We’ve returned from the lovely city of New Orleans, where within a short period of time I was able to sample shrimp and grits, bread pudding soufflé, turtle soup, chicken gumbo, soft-shelled crab with crawfish étouffée, and of course beignets. Oh yes, also participated in the Greer-Heard Forum, where I debated William Lane Craig, and then continued the discussion the next day along with Alex Rosenberg, Tim Maudlin, James Sinclair, and Robin Collins. The whole event was recorded, and will be released on the internet soon — hopefully within a couple of days.
[Update: Here is the video:]
In the meantime I thought I’d provide some quick post-debate reflections. Overall I think it went pretty well, although I certainly could have done better. Then again I’m biased, both by being hard on myself in terms of the debate performance, but understandably of the opinion that my actual ideas are correct. I think I mostly reached my primary goal of explaining why many of us think theism is undermined by modern science, and in particular why there is no support to be found for it in modern cosmology. For other perspectives see Rational Skepticism or the Reasonable Faith forums.
Short version: I think it went well, although I can easily think of several ways I could have done better. On the substance, my major points were that the demand for “causes” and “explanations” is completely inappropriate for modern fundamental physics/cosmology, and that theism is not taken seriously in professional cosmological circles because it is hopelessly ill-defined (no matter what happens in the universe, you can argue that God would have wanted it that way). He defended two of his favorite arguments, the “cosmological argument” and the fine-tuning argument; no real surprises there. In terms of style, from my perspective things got a bit frustrating, because the following pattern repeated multiple times: Craig would make an argument, I would reply, and Craig would just repeat the original argument. For example, he said that Boltzmann Brains were a problem for the multiverse; I said that they were a problem for certain multiverse models but not others, which is actually good because they help us to distinguish viable from non-viable models; and his response was the multiverse was not a viable theory because of the Boltzmann Brain problem. Or, he said that if the universe began to exist there must be a transcendent cause; I said that everyday notions of causation don’t apply to the beginning of the universe and explained why they might apply approximately inside the universe but not to it; and his response was that if the universe could just pop into existence, why not bicycles? I was honestly a bit surprised at the lack of real-time interaction, since one of Craig’s supporters’ biggest complaints is that his opponents don’t ever directly respond to his points, and I tried hard to do exactly that. To be fair, I bypassed some of his arguments (see below) because I thought they were irrelevant, and wanted to focus on the important issues; he might feel differently. I’m sure that others will have their own opinions, but soon enough the videos will allow all to judge for themselves. Overall I was moderately satisfied that I made the responses I had hoped to make, clarified some points, and gave folks something to think about.
Longer version (much longer, sorry): the format was 20-minute opening talks by each speaker (Craig going first), followed by 12-minute rebuttals, and then 8-minute closing statements. Among the pre-debate advice I was given was “make it a discussion, not a debate” and “don’t let WLC speak first,” both of which I intentionally ignored. I wanted all along to play by his rules, in front of his crowd, and do the best job I could do without any excuses.
In his opening speech Craig gave two arguments: the Kalam Cosmological Argument (the universe must be caused, and the cause is God), and the teleological/fine-tuning argument (the parameters of the universe appear designed for the existence of life). To his great credit, WLC actually stuck to arguments concerning physical cosmology, where presumably my expertise would be most valuable; he didn’t hide behind primarily metaphysical arguments like the ontological argument or the denial of realized infinities. The two he used were familiar from his repertoire, and they were the two that I was primarily interested in talking about myself, so we were off. (I’ll try to reconstruct the logic rather than doing a point-by-point recap, since I’m mostly working from memory. Naturally, my memory of my own parts will be sharper than my memory of WLC’s, so I’ll happily accept factual corrections.)
The cosmological argument has two premises: (1) If the universe had a beginning, it has a transcendent cause; and (2) The universe had a beginning. He took (1) as perfectly obvious, and put his effort into establishing (2). Partly he used the celebrated (by theologians) Borde-Guth-Vilenkin theorem, which says that a universe with an average expansion rate greater than zero must be geodesically incomplete in the past. But he also used an argument I hadn’t heard before: from the Second Law of Thermodynamics (entropy in a closed system doesn’t decrease). I think the argument was basically that the Second Law implies that we approach equilibrium, and in an infinitely-old universe we should therefore have reached equilibrium long ago, which we haven’t, so the universe began at some finite time in the past.
My attitude toward the above two premises is that (2) is completely uncertain, while the “obvious” one (1) is flat-out false. Or not even false, as I put it, because the notion of a “cause” isn’t part of an appropriate vocabulary to use for discussing fundamental physics. Rather, modern physical models take the form of unbreakable patterns — laws of Nature — that persist without any external causes. The Aristotelian analysis of causes is outdated when it comes to modern fundamental physics; what matters is whether you can find a formal mathematical model that accounts for the data. The Hartle-Hawking “no-boundary proposal” for the wave function of the universe, for example, is completely self-contained, not requiring any external cause.
Mostly Craig ignored this argument, which to me was the most important part of the debate. In the first rebuttal he said that the Hartle-Hawking model was indeed lacking something — a reason why the universe exists at all. To me this looks like confusing the cosmological argument with the argument from contingency, but since my objection applied to that case as well I didn’t raise that as an rebuttal. Rather, I pointed out that this response sailed right by my actual argument, which was that a self-contained physical model is all you need, and asking for anything more is completely unwarranted. To drive the point home, I elaborated on why things like “causes” and “explanations” make perfect sense for parts of the universe, but not for the universe itself: namely, that we live in a world with unbreakable patterns (laws of physics) and an arrow of time, but the universe itself (or the multiverse) is not one element of a much bigger pattern, it’s all there is. Finally in the closing speech WLC finally offered arguments in favor of the idea that the beginning of the universe implies a transcendental cause: (1) it’s a metaphysical principle; (2) if universe could pop into existence, why not bicycles?; and (3) there’s no reason to treat the universe differently than things inside the universe. To me, (1) isn’t actually an argument, just a restatement; and I had already explained why (2) and (3) were not true, and he didn’t actually respond to my explanation. So by the time my rebuttal came around I didn’t have much more new to say. Craig spent some time mocking the very idea that the universe could just “pop into existence.” I explained that this isn’t the right way to think about these models, which are better understood as “the universe has an earliest moment of time,” which doesn’t misleadingly appeal to our intuitions of temporal sequence; but my explanation seemed to have no effect.
The second premise of the Kalam argument is that the universe began to exist. Which may even be true! But we certainly don’t know, or even have strong reasons to think one way or the other. Craig thinks we do have a strong reason, the Borde-Guth-Vilenkin theorem. So I explained what every physicist who has thought about the issue understands: that the real world is governed by quantum mechanics, and the BGV theorem assumes a classical spacetime, so it says nothing definitive about what actually happens in the universe; it is only a guideline to when our classical description breaks down. Indeed, I quoted a stronger theorem, the “Quantum Eternity Theorem” (QET) — under conventional quantum mechanics, any universe with a non-zero energy and a time-independent Hamiltonian will necessarily last forever toward both the past and the future. For convenience I quoted my own paper as a reference, although I’m surely not the first to figure it out; it’s a fairly trivial result once you think about it. (The Hartle-Hawking model is not eternal to the past, which is fine because they imagine a universe with zero energy. In that situation time is an approximation rather than fundamental in any case — that’s the “problem of time” in quantum gravity.)
