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  1. #361
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    Re: A Rebuttal to the Cosmological Argument

    (BTW: "et. al." is not correct, "et al." stands for "et alii", so "et" is already the complete Latin word; for reference, "et" = "and" and "alii" = "others", so "et al." = "and others" or "and the rest")

    Quote Originally Posted by cstamford View Post
    So as to rescue your post from any possible appearance of a Machiavellian treatment of Craig's response to Carroll, I include his actual response below, alleviating anyone of the need to trust your characterization of it or its relevance to the actual issue of the thread:

    "I normally don’t take questions asking me to respond to some link, Shane, but the opportunity to interact with Sean Carroll on these important questions is one I don’t want to miss. I’ll address both his main points."

    [...]

    "In his oral presentation of his paper at the conference in Cambridge, Vilenkin was clear: “There are no models at this time that provide a satisfactory model for a universe without a beginning” (http://www.youtube.com/watch?v=NXCQelhKJ7A). Interestingly, if you take a close look at Vilenkin’s powerpoint slides for this presentation, you will find Prof. Carroll’s own model listed among the purported “eternal cosmologies” which in fact fail to avoid the beginning of the universe. The “eternal cosmologies based on quantum mechanics” so easily imagined by Prof. Carroll are not, in fact, tenable; but his unsuspecting readers would not know that."

    "For those who would like a fuller discussion of “eternal cosmologies,” including models which attempt to avert the force of the BGV Theorem, I recommend James Sinclair and my articles “The Kalam Cosmological Argument,” in The Blackwell Companion to Natural Theology, ed. Wm. L. Craig and J. P. Moreland (Oxford: Wiley-Blackwell, 2009), pp. 101-201; “On Non-Singular Spacetimes and the Beginning of the Universe,” in Scientific Approaches to the Philosophy of Religion, ed. Yujin Nagasawa, Palgrave Frontiers in Philosophy of Religion (London: Macmillan, 2012), pp. 95-142."

    "Finally, I’m disappointed that Carroll cannot find it in himself to have a collegial discussion of these important questions but feels the need to resort to snide, personal attacks in his closing paragraph. His unfamiliarity with my work is evident in his remark that I do not cite the relevant, original, scientific papers (despite my quoting the Vilenkin-Mithani paper in the very podcast to which he is responding), as well as the popular works of physicists (where they often feel freer to express what they take to be the philosophical and theological implications of their work). His condescension is especially awkward in light of his own missteps in correctly characterizing the BGV Theorem. Carroll will pardon us, I hope, for our scepticism about his counting himself among the ranks of the open-minded."


    Evidently Professor Vilenkin, et. al. are not subscribers to the "common lore" to which you and Carroll are. And Craig doesn't speak beyond his expertise on this subject.

    Nope, Vilenkin is definitely a subscriber to the common lore. Vilenkin gave his paper a nice spin, and it's a clever idea, but it's far from a reliable, case-closed argument. Let's not rely on Craig's summary; let's read what Professor Vilenkin has to say to WLC (Note that I've bolded the salient points; I've inserted full names for clarity):



    Vilenkin's Response Letter to WLC



    "Dear Bill [i.e.William Lane Craig],


    "I’m troubled that Lawrence Krauss in some respects misrepresented your views [on your work on the BVG theorem] in our dialogue in Sydney. In an attempt to rebut the evidence for a beginning of the universe, he showed a powerpoint of your letter with the last two sentences of the second paragraph deleted."


    My letter was in response to Lawrence’s email asking whether or not I thought the BGV theorem *definitively* rules out a universe with no beginning. The gist of my answer was that there is no such thing as "definitive ruling out" in science. I would say the theorem makes a plausible case that there was a beginning. But there are always caveats."



    Pause. A rhetorical point: Knowing my argument, do you care to guess what those caveats are?

    I'm going to skip ahead to WLC's question and Vilenkin's response, but you can get the full text here. Here, WLC asks Vilenkin:



    "I do have a question about your statement: 'the BGV theorem uses a classical picture of spacetime. In the regime where gravity becomes essentially quantum, we may not even know the right questions to ask.' Elsewhere you’ve written: 'A remarkable thing about this theorem is its sweeping generality. . . . We did not even assume that gravity is described by Einstein’s equations. So, if Einstein’s gravity requires some modification, our conclusion will still hold. The only assumption that we made was that the expansion rate of the universe never gets below some nonzero value' [Vilenkin, 2006, p. 175].

    How are these statements compatible? The 2006 statement sounds as if a quantum theory of gravitation would not undo the theorem. But the letter to Krauss sounds as if we are awash in uncertainty.

    I have my own idea of how you might understand these statements, but rather than burden you with my surmises, I’d prefer to simply ask you how you understand the situation."

    The question of whether or not the universe had a beginning assumes a classical spacetime, in which the notions of time and causality can be defined. On very small time and length scales, quantum fluctuations in the structure of spacetime could be so large that these classical concepts become totally inapplicable. Then we do not really have a language to describe what is happening, because all our physics concepts are deeply rooted in the concepts of space and time. This is what I mean when I say that we do not even know what the right questions are.

    But if the fluctuations are not so wild as to invalidate classical spacetime, the BGV theorem is immune to any possible modifications of Einstein's equations which may be caused by quantum effects.

    Best regards,

    Alex
    [i.e. Alexander Vilenkin]"


    In other words: Assuming (without any reason specified) that quantum physics doesn't matter very much, then the BVG theorem does apply. Assuming then they are large, the BVG theorem doesn't apply. It's worth noting that WLC had actually noticed Vilenkin conceding my exact point to Lawrence Krauss and bothered to make an e-mail asking him to clarify; Vilenkin concedes, clarifies, and explains that the point about quantum effects --which I've been saying here since my initial post-- is correct. Next, I move to the following question:


    Are Vilenkin's Assumptions Good Ones?


    Vilenkin's paper is good; he's just making one assumption and following the logical conclusions from it. However, and he should really be more clear about this in his e-mail to WLC, there's no reason to suspect that the quantum fluctuations won't become incredibly strong and there's no reason to believe that quantum gravity will (and there's really only evidence to the contrary) preserve the notion of a classical spacetime. We only have three* (currently mediocre) successful ideas about quantum gravity:

    1.) The noteworthy example of String theory.
    2.) The less noteworthy example of "loop quantum gravity"
    3.) The even less noteworthy idea of "causal dynamical triangulation".


    Every single one of them dispenses with the normal idea of a classical spacetime and in each of them we also know that extremely strong quantum gravity effects are present. In other words, if we want to talk about "evidence" in terms of theories that can at least potentially work, then we have 0 for 3 models where the BVG theorem applies. In other words, while we don't have a "satisfactory" model of quantum gravity, we still don't even have a theory of quantum gravity that satisfies the prerequisites of the BVG theorem. And while Squatch is fond of saying "We don't have a model where there are effects that lead to an infinite past", I can make the much stronger statement and say "Sure, but we equally don't have a model where the BVG theorem applies, either, so the only evidence that we have right now is that it won't apply to quantum gravity". This means that there's no good reason to discuss this theorem as though it's the most relevant piece of information. If you can show me any quantum gravity model which obeys the BVG theorem --and thus has a singularity-- then we could at least compare evidence. But you'd need 4 models before the evidence became 'stronger' that quantum theories of gravity seem to obey the BVG theorem. Because right now, we have no evidence they do and only evidence to the contrary. At this point, even if one of these models had a past singularity, it wouldn't be because the BVG theorem held; this continues to reenforce the fact that the BVG theorem is not the relevant fact to be discussing.




    * There's also a fourth attempt which tries to use the "non-perturbative RG running" of GR to go a "UV fixed point", but it's pretty much just speculation in pure GR; however, even there, too, there's not really a coherent picture of a classical spacetime because the quantum effects completely overwhelm the classical picture, which is why it has to use the "non-perturbative" RG flow. This technically makes it 0 for 4 models, but it is my understanding that this isn't any where near as fleshed out as the other three, so I don't feel like it is worth including.
    Last edited by GoldPhoenix; March 26th, 2014 at 09:42 AM.
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  3. #362
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by Squatch347 View Post
    Equivocation fallacy. "Probable" =/= "Probability" They are related words, but not of equivalent meaning.
    having more evidence for than against...
    http://dictionary.reference.com/browse/probable
    Statistics.
    a.
    the relative possibility that an event will occur, as expressed by the ratio of the number of actual occurrences to the total number of possible occurrences.
    b.
    the relative frequency with which an event occurs or is likely to occur.
    http://dictionary.reference.com/browse/probability

    We can see this in a relatively common demonstration. When going to a civil court we are asked to measure the evidence and decide whether or not the event in question "probably" occurred. Clearly they aren't collecting a statistical sample representing a population of possibilities and measuring the ratio of occurrences. The word "probable" does not mean that (neither does probability always mean that either).

    In short, you are failing to understand the definitions of the words offered here and how they are being used. You are are attempting to use a term in a manner that it was not implied as meaning in order to question the statement, an equivocation fallacy.
    First, if we're talking about how to compute and compare probabilities, we should probably be looking to technical definitions of probability, not colloquial ones.

    Second, you're confusing probability theory with statistics. Statistics is about the behavior of observable random variables; probability theory is about probability measures. The "relative frequency" interpretation of probability theory, often called frequentism, leads to different statistical methods (and interpretations of their results). Conversely, the Bayesian interpretation of probability theory leads to its own set of statistical methods (and interpretations of their results).

