that what it leaves behind - the "past" - will subsequently no longer exist. The temporal dynamism I criticize is at the very heart of presentism, and your attempts to dodge this by disputing the existence of the whole timeline are, well, simply irrelevant.

As for phenomenology, I'll grant there are some puzzling questions there. But I see that as much less serious than the incoherence of dynamism. Especially since dynamism couldn't offer any better answers, as explained in my section on 'superfluity' which you insist on ignoring.

Whatever experiences we have, we have them internally to our represented chronology. That includes experiences of time "in succession" (which I expect is heavily dependent on short-term memory, hence my previous comment). Now, the "temporal becoming" of presentism is an external feature. The 're-ordering' issues are relevant because there's no reason why the external chronology needs to match the internal one, as the movie projector analogies show. (I'm not sure what part of it is failing to make sense for you. It's unfortunate, because I find that analogy incredibly illuminating, and this mutual incomprehension may explain why we seem to be talking past each other here.) Even if presentism were true, there's no reason to think that the previous objective/external moment was from our past, rather than our future. As I extended the analogy, God could be playing the universe backwards, and we wouldn't know it. This external ("viewing") process can have no impact on our experiences, since the latter occur internally to moments; and the former merely offers a presentation of the moments, it does not alter their contents. So the external process cannot explain our experiences. I have the experiences I do because of the intrinsic nature of the universe at each moment in time. The external relations between these moments, such as the presentist's "temporal becoming", are not accessible to me, stuck as I am always inside the "frame" of each moment.

17. > There would be little point in my talking to you otherwise!

haha is there an implicit "because I sure as hell wont reconsider mine!" hidden in there?
Just kidding - mostly.

18. You'd need to clarify what you mean by "the 'one true present' changing over time" because that can misrepresent presentism if construed wrongly.

The reason your whole present-marker argument breaks down against presentism is because of how you are proposing the argument. In your original entry you say, "The problem lies in conceiving of 'the passage of time' as being a kind of movement. We imagine the present-marker 'starting' at the beginning of time, and moving forward into the future."

In presentism, the present doesn't move; the present doesn't start at the beginning of time and move into the future. Again, that's a hybrid A-B theory of time, not presentism. Because this movement is necessary for your argument to go through, presentism doesn't fall subject to it.

The problem is that in your modifications you're not modifying anything. You're simply trying to apply your original argument—which requires an equally existent line or dimension—to presentism, and that doesn't work. For instance, in your last comment you admit that future dates (you use April 13th as an example) don't yet exist on presentism. But then you say, "But [they] will be . . . So the present must 'move' or change from here to there, or rather now to then . . ." But, again, you're using the term "move" incorrectly. That error arises, I think, from (wrongly) picturing time within presentism as being a sort of string of light bulbs where the present is whatever light bulb is currently lit and where time (or the present) progress down the line of light bulbs. But that is not presentism. On presentism only the present exists; it doesn't move.

You said that I was ignoring your section on "superfluity." I'm not trying to ignore any of your arguments. I apologize if I did. The one I did not comment on (the project analogy), I gave a reason why (i.e., because I didn't understand it) so that you would at least know it wasn't my intention to skip over it. I did a word search on the page and I couldn't even find the term "superfluity" other than when you just used it so I'm not sure what section you're speaking of there. If you let me know I will respond to it, if you like. But I'm not trying to ignore any of your points to make my case look stronger or for any other reasons. That would just defeat the whole purpose of this discussion.

In reading your last paragraph I think I may better understand your project analogy, but if I have it right I just don't think it portrays a correct representation of presentism. That analogy seems to be, again, akin to the light bulb string thinking, and then it goes on the suppose what if the lit light bulb, instead of progressing normally, skipped around randomly along the string of light bulbs. But, once again, that's just not possible given presentism because the string doesn't exist. Temporal becoming isn't the simple highlighting of some future event. Assuming that on presentism events could occur out of sequence just begs the question against presentism (or is a malformed questions), since that isn't possible on presentism. It assumes that there is already some existent line of time and that the event that is present is simply the event that happens to be highlighted (and that the present could possibly skip from event to event on the already existent line of events). Even if one says (as you did in your projector analogy) that the present event comes into existence (which isn't exactly accurate, by the way), if one assumes that it can come into existence out of order then that's just begging the question once again, because that isn't possible on presentism, since that notion assumes that the present can hop from event to event along some preexistent line of events.