Sadly, Craig never responded to my point about the QET. Instead, he emphasized another “theorem” in a paper by Aron Wall. This is a great paper, well worth reading — but it doesn’t say what Craig wants it to say, which I was only able to check after the debate. Wall (like BGV) proves theorems that apply to semiclassical gravity (classical spacetime with propagating quantum fields — see comment from Aron below), and then speculates “the results may hold in full quantum gravity” and “there is a reasonable possibility that the Penrose singularity theorem can be proven even in the context of full quantum gravity.” As good as the paper is, proving a theorem in the semiclassical case and then opining that it is probably extendable to the full quantum gravity case does not actually represent a “theorem” about the quantum case. And in fact I think it’s highly unlikely to be extendable in the sense Craig wants it to be, since the QET says that’s impossible (unless the universe has zero energy or a time-dependent Hamiltonian, in which case it’s easy to avoid eternity). But I had never seen Wall’s paper before, and Craig didn’t give a precise statement of the purported theorem, only the above quote about “reasonable possibility”; as a result I didn’t know the range of applicability of the “theorem” or its assumptions, so chose not to talk about it rather than making guesses. That was probably a strategic mistake on my part.
While I’m lingering over my mistakes, I made a related one, when Craig emphasized a recent paper by Anthony Aguirre and John Kehayias. They examined the “emergent universe” scenario of George Ellis and Roy Maartens, in which the universe is in a quasi-static pre-Big-Bang state infinitely far into the past. Aguirre and Kehayias showed that such behavior is unstable; you can’t last in a quasi-static state for half of eternity and then start evolving. Personally, I didn’t think this was worth talking about; I completely agree that it’s unstable, I never promoted or defended that particular model, and I just didn’t see the relevance. But he kept bringing it up. Only after the debate did it dawn on me that he takes the specific behavior of that model as representative of any model that has a quantum-gravity regime (the easiest way out of the “beginning” supposedly predicted by the BGV theorem). That’s completely false. Most models with a quantum-gravity phase are nothing like the emergent universe; typically the quantum part of the evolution is temporary, and is surrounded on both sides by classical spacetime. But that’s so false that I didn’t even pick up that WLC was presuming it, so I never responded. Bad debater.
The other argument from Craig in favor of the universe having a beginning comes from the fact that entropy is increasing, in accordance with the Second Law. This is another case where it took me a while to understand the point he was trying to get at. To me, it is perfectly obvious and well-understood that the Second Law comes about because of the configuration of matter in our local region of universe, not because of some ironclad fundamental law. (Otherwise Ludwig Boltzmann lived in vain — and I have his tombstone right up there on my blog header.) A theory like my model with Jennifer Chen tries to explain how the Second Law emerges in local regions of the universe, by showing how a universe with no equilibrium state can evolve forever (rather than settling down), and entropy will naturally increase both in the far past and the far future. Craig seems to think that the Second Law should be absolute, so that models like ours are ruled out because entropy doesn’t increase monotonically — i.e. they “violate” the Second Law. (Unless I’m still misunderstanding his point — his presentation was uncharacteristically muddled here.) This is a pretty straightforward misunderstanding of the origin of the Second Law and the point of our model, although to be fair I caught on too late to present a strong counterargument.
It was interesting that Craig spent so much time talking about the Carroll-Chen model, when I wouldn’t have brought it up at all if left to my own devices. I think the model is very useful as an illustration of an interesting fact: you can derive a natural dynamical origin of the Second Law in a universe that creates new entropy without bound by creating regions of space that look like our Big Bang. But I’m the first to admit that it’s speculative, and especially that the process of baby-universe creation is ill-understood, if it’s possible at all. So I probably wouldn’t have dwelt on it, but Craig really went to town on the model. Unfortunately, nearly everything he said about it was just wrong. First, he tried to claim that having a moment of time in the history of the universe when entropy was lowest counts as a “thermodynamic beginning,” even if there is more universe in both direction of time around that moment. That’s quite an innovative definition (to be polite), but more importantly that kind of “beginning” has nothing to do with the kind of “beginning” where God would create the universe. I made this point, but it wasn’t answered. Relatedly, he seemed to think it was a glaring mistake (or perhaps intentionally subterfuge?) that on one picture of our model I had the “time” axis have only one arrow, while on another version of the picture I put arrows pointing in both directions. I apologize for being sloppy, but it’s neither a mistake nor a dastardly plot; either version is acceptable, because you have a time coordinate that runs monotonically from -infinity to +infinity, but the direction of entropy increase (that defines the arrow of time) is not monotonic. Next, he tried to claim that our model violated unitarity (conservation of quantum information), which is flatly wrong. He supplied two pieces of evidence, in the form of quotes from Stephen Hawking and Chris Weaver. But the Hawking quote was completely out of context; he was talking about the fact that he no longer thought that wormholes would lead to violation of unitarity in black-hole evaporation, nothing to do with cosmology. And the Weaver quote that Craig read had nothing to do with unitarity at all; it merely pointed out that the process of baby-universe creation is speculative and not well-understood, which I’m the first to admit. Again — I didn’t actually hold up this model as a solution to anything, but he felt the need to attack it, so I had to defend its honor a little bit.
In contrast, I wanted to talk about a model developed by Anthony Aguirre and Stephen Gratton. They have a very simple and physically transparent model that (unlike my theory with Chen) imposes a low-entropy boundary condition at a mid-universe “bounce.” It’s a straightforward example of a perfectly well-defined theory that is clearly eternal, one that doesn’t have a beginning, and does so without invoking any hand-waving about quantum gravity. I challenged Craig to explain why this wasn’t a sensible example of an eternal universe, one that was in perfect accord with the BGV theorem, but he didn’t respond. It wasn’t until the talks on the following day that Craig’s teammate James Sinclair admitted that it seemed like a perfectly good model to him.
But again — my main point was not to push this or that specific model, but to argue that it’s the models that matter, not some general theorem in a regime we don’t pretend to understand. So I listed a bunch of plausible-looking eternal cosmologies. The point is not that all or some of these models is perfect; it’s that they’re eternal. So we should judge them on their merits, rather than claiming to have general arguments that there are no such things. (It’s as if WLC has a powerful general theorem against heavier-than-air flying machines, while airplanes keep buzzing overhead.) On occasion it would be as if Craig admitted that there were indeed eternal cosmologies, but they were all ruled out for various unspecified other problems. That sounds like a suspiciously far-reaching claim, but one that is hard to directly dispute without any details being presented. More importantly, it’s beside the point. Which, in case it isn’t yet clear, is that it’s the models that matter, not any general theorems. If there are some cosmological models that are eternal but have other problems, there’s no reason to stop looking for other models that are also eternal but don’t have those problems. This is a case where working scientists are quick to admit that we don’t know the answer, so we shouldn’t stop considering all legitimate possibilities.
The fine-tuning argument proceeded in a more straightforward way. Unlike the cosmological argument, where Craig presented a few twists I hadn’t heard before (though he may have used them in other debates, I don’t know), the fine-tuning presentation was pretty standard. I acknowledged that, unlike the cosmological argument that is based on outdated metaphysics, the fine-tuning argument is a respectable scientific claim: two models trying to account for some data. But I gave five reasons why it was nevertheless not a good argument for theism:
- We don’t really know that the universe is tuned specifically for life, since we don’t know the conditions under which life is possible.
- Fine-tuning for life would only potentially be relevant if we already accepted naturalism; God could create life under arbitrary physical conditions.