    Third, if your argument is that the available evidence makes it more likely than not (I'd love a precise definition of what exactly you're using that phrase--or its equivalents--to mean) that the universe has a finite age (or, began to exist a finite length of time in the past), I'd really like to see that evidence. As GP pointed out, applying the BVG result requires certain assumptions with regard to the magnitude of quantum effects; if you are applying the BVG result, you'll need evidence to show (assuming we're relying on the more likely than not requirement) that those assumptions probably hold.
    Last edited by CliveStaples; March 25th, 2014 at 12:33 PM.
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  5. #363
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    Re: A Rebuttal to the Cosmological Argument

    Hey everyone:

    I think that we should stop discussing this on this thread. In retrospect, although it was directly relevant on this thread and cstamford's false charges against me, I should have kept the discussion about WLC's argument on Clive's WLC 's Argument Against Actual Infinities thread and just posted a link to that thread on this one. For debaters who haven't been following this, we now have two more or less redundent, parallel discussions (i.e. the question of probabilities, the question of actual infinities, the question of the application of the BVG theorem, etc).


    I'm going to ask that the people who would have responded to me here instead respond to me on the following thread so we can keep things organized:

    Please post here, so we can keep the discussion linear and in one place.

    Last edited by GoldPhoenix; March 25th, 2014 at 12:36 PM.
    "Those who can make you believe absurdities, can make you commit atrocities." --Voltaire

  6. #364
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by GoldPhoenix View Post
    (BTW: "et. al." is not correct, "et al." stands for "et alii", so "et" is already the complete Latin word; for reference, "et" = "and" and "alii" = "others", so "et al." = "and others" or "and the rest")
    While this is certainly a valid criticism, for which I thank you, it is also a triviality that from a literary standpoint tends to confuse the reader as to the ordering of importance in your following critical remarks. Is my failure to place a period after "et" of more or less importance in your response than your quotes of Vilenkin's response letter to WLC, and is then Vilenkin's quoted letter more or less important that your annotations? Perhaps it would have been better located at the very end of your post, as a postscript, thereby making clear what is important here and what is a trivial aside? In any case...

    Quote Originally Posted by GoldPhoenix
    Nope, Vilenkin is definitely a subscriber to the common lore. Vilenkin gave his paper a nice spin, and it's a clever idea, but it's far from a reliable, case-closed argument.
    How so? In your last post disputing Craig's understanding of the physics behind the Borde-Guth-Vilenkin (BGV) singularity theorem, you quoted Carroll, who stated:

    "The theorems in question make a simple and interesting point...Like many technical results, its conclusions follow rigorously from the assumptions, but both the assumptions and the conclusions must be treated with care...Most importantly, I don’t think that any result dealing with classical spacetimes can teach us anything definitive about the beginning of the universe. The moment of the Big Bang is, if anything is, a place where quantum gravity is supremely important. The Borde-Guth-Vilenkin results are simply not about quantum gravity. It’s extremely easy to imagine eternal cosmologies based on quantum mechanics that do not correspond to simple classical spacetimes throughout their history."

    To which specific point that the BGV theorem is substantially undercut by quantum mechanics, Craig replied:

    "Carroll attempts to downplay the significance of the BGV Theorem (and, hence, to justify his ignoring it in his article)"

    And then went on to quote Vilenkin, twice, once here:

    "In answer to the question “Did the universe have a beginning?,” Vilenkin concludes “it seems that the answer to this question is probably yes” (arXiv:1204.4658v1 [hep-th] 20 Apr 2012, p. 5). One would never have guessed that from reading Carroll’s Blackwell Companion article. For my part, I have never claimed more than that in my defense of the second premiss of the kalam cosmological argument: in light of the evidence the premiss that the universe began to exist is more plausible than not."

    and again here:

    "In his oral presentation of his paper at the conference in Cambridge, Vilenkin was clear: “There are no models at this time that provide a satisfactory model for a universe without a beginning” (http://www.youtube.com/watch?v=NXCQelhKJ7A). Interestingly, if you take a close look at Vilenkin’s powerpoint slides for this presentation, you will find Prof. Carroll’s own model listed among the purported “eternal cosmologies” which in fact fail to avoid the beginning of the universe. The “eternal cosmologies based on quantum mechanics” so easily imagined by Prof. Carroll are not, in fact, tenable; but his unsuspecting readers would not know that."

    Now don't you think the bold italicized text above was pertinent enough to your characterization of Vilenkin as a subscriber to "the common lore" to be addressed by you?

    Quote Originally Posted by GoldPhoenix
    Let's not rely on Craig's summary; let's read what Professor Vilenkin has to say to WLC (Note that I've bolded the salient points; I've inserted full names for clarity):
    Which, of course, everyone would be happy to do, but I'd like an admission of the obvious from you, which is it is Vilenkin, not Craig, who is at odds with Carroll's reply to Craig concerning the evidence for a temporally finite universe being substantially greater than the evidence for its denial.

    Of course he leaves unsaid what I and most common sense thinkers would add, which is that if the temporally finite universe is more plausible than not, something made clear by Vilenkin's quotes, not Craig's interpretation of them, then it would follow that any argument for a temporally infinite universe would be more implausible than not. And if that more implausible than not argument included the claim that the "consensus" among physicists today was that the universe is temporally infinite, then that argument would conclude that the "consensus" of physicists today held to a theory of the universe that was more implausible than not. And I, for one, find that a truly remarkable claim, which, following David Hume, would need a remarkable amount of evidence for it's truth to be established, and that to my mind is not satisfied by your annotations of a redacted letter by Vilenkin to Craig. And as we shall see in a moment, not only a redacted and annotated letter, but a type of redaction that seriously misrepresents Vilenkin's attitude toward Craig's representation of the BGV theorem.

    Quote Originally Posted by GoldPhoenix
    Vilenkin's Response Letter to WLC
    "Dear Bill [i.e.William Lane Craig],

    "I’m troubled that Lawrence Krauss in some respects misrepresented your views [on your work on the BVG theorem] in our dialogue in Sydney. In an attempt to rebut the evidence for a beginning of the universe, he showed a powerpoint of your letter with the last two sentences of the second paragraph deleted."

    My letter was in response to Lawrence’s email asking whether or not I thought the BGV theorem *definitively* rules out a universe with no beginning. The gist of my answer was that there is no such thing as "definitive ruling out" in science. I would say the theorem makes a plausible case that there was a beginning. But there are always caveats."



    Pause. A rhetorical point: Knowing my argument, do you care to guess what those caveats are?
    Two points here: First, to be honest, I've not participated or followed this thread for some time, so my "understanding" of your argument is probably hopelessly out of date, and, frankly, when I believed I did understand it, it seemed to me to the extent it succeeded it did so by talking around the salient points as opposed to taking them head on. In short, no, I can't guess. That said, I am not here responding to your "argument" as you conceive it, but simply to your claim that Craig has misunderstood, and to that extent misrepresented Vilenkin's position on the BGV theorem. If this claim of yours is a part of your "argument" in this thread, the I guess I'm disputing your "argument" to this extent. If it's not part of your "argument", then all this is an aside...an important aside to my mind, but an aside nonetheless.

    Second, I think that in the section of Vilenkin's above that you've put in bold text, you've myopically focused on the word "caveats" to the exclusion of the phrase "plausible case", which Craig has already defined for us by previously quoting Vilenkin stating:

    "There are no models at this time that provide a satisfactory model for a universe without a beginning"

    This quote makes Vilenkin's "plausible case" a bit of an understatement.

    And then there's the matter of philosophical consistency to be considered here. You're a self-described atheist, which means that for you there is no "satisfactory model for a universe" with a God or gods included in it. Now that's a philosophically consistent positiion to take. It happens to be wrong from my perspective, but it's philosophically consistent within any philosophy that includes a substantial degree of some version of empiricism.

    However, here you seem to be taking a philosophically inconsistent position, if you can be understood to be in basic agreement with Vilenkin, as your opening remark that he, like you, is "...a subscriber to the common lore", would indicate. Here Vilenkin has stated that "at this time" there are no satisfactory models for a temporally finite universe, and yet "at this time" you are arguing there is no satisfactory evidence for a beginning to the universe. And not only is your argument here evidently based on a complete lack of "satisfactory models" (in Vilenkin's sense of that phrase), but the remainder of it seems to me to consist entirely in trying to explain why Vilenkin can't seem to express himself adequately in English, which I find another, in what has become an ongoing series of very strange claims.

    Quote Originally Posted by GoldPhoenix
    I'm going to skip ahead to WLC's question and Vilenkin's response, but you can get the full text here. Here, WLC asks Vilenkin:
    Again, I must interrupt to correct the record, since you've not defined "WLC's question", to which one response by Vilenkin was to furnish Craig with a copy of the e-mail in question, without the deletions to it Krauss made.

    We do not need to get into a point by point discussion of what Prof. Vilenkin thinks of Craig's representation of his (Vilenkin's) view on the BGV theorem. In a portion of Vilenkin's reply to Craig's "question" you've failed to include in your post, he writes:

    "I think you represented what I wrote about the BGV theorem in my papers and to you personally very accurately."

    That settles the question for me, and I would hope for all other truth seekers. There is absolutely nothing wrong with WLC's representation of Vilenkin's position on the BGV theorem, or Craig's characterization of the universe having a beginning to its existence being probable on the evidence from theoretical physics. I would add that I don't see how the fact there are a great many physicists today who are dissatisfied with the concept of a finite universe, and who are working on theories in which the universe is temporally infinite, amounts to this current direction in researh itself being evidence to the contrary, or being any sort of "basis" upon which one can sensibly stand to say, as you have above, that " Vilenkin gave his paper a nice spin." The term "spin" would imply an impression contrary to the fact, and I fail to see any "spin" provided by Vilenkin on Craig's point.

