Sean Carroll debates William Lane Craig on cosmology and God’s existence

British Spitfire and German Messerschmitt Me 109 locked in a dogfight
British Spitfire and German Messerschmitt Me 109 locked in a dogfight

Here’s the video of the debate:

Carroll was as good of a speaker as Craig in terms of style. Very easy to listen to, very quick on his feet, very civil. There was no clear winner on style.

It was difficult to assess the truth value of scientific points being made, especially for the layperson. I explained a few of them in my posts earlier this week, but I think laypeople might struggle with them if they are hearing about these things for the first time.

A couple of Craig’s slides: (click for larger images)

Slide 1 of 2:

Dr. Craig slide #1 of 2
Dr. Craig slide #1 of 2

Slide 2 of 2:

Dr. Craig slide #2 of 2
Dr. Craig slide #2 of 2

Quick summary: (this is not complete, because I couldn’t get everything they were saying noted)

Dr. Craig defended two arguments: 1) the kalam cosmological argument and the fine-tuning argument.

Dr. Craig supported the origin of the universe with 1) the expansion of the universe and 2) the second law of thermodynamics.

Dr. Craig said that the BGV theorem supports a beginning for the universe.

Dr. Craig said that the consensus of scientists did not accept Carroll’s naturalistic cosmology, quoting Stephen Hawking in support.

Dr. Craig said that multiverse models fall victim to the Boltzmann brain problem, where we should observe Boltzmann brains coming into existence and then phasing out again far more probably than embodied minds. But we observe embodied minds, and no Boltzmann brains.

Dr. Carroll said that science cannot study metaphysical questions.

Dr. Carroll said that science is about making models that may or may not be consistent with the experimental data.

Dr. Carroll said that the BGV theorem does not support a beginning for the universe.

Dr. Carroll proposed 17 alternative cosmologies, but did not provide a shred of scientific evidence for any of them, the way that Craig did for the standard model.

Dr. Carroll refuted Dr. Craig’s citation of Stephen Hawking, and Craig yielded the point.

Dr. Carroll speculated that science might progress to the point where the fine-tuning can be explained without an intelligent cause, and he gave an example of where that happened (inflation).

Dr. Craig argued that all 17 of the models suggested by Carroll either conflicted with evidence, had serious problems or did require a beginning.

Dr. Craig argued that Carroll’s own model required a beginning.

Dr. Craig argued that Carroll’s own model fell victim to the Boltzmann brain problem.

Dr. Craig argued that Carroll’s own model violated the second law of thermodynamics.

Dr. Craig re-stated his point that the baby universe spawning in Carroll’s model was speculative and incomplete, and cited Christopher Weaver’s work.

Dr. Carroll denied that things that pop into being out of nothing require a transcendent cause.

Dr. Carroll reiterated that science can only make naturalistic models, and that he did not have to answer questions about ultimate causes.

Dr. Carroll showed a photo of Alan Guth expressing his opinion that the universe is “probably” eternal. No evidence was given for this assertion.

Dr. Carroll said that the fine-tuning was not done in an optimal way, because one fine-tuned value was lower than it needed to be, and it should be exactly what it needed to be if God did it.

Dr. Carroll said that a finely-tuned universe is more probably in naturalism than in theism, because God can do anything he wants and doesn’t need a fine-tuned universe.

Dr. Carroll said he would stop defending his model now, and would instead defend Aguirre-Gratton.

Dr. Craig gave three reasons why the universe popping into being out of nothing requires a transcendent cause.

First, he said that nothing cannot cause anything to happen, because nothing is nothing.

Second, he said that if things pop into being out of nothing, then why don’t we see it happening all the time with other things.

Third, he said that we have no reason to dismiss the causal principle, especially when it is the basis of scientific inquiry and has been so fruitful in the progress of science.

Dr. Craig reiterated that baby universes in Carroll’s model would be dominated by Boltzmann brains, and we don’t observe that.

Dr. Craig said that even on the quantum gravity models that Carroll mentioned, there would still be a beginning.

Dr. Carroll said that Craig mustn’t say “popped into being” but instead that “there was a first moment of time”.

Dr. Carroll said that his model does indeed violate the second law of thermodynamics “YES!”.

At this point Carroll stopped talking about the topic of the debate and started expressing personal opinions about religion. It’s funny how often atheists do this in debates.

Dr. Carroll said that most theists don’t believe in God because of cosmology, but because of community and feelings.

Dr. Carroll said that science had learned a lot in the last 2000 years, so theism was false.

Dr. Carroll said that most philosophers don’t think that God exists, so theism was false.

Dr. Carroll said microscopes and telescopes were absent 2000 years ago, so theism was false.

Dr. Carroll said that religion should be about community and feelings, not about what is true.


My conclusion was that Carroll lost because he is just satisfied to throw theories out and not to argue that they are true by citing evidence. Carroll never seemed to be interested in finding out what is true, but instead he just wanted to tell a story that didn’t include God, and assert that by Occam’s Razor, his story was a better explanation. I am not impressed with theoretical speculations, although the layperson might be. I kept waiting for him to respond to Craig’s points about how his model was falsified by experimental evidence and observations, e.g. – the Boltzmann brains or the baby universe generation, and he never cited the evidence I wanted him to cite. Craig did have some evidence for his views, but he could have been stronger in making his case. He could have shown the e-mail from Vilenkin that stated that he had understood the BGV theorem, and was using it correctly, for example.

For me the winning side comes down to evidence. The standard model is the standard model because of scientific evidence. Until that evidence is overturned, then speculative models are of no interest to anyone who is evidence-driven. Speculations are not science. A philosophical presupposition of metaphysical naturalism is not science.

If you want to see a good lecture on scientific evidence related to cosmology, then there is the particle physicist Michael Strauss lecture on cosmology and fine-tuning at Stanford University and his more recent lecture at the University of Texas. Note that Strauss is an experimental physicist, not a theoretical physicist like Carroll.

Here’s another review of the debate by Randy Everist of Possible Worlds blog. He explains the back-and-forth over Boltzmann brains and the BGV theorem in more detail.

2 thoughts on “Sean Carroll debates William Lane Craig on cosmology and God’s existence”

  1. Nice review and I enjoyed Randy’s as well. I completely agree that Carroll’s use of Guth falls squarely into Argument from Authority fallacy.
    Another good review can be found at
    by Dr. Aron Wall who is a PhD theoretical physicist and a Christian. While he felt that Craig was a little out of his depth cosmologically speaking he discusses many of the problems with Carroll’s speeches during the debate. He also has a string of posts under the title “Did the Universe Have A Beginning?” that discusses many of the scientific models that Carroll speeds through knowing most of the listeners won’t know anything about, explains them in (mostly) understandable terms, and shows why many of these actually hurt Carroll’s case more than helps.


  2. I just watched this debate for the first time this weekend and have since done quite a bit of research to try and improve my understanding. I agree that much of it flies over the head of laypeople (including myself). However, Dr. Craig has since noted that as it turns out, Dr. Carroll holds to a tenseless theory of time (b-theory of time). And once you realize that, everything starts to make sense about why he can say that the beginning of the universe is exempt from the law of causality. The tenseless theory of time holds that all temporal becoming is an illusion and that the past present and future are all equally real. Thus, the universe (including the past, present, and future) is eternal and the passage of time is an illusion. I’ll have to do more reading on this, but at first glance it strikes me that this position can be dismissed as absurd. The passage of time seems to be real, and anyone arguing against it must assume the passage of time in order to make his argument (i.e. he must begin his argument at t1 and finish his argument at t2).


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