- Apparent fine-tunings may be explained by dynamical mechanisms or improved notions of probability.
- The multiverse is a perfectly viable naturalistic explanation.
- If God had finely-tuned the universe for life, it would look very different indeed.
Craig didn’t respond to 2. or 3. here. To counter 1. he simply noted that other physicists disagreed with me, which again really isn’t an argument; he didn’t offer any suggestion that we actually do know the conditions under which life can and cannot form. Against 5. he invoked an argument by Robin Collins that the universe is optimized for “discoverability,” at least when we consider the known physical parameters. To me this argument is completely implausible right on the face of it, since it’s trivially easy to imagine ways to make it easier to discover the universe (just make the Higgs boson lighter!). But I knew Collins was going to give a full discussion of that argument the next day, so I saved my response until then.
In my first speech I used 5. above as a launching pad to make a bigger point: the real reason theism isn’t taken seriously is because it’s completely ill-defined. If we would presume to contemplate theism from an intellectually honest perspective, we would try to decide what kind of universe we would expect to live in if theism were true; then we would do the same for naturalism; and finally we would compare those expectations to the real world. But when we do that we find theistic expectations failing to match reality over and over again. Now, I know perfectly well (from experience as well as from cogitation) that you can never make headway with theists by claiming “If God existed, He would do X, and He doesn’t” (where X is “prevent needless suffering,” “make His existence obvious,” “reveal useful non-trivial information to us,” “spread religious messages uniformly over the world,” etc.) Because they have always thought through these, and can come up with an explanation why God would never have done that. (According to Alvin Plantinga, our world — you know, the one with the Black Death, the Holocaust, AIDS, Hurricane Katrina, and so on — is “so good that no world could be appreciably better.”) But these apologetic moves come at a price: they imply a notion of theism so flexible that it becomes completely ill-defined. That’s the real problem. Craig’s way of putting it is to suggest that God is “like the cosmic artist who wants to splash his canvas with extravagance of design.” That’s precisely why naturalism has pulled so far ahead of theism in the intellectual race to best model our world: because it plays by rules and provides real explanations for why the world is this way rather than that way.
Against the multiverse, Craig’s major argument (surprisingly) was the Boltzmann Brain problem. I say “surprisingly” because it’s such an easy argument to rebut. Sure, Boltzmann Brains are a problem — for those models with a Boltzmann Brain problem. Not all models have them! And a good modern multiverse cosmologist focuses on those models that avoid them. In this sense, the BB problem is a good thing; it helps us distinguish viable models from non-viable ones. As far as I can tell, this straightforward response was completely ignored by Craig. He just kept repeating that Boltzmann Brains were really bad things. He aimed this criticism particularly at the Carroll-Chen model, which I would say is very bad aim; it’s much less likely that BB’s are a problem in our scenario than in most other multiverse theories, since you actually produce baby universes (with potentially billions of observers) more frequently than you produce individual Boltzmann Brains. But I didn’t emphasize that point, since my goal wasn’t to defend that particular model.
As an aside, the Boltzmann Brain discussion illustrated a problem with the debate as a whole: it was too technical (and I think mostly on WLC’s side, although I deserved some of the blame). I had prepared a single slide about the topic of BB’s, but upon reflection I figured that many people wouldn’t be familiar with the term, so I replaced it with “observers as random fluctuations.” But Craig just plowed right into the technicalities, without trying to explain what the Boltzmann Brain problem really was. When my term came I gave a one-sentence definition, but in retrospect that wasn’t really sufficient, so on Saturday (where we both gave five-minute responses to a series of 40-minute talks by the four other speakers) I took a few minutes to give a more careful explanation. It’s probably an inherent flaw of the format; if a speaker takes a minute to do a bit of pedagogy rather than argumentation, the audience benefits but the speaker suffers. So the game theory tells you to be obscure, to the general detriment.
A couple of words about the rebuttal speeches in particular. Each of us pulled one “gotcha” move in the rebuttals; mine worked, his didn’t (in my opinion, of course). His referred to fine-tuning: he found a quote by me saying that the low entropy of the early universe seems finely-tuned. Which is true! But he claimed that I had said we didn’t know whether fine-tuning was real. That part is completely false. I had said we didn’t know that fine-tuning for life was real; indeed, the words “for life” were italicized on my slide. And it’s perfectly obvious that the fine-tuning of our initial entropy isn’t necessary for life; the entropy could have been fantastically larger than it actually was and life still could have arisen. (For example, you could imagine a universe with our Solar System as it essentially is, but otherwise in thermal equilibrium.)
On my part, I knew that WLC liked to glide from the BGV theorem (which says that classical spacetime description fails in the past) to the stronger statement that the universe probably had a beginning, even though the latter is not implied by the former. And his favorite weapon is to use quotes from Alex Vilenkin, one of the authors of the BGV theorem. So I talked to Alan Guth, and he was gracious enough to agree to let me take pictures of him holding up signs with his perspective: namely, that the universe probably didn’t have a beginning, and is very likely eternal. Now, why would an author of the BGV theorem say such a thing? For exactly the reasons I was giving all along: the theorem says nothing definitive about the real universe, it is only a constraint on the classical regime. What matters are models, not theorems, and different scientists will quite naturally have different opinions about which types of models are most likely to prove fruitful once we understand things better. In Vilenkin’s opinion, the best models (in terms of being well-defined and accounting for the data) are ones with a beginning. In Guth’s opinion, the best models are ones that are eternal. And they are welcome to disagree, because we don’t know the answer! Not knowing the answer is perfectly fine. What’s not fine is pretending that we do know the answer, and using that pretend-knowledge to draw premature theological conclusions. (Chatter on Twitter reveals theists scrambling to find previous examples of Guth saying the universe probably had a beginning. As far as I can tell Alan was there talking about inflation beginning, not the universe, which is completely different. But it doesn’t matter; good scientists, it turns out, will actually change their minds in response to thinking about things.)
I very much hope that I hammered these points home enough to help clarify issues in the minds of listeners/readers. But from Craig’s (lack of) reaction, and from the online discussion from his supporters, I doubt it will make any difference. He will continue to quote Vilenkin saying the universe probably had a beginning, which is fine because that’s what Vilenkin actually thinks. He will not start adding in the fact that Guth thinks the universe is probably eternal, nor will he take the even more respectable position of not relying on people’s individual opinions at all and simply admitting that we don’t have good scientific reasons to think one way or the other at the moment. But we’ll see. (And to reiterate: I think the whole discussion is enormously less important than the bigger point that a “cause” is completely unnecessary even if the universe did have a beginning.)
For my closing statement, I couldn’t think of many responses to Craig’s closing statement that wouldn’t have simply be me reiterating points from my first two speeches. So I took the opportunity to pull back a little and look at the bigger picture. Namely: we’re talking about “God and Cosmology,” but nobody really becomes a believer in God because it provides the best cosmology. They become theists for other reasons, and the cosmology comes later. That’s because religion is enormously more than theism. Most people become religious for other (non-epistemic) reasons: it provides meaning and purpose, or a sense of community, or a way to be in contact with something transcendent, or simply because it’s an important part of their culture. The problem is that theism, while not identical to religion, forms its basis, at least in most Western religions. So — maybe, I suggested, tentatively — that could change. I give theists a hard time for not accepting the implications of modern science, but I am also happy to give naturalists a hard time when they don’t appreciate the enormous task we face in answering all of the questions that we used to think were answered by God. We don’t have final answers to the deep questions of meaning and fulfillment and what it means to lead a good life. Religion doesn’t have the final answers, either; but maybe it has learned something interesting over the course of thousands of years of thinking about these issues. Maybe there is some wisdom to be mined from religious traditions, even for naturalists (which everyone should be).