    Finally, I should stress again that you've implicitly recruited, so to speak, Vilenkin into your "consensus" of physicists who agree with you, by stating as fact: "Nope, Vilenkin is definitely a subscriber to the common lore.", of which "lore" you are a staunch advocate in this thread. Given that Craig is a staunch advocate for the probability the universe had a beginning, and you are an opponent of that view, this would make Vilenkin and you allies on the critically related question, did Craig misunderstand Vilenkin's position on the BGV theorem, and therefore misrepresent it to his audience and readers, or not? And you have, to the extent I've followed this thread, consistently maintained Craig has seriously misunderstood the BVG theorem and Vilenkin's remarks concerning it, and further that Craig can therefore safely be discounted as an interpreter of Vilenkin, while you, being a physicist yourself, may be trusted on this point.

    But lo and behold, it turns out that you and Vilenkin are at odds on this very point, and demonstrably so! Therefore, I am going to conclude that your take on Craig's understanding of Vilenkin's position on the BGV theorem is misguided. Further, I conclude that in so far as Craig's grasp of physics, or his personal integrity are concerned, they have been more than adequately confirmed by Vilenkin, even if called into serious question by you.

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  8. #365
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford
    While this is certainly a valid criticism, for which I thank you, it is also a triviality that from a literary standpoint tends to confuse the reader as to the ordering of importance in your following critical remarks. Is my failure to place a period after "et" of more or less importance in your response than your quotes of Vilenkin's response letter to WLC, and is then Vilenkin's quoted letter more or less important that your annotations? Perhaps it would have been better located at the very end of your post, as a postscript, thereby making clear what is important here and what is a trivial aside? In any case...
    Erm, nobody claimed that your grammatical error was more important than the Vilenkin vs. WLC issue. That's why GP prefaced his remark with "BTW", which means "By the way":

    http://dictionary.cambridge.org/us/d...ish/by-the-way

    used for introducing a statement or subject that may not be directlyrelated to the subject being discussed:

    "Side remarks" / tangential information is often made in parenthetical remarks, margin notes, and footnotes. Your request that they be specifically appended in a postscript is bizarre.

    Also, you didn't fail to place a period after "et". You did place a period after "et". That was the error that GP pointed out.
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  9. #366
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    Re: A Rebuttal to the Cosmological Argument

    This is my last response to you on this thread, cstamford. Your posts on this thread have displayed an intense lack of understanding of what is being discussed and you seem to have no reservations attacking a position which you don't understand (and can't be bothered to go back and read), which is horrid debating etiquette. This is a debating forum, cstamford; the onus is on you to understand your opponent's argument before you attack it or to ask for clarifications if you don't understand it. If you'd bothered to think for longer than half of a second about what my actual opinion was and actually bothered to spend 10 minutes to read what I had written, you might not have made an entire long-winded post that amounted to nothing more than a giant strawman fallacy and an excuse to insult me. I see this as precious little more than trolling, so we're done here.


    Quote Originally Posted by cstamford View Post
    While this is certainly a valid criticism, for which I thank you, it is also a triviality that from a literary standpoint tends to confuse the reader as to the ordering of importance in your following critical remarks. Is my failure to place a period after "et" of more or less importance in your response than your quotes of Vilenkin's response letter to WLC, and is then Vilenkin's quoted letter more or less important that your annotations? Perhaps it would have been better located at the very end of your post, as a postscript, thereby making clear what is important here and what is a trivial aside? In any case...
    I segregated it from the rest of my point for a reason, cstamford. I trust you can work it out for yourself why I did that.


    Quote Originally Posted by cstamford
    How so? In your last post disputing Craig's understanding of the physics behind the Borde-Guth-Vilenkin (BGV) singularity theorem, you quoted Carroll, who stated:
    I'm going to stop you right here. You're committing a blatant strawman fallacy:

    My argument has nothing to do with whether or not WLC has accurately represented Vilenkin's views; you made that up out of thin air.


    For the record, my argument has to do with:

    1.) Being told that I was basically a stupid idiot, by you and others, for thinking that quantum gravity effects matter. You told me in post#347 that I had no idea what I was talking about and I couldn't find any physicist who could corroborate my position. This is why I quoted Carroll, who reiterated my point exactly. At this point, I have multiple physicists, including an author of the BVG theorem, who admit quantum effects matter and can very possibly invalidate the theorem. So these ignorant responses have now been debunked.

    2.) That Vilenkin has admitted that these quantum effects matter after direct questioning from WLC, and he has admitted that if the true theory of quantum gravity doesn't obey the criterion he has outlined, then the BVG theorem does not apply.

    3.) We have no model that actually obeys the criterion necessary for the BVG theorem, therefore we have no reason to believe that the BVG theorem applies.

    4.) You seem to misunderstand this point, too, so I'll also explain that my point has never been that "The universe is past infinite." My point has only ever been "There is no convincing argument that the universe is past-infinite or past-finite. Until we understand quantum gravity, we have to remain agnostic."

    So my only problem with WLC has been his use and belief in the wide-ranging applicability of the BVG theorem and his frequent negligence in pointing out the importance of quantum corrections. WLC states the material content of the BVG theorem perfectly fine; the critique here is whether or not the theorem is applicable, much like asking whether or not the Pythagorean theorem is applicable to curved spacetimes.

    Quote Originally Posted by cstamford
    "The theorems in question make a simple and interesting point...Like many technical results, its conclusions follow rigorously from the assumptions, but both the assumptions and the conclusions must be treated with care...Most importantly, I don’t think that any result dealing with classical spacetimes can teach us anything definitive about the beginning of the universe. The moment of the Big Bang is, if anything is, a place where quantum gravity is supremely important. The Borde-Guth-Vilenkin results are simply not about quantum gravity. It’s extremely easy to imagine eternal cosmologies based on quantum mechanics that do not correspond to simple classical spacetimes throughout their history."

    To which specific point that the BGV theorem is substantially undercut by quantum mechanics, Craig replied:

    "Carroll attempts to downplay the significance of the BGV Theorem (and, hence, to justify his ignoring it in his article)"

    And then went on to quote Vilenkin, twice, once here:

    "In answer to the question “Did the universe have a beginning?,” Vilenkin concludes “it seems that the answer to this question is probably yes” (arXiv:1204.4658v1 [hep-th] 20 Apr 2012, p. 5). One would never have guessed that from reading Carroll’s Blackwell Companion article. For my part, I have never claimed more than that in my defense of the second premiss of the kalam cosmological argument: in light of the evidence the premiss that the universe began to exist is more plausible than not."

    and again here:

    "In his oral presentation of his paper at the conference in Cambridge, Vilenkin was clear: “There are no models at this time that provide a satisfactory model for a universe without a beginning” (http://www.youtube.com/watch?v=NXCQelhKJ7A). Interestingly, if you take a close look at Vilenkin’s powerpoint slides for this presentation, you will find Prof. Carroll’s own model listed among the purported “eternal cosmologies” which in fact fail to avoid the beginning of the universe. The “eternal cosmologies based on quantum mechanics” so easily imagined by Prof. Carroll are not, in fact, tenable; but his unsuspecting readers would not know that."

    Now don't you think the bold italicized text above was pertinent enough to your characterization of Vilenkin as a subscriber to "the common lore" to be addressed by you?
    Jesus, cstamford, addressing this point was the entire purpose of my last response to you. Did you not understand the arguments presented or did you just refuse to read the post? I'm guessing the latter, given that you blatantly strawman'ed my argument.

    I have no interest in swapping quotes of Vilenkin with you. I have addressed what Vilenkin has said, in his own words, when asked the specific question by WLC; no new quotes need to be introduced now. Vilenkin made the caveats to his theorem quite clear. At this point, either you comprehend the words of Vilenkin to WLC and my arguments against his assumptions, or you don't; however, I am not going to sit here and rebut, line by line, specific statements of Vilenkin --the same statements that Craig said were confusing, that he didn't understand, and that he asked Vilenkin to clarify, and the statements which Vilenkin did clarify in the letter I gave in my previous post.


    Quote Originally Posted by cstamford
    Which, of course, everyone would be happy to do, but I'd like an admission of the obvious from you, which is it is Vilenkin, not Craig, who is at odds with Carroll's reply to Craig concerning the evidence for a temporally finite universe being substantially greater than the evidence for its denial.

    Of course he leaves unsaid what I and most common sense thinkers would add, which is that if the temporally finite universe is more plausible than not, something made clear by Vilenkin's quotes, not Craig's interpretation of them, then it would follow that any argument for a temporally infinite universe would be more implausible than not. And if that more implausible than not argument included the claim that the "consensus" among physicists today was that the universe is temporally infinite, then that argument would conclude that the "consensus" of physicists today held to a theory of the universe that was more implausible than not. And I, for one, find that a truly remarkable claim, which, following David Hume, would need a remarkable amount of evidence for it's truth to be established, and that to my mind is not satisfied by your annotations of a redacted letter by Vilenkin to Craig. And as we shall see in a moment, not only a redacted and annotated letter, but a type of redaction that seriously misrepresents Vilenkin's attitude toward Craig's representation of the BGV theorem.

