• Philosophical Investigations, reading it together.
    Just let me be clear here. This "radical doubt" as you call it, is the consequence of Wittgenstein's ontology of rules. I am explaining how this form of doubt is the consequence of his ontology. I am not necessarily supporting this ontology, but it appears to be very forceful, and I see no good reason yet, to reject it — Metaphysician Undercover

    Firstly, it isn't a consequence of Wittgenstein's ontology or position; it is only your misreading.

    Secondly, you were presenting radical doubt as your own view on the previous page when you said that you do not accept that doubting requires an underlying level of certainty.

    No, I am never certain that my words mean what I think they mean. — Metaphysician Undercover

    Never? Rubbish.

    If that were the case then it would be senseless for me to carry on talking to you since you aren't sure of anything that you're saying. Ever. This is different from using a dictionary "incessantly" because you're unsure of the occasional word. Do you rely on your dictionary for every word? Ridiculous.
  • Philosophical Investigations, reading it together.
    Are you certain that the words mean what you think they mean? — Metaphysician Undercover

    You should ask yourself this question, given that you are the one making claims of radical doubt. Are you certain that your words mean what you think they mean? According to you, you cannot be certain what the word "doubt" (or any other word) means, so how can you maintain your argument?

    Can I be making a mistake, for example, in thinking that the words of which this sentence is composed are English words whose meaning I know? — On Certainty, 158
  • Philosophical Investigations, reading it together.
    The point is that having a reason quells your doubt, allowing you to decide, and proceed. But removing your doubt with respect to the meaning of the sign, no matter what the reason is, does not justify the claim that there is now no room for doubt. — Metaphysician Undercover

    The point is that having a reason quells your doubt, but removing your doubt does not remove doubt?
  • Philosophical Investigations, reading it together.
    Doubt as to the intent of the sign-post, is the natural state when you approach the sign-post, unless you have a reason to believe that you know how to understand the sign. If you have such a reason you can proceed from the sign-post without doubt. — Metaphysician Undercover

    What sort of a reason?
  • Private language, moral rules and Nietzsche
    But is it also conceivable that there be a language in which a person could write down or give voice to his inner experiences - his feelings, moods, and so on a for his own use? —– Well, can’t we do so in our ordinary language? - But that is not what I mean. The words of this language are to refer to what only the speaker can know - to his immediate private sensations. So another person cannot understand the language. — PI 243

    I have no criterion of correctness. — PI 258
  • Is reality a dream?
    383. The argument "I may be dreaming" is senseless for this reason: if I am dreaming, this remark is being dreamed as well and indeed it is also being dreamed that these words have any meaning.

    676. [...] I cannot seriously suppose that I am at this moment dreaming. Someone who, dreaming, says "I am dreaming", even if he speaks audibly in doing so, is no more right than if he said in his dream "it is raining", while it was in fact raining. Even if his dream were actually connected with the noise of the rain.     — Ludwig Wittgenstein, On Certainty
  • Zeno's paradoxes in the modern era
    ↪Michael
    Does that somehow make motion impossible?
  • Zeno's paradoxes in the modern era
    But if motion is continuous then there isn't a first position. — Michael

    If space (or the number line) is continuous, and motion is analogously continuous, then there shouldn't be a first position. Our inability to define the value of a first position is what we should expect. This should prove that continuous motion is possible rather than impossible.
  • Zeno's paradoxes in the modern era
    ↪Michael
    is there no start to the sequence or no first step after the start of the sequence? It makes a difference.
  • Zeno's paradoxes in the modern era
    I'm saying that continuous motion is impossible because continuous motion entails having started a sequential series with no start, which is contradictory. — Michael

    I thought the problem was in determining the first step after the start of the sequence (or after 0)?
  • Zeno's paradoxes in the modern era
    ↪Michael
    I still don't see how it prevents motion. I reject the assumption that motion requires counting or requires determining a first position. You (and Zeno) derive the impossibility of motion via the infinite divisibility of space, but space is not motion; position is not momentum. So how does one affect the other?
  • Zeno's paradoxes in the modern era
    ↪Michael
    But there is a first position to pass through, regardless of whether you can calculate it.
  • Zeno's paradoxes in the modern era
    We can say that the space between two points is infinitely divisible but that it is impossible to move through them all. — Michael

    Sounds odd. It's a bit like saying that since there is no highest number to count to, I can't ride a bike. How does one have any effect on the other?
  • Zeno's paradoxes in the modern era
    I don't know what you mean by this. — Michael

    This was a bit of a throwaway line for a separate argument (to my 'motion doesn't require counting' argument) that occurred to me late last night of trying to turn Zeno's logic against itself. I'm not sure whether it works, but I was thinking something along these lines:

    If you identify counting with motion, or if you define counting as a necessarily physical act (e.g. machine countability), then how can the physical act of halving a distance be achieved if you accept Zeno's conclusion that motion is impossible? Halving distances is required for Zeno's argument, yet it is apparently an impossible act. Therefore, either mathematical tasks are not necessarily physical acts or else halving distances is impossible.
  • Zeno's paradoxes in the modern era
    ↪Michael
    Only if you accept Zeno's assumption that counting is identifiable with motion. But we appear to be going around in circles, as impossible as it may sound. Besides, if it's the same logic, then how can you ever make the first division in order to prove the impossibility of motion?
  • Zeno's paradoxes in the modern era
    ↪Michael
    If I needed to say or count every distance that I moved (as I moved), then I agree that motion would be impossible. But I don't need to.
  • Zeno's paradoxes in the modern era
    ↪Michael
    I still don't understand what you mean by a "first event" in practical terms in relation to motion. The first distance that I count/pass through? But that theoretical first distance has only been defined into existence (or undefined into existence) by purely mathematical operations which are imposed on the assumed total distance travelled (or to be travelled). In reality, nothing prevents me from passing through that distance; especially not having to count it first.
  • Zeno's paradoxes in the modern era
    ↪Michael
    But counting is not required for motion (is it?), so it doesn't matter if the counting is impossible. It doesn't make the movement impossible.
  • Zeno's paradoxes in the modern era
    I'm not saying you have to figure it out. I'm saying that, assuming the infinite divisibility of space and continuous motion, each 1/(2n)m mark must be physically passed in ascending order, but that because there's no first 1/(2n)m mark, movement cannot start, just as because there's no first 1/(2n) number one cannot start to count each 1/(2n) number in ascending order. — Michael

    I don't see why I should accept that the mathematical problem of infinite divisibility should prevent movement from starting.
  • Zeno's paradoxes in the modern era
    ↪Michael
    Fair enough, and I have no issue that there might be a mathematical problem. I just don't see that there's any related problem of motion. I'm suggesting that the assumed relation between the maths and the motion, and that one somehow prevents the other, may be the only problem here.
  • Zeno's paradoxes in the modern era
    ↪Michael
    What does "there's no first distance to move to" mean (in practice)? Again, you seem to be saying that I need to figure out the first distance before I can pass through it. I still don't see why this mathematical step is necessary.
  • Zeno's paradoxes in the modern era
    ↪Michael
    Why equate the impossibility of counting with the impossibility of motion?
  • Zeno's paradoxes in the modern era
    ↪Michael
    So why do I need to figure out "the first distance I pass through" before I can pass through any?
  • Zeno's paradoxes in the modern era
    ↪Michael
    You assume that mathematical tasks must be completed before motion can begin. I reject this idea. Motion does not require the completion of any mathematical tasks.
  • Zeno's paradoxes in the modern era
    ↪Michael
    What makes it impossible?
  • Zeno's paradoxes in the modern era
    If motion is continuous (and space infinitely divisible) then I must pass through each 1/(2n) unit of distance (even if I don't stop at them), and surely that counts as a "task". — Michael

    I suppose. Is there a problem?
  • Zeno's paradoxes in the modern era
    A unit of distance can be infinitely halved, but these mathematical "tasks" are not required for motion. Otherwise, only mathematicians could move.
  • Is time travel possible if the A theory of time is correct?
    ↪Inis
    All I meant was that the flow of time and the passage of time can be used synonymously. You seem to have some special use for these terms. I use them both to refer to temporal passage. No response to the rest of my post?

    ETA: You appear to have overlooked the final sentence of the Wikipedia quote I posted:

    ...there is no objective flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time.
  • Is time travel possible if the A theory of time is correct?
    Clocks measure the passage of time, in their reference frame. — Inis

    Why couldn't the same be said about the flow of time? What makes that an "incoherent misconception"?

    You claimed that there is an objective flow of time. — Inis

    I never made this positive claim. The Wikipedia article states that there is no objective flow of time according to eternalism. I take "objective" here to refer to mind independence, not frame independence; that is, as opposed to "subjective".