More than once of the course of the weekend I spoke conciliatory-sounding words about how we’re really all in this together, theists and naturalists, trying to understand the deep questions in a confusing world. And I meant all of it, in complete sincerity. I will be absolutely uncompromising about what I think the truth is concerning questions of substance; but I don’t ever want to start thinking of people who disagree with me about those questions as my enemies. Many times in New Orleans, people on “the other side” came up after my presentations (in which I said that their most deeply held beliefs had been definitively refuted by the progress of modern science) and thanked me, saying how much they appreciated my ideas and that I had given them something to think about, even if they remained quite resolute in their beliefs. Not every single person was so gracious, but the vast majority. I admire those folks, and I hope I can be as sincere and open when people who I disagree with are speaking in good faith.
To me, Craig’s best moment of the weekend came at the very end, as part of the summary panel discussion. Earlier in the day, Tim Maudlin (who gave an great pro-naturalism talk, explaining that God’s existence wouldn’t have any moral consequences even if it were true) had grumped a little bit about the format. His point was that formal point-counterpoint debates aren’t really the way philosophy is done, which would be closer to a Socratic discussion where issues can be clarified and extended more efficiently. And I agree with that, as far as it goes. But Craig had a robust response, which I also agree with: yes, a debate like this isn’t how philosophy is done, but there are things worth doing other than philosophy, or even teaching philosophy. He said, candidly, that the advantage of the debate format is that it brings out audiences, who find a bit of give-and-take more exciting than a lecture or series of lectures. It’s hard to teach subtle and tricky concepts in such a format, but that’s always a hard thing to do; the point is that if you get the audience there in the first place, a good debater can at least plant a few new ideas in their heads, and hopefully inspire them to take the initiative and learn more on their own.
I completely agree. Events like this are valuable, not because they are efficient ways to find the truth, nor even because there is any reasonable chance of changing the minds of people who are relatively secure in their beliefs (on either side). It’s because there are a lot of people who are not secure in their beliefs, or at least are curious and willing to listen to a variety of ideas. If we think we have good ideas, we should do everything we can to bring them to as many people as possible. I think science and naturalism include some pretty awesome ideas, and I’m happy to share them with as many different people as I can.
p.s. Sorry I didn’t talk about Saturday’s talks, in which Tim Maudlin discussed the relationship between theism and morality (claiming there isn’t any), Alex Rosenberg drew connections between thermodynamics and natural selection to argue that theism is incompatible with Darwinism, Robin Collins argued that the discoverability of the universe is evidence for theism, and James Sinclair talked about notions of time and the origin of the universe. But I’m kind of all talked out on this topic for right now.
Or maybe simply because we are kind of wired in such a way that favor such beliefs… (Please don’t interpret this the wrong way. I’m not saying that it’s inevitable, nor that it’s the right way to be. I’m just saying that it might be a fact of the human condition…)
Also, I remember reading in The Self Illusion from Bruce Hood, that people who believe are generally speaking more happy. Just like people that think that a surgery will go fine have a 30% chance to have a better outcome (from the same book). Having “faith” in something may bring some chemical cocktail in one brain and body that makes this person feel happy and more healthy generally speaking…
Which bring me to the question I”m dying to ask. I’ve seen a movie called The Quantum Activist. I’m not a specialist in the matter, but I though that this interpretation of QM seems to me like a “reasonable” faith… One that doesn’t deny science and might never… But maybe I’m missing something… Anyone with proper background could comment on this?
(For the record, I only believe in science… I’m just curious about the vision presented in the movie.)
@Augustine
Not quite. I am rejecting your claim that physics and metaphysics should be considered independent domains of knowledge. I’m attributing the claim that all knowledge is dependent on “experience” to Lucretius, to gently imply you may be misinterpreting the intent of his dictum “ex nihilo nihil fit,” if you think its motivation is completely independent of empirical considerations.
As it happens I do consider it legitimate to use one extra-empirical criterion in forming reliable beliefs — Ockham’s razor, or a similar parsimony principle. But then, that consideration is used regularly in science, so it can’t be considered distinctly philosophical.
On your claims of extra-empirical knowledge: The existence of abstract objects is too controversial among philosophers to be considered reliable knowledge. Mathematical and logical truths are known from experience of the sort “if I assume these axioms I reach these conclusions.” (this type of proof checking exercise can be automated, if you prefer basing your mathematical truths on a physical experiments rather than psychological ones btw.) The axioms in both mathematics and logic are a matter of convention, so they only really count as anthropological knowledge, and whether the conventional system of axioms is consistent can ONLY be known through experience, per Godel. In any event, mathematical and logical truths may be asserted by scientists, qua scientists — as is quite self-evidently common practice in the writing of physics papers — so this does no good in staking out metaphysics as a legitimate and wholly independent domain of inquiry.
BTW, the rejection of a clear demarcation between physics and metaphysics of the sort you’re supposing isn’t even remotely unusual. Many modern philosophers, like Quine, have explicitly denied such a distinction — and I’ve seen little evidence that ancient or medieval philosophers regarded metaphysics and physics to be any more independent from one another than say, Astronomy and Geology. The only major groups of philosophers I know of that endorse such a strong distinction are those who would seek to deny any possibility of metaphysical knowledge at all, e.g. the logical positivists, and religious apologists, who want to shield their sacred doctrines from the same sort of rational scrutiny that speculation in other disciplines meets.
Great points.
Mason: “Firstly, exactly what kind of non-methodological naturalism “science” would you propose?”
None. It is perfectly appropriate for science to operate according to methodological naturalism, but that also renders science incapable of pronouncing on fundamentally metaphysical issues (i.e., issues which are “beyond” physics and nature).
Mason: “There is currently no interpretation of any model in cosmology which reads as “a universe popping into existence uncaused out of nothing.””
Right, they tend to say either that the universe is past-eternal or not past-eternal–as is appropriate, since speculating on the cause behind those which began to exist would be a metaphysical question outside their wheelhouse.
Mason: “I think the problem here is that apologists are trying to read certain philosophical doctrines into the physical models provided by scientists.”
I disagree. Craig, at least, is using the results of science as one way to support one premise in the Kalam (the universe began to exist). (He also uses purely philosophical arguments to support this premise, namely the impossibility of an actual infinite). The physics is subsidiary to the philosophical argument here, not the other way around.
Mason: “So physics can only support your theories, but never counteract them?”
Not at all, that’s why I said physics can provide support for or evidence against the second premise of the Kalam (e.g., if the preponderance of the scientific evidence showed that the universe did not begin to exist, that would weaken the second premise).
Mason: “Why should we assume this doctrine applies to the creation of the universe when our current physics suggests that such descriptions of the origins is misleading?”
If physics can demonstrate that “being can come from non-being” then I will agree with you. But since that is a metaphysical statement beyond the resources of physics to demonstrate, we should probably continue to agree to disagree, as you said. Thanks for the dialogue!
@Mason: Using the word “mystery” was a little poetic license implying that naturalists have no viable explanation for the transition from inanimate to life. I know this is an old quote, but it is from a respected Nobel laureate, George Wald:
One has only to contemplate the magnitude of this task to concede that the spontaneous generation of a living organism is impossible. Yet here we are — as a result, I believe, of spontaneous generation.