    Two points here: First, to be honest, I've not participated or followed this thread for some time, so my "understanding" of your argument is probably hopelessly out of date, and, frankly, when I believed I did understand it, it seemed to me to the extent it succeeded it did so by talking around the salient points as opposed to taking them head on. In short, no, I can't guess. That said, I am not here responding to your "argument" as you conceive it, but simply to your claim that Craig has misunderstood, and to that extent misrepresented Vilenkin's position on the BGV theorem.
    This is meandering bloviation which contributes no relevant commentary to Vilenkin's actual clarifications or my actual argument, and is therefore going to be ignored.

    Quote Originally Posted by cstamford
    If this claim of yours is a part of your "argument" in this thread, the I guess I'm disputing your "argument" to this extent. If it's not part of your "argument", then all this is an aside...an important aside to my mind, but an aside nonetheless.

    Second, I think that in the section of Vilenkin's above that you've put in bold text, you've myopically focused on the word "caveats" to the exclusion of the phrase "plausible case", which Craig has already defined for us by previously quoting Vilenkin stating:

    "There are no models at this time that provide a satisfactory model for a universe without a beginning"

    This quote makes Vilenkin's "plausible case" a bit of an understatement.
    To help spell this out for you:

    1.) Quantum gravity is true. (Vilenkin agrees with this claim, WLC seems to agree with this claim)
    2.) Quantum gravity effects affect the early universe when the universe is smaller than a Planck length. (Vilenkin/WLC do not dispute this)
    3.) No one has a good model of quantum gravity. (Vilenkin/WLC do not dispute this)
    4.) This includes all models of gravity which are past-finite. (No comment from either)

    I'm "myopically" fixating on the caveats of his theorem because it's the relevant issue my actual argument is addressing.

    BVG theorem does not propose a model of quantum gravity, so our ignorance of quantum gravity cuts both ways. BVG is a theorem that applies only to some quantum (and classical) theories of gravity, because it only follows if the quantum theory of gravity follows the assumptions outlined by Vilenkin. I have already addressed the fact that there are currently no theories of quantum gravity that obey the criterion necessary for the BVG theorem.

    Quote Originally Posted by cstamford
    And then there's the matter of philosophical consistency to be considered here. You're a self-described atheist, which means that for you there is no "satisfactory model for a universe" with a God or gods included in it. Now that's a philosophically consistent positiion to take. It happens to be wrong from my perspective, but it's philosophically consistent within any philosophy that includes a substantial degree of some version of empiricism.

    However, here you seem to be taking a philosophically inconsistent position, if you can be understood to be in basic agreement with Vilenkin, as your opening remark that he, like you, is "...a subscriber to the common lore", would indicate. Here Vilenkin has stated that "at this time" there are no satisfactory models for a temporally finite universe, and yet "at this time" you are arguing there is no satisfactory evidence for a beginning to the universe. And not only is your argument here evidently based on a complete lack of "satisfactory models" (in Vilenkin's sense of that phrase), but the remainder of it seems to me to consist entirely in trying to explain why Vilenkin can't seem to express himself adequately in English, which I find another, in what has become an ongoing series of very strange claims.
    This has nothing to do with my atheism. It only has to do with the fact that quantum effects are unknown but in the only toy models of quantum gravity that we have, they violate the BVG theorem. End of story.

    Quote Originally Posted by cstamford
    Again, I must interrupt to correct the record, since you've not defined "WLC's question", to which one response by Vilenkin was to furnish Craig with a copy of the e-mail in question, without the deletions to it Krauss made.
    Yes, and I also forgot to note whether or not WLC ate a tuna fish sandwich upon the reading of Vilenkin's e-mail... Relevance?

    Oh right, I forgot that you think that I'm arguing that WLC is misquoting Vilenkin, in which case the interceding dialog would have been relevant... *sigh*

    Quote Originally Posted by cstamford
    We do not need to get into a point by point discussion of what Prof. Vilenkin thinks of Craig's representation of his (Vilenkin's) view on the BGV theorem. In a portion of Vilenkin's reply to Craig's "question" you've failed to include in your post, he writes:

    "I think you represented what I wrote about the BGV theorem in my papers and to you personally very accurately."

    That settles the question for me, and I would hope for all other truth seekers. There is absolutely nothing wrong with WLC's representation of Vilenkin's position on the BGV theorem, or Craig's characterization of the universe having a beginning to its existence being probable on the evidence from theoretical physics. I would add that I don't see how the fact there are a great many physicists today who are dissatisfied with the concept of a finite universe, and who are working on theories in which the universe is temporally infinite, amounts to this current direction in researh itself being evidence to the contrary, or being any sort of "basis" upon which one can sensibly stand to say, as you have above, that " Vilenkin gave his paper a nice spin." The term "spin" would imply an impression contrary to the fact, and I fail to see any "spin" provided by Vilenkin on Craig's point.
    More irrelevant blovition that fails to address any argument that I've actually made... Summarily ignored.


    Quote Originally Posted by cstamford
    Finally, I should stress again that you've implicitly recruited, so to speak, Vilenkin into your "consensus" of physicists who agree with you, by stating as fact: "Nope, Vilenkin is definitely a subscriber to the common lore.", of which "lore" you are a staunch advocate in this thread. Given that Craig is a staunch advocate for the probability the universe had a beginning, and you are an opponent of that view, this would make Vilenkin and you allies on the critically related question, did Craig misunderstand Vilenkin's position on the BGV theorem, and therefore misrepresent it to his audience and readers, or not? And you have, to the extent I've followed this thread, consistently maintained Craig has seriously misunderstood the BVG theorem and Vilenkin's remarks concerning it, and further that Craig can therefore safely be discounted as an interpreter of Vilenkin, while you, being a physicist yourself, may be trusted on this point.

    But lo and behold, it turns out that you and Vilenkin are at odds on this very point, and demonstrably so! Therefore, I am going to conclude that your take on Craig's understanding of Vilenkin's position on the BGV theorem is misguided. Further, I conclude that in so far as Craig's grasp of physics, or his personal integrity are concerned, they have been more than adequately confirmed by Vilenkin, even if called into serious question by you.
    I'm failing to see anything resembling a valid logical inference here. I'd ask you to rephrase this without all of the non-sequiturs, but frankly I doubt that much would be left.
    Last edited by GoldPhoenix; March 25th, 2014 at 09:43 PM.
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by GoldPhoenix View Post
    So my only problem with WLC has been his use and belief in the wide-ranging applicability of the BVG theorem and his frequent negligence in pointing out the importance of quantum corrections.
    And yet it is the very fact that Craig has stressed the "wide ranging applicability of the BVG (sic) theorem", and his lack of agreement with you that "quantum corrections" are important to this "wide ranging applicability" of the theorem, with which Vilenkin agrees in his letter of response to Craig.

    Again, in Vilenkin's own words, Craig has "...represented what I (Vilenkin) wrote about the BGV theorem...very accurately."

    You'd do well to follow through on your stated aim to make your last response your last on this issue. After all, what more is there to say?

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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford View Post
    And yet it is the very fact that Craig has stressed the "wide ranging applicability of the BVG (sic) theorem", and his lack of agreement with you that "quantum corrections" are important to this "wide ranging applicability" of the theorem, with which Vilenkin agrees in his letter of response to Craig.

    Again, in Vilenkin's own words, Craig has "...represented what I (Vilenkin) wrote about the BGV theorem...very accurately."

    You'd do well to follow through on your stated aim to make your last response your last on this issue. After all, what more is there to say?
    Vilenkin also said that you can only apply the BGV result in models where quantum effects are small in magnitude. WLC just applies the BGV result without worrying if the necessary criteria are fulfilled; if he's made an argument that there's a good model for our universe, and that this model meets the criteria for the BGV result, I haven't seen it. Have you?
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by CliveStaples View Post
    Vilenkin also said that you can only apply the BGV result in models where quantum effects are small in magnitude. WLC just applies the BGV result without worrying if the necessary criteria are fulfilled
    If that were the case then why would Vilenkin say Craig had represented the BGV theorem "very accurately"? Furthermore, Vilenkin states there are no models of the universe that are "satisfactory", and that have quantum effects large enough to rule out the applicability of the BGV theorem. I take that as Vilenkin's assessment there are no currently viable models of the universe to which the BGV theorem does not apply, which is not the same thing as saying there are no models of the universe at all to which the BGV theorem does not apply. But then why should we be concerned in this thread by the mere possibility there may one day be what there isn't now, ie., a "satisfactory" model of the universe in which the quantum effects are large enough to make the BGV theorem inapplicable? So far it seems to me the only reason that has been offered to support that concern is the fact GoldPhoenix and a cadre of like-minded physicists are more intrigued by these currently "unsatisfactory" models that result in temporally infinite universes, than they are by the currently "satisfactory" models that result in temporally finite universes. I mean, that's fine and dandy, but is it evidence of anything? Not as I understand the concept of "evidence" it isn't.

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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by GoldPhoenix View Post
    In other words: Assuming (without any reason specified) that quantum physics doesn't matter very much, then the BVG theorem does apply.
    I think we need to be a bit more specific in what is meant by the break down in classical space time meant by Prof. Vilenkin here. The only elements required of space time to be in accordance with the BVG theorem are: a) events are causally ordered and b) it expands in a “forward” direction.

    I would submit the last paragraph of Prof. Vilenkin’s letter where he points out that the objection to his theorem only arises where causality and time cease to be meaningful concepts.

    That is a much bigger departure from current empirical standing than I think GP is indicating. It certainly isn’t ruled out in any sense of the term, but it is more than just the non-classical models put forward in his last post.

