Thoughts on the Carroll-Craig Debate

Recently, Sean Carroll (cosmologist and atheist, whom I have met a couple times at physics events) and St. William Lane Craig (philosopher and Christian apologist) had a debate about this topic:

"God and Cosmology: The Existence of God in Light of Contemporary Cosmology."

TranscriptVideoCarroll's post-debate reflections, Craig's: One Two Three

(Warning: when the debate transcript says something like 10500, it really means 10^{500}.  Apparently whoever (or whatever) transcribed it doesn't understand scientific notation.)

Several readers have asked me to comment on this debate, and I plan to write more than one post doing so.

Let me just say first that I am not particularly interested in the question of who "won" this debate (between two people whom I both respect).  The existence of God does not, of course, depend on any particular person's ability to effectively argue for (or against) him.  I'd rather just make some opportunistic comments based on what the participants said.  What limited comments I have about the debate as a debate I will try to confine to this post.

William Lane Craig is a skilled debater who has done his best to keep abreast of Modern Cosmology.  This is commendable, but it was inevitable that his depth of knowledge in Cosmology was not as great as Carroll, who works on this subject professionally.  And often it showed.  That is why Craig had to rely mainly on a lot of quotes from famous physicists such as Alex Vilenkin—and sometimes this backfired, as in the case of Alan Guth, who apparently believes that the universe is eternal.

Since the topic was limited to Cosmology, Craig was unable to bring in any other types of evidence for the existence of God, besides those related to the Cosmological or Fine-Tuning Arguments.  In other debates, Craig has focused more on the evidence for miracles (such as the Resurrection of Jesus), which personally for me is much stronger evidence for the existence of God than anything coming from Cosmology.  For me, if Modern Cosmology is sufficient to get people to even wonder, "Is there maybe somebody who did that?" that's enough to start with—so long as it makes them curious enough to start exploring other lines of evidence, based on History or personal experience.

In other words, it's not necessary for Cosmology by itself to get people to a belief in God.   What matters is the cumulative case from Cosmology plus everything else.  If there are puzzling things such as fine-tuning which might be explained by God, and might have a different explanation (e.g. the multiverse), to me the most natural response seems to be to keep an open mind about all possible explanations.  But that would imply, that at least the existence of God is not absurdly unlikely (so far as Cosmology is concerned).  And if a person gets that far, then when they examine historical evidence or religious experiences, at least they won't do so with a giant presupposition in favor of Naturalism that requires them to explain away practically anything.

Assuming they are rationally consistent, that is.  Most people, if you try to argue for some proposition X that they don't want to believe in, will ask only whether the argument is so compelling as to force them to believe in it.  If not—if they can think of any possible way to defeat or evade the argument—they will act as though the argument has no force at all.  They are like the fearsome Barghest of legend, a monstrous black dog which can only be killed with a single blow.  If you do not strike hard enough to kill, then all of the damage is transferred from it to you.  (At least, that's how it works in Pendragon, the Arthurian Roleplaying System.)  With such people, if they can find any clever loophole in your argument—even if it involves totally speculative new physics—the next day they will say that the argument was refuted and provides no evidence for X at all.  This makes it impossible to make a cumulative case argument.

Anyways, I thought Craig did a pretty good job of sticking to the restricted topic of Cosmology.  Carroll somewhat less so, when he said:

If theism were really true there’s no reason for God to be hard to find. He should be perfectly obvious whereas in naturalism you might expect people to believe in God but the evidence to be thin on the ground. Under theism you’d expect that religious beliefs should be universal. There’s no reason for God to give special messages to this or that primitive tribe thousands of years ago. Why not give it to anyone? Whereas under naturalism you’d expect different religious beliefs inconsistent with each other to grow up under different local conditions. Under theism you’d expect religious doctrines to last a long time in a stable way. Under naturalism you’d expect them to adapt to social conditions. Under theism you’d expect the moral teachings of religion to be transcendent, progressive, sexism is wrong, slavery is wrong. Under naturalism you’d expect they reflect, once again, local mores, sometimes good rules, sometimes not so good. You’d expect the sacred texts, under theism, to give us interesting information. Tell us about the germ theory of disease. Tell us to wash our hands before we have dinner. Under naturalism you’d expect the sacred texts to be a mishmash—some really good parts, some poetic parts, and some boring parts and mythological parts.

[As an aside, there's something a bit funny here.  Carroll thinks that God should have provided us with some scientific information in the Bible.  The most useful scientific fact he can think of is the importance of good hygiene.  And it is a fact that the most famously boring book of the Bible, the book of Leviticus, is chalk full of hygiene rules about cleanliness (embedded among other religious rituals).  Fairly decent rules too, given the 2nd millennium BC context.  No germ theory of disease, I admit.  But highly practical nonetheless.  Now, I'm not a religious fundamentalist who thinks that the Bible is a Science textbook.  Nor am I an antireligious fundamentalist who thinks it ought to have been a Science textbook.  But I do think it is ironic that the particular thing Carroll demands is, in some sense, present in the least-loved book of the Bible!  Carroll continues:]

Under theism you’d expect biological forms to be designed, under naturalism they would derive from the twists and turns of evolutionary history. Under theism, minds should be independent of bodies.  Under naturalism, your personality should change if you’re injured, tired, or you haven’t had your cup of coffee yet.