I admire his “faith”.
As Dr. Wald observed, when you do the math on the formation of DNA (the language of DNA—who “wrote” that?) and everything necessary to create a living cell, you get a 1 chance in 1 with a whole lot of zeroes after it. I mean a LOT of zeroes.
You state that the fact that there exists no naturalist solution does not automatically imply God—ok fair point, but what other options are available? Aliens? Where did they come from? Mathematically, there would have to be some sort of weight factor that drastically skews these probabilities toward the formation of life and the continued development/improvement of living organisms. Archeological evidence shows that the 33 or so Phylum classes all dramatically came on the scene in the Cambrian explosion which proves that Darwin was oh so wrong—like not even nuclear bomb level close.
Thus my choice of the poetic word, “mystery” for the naturalist point of view. The deduction of “God did it” is certainly not an absolute conclusion for all of this, but given Dr. Craig’s arguments, these brief origin of life arguments, the Biblical testimony of the Jewish people, the amazing teaching, healings, death and resurrection of Jesus, and my personal experience have led me to the conclusion that, “In the beginning, God created the heavens and the earth.”
Have a blessed evening!
Ray: “Not quite. I am rejecting your claim that physics and metaphysics should be considered independent domains of knowledge. I’m attributing the claim that all knowledge is dependent on “experience” to Lucretius, to gently imply you may be misinterpreting the intent of his dictum “ex nihilo nihil fit,” if you think its motivation is completely independent of empirical considerations.
As it happens I do consider it legitimate to use one extra-empirical criterion in forming reliable beliefs — Ockham’s razor, or a similar parsimony principle. But then, that consideration is used regularly in science, so it can’t be considered distinctly philosophical.”
Well, I agree that if your epistemology is purely empirical (with the exception of Ockham’s razor), then metaphysics collapses into physics, since physics is based upon the empirical. But then it is a debate in epistemology, which is a philosophical debate–as is appropriate, since it the philosophical field on which these ultimate matters should be discussed.
However, as with Mason, I doubt we will agree on that–but thanks for the informative discussion!
@Augustine1938
You’re equivocating. Krauss’s nothing is not a philosopher’s nothing of absolute nothingness. Krauss’s nothing has natural properties. But if you want “nothing” to mean Krauss’s nothing, then there’s no problem for a naturalistic origin, as he and others have explained.
But if you do want the philosopher’s nothing then there’s no good reason to think there was ever such a state. And metaphysical intuition (as all metaphysical noodling is) would say that it’s very unlikely there was ever such a state. Even the nothing of the theist has God lurking around there somewhere.
Kalam fails on this very point alone, that absolute nothingness is unfounded and that a universe naturalistically beginning from a physicist’s nothing is plausible.
There is no meaningful distinction between “necessity of own nature” and “brute fact” in effect. And again, there is no good reason to think that the universe or any reality at all couldn’t have just always existed. It’s special pleading to assert that only the theist’s god could be a brute or necessary fact.
Augustine1938,
“None. It is perfectly appropriate for science to operate according to methodological naturalism, but that also renders science incapable of pronouncing on fundamentally metaphysical issues (i.e., issues which are “beyond” physics and nature).”
I tend to agree more with Ray above. The lines between strict-philosophy and strict-physics are not always very sharp. Nonetheless, I am glad that you at least recognize that methodological naturalism isn’t some “curse” in science that needs removed.
“Right, they tend to say either that the universe is past-eternal or not past-eternal–as is appropriate, since speculating on the cause behind those which began to exist would be a metaphysical question outside their wheelhouse.”
I’m not sure I understand why- even if talk of causality could be understood in the context of a pre-universe scenario, all talk of those causes must necessarily by strictly metaphysical. But I suppose it will probably depend on what is meant by the word “universe.” (I for one dislike the defintion of “universe” as “all of physical reality.”).
“I disagree. Craig, at least, is using the results of science as one way to support one premise in the Kalam (the universe began to exist). (He also uses purely philosophical arguments to support this premise, namely the impossibility of an actual infinite). The physics is subsidiary to the philosophical argument here, not the other way around.”
Firstly, I dispute the idea that Dr.Craig is using the results of science to support his premises. I would say that Dr.Craig is using his interpretations of curent results from science to support his premises. As I think comments by physicists like Sean Carroll reveal- his interpretation of say, the BGV theorem, is incrorrect. Secondly, it seems to me the physics, even when it does not directly falsify philosophical doctrines, at the very least clearly suggests these are misleading conceptualizations that do not necessarily apply.
I think this may be the main difference between us on his point. I would say that our philosophical doctrines should follow from the scientific evidence- and if science does not support or suggest some doctrine is accurate at some level- we ought to reject it or accept limitations on it. Craig, among others, seem to suggest that despite the results from the scientific evidence, these philosophical doctrines should remain accepted and applied universally. I would strongly disagree, but I suppose that is why I idenify more with empiricism.
“Not at all, that’s why I said physics can provide support for or evidence against the second premise of the Kalam…”
Well certainly with respect to this premise, I agree. My point was, I was not following you as to why the physics was irrelevant with respect to say- big bang cosmology and “ex nihilo, nihil fit.” The best physical model of BB theory do not suggest the universe popped into existence ex nihilo, so why can we not say here that the physics suggests ex nihilo nihil fit is unappliciable?
“If physics can demonstrate that “being can come from non-being” then I will agree with you. But since that is a metaphysical statement beyond the resources of physics to demonstrate….”
Here I think it might be best to clarify some distinctions here. I would argue that, at least in this context- the scientific evidence can be used to do two things:
1. Provide evidence in support of, or against the truth of some empirical claims.
2. Provide us with an understanding of how some process, event or mechanism works.
Now, given (2), I would say that even if physics cannot reject metaphysical claims, physics nonetheless can suggest whether or not those metaphysical claims do or do not fit with our current scientific understanding. I suggest that if doctrine like ex nihilo nihil fit do not fit with our current understanding of fundamental physics- then any talk of creation ex nihilo with respect to say big bang cosmology will be misleading and does not apply.
Perhaps Kalam can make a compelling philosophical argument for theism given it’s premises- but since it is not clear that creation ex nihilo applies to this universe or any big bang scenario- I would suggest that it’s not an argument that is really supported by empirical science within this universe.
I hope that clear up the points I am trying to make here. Great discussion though!
Cheers!
Craig needs to retire BGV after this. If he keeps using it, it would be exceedingly poor form. The authors disagree with him about the implications. Guth says it’s not conclusive for a beginning. And Vilenkin doesn’t think a beginning is a problem for a naturalistic origin. He’s an atheist and has is own solution for a beginning involving quantum tunneling.
Sean, thanks for the additional comments. I would say it boils down to two issues:
1. there are no knowledgeable bases for the hypothesis of God, so it can just be rationally ignored until a miracle happens (unless you prefer a folk definition of belief as “anything goes”); and
2. causation may well exist without original creation.
But I don’t think you quite grasp how causation applies without original creation – which means matter cannot be created and destroyed, and gravitational and electromagnetic masses are preserved.
Being causal and effected are dual properties of every state of momentum. Obviously momentum causes others to move, and the mover is likewise effected by the moved. They resolve fundamentally for electromagnetism as orbitals (intact), and gravitation as solar systems (intact from a supernova cloud rotation) .