    More proof of my characterisation of eternalism can be found in the article that Walter Pound attached to his post earlier:

    We should begin at the beginning: what are the theories of time under dispute here?
    In one corner we have the B-theory. The B-theory says: there are times; the
    times are structured by the relation x is r seconds earlier than y; this relation gives
    time the same order and metric structure as the real numbers. And that is all.
    In the other corner we have the moving spotlight theory. The moving spotlight
    theory says that the B-theory leaves something out. In addition to the characteristics
    the B-theory says time has, there is also this: exactly one time has the intrinsic
    property presentness. (Maybe things located at that time and events that occur at
    that time also have presentness.) Presentness is the “spotlight” that shines on just
    one time. Moreover, which time has presentness changes. Some time has it, but
    later times will have it, and earlier times have had it. The spotlight moves along
    the series of times at a steady pace. It is this continual change in which time has
    presentness that in the moving spotlight theory constitutes the passage of time, or
    “objective becoming.” When B-theorists deny that the passage of time is a real
    phenomenon they mean to deny that anything like this goes on; there is no such
    property as presentness that is instantiated first by earlier and then by later times.     — Experience and the Passage of Time - Bradford Skow

    The B-theory is often synonymous with eternalism, which is how I have been using it throughout this discussion. According to Skow's article, "B-theorists [or eternalists] deny that the passage of time is a real phenomenon".
  • Is time travel possible if the A theory of time is correct?
    What is this flow supposed to be relative to? — Inis

    I don't buy your distinction. What is the passage of time supposed to be relative to? And where is your proof?

    If someone were to claim that one of the spatial dimensions did not exist, that it was an illusion, you would think they were joking. — Inis

    I never said there was no time, but eternalism says there is no passage.
  • Is time travel possible if the A theory of time is correct?
    Eternalists have clocks. — Inis

    So what? Eternalists claim that temporal passage is an illusion.

    Eternalism doesn't claim that, though — Inis

    Prove it. I'll go first:

    Eternalism is a philosophical approach to the ontological nature of time, which takes the view that all existence in time is equally real, as opposed to presentism or the growing block universe theory of time, in which at least the future is not the same as any other time. Some forms of eternalism give time a similar ontology to that of space, as a dimension, with different times being as real as different places, and future events are "already there" in the same sense other places are already there, and that there is no objective flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time. — Wikipedia
  • Is time travel possible if the A theory of time is correct?
    I don't understand your question. — SophistiCat

    Which question?

    Again, motion is change (specifically, of position, or more generally, of any property) over time. How is this a problem for eternalism? — SophistiCat

    Motion is a problem for eternalism because temporal passage is an illusion according to eternalism. Without passage through time, there can be no motion. How do we get from one time to the next?

    There are timelines, and there are properties that change along those timelines. What, specifically, is incoherent in this picture? — SophistiCat

    It seems odd to call it "change" when nothing actually changes. Everything just exists. There is nothing to transport us from one time to another. Temporal passage is an illusion. There is no motion.

    You are just needlessly confusing yourself with this existence business. — SophistiCat

    The disagreement between us seems to be that you (and some others) are speaking from a physics point of view, whereas I am speaking from a philosophy of time point of view. In philosophy of time, eternalism is an ontological theory (about existence) which says that all times equally exist and objective temporal passage is an illusion.

    I have been trying to convince you that motion is not possible for eternalism purely as a logical consequence of the principles of eternalism, but since that doesn't seem to be working, take a look at the online article I posted, or the articles that
    ↪Walter Pound
    recently posted. I thought we would be discussing things in terms of philosophy of time since this is a philosophy forum.

    Like I said, I don't see much use for it, but if you insist on talking about it, just think logically. Every event in a block universe has a spacial and a temporal coordinate: (x, t). So if you ask when an event exists, the only sensible answer is the obvious one: it exists at t. Just as if you ask where it exists, the answer would be x. — SophistiCat

    I never asked you when or where an event exists; I asked you to explain how anything can happen in a block universe, in which temporal passage is an illusion and everything already exists at all times. Perhaps you could finally address my questions regarding this illusion.
  • Is time travel possible if the A theory of time is correct?
    Frankly have no clue what you mean. — Inis

    I think they might be suggesting that the present moment is when observations are made. Why do we need to define it as time of observation minus information processing time instead?
  • Is time travel possible if the A theory of time is correct?
    Luke, Please note that I don't intend to argue that eternalism is true, only that the reductio ad absurdum style argument you make does not succeed. Indeed, it may even be the case that eternalism is false, but not for the argument from experience that you make. — Walter Pound

    I don't believe that I've made any argument from experience. I have only been trying to point out to those who are quick to dismiss presentism, that eternalism has problems of its own.

    The argument you are making seems to follow this rationale:
    Premise 1. I experience a changing state of affairs.
    Premise 2. If I experience a changing state of affairs, then becoming is a real feature of the reality.
    Premise 3: If becoming is a real feature of reality, then eternalism is false.
    Conclusion: Therefore eternalism is false.     — Walter Pound

    I wouldn't argue only from my own experience; it seems that we're all in this together at present (or, at least, you and I are). More than just my personal experience; physical aging, our use of calendars, many of our scientific theories, and the one-way arrow of time all support the "argument" (or require the fact) that time actually passes or that we pass through time.