[Huh?  Theism is the belief that God exists.  It does not commit one to any particular view about the soul's relationship to the body.  The fact that our personalities are encoded in our brains is logically independent to the question of whether God exists.  Particular religious traditions might have particular views about the soul, but that's not what we're talking about here.]

Under theism, you’d expect that maybe you can explain the problem of evil – God wants us to have free will. But there shouldn’t be random suffering in the universe. Life should be essentially just. At the end of the day with theism you basically expect the universe to be perfect. Under naturalism, it should be kind of a mess—this is very strong empirical evidence.

This, however, strayed from the parameters of the debate topic.  Whatever the merits of the Argument from Evil, it cannot be said that Evil is a discovery of Science.   It has nothing to do with Cosmology.  It is not a discovery of contemporary physics that there is random suffering, and that the universe isn't fair.  (What would a scientific theory of "Justice" even look like?)  Granted, the Argument from Evil is relevant to the cumulative case concerning God's existence (some of my own thoughts about that are here.)  But then Craig would also be entitled to throw in historical data about Jesus and anything else that might be relevant to the inquiry.

Naturally Craig called him on it:

He is very concerned to show that God’s existence is improbable relative to certain non-cosmological data. For example, the problem of evil, our insignificant size, and so forth. The very fact that these are non-cosmological data shows that they are not relevant in tonight’s debate. I have addressed things like the problem of evil extensively, for example, in Philosophical Foundations for a Christian Worldview.  So the debate tonight is not over the probability of theism versus naturalism. That would require us to assess all sorts of non-cosmological data. Rather, the question is: is God’s existence more probable given the data of contemporary cosmology than it would have been without it? And I think it certainly is.

Craig, being a skilled debater, makes sure to frame the debate question to be one which is comparatively easy to show.  According to Craig's framing, he only needs to show that Theism is more plausible given e.g. our current understanding of the Big Bang Model, compared to if we didn't know these facts.  This is a fairly modest ambition.  It certainly seems more likely now that the universe has a beginning than it would have seemed to a materialist living 500 years ago.  So if the beginning of the universe is a relevant datum for the existence of God, then cosmology provides some positive evidence.   (On the other hand, if it isn't relevant, why are we even discussing whether there was a beginning?)

At times, Carroll even seems to assume that if Craig doesn't believe in Theism for scientific reasons, his views can't be based on evidence at all:

There are very few people in the modern world who become religious, to come to believe in God, because it provides the best cosmology or because it provides the best physics or biology, or psychology, or anything like that. And that includes Dr. Craig. There’s a famous quote by him that says, “The real reason, the primary reason, for believing in Christianity isn’t cosmological arguments.”

[I was unable to track this quote down, but having some knowledge of Craig's views in other contexts, I highly doubt that Craig was referring to some inarticulate leap of faith not grounded in any good evidence at all.  I imagine—especially since he referred to Christianity—that he was thinking about some type of historical evidence that has to do with, say, Jesus or something.  Maybe something related to the fact that he did lots of miracles, and rose from the dead, and was seen by many eyewitnesses, who themselves did several miracles, leaving a band of committed followers to this day, who sometimes do miracles in his name, including naturalistically inexplicable healings with solid medical documentation—have I made my point yet?]

I’m not mentioning this as a criticism; it is simply an observation of fact. There are other reasons to be a theist other than cosmology, and I think that is true. I think that makes sense. Most people who become religious do so for other reasons—because it gives them a sense of community, a sense of connection with the transcendent, it provides meaning or fellowship in their lives.

These subjective warm fuzzy feelings are nice and all, but it is scientism to think that they are the only thing left after we remove stuff like Cosmology.  For example, History is also an evidence-driven field, and it has plenty of data supporting things like miracles.  Carroll made a joke about taking into account new evidence if the roof were to fall on his head, but perhaps if Carroll does some historical investigation, there might be more subtle ways for God to make a point.

The problem is that the basis of religion in the modern Western world is theism, belief in the existence of God. I’ve tried to make the case that science undermines theism pretty devastatingly. Five hundred years ago it would have made perfect sense to be a theist. I would have been a theist five hundred years ago. By two hundred years ago science had progressed to the point where it was no longer the best theory. By a hundred years ago after Darwin it was a rout. And by these days with modern cosmology there’s no longer any reason to take that as your fundamental worldview.

I always find it interesting, that when you poke a person who makes grand claims about the philosophical implications of Science, sooner or later they end up telling one of these historical just-so stories about how things used to be completely different before Science came along.