Each particle and field can be precisely measured for its capacity both to cause and to be effected, and these alternative are already enshrined in every law of physics for equal and opposite (reciprocal) exchange to reconciliations around pivots. QED
You don’t have to reinvent to wheel to completely secure physics with cause and effect running entirely through it. They can be, in that form, and intact system of exchange or “equilibrium” not only as atoms and solar systems, but as supernovae and potentially also in compression at a Big Bang.
These properties are permanent, and balanced, so that something intact need not be created. The relationship between a capacity to shift something else and to be shifted is dynamic. An intact state can “spilt apart” by constituent masses with properties to shift and be shifted. Revise your thinking entirely, as this formalism is strict and fully applicable to all masses.
This has been bugging me since watching the event, and I haven’t seen it addressed yet. In the closing panel, an audience member asked WLC whether God would be unnecessary if the universe didn’t have a beginning. WLC replied, no, but it would be a different argument for God’s existence (I forget which specific argument). What?! Doesn’t this refute his entire thesis, namely that theism is more likely given the evidence that the universe had a beginning? Unless he doesn’t think the other argument is valid, but then why bring it up at all.
I should have simplified it for you: all inertia in the universe is cause, and to the extent that inertia affects the inertia of others, there are effects, and they find balance using rotations or in compressions (supernovae & Big Bang).
BTW very good Ray, mostly correct 🙂
BA Brightlight,
“Using the word “mystery” was a little poetic license implying that naturalists have no viable explanation for the transition from inanimate to life. ”
On the claim that naturalists have “no viable explanation”- this is clearly false. Naturalists (or rather, scientists in general – regardless of their theological views) have partial explanations for some aspects of abiogenesis with plenty of questions remaining.
“One has only to contemplate the magnitude of this task to concede that the spontaneous generation of a living organism is impossible. Yet here we are — as a result, I believe, of spontaneous generation. I admire his “faith”.”
Nobody in the current literature that I’ve read- regardless if they are evolutionary biologists, molecular biologists, chemists, geologists, etc.- refers to origin of life theories as “spontaenous generation” any more. That is because there are no practicing biologists or chemists I know of you take seriously the idea that the origin of life occurred in a single step by purely chance occurrences.
“math on the formation of DNA (the language of DNA—who “wrote” that?) and everything necessary to create a living cell, you get a 1 chance in 1 with a whole lot of zeroes after it. I mean a LOT of zeroes.”
Firstly, again you completely undercut your ability to make reference to this claim but your claim that the origin of life is “mysterious” with “no viable explanations.” The best you could say (if that were true, which it is not) is that given our CURRENT understanding of origin of DNA, it SEEMS mathematically improbable.” That however is again, very different (and indeed a tremendous leap) from saying that it is a fact that the formation of DNA is mathematically improbable.
Secondly, the current theories behind abiogenesis strongly support an RNA-world, in which RNA was the genetic precursor to DNA. RNA is less complex (it is single-stranded) than DNA molecules and thus all talk about how to assemble DNA randomly is simply not keeping up with the current literature.
Thirdly, there is no “language” in DNA. See this talkorigins article for a good summary of some basis reasons why this analogy fails:
http://www.talkorigins.org/indexcc/CB/CB180.html
Fourthly, this argument misses the objection I raised with respect to Neil Manson. The argument is asking: what is the probability that some very specific result will occur, given all the space of possibilities? It is not at all surprising that you obtain an answer or low probability. The better question to ask is “what is the probability that something like x will occur?”
BA Brightlight,
“Archeological evidence shows that the 33 or so Phylum classes all dramatically came on the scene in the Cambrian explosion which proves that Darwin was oh so wrong—like not even nuclear bomb level close.”
The fact that departments of paleontology dedicated to researching evolutionary biology are not shutting down their graduate programs or their universities have refused to fund (apparently fruitless) research strikes me as strong prima facie evidence that this claim is complete nonsense. And the fact that these arguments have been raised by non-experts strikes me as an additional point of concern.
Nonetheless, this is a massive claim that requires a lot of discussion that I have not the time to reproduce here. Instead I suggest you research this topic by looking at the scientific literature.
“Thus my choice of the poetic word, “mystery” for the naturalist point of view.”
See my analogy above about the futility of poking holes in defense of a worldview.
Cheers!
Hi Sean,
Thanks very much for your kind words about my paper, “The Generalized Second Law implies a Quantum Singularity Theorem” which Craig cited during the debate. I feel however that I must register a correction. You write:
But my article does not stay fully in the classical regime (hence the word “quantum” in the title). It is possible to make sense of the Generalized Second Law at least in the semiclassical context, by which I mean something like QFT in curved spacetime, plus a small backreaction to the metric due to the stress-energy tensor of the quantum matter. This is not really a “classical” regime (for example, all local energy conditions are necessarily violated). So I think that in any case I’ve extended the Penrose singularity theorem to a more “quantum” context, quite aside from my speculative remarks that it may also apply in full-blown quantum gravity.
By the way, Craig found my article before the debate and emailed me asking some questions about it. (He didn’t know until I told him that I am also a Christian.) I tried to give him some guidance about the relevant physics, although I take no responsibility for the final result. It’s tricky to explain some of the nuances to an outsider, although I think Craig probably deserves some credit for having a better understanding of the relevant physics than most philosophers ever get to.
Craig’s comment about the universe having a “thermodynamic beginning” at the moment of lowest entropy was taken from the discussion section of my paper, by the way, where I said:
I guess you could regard that parenthetical comment as an open invitation for philosophers to attempt to construct Cosmological Arguments, if they can… although of course, that wasn’t my main motivation in writing the paper!
Aron– Thanks. I take your point, although I think we’re both right. Semiclassical gravity is usually taken to mean “classical spacetime with quantum fields on top.” My adjective “classical” modified “spacetime,” rather than the whole theory, so when I was originally writing the post I thought that was the most accurate description. I’ll expand on that a bit in the post and link down here. Although I still don’t believe there will be an analogous result in quantum gravity, at least not one that would imply that time would “end”; the QET (which is basically just linearity of the Schrödinger equation) would seem to forbid that.
The philosophical/scientific debate about the origins of everything will go on. More to the point is the claims of Christians that some divine entity is concerned with whether or not you believe in him. Hitchens performed poorly in his debate with Craig but here was the most telling point:
HITCHENS: So you believe that Jesus of Nazareth caused devils to leave the body of a madman and go into a flock of pigs that hurled themselves down the Gadarene slopes into the sea?
CRAIG: Do I believe that’s historical? Yes.
This kind of nonsense is what Craig, Platinga and the rest really believe. All those philosophical gymnastics are attempts to shore up something deeply silly.
Dr. Carroll,
I want to thank you again for all of the thought-provoking material you produced over the two days of the conference. I say “again” because I was fortunate enough to have the opportunity to thank you in person on Saturday after the conference had concluded. You might remember me; I was the really conspicuously good-looking guy who, during the Q & A on Friday and Saturday, asked you about (1) an eternal set of necessary and sufficient mechanical conditions producing a universe containing a first moment of time, and (2) the specifics of Alan Guth’s affirmation of the probable eternality of the universe, respectively. Alright, alright, I may have exaggerated the part about my good-looks a little, but in all seriousness you might possibly remember the questions. Nevertheless, it was a real privilege to shake your hand and I thoroughly enjoyed hearing your take on these interesting issues. Having familiarized myself with some of your published work, I’m well aware that you are skilled writer. But having never seen you lecture or debate, I had no idea that you would prove to be such a wonderful public speaker and formidable debater. I look forward to more of it in the future.