    And interestingly, these are all objections both Prof. Vilenkin and Dr. Craig have referenced before. Prof. Vilenkin has put forward three possible exceptions to the theorem. The first two are dealt with in the paper originally published. The third, is discussed here, http://arxiv.org/abs/1204.4658 in which Vilenkin and Mithani discuss three possible models and show why they cannot have been past eternal.
    Dr. Craig has also discussed possible exceptions to the BVG theorem and has a specific response authored by James Sinclair here, http://www.reasonablefaith.org/conte...f-the-universe. This discussion includes four types of quantum gravity models and the objections to them (BVG is one, Thermodynamics is another, boundary conditions is a third).

    Quote Originally Posted by GP
    And while Squatch is fond of saying "We don't have a model where there are effects that lead to an infinite past", I can make the much stronger statement and say "Sure, but we equally don't have a model where the BVG theorem applies, either, so the only evidence that we have right now is that it won't apply to quantum gravity".
    I’m not sure I would agree with GP’s conclusion here. Several of the models presented in the above documents are finite in the past. I would agree that it isn’t as if any of them have been settled on and as such we have a clear winner. The Standard Model of Cosmology is temporally finite and has a pretty solid track record (it also has some notable holes and issues, but nothing currently on the verge of creating a discarding of it).

    Further, some of the models objected to above are ones where the BVG model does apply and simply requires the model to be past finite. For example, String Landscape (multi-verse models) are quite popular, BVG applies and they are finite in the past (since the landscape itself is, on average expanding).

    Quote Originally Posted by CliveStaples View Post
    First, if we're talking about how to compute and compare probabilities, we should probably be looking to technical definitions of probability, not colloquial ones.
    Of course, I’m not arguing that we are. I’m pointing out that you can make the statement “That premise is probably true” without resorting to a full probability model.

    For example, when Sean Carroll says “The universe is probably eternally old” we don’t ask him for his exact calculation, his population of possible outcomes and sub-set of eternal outcomes. We take him for what he meant, that by the evidence he is seeing, he thinks it more likely than not that the universe is eternally old.

    When Prof. Vilenkin says “it seems that the answer to this question is probably yes” we understand the same meaning.

    When you said, “so my "understanding" of your argument is probably hopelessly out of date” I don’t come back and ask you for your complete calculation set right? I understand that you are using the term in the manner proscribed by general English usage.

    When GP said, “Your quibbling here, probably because at this point your argument is transparently wrong even to you now.” No one asked for his psychological profile of Cstam and said he was equivocating because he hadn’t shown all possible states of Cstam’s mind right?

    I was simply pointing out to Mdougie what everyone else, including you, me, GP, Sean Carroll and Craig have already taken for granted. That the work “probable” is not a perfect synonym for “probability.”

    Whether you agree or not with that assessment is another matter (as discussed below), but that I am using the term “probable” in some inappropriate manner is incorrect.

    Quote Originally Posted by CS
    Third, if your argument is that the available evidence makes it more likely than not (I'd love a precise definition of what exactly you're using that phrase--or its equivalents--to mean) that the universe has a finite age (or, began to exist a finite length of time in the past), I'd really like to see that evidence. As GP pointed out, applying the BVG result requires certain assumptions with regard to the magnitude of quantum effects; if you are applying the BVG result, you'll need evidence to show (assuming we're relying on the more likely than not requirement) that those assumptions probably hold.
    I have stated that position several times before, though perhaps you were not involved in those discussions. The position is quite clear, the premise “the universe began to exist” is held as probably true, IE that it is more likely true than not.

    As for the supporting evidence, I think both you and GP are under a misapprehension concerning the BVG theorem. It is not a panacea we are using for any discussion on the issue. It is a response to an objection to one piece of evidence supporting the premise (just as thermodynamics or empirical evidence are responses to other objections). Other evidence is the claim that gave rise to the thread you and I are discussing elsewhere. I would also commend you to Chad’s excellent thread and follow ups here: http://www.onlinedebate.net/forums/s...ical-Argument?
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford View Post
    If that were the case then why would Vilenkin say Craig had represented the BGV theorem "very accurately"?
    WLC can describe the BGV result very accurately without applying it properly in a particular case.

    Furthermore, Vilenkin states there are no models of the universe that are "satisfactory", and that have quantum effects large enough to rule out the applicability of the BGV theorem. I take that as Vilenkin's assessment there are no currently viable models of the universe to which the BGV theorem does not apply, which is not the same thing as saying there are no models of the universe at all to which the BGV theorem does not apply. But then why should we be concerned in this thread by the mere possibility there may one day be what there isn't now, ie., a "satisfactory" model of the universe in which the quantum effects are large enough to make the BGV theorem inapplicable? So far it seems to me the only reason that has been offered to support that concern is the fact GoldPhoenix and a cadre of like-minded physicists are more intrigued by these currently "unsatisfactory" models that result in temporally infinite universes, than they are by the currently "satisfactory" models that result in temporally finite universes. I mean, that's fine and dandy, but is it evidence of anything? Not as I understand the concept of "evidence" it isn't.
    There are no currently viable models at all that describe quantum gravity. In particular, there are no currently viable models where quantum effects are large; there are also no currently viable models where the quantum effects are small (allowing application of the BGV result).

    ---------- Post added at 09:37 AM ---------- Previous post was at 09:28 AM ----------

    Quote Originally Posted by Squatch347 View Post
    Of course, I’m not arguing that we are. I’m pointing out that you can make the statement “That premise is probably true” without resorting to a full probability model.

    For example, when Sean Carroll says “The universe is probably eternally old” we don’t ask him for his exact calculation, his population of possible outcomes and sub-set of eternal outcomes. We take him for what he meant, that by the evidence he is seeing, he thinks it more likely than not that the universe is eternally old.

    When Prof. Vilenkin says “it seems that the answer to this question is probably yes” we understand the same meaning.

    When you said, “so my "understanding" of your argument is probably hopelessly out of date” I don’t come back and ask you for your complete calculation set right? I understand that you are using the term in the manner proscribed by general English usage.

    When GP said, “Your quibbling here, probably because at this point your argument is transparently wrong even to you now.” No one asked for his psychological profile of Cstam and said he was equivocating because he hadn’t shown all possible states of Cstam’s mind right?

    I was simply pointing out to Mdougie what everyone else, including you, me, GP, Sean Carroll and Craig have already taken for granted. That the work “probable” is not a perfect synonym for “probability.”

    Whether you agree or not with that assessment is another matter (as discussed below), but that I am using the term “probable” in some inappropriate manner is incorrect.
    I'm not sure what your point is. Whether we call it probability or likelihood is irrelevant. Can anyone say anything about the likelihood of the universe being infinitely old? How would you object? Isn't this comparing the likelihood of a particular event to the likelihood of another event (in the abstract sense of event)?

    When Carroll et al. say that P is more likely than ~P, or that P is probable, I take that to be more than just a description of the speaker's subjective psychological state, but rather a tacit argument that some body of evidence is sufficient to conclude that P is more likely than ~P. What are these rules of inference regarding likelihood? If you don't like Kolmogrov probability, what inference system is being used?

    I have stated that position several times before, though perhaps you were not involved in those discussions. The position is quite clear, the premise “the universe began to exist” is held as probably true, IE that it is more likely true than not.
    More likely true than not on some set of evidence, or irrespective of any body evidence?

    As for the supporting evidence, I think both you and GP are under a misapprehension concerning the BVG theorem. It is not a panacea we are using for any discussion on the issue. It is a response to an objection to one piece of evidence supporting the premise (just as thermodynamics or empirical evidence are responses to other objections). Other evidence is the claim that gave rise to the thread you and I are discussing elsewhere. I would also commend you to Chad’s excellent thread and follow ups here: www.onlinedebate.net/forums/showthread.php/15307-On-God-s-Existence-Part-1-The-Cosmological-Argument?
    Can you be specific about what evidence you're relying on? You're basically just saying, "Yeah, I have evidence."
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by CliveStaples View Post
    WLC can describe the BGV result very accurately without applying it properly in a particular case.
    That is true, but Vilenkin's statement as to what Craig did with the BGV theorem included Craig's application of it as I read Vilenkin's statement to Craig in his letter responding to Craig's "question". Furthermore, Vilenkin's other statement I quoted Craig quoting, to the effect there are currently no "satisfactory" models of the universe in which an application of the BGV theorem would be incorrect, seals the deal to my way of thinking. It provides the needed context by which to interpret Vilenkin's intent in saying Craig had "very accurately" represented Vilenkin's take on the BGV theorem's applicability, which is to say that it is generally applicable, given the state of today's theoretical physics.

    Quote Originally Posted by CliveStaples
    There are no currently viable models at all that describe quantum gravity.
    Would not "quantum gravity", assuming there is such a thing, ie., that one day it will be consistently conceptualized (ie. "discovered), be something that is then simply folded into the term "quantum effects"? If so, I can see no purpose here in singling it out for individual attention. I'm confident that when Vilenkin says "quantum effects" in a context such as we are now discussing, he refers to a category that will accurately and adequately hold any and all phenomena exclusive to the quantum scale, whenever, if ever, they are "discovered".

    Quote Originally Posted by CliveStaples
    ...there are no currently viable models where quantum effects are large; there are also no currently viable models where the quantum effects are small (allowing application of the BGV result).
    Then what you seem to me to be suggesting is: whether quantum effects are small or large in a particular model of the universe, the BGV theorem is not applicable to that model. This seems to me to be the clear denial of what Vilenkin has been quoted saying!