You know the drill.  Once upon a time, people used to use God to explain everything, and then one or two things got explained by Science, and then some more things got explained by Science, and now there are only two or three gaps in our knowledge, which stubborn religious people cling to in order to justify Theism, but we all know (by linear interpolation, I guess) that Science will eventually explain these things too, which is just as good as if it already had done so.  (This is closely related to the infamous "God-of-the-Gaps"™ strawman, about which I will have more to say later.)

In order to tell this story properly, Carroll needs to insist that he would have been a pious religious person 500 years ago.  But I'm not at all sure this is true.  He didn't really present any arguments for Theism based on the Science of 500 years ago, let alone one which is refuted by our present day understanding.  All he did was say why he doesn't believe in Craig's arguments (which, whether you believe them or not, are based on Modern Science, and couldn't even have been made 100 years ago, let alone 500).   All that stuff about random suffering, and multiple religions, and weird stuff in the Bible, and that the universe is really big while Earth is really small, and that tiredness and drugs and physiological secretions influence the mind, was just as evident to smart people 500 years ago as it is now.

No matter how much lecturing you hear about how Science works because we can always correct our theories with new data, they seldom bother to check these supposedly historical narratives with any actual data.  When you do, you usually find the story is far more complicated.

In the paragraph quoted above, the only actual Scientific revolution mentioned is that due to Darwin.  The rest is left suspiciously vague (for example, I'm not sure from the description what exactly is supposed to have happened 200 years ago, that made Theism "no longer the best theory").

In fact, for the most part it's pretty unclear what the implications of scientific theories are for or against Theism.  Take for example Maxwell's equations.  One could try to argue that: 1) lots of stuff is described by equations, 2) Maxwell's equations mean that one more thing is described by equations, 3) therefore probably everything is described by equations, 4) God is not an equation, therefore 5) God does not exist, but this seems like a rather weak argument from induction, not something that "undermines theism pretty devastatingly".  It's not like anyone in the 1500's was saying that magnetism couldn't be understood except as a special miracle of God, and then St. Maxwell showed they were all wrong.

There's a reason, therefore, why people fixate on Darwin.  Darwin's theory of Evolution really did remove one possible argument for the existence of God: namely that an act of special creation was necessary to explain the existence of each individual species, and its close adaptation to its environment.

Of course, the removal of a particular argument for God's existence isn't the same as disproving Theism.   In particular, this argument for the existence of God was not by any means the historically most important one.  In fact, you only really see people shortly before Darwin (like St. William Paley) making this argument.   In medieval times, people used to think that life-forms like flies would spontaneously generate in rotting meat.  Obviously, they wouldn't have thought much of Paley's view that each species needed to be created individually by God.  It was only with the increase of scientific understanding that this "gap" in our understanding was noticed.  Thus, to say that filling this gap refutes the ideas of the medievals (who didn't even know there was a gap here to be filled) is absurd.

What history actually shows, is not a monotonic replacement of Theology by Science, but a complicated back-and-forth process where new Science produces some new arguments for Theism (Paley, fine-tuning...), discredits others (Paley, the need for a Prime Mover rotating the outer heavenly sphere...), and so on.  But that's too complicated to reduce to a tidy, one-sided historical meta-narrative, so lots of people just make up a story about Science and Religion being enemies, and stuff everything into that mold.

All of this was just picking around the edges.  In the next post, I will talk more about the so-called God-of-the-Gaps™-fallacy, which both Carroll and Craig pay their obligatory disrespects to.  Then I'll try to get to the actual substantive questions about whether the universe had a beginning, according to Modern Science.  And whether that has any theological implications.  And fine-tuning.  And about Carroll's arguments that Theism is ill-defined and false.   Things that relate to the actual substance of the Carroll-Craig debate.  That sounds like a plan.

About Aron Wall

I am a postdoctoral researcher studying quantum gravity and black hole thermodynamics at the Institute for Advanced Study in Princeton. Before that, I read Great Books at St. John's College (Santa Fe), got my physics Ph.D. from U Maryland, and did my first postdoc at UC Santa Barbara.
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28 Responses to Thoughts on the Carroll-Craig Debate

  1. Jack Spell says:

    Well done, Sir.

  2. T.Yhip says:

    Thank you St Aron (Wall) for this follow up commentary. You and the likes of St William (Craig) do a great service to theism by logical and reasonable discourse. Coming from respectable physicists as you are, the theistic arguments carry weight and credibility. I look forward to your Plan outlined in the closing paragraph, particularly (a) does the second law of thermodynamics support a finite time in the past? (b) does quantum physics provide a good argument against materialism, and (c) Boltzmann Brains.

  3. Kevin V says:

    Yes, keep up the great service of analyzing the Craig-Carroll debate (particularly the scientific issues) for those of us who aren't Reformed Epistemologists 7 days a week.

  4. Aron Wall says:

    Thanks everyone, for your encouragement.