While I’m sure that you have entirely too much on your plate to respond to every reply on your blog, nevertheless I would owe you a great debt of gratitude if you’re able to somehow find the time to respond to this one; that is, provided it’s substantive enough to warrant a response.
In light of a recent post, you seemed to have cleared up what led to a persistent confusion for some during the debate: namely, your maintaining that a universe with a “first moment of time” isn’t necessarily one that “begins to exist.” It seems to me that you are able to consistently hold to this view because you ascribe to a tenseless or, B-Theory, of time. That is what I suspected. So if I understand you correctly, are you saying that a universe with a first moment of time doesn’t “begin to exist” because, on the B-Theory, the entire universe exists *timelessly* for all eternity as a static, 4-dimensional block? If so, is it not perfectly legitimate to inquire as to what determines that this particular statically-existing universe obtains, rather than some other one or none at all? Also, would you agree that the A-Theory of time is the much more common sense view?
Moreover, there appears to be a few points in your post-debate reflections that might be cause for reflection. First, regarding your denial of both the premises in the Kalam Cosmological Argument (KCA), you said,
“My attitude toward the above two premises is that (2) is completely uncertain, while the “obvious” one (1) is flat-out false. Or not even false, as I put it, because the notion of a “cause” isn’t part of an appropriate vocabulary to use for discussing fundamental physics.”
As WLC has repeatedly emphasized, he does not claim anything near “certainty” for the truth of these premises. Rather, he merely defends the notion that they are more plausibly true than their negations; the greater the degree to which they are more plausibly true than not, the stronger the argument becomes. So while I agree that we don’t have certainty with respect to the truth of premise (2), I do believe that we have good reason to believe that it is much more plausibly than not; which is what a good argument entails.
With respect to the notion of a “cause,” I would have to disagree with your thinking this isn’t the appropriate vocabulary to use here. The univocal meaning employed in KCA is “that which produces the effect.” Thus, if we were to ask, “What is the ’cause’ of virtual particles?”, we would be asking, “What ‘produces’ virtual particles?”, with the answer to which — quantum fluctuations in the vacuum — being completely legitimate. Similarly we could ask, “What is the ’cause’ of the binding of like-charged nucleons in the atomic nucleus?”; and someone would answer “The strong force is what produces that effect.” So it seems to me that a clear definition of terms makes appropriate the use of a “cause.”
With that being said, when you say that, “The Hartle-Hawking “no-boundary proposal” for the wave function of the universe, for example, is completely self-contained, not requiring any external cause,” in what sense do you mean, “self-contained?” It was pointed out in [http://arxiv.org/abs/astro-ph/9712344] that,
“The problem with this model is that it ignores the “zero-point-energy”. . . . Thus, when the “zero-point-energy” is considered, we see that the initial state is not a point but a tiny oscillating (0 ≤ a ≤ a1) Big Bang universe, that oscillates between Big Bangs and Big Crunches (though the singularities at the Big Bangs and Big Crunches might be smeared by quantum effects). This is the initial classical state from which the tunneling occurs. It is metastable, so this oscillating universe could not have existed forever: after a finite half-life, it is likely to decay.”
Therefore it seems to me that on this model the universe has only existed for a finite duration of time. So we could still validly inquire as to what produced it (Or, given the more radical B-Theory of time, what determined that this universe tenselessly exists rather than some other). Moreover, why think that this model shouldn’t be treated as nonrealist in character? How does changing from a Lorentzian metric signature to a Euclidean metric imply an ontological commitment? Given the fact that the Wick rotation performed takes the real time variable “T” and replaces it with the imaginary quantity “I × T”, Hartle and Hawking are said to employ “imaginary time” in their model. So how does one intelligibly give a realistic interpretation to any value of “imaginary time?”
You later go on to state the following:
“The second premise of the Kalam argument is that the universe began to exist. Which may even be true! But we certainly don’t know, or even have strong reasons to think one way or the other. Craig thinks we do have a strong reason, the Borde-Guth-Vilenkin theorem. So I explained what every physicist who has thought about the issue understands: that the real world is governed by quantum mechanics, and the BGV theorem assumes a classical spacetime, so it says nothing definitive about what actually happens in the universe; it is only a guideline to when our classical description breaks down.”
It goes without saying that I would never claim to be any kind of subject matter expert on cosmology, especially more of one than you certainly are. But in my amateur opinion, I think it’s fair to say that last statement downplays the significance of BVG and, as far as I can tell, is false. While I agree that we can’t infer anything “definitive,” I think we can, however, make some significant inferences: given the fact that we have *substantial* evidence that our universe satisfies the only condition of BVG — Hav > 0 — all the way back until 10^-43 seconds, then according to [http://arxiv.org/abs/gr-qc/0110012],
“Whatever the possibilities for the boundary, it is clear that unless the averaged expansion condition can somehow be avoided for all past-directed geodesics, inflation alone is not sufficient to provide a complete description of the Universe, and some new physics is necessary in order to determine the correct conditions at the boundary [20]. This is the chief result of our paper. The result depends on just one assumption: the Hubble parameter H has a positive value when averaged over the affine parameter of a past-directed null or noncomoving timelike geodesic.
“The class of cosmologies satisfying this assumption is
not limited to inflating universes.”
Vilenkin reiterates:
“A remarkable thing about this theorem is its sweeping generality. We made no assumptions about the material content of the universe. 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, no matter how small. This assumption should certainly be satisfied in the inflating false vacuum. The conclusion is that past-eternal inflation without a beginning is impossible.” [Vilenkin, Many Worlds in One, p. 175]
Thus, we have very good reason to think that unless the Planck epoch can avoid Hav > 0, our universe cannot be past-eternal. One possible way for this to happen is via an “emergent universe” scenario. In discussing a model of this type, you mentioned a paper by Anthony Aguirre and John Kehayias; one that WLC cited in the debate:
“They examined the “emergent universe” scenario of George Ellis and Roy Maartens, in which the universe is in a quasi-static pre-Big-Bang state infinitely far into the past. Aguirre and Kehayias showed that such behavior is unstable; you can’t last in a quasi-static state for half of eternity and then start evolving. Personally, I didn’t think this was worth talking about; I completely agree that it’s unstable, I never promoted or defended that particular model, and I just didn’t see the relevance. But he kept bringing it up. Only after the debate did it dawn on me that he takes the specific behavior of that model as representative of any model that has a quantum-gravity regime (the easiest way out of the “beginning” supposedly predicted by the BGV theorem). That’s completely false. Most models with a quantum-gravity phase are nothing like the emergent universe; typically the quantum part of the evolution is temporary, and is surrounded on both sides by classical spacetime. But that’s so false that I didn’t even pick up that WLC was presuming it, so I never responded. Bad debater.”