    Worse, it seems to me "large" can be conceptually extended indefinitely in the "larger than" direction, making the possible impact on a particular model of the universe utilizing "large" quantum effects potentially infinitely "large". Likewise, it seems to me that "small" can be conceptually extended indefinitely in the "smaller than" direction, making the possible impact on any particular model of the universe utilizing "small" quantum effects potentially infinitely "small". Finally, because what is "not large" is conceptually equivalent to "small", relative to "large", and what is "not small" is conceptually equivalent to "large" relative to "small", it would seem to follow from the conjunction of your two suggestions just now that there simply are no models of the universe to which the BGV theorem is accurately applicable.

    Since I sincerely doubt you'd offer the proposition that there are no models of the universe to which the BGV theorem accurately applies, what were you trying to tell me that I evidently missed entirely?

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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford View Post
    That is true, but Vilenkin's statement as to what Craig did with the BGV theorem included Craig's application of it as I read Vilenkin's statement to Craig in his letter responding to Craig's "question". Furthermore, Vilenkin's other statement I quoted Craig quoting, to the effect there are currently no "satisfactory" models of the universe in which an application of the BGV theorem would be incorrect, seals the deal to my way of thinking. It provides the needed context by which to interpret Vilenkin's intent in saying Craig had "very accurately" represented Vilenkin's take on the BGV theorem's applicability, which is to say that it is generally applicable, given the state of today's theoretical physics.
    Vilenkin tells WLC that the BGV result only applies when quantum effects are small. There aren't any "satisfactory" models of the universe in which an application of the BGV theorem would be correct, either.

    Would not "quantum gravity", assuming there is such a thing, ie., that one day it will be consistently conceptualized (ie. "discovered), be something that is then simply folded into the term "quantum effects"? If so, I can see no purpose here in singling it out for individual attention. I'm confident that when Vilenkin says "quantum effects" in a context such as we are now discussing, he refers to a category that will accurately and adequately hold any and all phenomena exclusive to the quantum scale, whenever, if ever, they are "discovered".
    The BGV result only holds when quantum effects are small. Unless you have a satisfactory model of quantum gravity, you don't know what the magnitude of the quantum effects are going to be.

    Then what you seem to me to be suggesting is: whether quantum effects are small or large in a particular model of the universe, the BGV theorem is not applicable to that model. This seems to me to be the clear denial of what Vilenkin has been quoted saying!
    The point is that you can't say, "The BGV result tells us that our universe probably had a beginning", because you don't know if you can apply BGV since you don't know enough about quantum gravity.

    Worse, it seems to me "large" can be conceptually extended indefinitely in the "larger than" direction, making the possible impact on a particular model of the universe utilizing "large" quantum effects potentially infinitely "large". Likewise, it seems to me that "small" can be conceptually extended indefinitely in the "smaller than" direction, making the possible impact on any particular model of the universe utilizing "small" quantum effects potentially infinitely "small". Finally, because what is "not large" is conceptually equivalent to "small", relative to "large", and what is "not small" is conceptually equivalent to "large" relative to "small", it would seem to follow from the conjunction of your two suggestions just now that there simply are no models of the universe to which the BGV theorem is accurately applicable.

    Since I sincerely doubt you'd offer the proposition that there are no models of the universe to which the BGV theorem accurately applies, what were you trying to tell me that I evidently missed entirely?
    There are not satisfactory models of the universe to which the BGV theorem accurately applies, because there are no satisfactory models of the universe at all. We won't have a satisfactory model until we understand quantum gravity; until then, our current models will only apply where spacetime is approximately classical (i.e. where quantum effects are small), which is emphatically not the case in regions of spacetime sufficiently close to the "Big Bang" singularity, where quantum effects are large and thus invalidate the classical picture.

    Imagine that the radius of the Earth has been growing over time, so the Earth becomes a larger and larger sphere/ball (in reality, the Earth isn't precisely spherical, but the precise shape of the Earth isn't the issue here). Now suppose you live on the surface of this ball/sphere/Earth. When the radius is large, the regions around you look roughly flat; the larger the radius, the flatter the regions around you look. At a large enough radius value, you could just assume the region around actually is flat, and your calculations wouldn't be that far off.

    However, as you go back in time, the radius shrinks and shrinks, making the region around less and less flat--and therefore more and more curved. At some point, your calculations (which assume the region around you is flat) will be wildly off as the effect of curvature becomes large. So the fact that your calculations say that X holds becomes unreliable.
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by Squatch347 View Post
    I think we need to be a bit more specific in what is meant by the break down in classical space time meant by Prof. Vilenkin here. The only elements required of space time to be in accordance with the BVG theorem are: a) events are causally ordered and b) it expands in a “forward” direction.

    I would submit the last paragraph of Prof. Vilenkin’s letter where he points out that the objection to his theorem only arises where causality and time cease to be meaningful concepts.
    Sorry, but no. You misunderstand him what he means or you misunderstand how radically our notion of spacetime has to be twisted under quantum deformations. If you directly interpret his words into colloquial English, your interpretation isn't wrong. But if you want to "be a bit more specific", as you stated, then you have to understand what is meant in terms of mathematics.


    1.) The BVG theorem applies to "classical spacetimes". This means "differentiable manifolds endowed with a Lorentzian metric of signature (1,d).", aka "Lorentzian manifolds". If you read Carroll's GR book, you'll learn all about them. In other words, this is what is meant by a "classical spacetime" is something that is described in terms of collections of points in spacetime where you can define relevant topological, differentiable, and metric structures on them (Roughly speaking this means you know how quantities continuously flow as you move between points --which is exactly what the BVG theorem is talking about, they're called 'geodesic sprays'-- and you know how to define the 'length' between any two points). (See the following quote).

    2.) The BVG theorem needs quantum corrections to be a small departure away from GR, because otherwise the concept of classical spacetimes is clearly untrustworthy (i.e. the Lorentzian manifold picture). The quantum fluctuations make it very difficult to believe that there's a meaningful classical picture of spacetime; the caveats that Vilenkin laid out about quantum gravity were not chosen at random. They were chosen because these are the most relevant physics in this regime. (See the following quote).


    This is because the generic toy models (as listed in my last post) break both (1.) and (2.). For instance, String theory does not give you a classical spacetime and this is because String theory gives you very strong quantum corrections to "spacetime", as defined in string theory. Same with (to the best of their abilities to calculate, anyways) loop quantum gravity and casual triangulation. There's a whole discipline, called "quantum geometry", which attempts to deal with these issues., To quote a mathematics website from a professor who specializes in this discipline, issues of quantum geometry (arising in different but similar ways in all theories of quantum gravity) are quite different than classical spacetime:



    "Quantum geometry is a new branch of mathematics. It introduces a completely new concept of space, by unifying methods of classical geometry with non-commutative C*-algebras and functional analysis, and incoprorating into geometry various ideas from quantum physics. [...] In classical geometry spaces are always understandable as collections of points, equipped with the appropriate additional structure (as for example a topological structure given by the collection of open sets, or a smooth structure given by the atlas). In contrast to classical geometry, quantum spaces are not interpretable in this way. In general, quantum spaces have no points at all! They exhibit non-trivial quantum fluctuations of geometry at all scales.

    A very interesting potential application of quantum geometry in physics is to provide a mathematically coherent description of the physical space-time, at all scales---in particular at the level of ultra-small distances, characterized by the Planck lenght [sic]. This lenght [sic] is a universal physical constant, defined as a unique combination of gravitational constant gravitational-constant $\gamma$, Planck's constant $\hbar$, and the velocity of light c. Explicitly,

    $$ \el = \sqrt{ \frac{\gamma \hbar}{c^3} } $$

    As we can see, it is an exorbitantly small number! There are many reasons to believe that Planck's lenght [sic] marks a boundary for the applicability of classical concepts of space and time in physics."



    In other words, all current attempts with quantum gravity lead to concept like the above mentioned "quantum spacetimes" (as described above), where the picture of "classical spacetimes" breaks down.


    Again, and I really cannot emphasize this enough, there is not even a single half-baked theory of quantum gravity that is capable of preserving the classical notion of spacetime. This means that there is no theory of quantum gravity where the BVG theorem holds. We have three toy models where they don't hold, however. This casts serious doubt onto the validity of the application of the BVG theorem to quantum theories of gravity. And since we're talking about singularities, quantum gravity is the only relevant physics.


    Quote Originally Posted by Squatch
    That is a much bigger departure from current empirical standing than I think GP is indicating. It certainly isn’t ruled out in any sense of the term, but it is more than just the non-classical models put forward in his last post.
    Sorry, but again: No. The modern view of gravity is as an "effective field theory", this means that all models of quantum gravity (which looks like GR at low energies) will be consistent with current experiments. It's actually one of the most remarkable predictions of quantum field theory/quantum gravity that we currently know. I'll let Professor Donoghue explain in his well-known work on the subject from the early 90's:

    "I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well behaved quantum field theory at ordinary energies."

    This is a rather well-known review on the subject, although the ideas about how quantum gravity should operate had come about earlier by Deser, Weinberg, and 't Hooft in the 1970's.