  5. Jack Spell says:

    St. Aron,

    If it's not too much trouble, I was wondering if you might do me the honor of giving my letter to Dr. Carroll a critique. The reason that I ask is because, after posting it to his blog, several folks took notice and one in particular asked if he could publish it on his own website. Since I do my best to spread the Truth, I want to avoid the spread of any and all false claims. Thus, if you would be so kind as to lend your expertise in these matters I would owe you a debt of gratitude. I understand that in all likelihood you have a lot on your plate; so if it takes you awhile (or if you cannot find the time at all) I'll understand. Thanks and God bless.

    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 Dr. Craig (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 true 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 that this isn’t the appropriate vocabulary to use here. The univocal meaning employed in the 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 could 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” in this context.

    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 [] 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 truth of 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. 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 when in comparison with your current level of expertise. However, in my novice 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 (classical spacetime) satisfies the only condition of BVG — Hav > 0 — all the way back until 10^-43 seconds, then according to [],

    “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. 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 the point:

    “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 [],

    “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 Gravity, and others (see, for instance, [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* emergent scenario — regardless of if whether it’s an unstable state (ESS) or a metastable state (LQG) — from being past-eternal. Moreover, this notion appears to be reinforced here [] 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 the Aguirre-Gratton model (which 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 arrow of time, this model, according to Vilenkin, still 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.

  6. Aron Wall says:

    Dear Jack,

    My critique is that your proposed letter is much too long to politely post on Dr. Carroll's blog. ;-)

    But since you seem to already have done so, I'm not sure that piece of advice will help very much. I'm flattered that you should turn to me for help with scientifically critiquing your letter---I'm not offended that you asked me---but unfortunately this would require me to essentially rehash the debate an entire additional time, as viewed through the lens of your letter. It is hard enough work critiquing the debate once...

    Since in your letter you made clear that you are not a professional cosmologist, I think you can reasonably expect that people will take the letter in the spirit in which it was intended, and won't assume that you are claiming any sort of infallibility for your opinions. But you could always ask the people posting it on their websites to add a disclaimer, if you think that is necessary.

    [Just to clarify the situation for any visitors, on this blog I do not use the title "saint" when addressing someone in the second person, and I certainly don't require other commenters to refer to me (or anyone else, for that matter) in that way!]

  7. Jack Spell says:

    Dear Aron,

    Thank you for your response. I apologize for the length of the letter; I just felt it was a necessary evil in order to properly combat (what I perceived to be) false claims propagated by Dr. Carroll's post-debate reflections.

    As I previously stated, I fully understand if you cannot give it a proper critique; doing so would certainly exaust a considerable amount of your free time.

    My primary concern (which I should have tried to state more clearly) was whether or not the papers that I cited were relevant and appropriate as refutations for Prof. Carroll's claims; that is all that I was hoping for your thoughts on. Nevertheless, again, I understand your position and thank you again for the response.

  8. T.Yhip says:


    St. Paul wrote in (Rom. 1:16,17):”For I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes, for the Jew first and also for the Greek. For in it the righteousness of God is revealed from faith to faith; as it is written, 'The just shall live by faith'.”

    It is reassuring to know there are respectable physicists and mathematicians like you and others (Stephen Barr, John Lennox, John Polkinghorne, just to name a few) who are not ashamed to be Christians, and who confidently profess their faith through their writings and speeches in a rigorous defence of theism and Christianity.

    Keep up the good work.

  9. LaplaceDemon says:

    I think when you like at the argument map, Craig had the better argumention

    There was a lot of stuff like "Craig saying this , but there are models that avoid this problem". And Craig would respond that "there are other problems with such models and Carroll has to come to grips with the problem" that I didn't know how to evaluate , because I only have a layman's knowledge of cosmology.

  10. Benard Holborn says:


    I discovered your blog rather randomly, but I think it's great. Regarding this debate...

    I found the debate to be uncharacteristically challenging for WLC. Perhaps it was for Carroll as well, but I wouldn't know as I've not seen him debate before. I say this because Carroll has the authoritative advantage in this debate. If Craig called him out on something he wrote, or a theorem, all Carroll had to do was say "No, that's not what it's saying" and then give little to no justification. Yeah, perhaps he's right, but laymen such as me wouldn't know. We would have to just assume Carroll is correct because...he's the physicist and WLC isn't.

    What I specifically found unsatisfying about his rebuttals to the Kalam's first premise (whatever begins to exist has a cause) is when Carroll said "This kind of Aristotelian analysis of causation was cutting edge stuff 2,500 years ago. Today we know better." Later he said "But crucially, both of these features of the universe that allow us to speak the language of causes and effects are completely absent when we talk about the universe as a whole. We don’t think that our universe is part of a bigger ensemble that obeys laws."

    Is this accurate? If it is true, he didn't explain what scientific discovery it was that made universal causation obsolete. And if the premise is true of everything in the universe, but not of the universe itself, he also didn't explain why. It would be like saying that all written works have a cause, but literature doesn't.