According to that paper [http://arxiv.org/abs/1306.3232],
“We stress that we have analyzed only one version of the Emergent Universe, with a simplified model. Nonetheless, we believe that the effect that this analysis points to may be rather generic. For example, consider alternative theories of gravity. The Emergent Universe has been studied extensively in theories such as Hoˇrava-Lifshitz, f(R), Loop Quantum Gravity7, and others (see, for in- stance, [8–11], respectively). There have also been several studies of the stability of the Einstein static universe in alternative theories (see [12], for example). However, in our framework we have, in a sense, decoupled gravity – it enters only when assessing the affect of the spreading wave-functional. Even in alternative theories in which the Einstein static universe is more stable than in standard General Relativity, we anticipate that once the wavefunctional has spread enough, the geometry must follow, and the spacetime becomes classically ill-defined as well as containing portions corresponding to singularities. Therefore, this seems like a generic (and perhaps expected, given our construction of the scenario) problem with such an eternal and precisely tuned inflationary scheme. . . .”
“. . . Models in which the field dynamics and material content are very different would require separate analysis, but may lead to a similar basic conclusion. For example, Graham et al. [14] construct static and oscillating universes with a specific non-perfect-fluid energy component that are stable against small perturbations. However, Mithani & Vilenkin [15] have shown that this model is unstable to decay via tunneling.
“Although we have analyzed only one version of the Emergent Universe, we would argue that our analysis is pointing to a more general problem: it is very difficult to devise a system – especially a quantum one – that does nothing “forever,” then evolves. A truly stationary or periodic quantum state, which would last forever, would never evolve, whereas one with any instability will not endure for an indefinite time.”
Unless I’m missing something, this paper seems to strongly support WLC’s contention: quantum instability seems to prevent *any* scenario — regardless of if it’s an unstable state (ESS) or a metastable state (LQG) — from being past-eternal. Moreover, this notion appears to be reinforced here [http://arxiv.org/abs/arXiv:1305.3836] as well:
“A number of authors emphasized that the beginning of inflation does not have to be the beginning of the universe. The ‘emergent universe’ scenario [11–15] assumes that the universe approaches a static or oscillating regime in the asymptotic past. In this case, the average expansion rate is Hav = 0, so the condition (1) is violated. The problem with this scenario is that static or oscillating universes are generally unstable with respect to quantum collapse and therefore could not have survived for an infinite time before the onset of inflation [16–18].”
I’m just not following you here; what would lead you to say that this belief of WLC is “completely false?”
With respect to a model that posits a different scenario, you said,
“In contrast, I wanted to talk about a model developed by Anthony Aguirre and Stephen Gratton. They have a very simple and physically transparent model that (unlike my theory with Chen) imposes a low-entropy boundary condition at a mid-universe “bounce.” It’s a straightforward example of a perfectly well-defined theory that is clearly eternal, one that doesn’t have a beginning, and does so without invoking any hand-waving about quantum gravity. I challenged Craig to explain why this wasn’t a sensible example of an eternal universe, one that was in perfect accord with the BGV theorem, but he didn’t respond. It wasn’t until the talks on the following day that Craig’s teammate James Sinclair admitted that it seemed like a perfectly good model to him.”
Vilenkin also addressed this model in the last paper I mentioned, and noted:
“Even though the spacetime has no boundary in the AG model, it does include a hyper-surface on which the low-entropy (vacuum) boundary condition must be enforced by some mechanism. This surface of minimum entropy plays the role of the beginning of the universe in this scenario. . . .”
“. . .Suppose the vacuum that fills this de Sitter space is a metastable (false) vacuum and that it can decay to one or more lower-energy vacua through bubble nucleation. Suppose further that we impose a boundary condition that the entire universe is in a false vacuum state in the asymptotic past, τ → −∞. Then bubbles nucleating at τ → −∞ will fill the space, the energy in the bubble walls will thermalize, and the universe will contract to a big crunch and will never get to the bounce and to the expanding phase.”
Even if one ignores the questionable reversal of the AOT, this model, according to Vilenkin, it cannot plausibly be past-eternal.
Nevertheless, this post is beyond lengthy already so I’ll stop here, despite my remaining questions. As I said, thanks again for such a civil, competitive debate and I appreciate your taking the time to entertain my questions.
Sean,
Thanks for your response, and for your link from the article.
Regarding the QET, to my mind the most conservative belief about quantum gravity is that it is—like GR—governed by a Hamiltonian constraint rather than an ordinary Hamiltonian (as in standard QM). In this setup, it’s not obvious that the QET applies.
What’s more, since there is no “absolute time” in GR, there are lots of different, inequivalent ways to evolve space forwards in time. As Wheeler put it, time is many fingered. This concept of time evolution will be much more subtle to quantize, and it’s far from obvious (to me, at any rate) that it’s forbidden for time to begin or end. In any case, this is quantum gravity, so none of us really know what we’re talking about!
@Jack Spell, that was a lot of words to show you miss the point that if the universe definitely had a beginning, it’s not a refutation of naturalism as there are naturalistic models with a beginning, which then defeats Kalam. At best the conclusion could be “maybe there was a divine cause.”
And of course that conclusion would also be true if it were known that there was no beginning. As Sean explained well, theism is poorly defined and could account for any observation. It has zero explanatory power.
Aron– That’s certainly a respectable point of view. It’s basically choosing the option that the energy is zero, which is definitely a possibility. And if that does turn out to be the case, time can certainly “end,” but in a very funny sense, since “time” was only emergent to begin with.
But the other option, that the energy is not zero and the ordinary time-dependent Schrödinger equation applies, is at the very least equally reasonable (perhaps more so). Our best-understood example of quantum gravity is the AdS/CFT correspondence, where the theory is most carefully defined in terms of the Hamiltonian of the boundary theory — in which perfectly conventional Schrödinger evolution applies. My suspicion is that quantum gravity will work similarly in other cases as well. But as you say, it’s quantum gravity, so we’re allowed to speculate but not allowed to act like we know the answer.
Sean & Aron, I will try to buy in to your exchanges as an observer trying to learn something. The adjustments you make to preserve observations shift the structure of reality this way and that with ease. But is it so easy just to adjust G.R. or put a Q.M mechanisms here and there within expanding Spacetime? The way you adjust looks seismic and structural, definitely not inconsequential, and quite frankly the field of physics needs new formalisms. As a lay reader with several other degrees it is so contradictory across different versions of reality as to be “bogged down”. I don’t think these are trifling differences in views between physicists about the fundamentals. It one sense its good to question, but that is a striking level of instability.
I may not get traction with this point but it is secure and needs to be stated unless refuted. Cause and effect are equal and opposite capacities of every particle and field. It’s as simple as that. You need to use the most fundamental capacities of mass with a strict division between them. I write about the full structure to that formalism in my free book (click my name) and they are easy to understand.
Gravitation is a state of causal inertial (spatial-temporal) extension. Basic. It is also a state of effected inertial compression when those states of extension attract each other and compress. You divide gravitational mass between extension and compression as alternative directions of motion, and the resolution is automatic – mass extends and compresses as dual, equal, properties. There is “equivalence” between them in interactions between masses with those dual capacities, enshrined within the laws of gravitation itself.
Unfortunately, at this late stage of physics’ journey, correcting your formalisms is a heavy task. It’s basically a “penny drop” point that you either grasp the value of intellectually, or not. Physics can be easily and sensibly rewritten, but you will need to take the short journey I set out in my free book, as time and patience does not permit anything other than the above sampler about gravitation.
Sean,
I missed the exchanges on Boltzmann Brains, but I don’t understand how this would help theism anyway since a BB would be a naturalistic phenomenon. How exactly is Craig using it to support theism?
Lucy– He was just claiming that the BB problem rendered the multiverse nonviable, and therefore naturalists have no mechanism for explaining fine-tuning. Not true, for the reasons mentioned above.