    Quote Originally Posted by Squatch
    And interestingly, these are all objections both Prof. Vilenkin and Dr. Craig have referenced before. Prof. Vilenkin has put forward three possible exceptions to the theorem. The first two are dealt with in the paper originally published. The third, is discussed here, http://arxiv.org/abs/1204.4658 in which Vilenkin and Mithani discuss three possible models and show why they cannot have been past eternal.
    Dr. Craig has also discussed possible exceptions to the BVG theorem and has a specific response authored by James Sinclair here, http://www.reasonablefaith.org/conte...f-the-universe. This discussion includes four types of quantum gravity models and the objections to them (BVG is one, Thermodynamics is another, boundary conditions is a third).
    Cyclic universes are not "string theory", they are "string-inspired models". This means that they don't actually use the full quantum effects of string theory, and aren't necessarily derived from string theory at all (e.g. the Randall-Sundrum models). They are, in some sense, more ad hoc and not super-well motivated from string theory, which is the main reason why I said I didn't believe them way back earlier in this thread (or Clive's, I don't recall).

    Quote Originally Posted by Squatch
    I’m not sure I would agree with GP’s conclusion here. Several of the models presented in the above documents are finite in the past. I would agree that it isn’t as if any of them have been settled on and as such we have a clear winner. The Standard Model of Cosmology is temporally finite and has a pretty solid track record (it also has some notable holes and issues, but nothing currently on the verge of creating a discarding of it).
    It's track record is irrelevant; Newtonian mechancis has had a great track record of describing nearly all of the engineering taking place on Earth, but it doesn't mean that I'd use it to compute the physics of objects moving near the speed of light. It's a great model of cosmology, but that doesn't mean that it's a great model of cosmology for all times and at all scales. All models have regimes of validity, at least until we find a "Theory of Everything". Until that theory is discovered, all models will break down somewhere, like Newtonian mechanics, like Special Relativity, like Quantum Mechanics, and eventually, just like General Relativity and Quantum Field Theory.

    The Concordance Model of Cosmology is only been experimantally probed for times around BBN (order 100 = 10^2 seconds after the Big Bang; and quantum gravity effects come in between 10^-34 to 10^-43 seconds), although if the Bicep 2 results are confirmed this will push us back considerably. Also, technically, the Concordance Model does not include inflation, so it fails to explain the scale-invariance of our universe, it cannot explain the recently discovered abundence of gravitational waves, and most importantly for this discussion, it doesn't include quantum gravity so it is necessarily incomplete at or before it contracted to length scales of order 10^-35 meters. The only nice thing about the problem of quantum gravity is that we know where we can't extrapolate our theories to.

    Stop thinking about the Concordance Model as being on the interval [0 years (= singularity), 10^10 years]. It is only valid, at a maximum, on the interval [10^-33 seconds, 10^10 years]. The universe from [???, 10^-33] is all described by and only by quantum gravity.


    Quote Originally Posted by Squatch
    Further, some of the models objected to above are ones where the BVG model does apply and simply requires the model to be past finite. For example, String Landscape (multi-verse models) are quite popular, BVG applies and they are finite in the past (since the landscape itself is, on average expanding).
    Again, "string-inspired models"; they aren't actual string theory. They don't include actual string theory corrections when the universe is near the Planck length, so the point is moot. The full string theory does predict huge quantum corrections when you go down to these length scales. So these models are themselves missing important physical effects from quantum gravity, no different than any other model.

    Quote Originally Posted by Squatch
    As for the supporting evidence, I think both you and GP are under a misapprehension concerning the BVG theorem. It is not a panacea we are using for any discussion on the issue. It is a response to an objection to one piece of evidence supporting the premise (just as thermodynamics or empirical evidence are responses to other objections). Other evidence is the claim that gave rise to the thread you and I are discussing elsewhere. I would also commend you to Chad’s excellent thread and follow ups here: http://www.onlinedebate.net/forums/s...ical-Argument?
    1.) I read it and I rebutted it with the same argument that I'm using now before Chad left the thread. I've offered to take the debate up again (multiple times now) with Chad, which he has refused. To be fair to him, it's because he is busy and I understand that. But nevertheless, you can't throw up this thread as a counter argument to my point, when the original author had failed to rebut the same claims raised on this thread.


    2.) You're shifting the goal post, at some level here. The issue here is not so narrowed as the cyclic model, or the other two models that you claim WLC has argued against. You're looking at two or three models, defeating them, and then rejoicing that you've won. This is the fallacy of proof by example. If you wanted to summate my point, it's the following:


    You keep on saying that "no model is being proposed that would cause the universe to be past-infinite." What you are neglecting in this analysis is there are no valid models that are past-finite, either, because there are no valid models of quantum gravity period; all claims about what went on during this region are completely speculative. This is why I bring up the whole issue of quantum geometry above; we have no reason to suspect that any of our cherished ideas of classical spacetime are upheld. Again, amongst toy models they are always discarded and replaced with much more complex concepts that we are far from fully understanding. This is why quantum gravity is an open research field. Without a valid theory of quantum gravity, we don't have the right to sit back and talk about what is or isn't probable about the absolute origins of our universe. I've already debunked the usefulness of the BGV theorem as it is applied to quantum theories of gravity; so far, it only seems like it won't apply. As Vilenkin said himself, a theorem is only as useful as it's premises are true.


    Either you have a model which demonstrates that the universe began a certain time in the past, or you have nothing to contribute to the conversation. What you're not understanding is that the sword cuts both ways. I have yet to provide a model where the universe is past-infinite (fortunately, I'm not making this claim, so I have no need to defend it), but --and what is relevant because you're claiming that science has nearly definitively proven-- you have not provided a model of the universe that is past-finite and correctly accounts for quantum gravity effects. (How could you? No such model exists yet!)


    I'll repeat this: My position is agnosticism; it could be past-infinite or past-finite. Your position is that we very nearly know for sure. Guess where the burden of proof goes, especially regarding the issues of appropriately accounting for quantum gravity? Honestly, I really don't know what's so hard to understand about my position or my arguments. Please tell me if I am not explaining this correctly.
    "Those who can make you believe absurdities, can make you commit atrocities." --Voltaire

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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by CliveStaples View Post
    Vilenkin tells WLC that the BGV result only applies when quantum effects are small.
    What Vilenkin actually tells Craig is:

    "The question of whether or not the universe had a beginning assumes a classical spacetime, in which the notions of time and causality can be defined. On very small time and length scales, quantum fluctuations in the structure of spacetime could be so large that these classical concepts become totally inapplicable. Then we do not really have a language to describe what is happening, because all our physics concepts are deeply rooted in the concepts of space and time. This is what I mean when I say that we do not even know what the right questions are."
    "But if the fluctuations are not so wild as to invalidate classical spacetime, the BGV theorem is immune to any possible modifications of Einstein's equations which may be caused by quantum effects."
    (source: http://www.reasonablefaith.org/hones...#ixzz2xEyhmXCH)

    So he's not saying "when quantum effects are small". He's saying when "the fluctuations are not so wild", ie., not so large. You're the one saying they have to be small, not Vilenkin.


    Quote Originally Posted by CliveStaples
    There aren't any "satisfactory" models of the universe in which an application of the BGV theorem would be correct, either.
    Craig writes:

    "For the two models mentioned (Aguirre-Gratton and Carroll-Chen) were specifically addressed by name by Vilenkin in the paper from the Cambridge conference which I quoted in my opening speech. These models were comprised in Vilenkin’s conclusion, “None of these scenarios can actually be past-eternal.” So when Vilenkin says that they afford a “possible loophole,” the idea must be that because they deny the single assumption of the theorem, maybe that’s a way to avoid the beginning of the universe. But in his paper Vilenkin proceeds to close this loophole by showing that these models cannot be past-eternal for other reasons."
    (ibid)

    Vilenkin is quoted later by Craig agreeing with him here.

    Then Craig quotes from a letter Vilenkin wrote to Victor Stenger:

    "You can evade the theorem by postulating that the universe was contracting prior to some time. . . . This sounds as if there is nothing wrong with having contraction prior to expansion. But the problem is that a contracting universe is highly unstable. Small perturbations would cause it to develop all sorts of messy singularities, so it would never make it to the expanding phase. (A Vilenkin to V Stenger, cited by http://arizonaatheist.blogspot.com/2...s-for-god.html)
    (ibid)

    Again, Vilenkin states the BGV theorem is applicable to all models of the universe that are relatively stable, lacking ""all sorts of messy singularities". Certainly there are many such models in existence today, so I fail to see how your claim there aren't any holds water.

    Further down we come to a copy of Craig's letter to Vilenkin where we can read for ourselves:

    "You should be aware that your work has entered into popular culture, where it has become the subject of heated debate. Certain staunchly secular thinkers want to avoid the beginning of the universe because to them it smacks of theism, and so they are bent on reconstruing the significance of your work. That is why you are receiving letters from people like Stenger, Krauss, et al. I hope to have understood and represented you accurately. If not, I want to be corrected."
    "In that vein, I do have a question about your statement: “the BGV theorem uses a classical picture of spacetime. In the regime where gravity becomes essentially quantum, we may not even know the right questions to ask.” Elsewhere you’ve written:"
    "“A remarkable thing about this theorem is its sweeping generality. . . . We did not even assume that gravity is described by Einstein’s equations. So, if Einstein’s gravity requires some modification, our conclusion will still hold. The only assumption that we made was that the expansion rate of the universe never gets below some nonzero value” [Vilenkin, 2006, p. 175]."
    "How are these statements compatible?"
    (ibid)

    And to that specific question Vilenkin responded:

    "The question of whether or not the universe had a beginning assumes a classical spacetime, in which the notions of time and causality can be defined. On very small time and length scales, quantum fluctuations in the structure of spacetime could be so large that these classical concepts become totally inapplicable. Then we do not really have a language to describe what is happening, because all our physics concepts are deeply rooted in the concepts of space and time. This is what I mean when I say that we do not even know what the right questions are."
    "But if the fluctuations are not so wild as to invalidate classical spacetime, the BGV theorem is immune to any possible modifications of Einstein's equations which may be caused by quantum effects."
    (ibid)


    Now, frankly, and with all due respect, I don't need you or anyone else to tell me what Vilenkin just said. It's very clear. Any model of the universe to which "our physics concepts" are applicable, is one to which the BGV theorem is applicable. So the only way anyone can accurately say there is no model of the universe to which the BGV theorem is applicable, is to claim there is no model of the universe to which our physics concepts are applicable. And while I don't know to a logical certainty, I reject the notion there are no cosmological models of our universe to which our "physics concepts" apply.