    He took Craig to task for asking how the universe could "pop into existence from nothing", to which Carroll responded with "It sounds as if you waited a while, and then, pop, there was the universe. But that's exactly wrong. The correct statement is that there are models that are complete and consistent in which there is a first moment of time."

    Okay, so isn't the question still valid; how could the universe have a first moment in time from nothing?

    Basically, what Carroll said doesn't really make sense to me, but perhaps it would to physicists. Am I missing something?

  11. Aron Wall says:

    Welcome to my blog, Benard.

    You make some good points. No, I don't think you're missing all that much. Carroll is really doing philosophy here, not physics, so when you ask "Is this accurate?" as though he or I were especially equipped as a physicist to answer that question, I have little more to give you. As a physicist, I certainly agree that modern day physics emphasizes finding consistent mathematical models, as compared to metaphysical or mechanical analyses of causation, but there's more than one lesson one might draw from that.

    I've just written my own response to his comments here.

  12. Benard Holborn says:


    Wow, your response pretty much answers the issues I raised. In the spirit of fairness, I did find that Carroll conducted himself well and I commend him for that. Unlike his fellow cosmologist Dr. Krauss, he was able to stick to the task at hand and show respect for the opposing viewpoint and the people who hold it (theism). As a result of his civility, his arguments were strengthened. He was able to fair much better than his most of the people that went before him. Craig referred to the debate as one of his most challenging, which is a huge complement for Carroll as far as I'm concerned.

    I've been reading more on your site and it is a breath of fresh air. I will share it with my like-minded friends.

  13. Aron Wall says:


    I agree that Carroll conducted himself well. I hope that my numerous criticisms of specific points doesn't distract from my other assertion that I have high respect for him as a physicist who tries to think deeply about important issues, and as a communicator who can clearly ariticulate positions that I disagree with. (It's so much more pleasant to try to refute people who are clear in this way! With most people, you have to do a lot of work to explain and reinterpret their own position to make it a bit more coherent, before you can even start to respond to it.)

  14. Benard Holborn says:


    From what I have read so far, it is clear that you respect both Carroll and any other of your fellow physicists whom you disagree with. I doubt that any of them would take offence if they were to read what you wrote about them.

    I could be wrong, but one thing I admire about your field of work is that it seems easier than other lines of work to separate the personal views of the person from their professional contributions.

  15. Robert Ford says:

    Carroll had the credentials to finally put Craig's Kalam argument to rest in real-time by pointing out the unsoundness of the second premise "the universe had a beginning." There is not sufficient evidence to accept such a premise. It was also enlightening to see Carroll get the testimony of Guth, one of the authors of the Borde-Guth-Vilenkin theorem saying the universe probably didn't have a beginning since Craig misuses the theorem and did so in the debate.

    Craig simply didn't have the credentials to go up against Carroll on cosmology. He was trounced, but it was good to air out these ideas especially since Craig uses them all the time. The person who makes the claim must provide the proof. Craig was unable to provide good evidence to support his claim that cosmology indicates the existence of a god.

  16. Scott Church says:

    "Carroll had the credentials to finally put Craig's Kalam argument to rest in real-time by pointing out the unsoundness of the second premise 'the universe had a beginning.' There is not sufficient evidence to accept such a premise."

    Robert, it is true that St. Craig is less qualified to speak on matters of cosmology that Carroll, but it hardly follows that he has no knowledge of the subject or qualifications whatsoever, nor does it follow that Carroll adequately addressed his most salient points (he in fact did not). This is a textbook example of an Authoritarian fallacy. It is also true as you say, that there are viable inflationary models which allow us to get around BVG. But nearly all of those that yield eternal universes are highly contrived toy models that have little or no observational support. Of the few that are even remotely viable, the most promising is the Aguirre-Gratton model, which although it avoids past-indefinite timelike worldlines, it does in fact have a reversal of time assymetry which essentially defines a t=0 moment and past/future arrows in "opposite" directions from it. In terms of everything we know and understand about how time actually works in the universe we live in, it's far simpler and more to the point to view this as an event (or more properly, a hypersurface) from which two universes emerge and evolve in their own future directions. Aron, correct me if I'm wrong here, but to me such a model is only "past eternal" if we arbitrarily decide to redefine past and future on the side of t=0 in our past so that it runs opposite to the world we live in. I see no valid reason to do that. The only caveat here is that spacetime cannot be said to "end" here in the sense of being past-indefinite, so it's less obviously ex-nihilo.