Inevitably, I see someone bringing up the possibility of foreknowledge, then, on presentism: If there is no preexistent line of events then how can the future be known (or something like that)? I think that gets way off of the subject, so I won't comment on it extensively. I'll just briefly say that knowing, not what is to come (or what is to be "highlighted), but what is to be doesn't require that that which is to be is already existent. And being able to know what is to be (or having foreknowledge) doesn't suggest that any future event could happen out of order (for reasons mentioned in the above paragraph).

I apologize for the length of this comment.

19. To add to my last comments, I still don't see why the re-ordering, projector issue is relevant. You say, "The 're-ordering' issues are relevant because there's no reason why the external chronology needs to match the internal one, as the movie projector analogies show." I'm still not seeing how that is relevant to your present-marker argument. But let's assume that the ordering can (somehow) get mixed up. What's that got to do with anything? Also, you speak of the "external" chronology, which makes sense; but you also mention the "internal" chronology. What exactly is the internal chronology, and how does it differ from the external chronology?

20. The internal chronology is that which we have access to from within a moment: the set of "before" and "after" relations that hold between moments. For example, April 13 is determinately after April 12, according to the internal chronology of our world. (It's "time as we know it". Again, I find the analogy to the movie characters helpful here. The story internally represents some events as 'before' or 'after' others. This doesn't require any external support, as the superfluity of the projector shows. The temporal relations hold intrinsically, no matter whether we go to the bother of actually playing the movie through.) Externally, of course, anything could happen, and we'd never notice. This shows that external dynamism (as posited by presentism, etc.) cannot do anything to explain our experiences.

Your long comment keeps repeating the irrelevant fact that presentism doesn't think the other points on the timeline exist, without addressing my point that presentism is obviously committed to the dynamism of a changing "one true present". It's extremely frustrating.

I addressed your concerns in my very first comment, and several times since, but let me try one last time before giving up on this conversation. Here's the thing: it doesn't help to say the other points on the timeline (the other "light bulbs", as you put it) don't "exist". The only difference is the insistence that only one light bulb exists at a time. You say the previous lightbulb winks out of existence when its turn is done, and the next one pops into existence bright and ready. So what? That doesn't change anything. The light still moves from one bulb to the next: it's just that the unlighted ones immediated cease to exist. (Even if only one bulb exists at a time, we can easily reconstruct the whole string of them, based on what has or will exist.) So please, shut up about existence already. Let's face the undeniable presentist claim of "temporal becoming" -- that's what's really relevant here.

You believe that April 12 used to be, but is no longer, the one true present. This entails that the present has changed ("moved", perhaps metaphorically speaking) from April 12 to 13. All your irrelevant handwaving about "existence" merely serves to obscure this crucial point, effectively changing the topic. If you want to continue the discussion, you have to address this point.

21. I'd like to add a comment that talking about "time" is complicated because we use time and temporal metaphors "all the time". For instance, I think it is quite tautological that only one moment of time "exists at a time." Just like my apartment is the only apartment which exists "at my apartment". You certainly wouldn't want to say that every moment of time exists at each moment of time. The passage of time is so ingrained in our thinking that these kinds of conversations are almost impossible.

I am reminded of conversations I've had with friends in which I've tried to explain that the question "what happened before the Big Bang?" just isn't a well-posed question because the word "before" is inappropriate.

Also, on a separate note, the analogy that "at this time" is similar to "at this place" is not merely a good analogy. It is also physically correct. Time and space really are intertwined. They are not separate objects.

22. Richard, I'm sorry that I'm frustrating you by seeming to be obtuse; that's not my goal—honestly.

Measuring April 12 against April 13 can only be done with reference to an external timeline, so your term "internal chronology" is, as far as I tell, incoherent, if you're going to continue to use it in the manner that you're using it; or, if handled properly, it's at least useless.

