October 07, 2012
Sean Carroll’s Reply to the RF Podcast
Hey I saw this website while surfing the internet that claims to refute William Lane Craig's podcasts about Sean Carroll. Can you please email me back and let me know if this website can be refuted?
Let the Universe Be the Universe
by Sean Carroll
My article in the Blackwell Companion to Science and Christianity, which asks “Does the Universe Need God?” (and answers “nope”), got a bit of play last week, thanks to an article by Natalie Wolchover that got picked up by Yahoo, MSNBC, HuffPo, and elsewhere. As a result, views that are pretty commonplace around here reached a somewhat different audience. I started getting more emails than usual, as well as a couple of phone calls, and some online responses. A representative sample:
• “Sean Carroll, servant of Satan…”
• “God has a way of bring His judgement to those who mock Him… John Lennon stated “Christianity will end, it will disappear.” Lennon was shot six times after saying that… Marilyn Monroe said to Billy Graham after Graham said the Spirit of God had sent him to preach to her: “I don’t need your Jesus.” A week later she was found dead in her apartment.”
• “See you in hell.”
• “Maybe GOD is just a DOG that you will meet when you are walking on the Beach trying to figure out how to get sand out of your butt crack.”
I admit that last one is a bit hard to interpret. The others I think are pretty straightforward.
A more temperate response came from theologian William Lane Craig (a fellow Blackwell Companion contributor) on his Reasonable Faith podcast. I mentioned Craig once before, and here we can see him in action. I’m not going to attempt a point-by-point rebuttal of his comments, but I did want to highlight the two points I think are most central to what he’s saying.
One point he makes repeatedly — really the foundational idea from which everything else he has to say flows — is that a naturalist account of the form I advocate simply doesn’t explain why the universe exists at all, and that in my essay I don’t even try. Our old friend the Primordial Existential Question, or Why is there something rather than nothing?
I have to admit I’m a bit baffled here. I suppose it’s literally true that I don’t offer a reason why there is something rather than nothing, but it’s completely false that I ignore the question. There’s a whole section of my paper, entitled “Accounting for the world,” which addresses precisely this point. It’s over a thousand words long. I even mention Craig by name! And he seems not to have noticed that this section was there. (Among my minor sins, I’m happy to confess that I would always check first to see if my name would appear in someone else’s paper. Apparently not everyone works that way.) It would be okay — maybe even interesting — if he had disagreed with the argument and addressed it, but pretending that it’s not there is puzzling. (The podcast is advertised as “Part One,” so maybe this question will be addressed in Part Two, but I still wouldn’t understand the assertion in Part One that I ignored the question.)
The idea is simple, if we may boil it down to the essence: some things happen for “reasons,” and some don’t, and you don’t get to demand that this or that thing must have a reason. Some things just are. Claims to the contrary are merely assertions, and we are as free to ignore them as you are to assert them. The second major point Craig makes is a claim that I ignored something important: namely, the Borde-Guth-Vilenkin singularity theorem. This is Craig’s favorite bit of cosmology, because it can be used to argue that the universe had a beginning (rather than stretching infinitely far backwards in time), and Craig is really devoted to the idea that the universe had a beginning. As a scientist, I’m not really devoted to any particular cosmological scenario at all, so in my paper I tried to speak fairly about both “beginning cosmologies” and “eternal cosmologies.” Craig quotes (misleadingly) a recent paper by Audrey Mithani and Alex Vilenkin, which concludes by saying “Did the universe have a beginning? At this point, it seems that the answer to this question is probably yes.” Mithani and Vilenkin are also scientists, and are correspondingly willing to be honest about our state of ignorance: thus, “probably” yes. I personally think the answer is “probably no,” but none of us actually knows. The distinction is that the scientists are willing to admit that they don’t really know.
The theorems in question make a simple and interesting point. Start with a classical spacetime — “classical” in the sense that it is a definite four-dimensional Lorentzian manifold, not necessarily one that obeys Einstein’s equation of general relativity. (It’s like saying “start with a path of a particle, but not necessarily one that obeys Newton’s Laws.”) The theorem says that such a spacetime, if it has been expanding sufficiently fast forever, must have a singularity in the past. That’s a good thing to know, if you’re thinking about what kinds of spacetimes there are.
The reason I didn’t explicitly mention this technical result in my essay is that I don’t think it’s extremely relevant to the question. Like many technical results, its conclusions follow rigorously from the assumptions, but both the assumptions and the conclusions must be treated with care. It’s easy, for example, to find examples of eternally-existing cosmologies which simply don’t expand all the time. (We can argue about whether they are realistic models of the world, but that’s a long and inconclusive conversation.) The definition of “singularity in the past” is not really the same as “had a beginning” — it means that some geodesics must eventually come to an end. (Others might not.) Most importantly, I don’t think that any result dealing with classical spacetimes can teach us anything definitive about the beginning of the universe. The moment of the Big Bang is, if anything is, a place where quantum gravity is supremely important. The Borde-Guth-Vilenkin results are simply not about quantum gravity. It’s extremely easy to imagine eternal cosmologies based on quantum mechanics that do not correspond to simple classical spacetimes throughout their history. It’s an interesting result to keep in mind, but nowhere near the end of our investigations into possible histories of the universe.
None of this matters to Craig. He knows what answer he wants to get — the universe had a beginning — and he’ll comb through the cosmology literature looking to cherry-pick quotes that bolster this conclusion. He doesn’t understand the literature at a technical level, which is why he’s always quoting (necessarily imprecise) popular books by Hawking and others, rather than the original papers. That’s fine; we can’t all be experts in everything. But when we’re not experts, it’s not intellectually honest to distort the words of experts to make them sound like they fit our pre-conceived narrative. That’s why engagement with people like Craig is fundamentally less interesting than engagement with open-minded people who are willing to take what the universe has to offer, rather than forcing it into their favorite boxes.