    I agree that from a cosmological standpoint past-eternal universes are possible. But the fact of the matter is that for every toy model that allows for one there are many more that render them highly unlikely, and these are supported by observational data in ways their past-eternal toy model competitors are not. You are correct to say that BVG does not irrefutably prove the universe began to exist. But at a bare minimum it, and other advances put the overwhelming burden of proof on those who deny that it did (I would recommend Aron's recent series of cosmological argument posts here). If this is an "unsound" premise for which there is "not sufficient evidence" we have to wonder what would be sufficient. Perhaps this is why Carroll restricts himself merely to asking, "Can I build a model?" Of course he can build a model... anyone can. Given the current status of observational cosmology and quantum gravity there are probably more models than there are gainfully employed cosmologists. The real question is... can he build a past-eternal model that has better observational support than those that aren't? He can't... and to date at least, neither can anyone else. Which is probably why he avoids any discussion of verifiable observational support in discussions like this. ;-)

    Btw, we haven't even gotten yet to another point everyone seems to avoid... You make an issue of the fact that Craig isn't a cosmologist. Well, the origin of the universe isn't just a cosmological topic--it involves philosophy as well. And guess what... St. Craig is in fact a leading publisher philosopher, and to be blunt, Carroll is illiterate in the subject. Craig is far more well-versed in Carroll's field than he is in Craig's, and it shows.

    To put all this in perspective ask yourself a simple question: What if it was religion that required a past-eternal universe and a beginning presented a huge theological problem for theists (especially Christians like Aron and I)? Let's be honest... if that were the case atheists everywhere would be wielding BVG like a mighty sword Excaliber and condescendingly bludgeoning theists silly with it. Oh, what irrational obscurantists Christians like Aron and I would be if it was we who were protecting our worldviews by clinging to a handful of contrived toy models that had no observational support whatsoever! If this isn't true--if a universe that began to exist really is such a non-issue--then why are so many atheist cosmologists today killing themselves to come up with models that avoid one--or like Krauss, equivocating on the meaning of the word nothing in an attempt to convince us that something could have come from it a finite time ago?

    The reason is clear. They're afraid of a beginning... and with good reason.


  17. Robert, Carroll did not show the second premise to be unsound and Craig did not misuse the BGV theorem and he certainly was not “trounced.” You are making claims you cannot support, unless, of course, you intend to merely appeal to Carroll’s authority. (Why does it seem skeptics have to constantly appeal to authority to present a case?)

    Remember that Vilenkin still maintains that there is no good model that provides a satisfactory model for a beginningless universe (unless he’s made a more recent statement I hadn’t heard) and in this blog site Aron Wall has also concluded that the probability is on the side of a beginning. Aron’s careful analysis of the arguments demonstrates this. Even without the scientific evidence, I’ve argued that the philosophical evidence is sufficient to demonstrate a beginning to be more probable.

    Also notice that Guth said he did not know whether the universe is past eternal; he said he suspected that it is and “it’s very likely eternal but nobody knows.” Maybe he was trying to be vague enough to sound like he wasn’t contradicting his earlier claims that given some reasonable assumptions there had to be an ultimate beginning. My understanding is that Guth has become involved with the Carroll-Chen model and he thinks this allows for a past eternal universe. This may be why he now more strongly “suspects” the universe is past eternal. This is pointless, however, since Craig showed that the Carroll-Chen model does have an origin point.

  18. David says:

    I'm not sure that Carroll's expectations of naturalism and theism are even coherent:
    Under theism you’d expect religious doctrines to last a long time in a stable way. Under naturalism you’d expect them to adapt to social conditions. Under theism you’d expect the moral teachings of religion to be transcendent, progressive, sexism is wrong, slavery is wrong. Under naturalism you’d expect they reflect, once again, local mores, sometimes good rules, sometimes not so good.
    In one breath, he complains that religion is too malleable; in the next he complains that it didn't anticipate one particular culture (ours) at one particular time! There is quite simply no reason on naturalism or theism to regard 20th century Western "progressive" values as being one whit less a set of "local mores" than those of the most hierarchical, patriarchal, authoritarian culture in history.

    He's also historically ill informed:
    Under theism, minds should be independent of bodies.  Under naturalism, your personality should change if you’re injured, tired, or you haven’t had your cup of coffee yet.
    The medievals would have given him an incredulous stare over this one. I'm sure that he knows all about the theory of the four humors when medieval bashing time comes along, but he never suspects that they would have rejected the "angel-stapled-to-an-ape" cartesian model on that basis.

  19. Aron Wall says:

    Angel stapled to an ape? HA! That's the funniest put-down of Cartesian dualism I've ever heard!

    I think you're right that his ethical expectations of Theism aren't particularly coherent or consistent. But this does raise some interesting questions on the degree to which we can make inferences based on our own moral ideas.

    I don't accept the "Whig" theory of history shows inevitable moral progress on all fronts. However, I do think that taken as the whole there has been some significant moral improvement throughout history, especially but not exclusively in cultures influenced by Christianity and the Enlightenment.

    In order to make any moral judgements at all we need a place to stand from, and I don't think it is crazy to evaluate a purported religous revelation based on its general conformity with morality, so long as we bear in mind that (a) there is no good reason to expect that our present culture has correct moral beliefs in EVERY RESPECT, something which would really be a heck of a coincidence, that we have just now acquired the correct moral beliefs about everything, and (b) there is no point in having a religion unless we are prepared to accept that God knows better than we do about certain things. (It always amazes me how modern people can be so damn sure that the Sexual Revolution was a good thing...)