    The eternalist will counter this experience based argument for the A theory of time with an analogy with space. You are only ever aware of one location in space and that is the one you experience, which we tend to call "right here." You experience your location in space, but you do not experience any other location in space or all locations of space. However, simply because you experience your location of space that does not mean that that location of space is the only location of space that exists. Indeed, I may never go to China or to Pluto or outside the milky way galaxy, but I don't assume that those locations are simply mental fictions. If someone asked, "if other locations in space exist, then why don't I experience them" it would be best to respond with "why would one assume that X exists only if one experiences X?" — Walter Pound

    I find it odd that you attached articles by someone who does not support this spatial analogy (see the author's example of the red and green rooms in the 'experience.pdf' article you posted). The author of those articles advocates the moving spotlight theory, which is a mixed view of eternalism and presentism. Furthermore, the analogy is quite weak. Unlike my freedom of movement in space, I am not free to travel to the past, and I am extremely limited in my "choice" of future time travel destinations.

    But neither am I arguing only in favour of presentism, so this is neither here nor there (so to speak). Nevertheless, I enjoyed the articles which again note that illusion of passage is an intrinsic feature of the B-theory, so thanks for posting them.
  • Is time travel possible if the A theory of time is correct?
    We directly perceive motion with our senses in our subjective present (obviously), but we conceptualize motion as change over time, which can happen in the past or in the future, here or there, perceived or unnoticed. This concept of motion is available to both presentists and eternalists, but presentists will additionally qualify it with an objective temporal modality. — SophistiCat

    You say that the concept of motion is available to eternalists, but it seems logically incoherent to me. You claim that motion or change can(?) happen in the past or in the future, but it fails to explain when anything actually happens in the block universe. Future events already exist, so have they already happened? Also, I still have no idea how you account for the illusion mentioned in the article.

    Yeah, this is where I definitely part company with both parties. Not that I think that either of them is wrong - I just think that this talk of existence is both confusing and pointless. I'll leave it to advocates to untangle this mess. — SophistiCat

    I'm not sure what you were previously defending then, if not eternalism. But I understand if you don't wish to continue.
  • Is time travel possible if the A theory of time is correct?
    And the illusion?

    When presentists posit a passage of time, what they mean (or at least what some of them mean) is that the present time is an objective fact. Time flows by way of the present time constantly progressing forward - and that too is an objective fact of the world. This present time, which is like a moving index on every timeline, is not implied or required by any physical law. As far as physics is concerned, positing such an index is unjustified. And that is what moves (at least some) eternalists to deny the objective existence of such an index. — SophistiCat

    If the passage or flow of time has no objective existence, then I guess it must have subjective existence? It certainly appears as though time/events/things pass from the future to the past via the present moment. I take it this is the illusion? You seem to be saying that motion is separate from temporal passage, but isn't the present moment when motion occurs and events happen?

    If I threw a ball in the air yesterday, and that event eternally exists according to eternalism, then is that ball still in motion (now) according to eternalism? Maybe you will say that it was only in motion yesterday when that event happened. But when do events happen according to eternalism? When are those events set in motion, so to speak? Does my ball keep getting tossed in the air repeatedly on an endless loop, or did it only happen once, or does it never actually happen? Without a present moment and passage of time in which events occur, it seems that they never can or do, according to eternalism.

    Even if temporal passage is "not required by any physical law", eternalists still need to account for the appearance or illusion of passage. How can time appear to pass if no time actually passes?
  • Is time travel possible if the A theory of time is correct?
    Because it is talking about "the flow of time, or passage through space-time," rather than motion. There is no difference in dynamics between eternalism and presentism. In fact, there is no physical difference, period. The difference is entirely metaphysical and has to do with metaphysical notions, such as the objective present, the passage of time, the existence of past and future, etc. — SophistiCat

    I still don't understand. If presentism posits a passage of time while eternalism does not, then how is motion possible according to eternalism? Why is it referred to as a static block universe? What is the illusion supposed to be (in the section you quoted)?
  • Is time travel possible if the A theory of time is correct?
    Yes. That quote does not say there is no motion or no time. It just says time doesn't flow in that model. — noAxioms

    What do you take "a static block of space-time" to mean? How is motion possible if there is no flow of time or any passage through space-time? Why does the article say that the flow of time, or passage through space-time, "must presumably be a mental construct or other illusion"?
  • Is time travel possible if the A theory of time is correct?
    It surprises me how advocates of eternalism presume the right to the only redeeming aspect of presentism.
  • Is time travel possible if the A theory of time is correct?
    ↪noAxioms
    Did you not see the quote I posted on the previous page of this discussion:

    The resulting timeless cosmos is sometimes called a “block universe” — a static block of space-time in which any flow of time, or passage through it, must presumably be a mental construct or other illusion.

    It seems quite clear to me.
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