You say, "Externally, of course, anything could happen, and we'd never notice." Are you saying that April 13 could happen (externally) before April 12, yet still remain (internally) before April 12? I just don't think that makes any sense, if that's what you're trying to say (or even if that's not what you're trying to say).

I never said, in explaining presentism, that one light bulb winks out of existence and another comes into existence. The idea of a line of light bulbs was the very notion I was arguing against (whether one wants to say that the whole line of light bulbs is existent or that various light bulbs "wink" into and out of existence; it's all boils down to the same misconception, as explained in my last post). Given presentism, that would mean that I, if I exist over a span of time, continually wink out of existence and back into existence, which, in my opinion, is nonsensical.

My wrist is aching from all the (supposed) handwaving I've been doing, but at the risk of serious injury I'll try once more. In the end I'm sure we'll probably just have to agree to disagree. Or battle to the death. (I've actually done that twice, lost once. . . .)

You're last paragraph seems to articulate the point that you want to get at now. Given your mentioning that saying the present has "moved" is simply metaphorical, which it is on presentism, then I no longer see any issue here. Presentism is guilty of something (I'm not sure what) just because April 12th is no longer present? As long as it is understood that, given presentism, the present doesn't actually move—but rather simply exists—then I don't see the issue.

Note: I realize this (i.e., what was said in the latter part of the last paragraph) tends to raise another issue for presentism, namely, "the problem of the extent of the present," as William Lane Craig puts it. Just for any interested, Craig states this problem in his Time and Eternity:

While an instantaneous state seems to make sense, however, it is not clear how such a conception of reality is to be united with temporal becoming. Put as simply as possible, the problem is that since instants have no immediate successors (between any two instants there is always an infinity of intermediate instants), it is difficult to see how time can elapse instant by instant, one at a time, consecutively. Moreover, how could any non-zero internal of time ever elapse, since the addition of durationless instants can never add up to a non-zero interval?

He provides a resolution to the problem afterward; but, just to be sure, this issue is a completely separate issue from that which is being debated here, in the current discussion. The current accusation against presentism is that it is a theory of time which entails that the present changes or moves. The other issue, the "extent of the present" issue, argues the direct opposite; it argues that presentism doesn't allow for temporal movement. I provide this "Note" just to avoid the two issues being confused as if they were the same, which they're not.

23. I think the point is if a perspective or piece of logic doesnt exist it cannot be used to logicaly disprove anything.
eg a statement like "X god exists so humanism is immoral"
So the question remains "can you prove the perspective exists?"
If not maybe you are just introducing a "false" fact.

For example while I can concieve of momento example I expect the laws of physics preclude it from genuinely happening. (one could argue that as being a side effect of presentism?)

I am as it happens more convinced by the space time duality and more than 4 dimensions (ie not giving time some sort of ultimate status) and I dont see presentism as a very useful perspective it just makes it slightly harder to conceptuaize certain problems.

24. With respect to Alejandro's statement "that for every instant t there is a previous instant t' ", should this not read "for every instant t there are previous instants t' "? The former makes time sound discrete, which it may be, but shouldn't this come with an argument?

Also, did Relativity not show us that "before" and "after" are in fact relative?

25. Actually, relativity preserves before/after causality for all luminal and subluminal processes. What it doesn't preserve is simultaneity.

But that's not the point.

All this talk of objective time, as far as I'm concerned, neglects something absolutely crucial:

I experience a subjective flow of time. That illusion, that sensation, is absolutely real for me.

If time really is a motionless "loaf" of coordinates, I couldn't possibly have that illusion! There would be nothing for me to move through in order to think I'm moving! I'd just simultaneously exist for all of my spatial and temporal extent.

Since I don't, there must be an objective motion to time, or at least to something like time ("meta-time" as you call it).

No, we don't need an infinite regression.

All we need is this:
There is an independent variable to the universe. A parameter if you will.

All other entities evolve according to the motion of this parameter.
This motion is constant and continuously forward (by definition).

May as well call it t. (Or tau, if you really love your relativity).

26. "The Illusion of Endurance" addresses that issue.

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