    On a somewhat more revisionist / liberal note, Carroll does not seem to be taking into account the possibility that God might have (in certain respects) accomodated his message to the moral sensibilities of those he was talking to. It was hard enough to get the ancient Israelites to accept a culture-building project based around Ethical Monotheism (with its attendant obligation to shun polytheism and idolatry, and work for justice for the poor and oppressed); it's not that surprising that on other issues God merely limited the worst abuses in other areas. When Christ came, then he required monogamy and rasied the status of women, etc. But it was clear from Genesis onwards, that God values women as people and wants to have a relationship with them, as well as with the men... If Theism is true, we are all a work in progress!

  20. Dunce says:

    Saying someone is illiterate of philosophy but an expert in cosmology is like saying someone is illiterate of astrology but an expert in astronomy. Lame. To be blunt, a lot of philosophy is bullshit.

  21. Aron Wall says:

    "A lot" is very different from "all". There is no legitimate subset of astrological predictions, whereas there are some legitimate philosophical arguments.

    Any argument that all philosophy is BS is automatically self-undermining, because that argument would itself be a philosophical argument, and would therefore refute itself.

    In any case, someone illiterate in philosophy would hardly be in a good position to tell which stuff is BS and which isn't.

  22. David says:

    Dunce, as soon as a physicist opens their mouth to start talking about something that isn't a part of a mathematical model - as soon as issues of interpretation or the "nature of reality" get brought up - they're going to be doing philosophy. The only question is whether they'll recognize that fact, be well informed about philosophy, and make a conscious effort to do philosophy well, or ignore that fact, speak about something they don't understand, and let a hodgepodge of unexamined philosophical intuitions get mingled in with what they say about science in such a way that neither they nor their listeners will be able to sort out the physics from the philosophy.

  23. JP says:


    It's been said that if someone claims metaphysics is nonsense, he's just a brother metaphysician with a rival theory!

  24. louis cyfer says:

    interesting thoughts. why do you think that miracles are better evidence of god than cosmological arguments? at most you can get to is that there is an event we can not currently explain. done. how do you make the leap to be able to justify that a god did it, and that it's your particular god?
    as far as the kalam, premise one is completely flawed. it is an equivocation fallacy, trying to equivocate causation necessary for things starting out by the transformation of matter, which we have observed, with causation necessary for the emergence of matter. it is a category error, and until such time that we have even a single example observed of matter emerging needing a cause, we do not have to bother ourselves with premise one.
    wlc is very dishonest. he constantly switches arguments to personal incredulity arguments, and says things like "i just don't see how that could happen" and the like. carroll pointed out this at least once, that wlc's lack of imagination or ability to think of something is not really a counter argument. even more dishonest of wlc is that when pressed about if all his arguments were negated, and scientific evidence emerged against them, he would not change his beliefs, because none of the arguments he proposes are the reason why believes.

  25. louis cyfer says:

    @jp, i don't think the term metaphysician makes sense, since it is metaphysics, and people who deal with physics are physicists, not physicians. wouldn't it be metaphysicist?

  26. Aron Wall says:

    What, you think the rules for English suffixes are supposed to make sense? ;-)

    It looks like the term "metaphysician" is actually OLDER than the term "physicist". And that nobody says "metaphysicist".

    Presumably my job is called "physicist" because "physician" was already taken.

    (As for your other comment, I'll respond to it later.)

  27. Aron Wall says:

    You are entitled not to believe the first premise of the kalam argument if you don't think it is plausible. (I myself think that there are other versions of the Cosmological Argument which are more plausible.)

    But that does not mean that anyone who disagrees with you is dishonest. Philosophy is hard! Since a lot of metaphysical arguments come down to intuitions about the universe, appealing to personal incredulity is not completely off-base, even if there are stronger forms of argumentation. I actually agree with you that he's putting a bit more rhetorical weight on this than it can bear, but accusing somebody of dishonesty is a pretty serious thing and I don't think you should do it casually. Nor do I see how it is dishonest to say: "I think that argument A provides evidence for conclusion X, but even if A were refuted I would still personally believe it because of this other reason B", especially if one is open about that when asked.

    As for what we can deduce from miracles, I think it really depends on the context. If, for example, a man blind from birth suddenly recovers his sight for no reason that we can tell, then that is just an inexplicable mystery. But if it happens right after somebody prayed for his eyes to be opened in the name of Jesus, then it starts to suggest a possible interpretation of why it happened.

    The Undertermination of Theory by Data is a classic problem that also affects Science. For example, after St. Kepler, it was still compatible with all observations to hold that all the planets go around the Earth, it's just that geocentric models were a lot more complicated. So, we should select the best hypothesis that explains the data.