I normally don’t take questions asking me to respond to some link, Shane, but the opportunity to interact with Sean Carroll on these important questions is one I don’t want to miss. I’ll address both his main points.
With respect to his first complaint, let me clear up Prof. Carroll’s bafflement. The reason I didn’t address his response to what he calls the Primordial Existential Question is that we recorded, not one, but three podcasts on Prof. Carroll’s article, the first dealing with the kalam cosmological argument, the second with the teleological argument from fine-tuning, and the third with the Leibnizian cosmological argument. The Primordial Existential Question “Why is there something rather than nothing?” comes up in the third segment. So hold on, it will come!
The kalam cosmological argument concerns the different question of what brought the universe into being. As I explained in the podcast, Carroll avoids this question only by gratuitously reading a tenseless theory of time into certain cosmological models.
With respect to his second point, Carroll attempts to downplay the significance of the BGV Theorem (and, hence, to justify his ignoring it in his article). Here it is I who must admit to being baffled, indeed, astonished. This is what Carroll says about the BGV Theorem:
The theorem says that such a spacetime, if it has been expanding sufficiently fast forever, must have a singularity in the past. . . . The definition of “singularity in the past” is not really the same as “had a beginning” — it means that some geodesics must eventually come to an end. (Others might not.)
When I first read this characterization, I thought Carroll was just being misleading in saying that the assumption of the BGV Theorem is that a spacetime “has been expanding sufficiently fast forever.” For the word “forever” connotes a beginningless or infinite past; but the requirement of the BGV Theorem is merely that the average expansion rate is greater than zero over the past history of the universe, which the theorem will then prove to be finite, not infinite. Such a universe can be said to have been expanding “forever” only in the Pickwickian sense that it has been expanding for all past time (which the theorem will prove to be finite).
Now, as I say, I was inclined to overlook this characterization as merely misleading—until I came to the second sentence above. Here Carroll claims that to have a singularity in the past does not mean to have a beginning; it means only that SOME [past-directed] geodesics come to an end. He says that others might not. On this interpretation, the BGV Theorem is consistent with some geodesics’ being infinitely extended into the past. But that is precisely what the theorem proves to be impossible. The theorem requires that ALL actual, past-directed geodesics eventually come to an end. In order for the universe to be beginningless, there must be infinite, past-directed geodesics. That’s why Borde, Guth, and Vilenkin take their theorem to prove that any universe which has, on average, been in a state of cosmic expansion throughout its history cannot be past-eternal but must have a beginning.
So if “having a singularity in the past” is taken, with Carroll, to mean merely that some geodesics come to an end, then Carroll has seriously misstated the BGV Theorem. In a spacetime in which merely some geodesics come to an end, there will be local singularities (black holes), but such a universe could be past-eternal. In other words, it could have been expanding forever—which is just what Carroll said. This is not the import of the BGV Theorem. The import of that theorem is not the triviality that there are local singularities in the past; it is rather that there is a cosmic singularity.
Carroll also downplays the conclusions Vilenkin draws from the BGV Theorem in his recent paper that I cited. In answer to the question “Did the universe have a beginning?,” Vilenkin concludes “it seems that the answer to this question is probably yes” (arXiv:1204.4658v1 [hep-th] 20 Apr 2012, p. 5). One would never have guessed that from reading Carroll’s Blackwell Companion article. For my part, I have never claimed more than that in my defense of the second premiss of the kalam cosmological argument: in light of the evidence the premiss that the universe began to exist is more plausible than not.
In his oral presentation of his paper at the conference in Cambridge, Vilenkin was clear: “There are no models at this time that provide a satisfactory model for a universe without a beginning” (http://www.youtube.com/watch?v=NXCQelhKJ7A). Interestingly, if you take a close look at Vilenkin’s powerpoint slides for this presentation, you will find Prof. Carroll’s own model listed among the purported “eternal cosmologies” which in fact fail to avoid the beginning of the universe. The “eternal cosmologies based on quantum mechanics” so easily imagined by Prof. Carroll are not, in fact, tenable; but his unsuspecting readers would not know that.
For those who would like a fuller discussion of “eternal cosmologies,” including models which attempt to avert the force of the BGV Theorem, I recommend James Sinclair and my articles “The Kalam Cosmological Argument,” in The Blackwell Companion to Natural Theology, ed. Wm. L. Craig and J. P. Moreland (Oxford: Wiley-Blackwell, 2009), pp. 101-201; “On Non-Singular Spacetimes and the Beginning of the Universe,” in Scientific Approaches to the Philosophy of Religion, ed. Yujin Nagasawa, Palgrave Frontiers in Philosophy of Religion (London: Macmillan, 2012), pp. 95-142.
Finally, I’m disappointed that Carroll cannot find it in himself to have a collegial discussion of these important questions but feels the need to resort to snide, personal attacks in his closing paragraph. His unfamiliarity with my work is evident in his remark that I do not cite the relevant, original, scientific papers (despite my quoting the Vilenkin-Mithani paper in the very podcast to which he is responding), as well as the popular works of physicists (where they often feel freer to express what they take to be the philosophical and theological implications of their work). His condescension is especially awkward in light of his own missteps in correctly characterizing the BGV Theorem. Carroll will pardon us, I hope, for our scepticism about his counting himself among the ranks of the open-minded.