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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford View Post
    What Vilenkin actually tells Craig is:

    "The question of whether or not the universe had a beginning assumes a classical spacetime, in which the notions of time and causality can be defined. On very small time and length scales, quantum fluctuations in the structure of spacetime could be so large that these classical concepts become totally inapplicable. Then we do not really have a language to describe what is happening, because all our physics concepts are deeply rooted in the concepts of space and time. This is what I mean when I say that we do not even know what the right questions are."
    "But if the fluctuations are not so wild as to invalidate classical spacetime, the BGV theorem is immune to any possible modifications of Einstein's equations which may be caused by quantum effects."
    (source: http://www.reasonablefaith.org/hones...#ixzz2xEyhmXCH)

    So he's not saying "when quantum effects are small". He's saying when "the fluctuations are not so wild", ie., not so large. You're the one saying they have to be small, not Vilenkin.
    Those statements mean the same thing, cstamford. So long as quantum fluctuations are not so large as to overly distort classical spacetime, BGV applies. I.e., so long as quantum fluctuations are "small" (i.e., not so large as to overly distort classical spacetime), BGV applies.




    Craig writes:

    "For the two models mentioned (Aguirre-Gratton and Carroll-Chen) were specifically addressed by name by Vilenkin in the paper from the Cambridge conference which I quoted in my opening speech. These models were comprised in Vilenkin’s conclusion, “None of these scenarios can actually be past-eternal.” So when Vilenkin says that they afford a “possible loophole,” the idea must be that because they deny the single assumption of the theorem, maybe that’s a way to avoid the beginning of the universe. But in his paper Vilenkin proceeds to close this loophole by showing that these models cannot be past-eternal for other reasons."
    (ibid)

    Vilenkin is quoted later by Craig agreeing with him here.
    Do the Aguirre-Gratton and Carroll-Chen models give a satisfactory theory of quantum gravity? If not, then they aren't acceptable models.

    Then Craig quotes from a letter Vilenkin wrote to Victor Stenger:

    "You can evade the theorem by postulating that the universe was contracting prior to some time. . . . This sounds as if there is nothing wrong with having contraction prior to expansion. But the problem is that a contracting universe is highly unstable. Small perturbations would cause it to develop all sorts of messy singularities, so it would never make it to the expanding phase. (A Vilenkin to V Stenger, cited by http://arizonaatheist.blogspot.com/2...s-for-god.html)
    (ibid)

    Again, Vilenkin states the BGV theorem is applicable to all models of the universe that are relatively stable, lacking ""all sorts of messy singularities". Certainly there are many such models in existence today, so I fail to see how your claim there aren't any holds water.


    Vilenkin also stated that BGV only applies when quantum fluctuations aren't so large as to distort classical spacetime. Without a theory of quantum gravity, you don't know what the right values for those quantum fluctuations are.

    Further down we come to a copy of Craig's letter to Vilenkin where we can read for ourselves:

    "You should be aware that your work has entered into popular culture, where it has become the subject of heated debate. Certain staunchly secular thinkers want to avoid the beginning of the universe because to them it smacks of theism, and so they are bent on reconstruing the significance of your work. That is why you are receiving letters from people like Stenger, Krauss, et al. I hope to have understood and represented you accurately. If not, I want to be corrected."
    "In that vein, I do have a question about your statement: “the BGV theorem uses a classical picture of spacetime. In the regime where gravity becomes essentially quantum, we may not even know the right questions to ask.” Elsewhere you’ve written:"
    "“A remarkable thing about this theorem is its sweeping generality. . . . We did not even assume that gravity is described by Einstein’s equations. So, if Einstein’s gravity requires some modification, our conclusion will still hold. The only assumption that we made was that the expansion rate of the universe never gets below some nonzero value” [Vilenkin, 2006, p. 175]."
    "How are these statements compatible?"
    (ibid)

    And to that specific question Vilenkin responded:

    "The question of whether or not the universe had a beginning assumes a classical spacetime, in which the notions of time and causality can be defined. On very small time and length scales, quantum fluctuations in the structure of spacetime could be so large that these classical concepts become totally inapplicable. Then we do not really have a language to describe what is happening, because all our physics concepts are deeply rooted in the concepts of space and time. This is what I mean when I say that we do not even know what the right questions are."
    "But if the fluctuations are not so wild as to invalidate classical spacetime, the BGV theorem is immune to any possible modifications of Einstein's equations which may be caused by quantum effects."
    (ibid)


    Now, frankly, and with all due respect, I don't need you or anyone else to tell me what Vilenkin just said. It's very clear. Any model of the universe to which "our physics concepts" are applicable, is one to which the BGV theorem is applicable. So the only way anyone can accurately say there is no model of the universe to which the BGV theorem is applicable, is to claim there is no model of the universe to which our physics concepts are applicable. And while I don't know to a logical certainty, I reject the notion there are no cosmological models of our universe to which our "physics concepts" apply.
    There are no currently-available satisfactory models of our universe, since we can't make computations above certain energy thresholds because we lack a theory of quantum gravity. Our current models are excellent approximations at most commonly-seen energy levels (ala Newtonian physics being a good approximation at speeds much lower than the speed of light), which lets us reach many very, very confident conclusions. But it's precisely in high-energy contexts that our current physical models become inadequate; we cannot rely on those models outside their intervals of accuracy.
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by CliveStaples View Post
    Those statements mean the same thing, cstamford. So long as quantum fluctuations are not so large as to overly distort classical spacetime, BGV applies. I.e., so long as quantum fluctuations are "small" (i.e., not so large as to overly distort classical spacetime), BGV applies.
    Well, they do now, after your much needed clarification of your meaning. But now that you've properly clarified your remark, are you still willing to claim there are no models of the universe to which the BGV theorem is applicable?

    Quote Originally Posted by CS
    Do the Aguirre-Gratton and Carroll-Chen models give a satisfactory theory of quantum gravity? If not, then they aren't acceptable models.
    Evidently so. Here (and in the below I've deleted as useless) this is you forwarding, using a slightly different approach, the claim there are no "satisfactory models" of the universe. Until you can support that claim in some compelling way, I'm going to continue to ignore it as the equivocation of Vilenkin's use of the term "satisfactory" it so obviously is. Clearly, being one of the inventors of the theorem, he must think there are some "satisfactory" models to which it applies. It could hardly be a theorem otherwise.

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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford View Post
    Well, they do now, after your much needed clarification of your meaning. But now that you've properly clarified your remark, are you still willing to claim there are no models of the universe to which the BGV theorem is applicable?
    Yes.

    Evidently so. Here (and in the below I've deleted as useless) this is you forwarding, using a slightly different approach, the claim there are no "satisfactory models" of the universe. Until you can support that claim in some compelling way, I'm going to continue to ignore it as the equivocation of Vilenkin's use of the term "satisfactory" it so obviously is. Clearly, being one of the inventors of the theorem, he must think there are some "satisfactory" models to which it applies. It could hardly be a theorem otherwise.
    Well, it depends on what you mean by "satisfactory". All current physical models break down at sufficiently-high energy points (which is why they can only reach certain time periods after the Big Bang--the farther back you go, the higher energy-state you're in) because quantum corrections get large as energy increases.

    If you're calling a model "satisfactory" if it works at 'common' or 'normal' energy points--e.g., the kind of energy we observe from Earth--then we have satisfactory models. That's why we can do chemical and structural engineering. Heck, the Newtonian model is "satisfactory" in that sense.

    But the discussion is not about events that happen at 'common' or 'normal' energy points. The discussion is about the Big Bang, which is a high-energy region--precisely the kind of region where our previously-satisfactory models lose their validity.

    I will of course defer to GP's expertise on the matter.
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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by CliveStaples View Post
    Well, it depends on what you mean by "satisfactory".
    That's where you're wrong; in fact where you've always been wrong. Nothing depends on what I mean by "satisfactory" in this thread.

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    Re: A Rebuttal to the Cosmological Argument

    Quote Originally Posted by cstamford View Post
    That's where you're wrong; in fact where you've always been wrong. Nothing depends on what I mean by "satisfactory" in this thread.
    I take it that you mean to defer to Vilenkin's meaning of "satisfactory"?

    If that's the case, do you think that there's a "satisfactory" model of the universe under Vilenkin's meaning? Do you think that Vilenkin thinks that there's a "satisfactory" model of the universe under Vilenkin's theory? If there are any "satisfactory" models of the universe (under Vilenkin's meaning), do any account for quantum gravity? If they do not, how are their predictions valid for high energy states (specifically, energy states corresponding to regions of spacetime within 10^-33 seconds after the Big Bang)?
    If I am capable of grasping God objectively, I do not believe, but precisely because I cannot do this I must believe. - Soren Kierkegaard
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