    If you haven't read any of the Gospels recently, go and read one. (St. Mark's is the shortest, and also very likely the first to be written. Note that there is good evidence that the original text ended at 16:8.) Suppose hypothetically, for the sake of argument, that the historical claims described in this book--Jesus healing people, claiming to be the Son of God and teaching about his Father, being killed and then rising from the dead---occurred just as written. Wouldn't you say that this is good evidence that God exists and that Jesus had some special relationship with him?

    (What is this talk about my particular god? All monotheistic religions agree that there is only one God. We disagree about who speaks for him, and how best to describe him, but agree on his existence and many of his attributes.)

    Of course there are always going to be alternative explanations. Maybe advanced aliens were visiting Earth, and decided to play a trick on humanity. I just do not think that is the most natural interpretation of the data. And certainly there is a lot more relevant data here, in terms of total information content, then in the very basic facts about the universe on which Cosmological Arguments depend.

  28. Scott Church says:


    Causality deals with how the contingent existence of things, or actuality, is either maintained or changed from one state to another by the actualization of innate potentials for such (the formal terms are act and potency). Effects that follow their causes temporally and continue to exist apart from them are said to be accidentally ordered (e.g. - sons and daughters that have continue to have their own existence apart from their parents). Those which maintain their state of existence only while their causes are actualizing them as said to be essentially ordered (e.g. - music that exists only while a musician is playing his/her instrument). What you refer to as "the transformation of matter" and "the emergence of matter" both involve the actualization of contingently existing states of being, and as such are well within the purview of causal inquiry. There is no "category error" here... you're using word games to create a false dichotomy.

    While I find much of value in the kalam argument, I agree with you that it isn't as strong as St. Craig makes it out to be. It rests on a few premises that although defensible are on rather shaky ground, and like Aron I believe there are much better cosmological arguments. I also agree that he could've made his case for the first kalam premise a lot better... for the most part he merely asserted it when he could've offered a number of formal arguments. But that said, if anyone is being disingenuous here it's Carroll, not him, and in multiple ways. For starters, speaking of it in the debate Carroll tells us that,

    "The problem with this premise is that it is false. There’s almost no explanation or justification given for this premise in Dr. Craig’s presentation. But there’s a bigger problem with it, which is that it is not even false. The real problem is that these are not the right vocabulary words to be using when we discuss fundamental physics and cosmology. This kind of Aristotelian analysis of causation was cutting edge stuff 2,500 years ago. Today we know better. Our metaphysics must follow our physics. That’s what the word metaphysics means."

    Virtually every word of this is incorrect. Aristotelian analyses of causation were never superseded by philosophers--they were discarded during the Enlightenment by scientists and anti-religion activists like the Philisophes for reasons that had more to do with fashion and political correctness than anything else. To this day they continue to be actively pursued fields of inquiry in analytic philosophy that among other things, have given rise to a growing school of thought called Essentialism (which is beyond the scope of this discussion). But more to the point here, is that Carroll of all people should've known this. Unlike most atheistic scientists today, he actually has some background in philosophy and has rightly criticized many of his colleagues (e.g. - Laurence Krauss and Neil DeGrass Tyson) for their cavalier ignorance of philosophical issues. So it would appear that he's either forgotten much of his undergraduate philosophy education, or more insidiously, is deliberately ignoring it. IMHO, Carroll is a great cosmologist and an eloquent and fair-minded speaker, so I sincerely hope it's the former. But it's difficult to see how someone of his pedigree could so conveniently unlearn this much. Even if we give him the benefit of a doubt on that, he carefully avoids the larger subject of causality as it's treated within analytic philosophy and redefines it to include only the accidentally ordered efficient causes which happen to fall within the realm of his chosen profession. To wit,

    "Therefore, when you find some event or state of affairs B today, we can very often trace it back in time to one or a couple of possible predecessor events that we therefore call the cause of that, which leads to B according to the laws of physics. But crucially, both of these features of the universe that allow us to speak the language of causes and effects are completely absent when we talk about the universe as a whole."

    In other words, he allows for causality involving the contingent states of existence of any particular thing/s in the universe, but not for the ultimate of such--the beginning of the contingent existence of the universe itself. This is a textbook example of a Taxicab fallacy--follow your axioms wherever they lead... until they stop giving you the answers you want, at which point you conveniently dispense with them. To say that causes and effects are absent from "the universe as a whole" presumes that the universe is the whole, which begs the very question that was being debated in the first place.

    There's a term for things beginning to exist without causes... it's called magic. Anything is possible in fairy tales, and illusionists dazzle audiences by making rabbits "begin to exist" in hats before pulling them out. Dress this sort of thing up in suitably scientific rhetoric, apply it to the universe as a whole... and presto! The ultimate get-out-of-jail-free card!

    Ironic, isn't it? Atheists like Carroll presumptuously dismiss miracles as quaint, bucolic superstitions... and then, without missing a beat turn around and defend bibbity bobbity boo magic as "science." :-)

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