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Is Sean Carroll a Boltzmann Brain?

Sean Carroll

Sean M. Carroll has published a physics paper in which he claims to have “squelched” Boltzmann brains. Carroll, a cosmologist and physicist specializing in general relativity and cosmology at Caltech, is highly regarded by the New Atheist community. Carroll calls himself a “poetic naturalist,” by which he means an atheist who’s not boring. He denies libertarian free will, is a determinist, and denies that religion and science are compatible. The subtitle of his website is “In truth, only atoms and the void.” You see where he’s coming from.

His pronouncement on Boltzmann brains is remarkable. Not for its erudition — the physics may be fine but the logic is atrocious — but for Carroll’s glaring error and the gullibility of the atheist and materialist community that accepts his conclusion.

First, some background.

Ludwig Boltzmann was an Austrian physicist who worked in the late 19th century. He was a pioneer in statistical mechanics, and made fundamental contributions to the physics of atoms, molecules, and of thermodynamics and of the kinetic theory of gasses.

Boltzmann noted a bizarre consequence of his statistical understanding of matter. Because all that is necessary for man to understand himself and nature is his mind, and because it is statistically much more likely that an isolated brain should exist than that a highly complex universe full of billions of human beings (with brains) should exist, it is much more likely that each of us is an isolated brain in a disorganized universe that is deluded into thinking that the complex universe exists. Boltzmann’s idea is a 19th-century “brain-in-a-vat” concept.

Boltzmann’s idea was developed in greater detail in the late 20th century (Boltzmann himself only mentioned it briefly). It would seem, if one accepts a materialistic (and Godless) universe, that an isolated brain is much more likely to exist than the complex intricate universe that we believe exists around us. For some materialists and atheists, the Boltzmann Brain paradox poses quite a metaphysical challenge. It seems to lead to a peculiar variant of solipsism. From the perspective of probability, if we are mere material beings in a Godless universe, it would seem that this naked-brain solipsism is vastly the most likely scenario, because it is much simpler, and thus much more likely, than an entire universe. This appears to have caused the materialist/atheist community some angst.

Sean Carroll rides to the rescue. He tells his audience not to worry:

Kim Boddy, Jason Pollack and I have been re-examining how quantum fluctuations work in cosmology, and in a new paper we’ve come to a surprising conclusion: cosmologists have been getting it wrong for decades now. In an expanding universe that has nothing in it but vacuum energy, there simply aren’t any quantum fluctuations at all. Our approach shows that the conventional understanding of inflationary perturbations gets the right answer, although the perturbations aren’t due to “fluctuations”; they’re due to an effective measurement of the quantum state of the inflaton field when the universe reheats at the end of inflation. In contrast, less empirically-grounded ideas such as Boltzmann brains and eternal inflation both rely crucially on treating fluctuations as true dynamical events, occurring in real time — and we say that’s just wrong…This reasoning provides an escape from the Boltzmann brain problem…

Carroll argues that his new perspective on cosmology rules out quantum fluctuations as genuine events, which undermines the logic underlying the Boltzmann brain paradox. In the modern interpretation of Boltzmann brains, they would arise by quantum fluctuations. No fluctuations, no Boltzmann brains.

Carroll got his paper published, and his refutation of the Boltzmann brain paradox has garnered quite a bit of attention.

But Carroll makes a remarkable error. If we are comparing the likelihood between a universe actually as we conceive it, and a Boltzmann brain in chaos soup, we can’t use the laws of quantum mechanics to adjudicate the question, because if you are a Boltzmann brain, then your conception of laws of physics is unreliable and you can’t rely on your concept of quantum mechanics to get you out of the dilemma. To invoke quantum mechanics to “prove” that you’re not a Boltzmann brain is to ignore the fact that being a Boltzmann brain means that you have no reliable knowledge of nature, and no reliable knowledge of quantum mechanics.

Carroll can’t appeal to laws of physics to adjudicate a debate on whether we are capable of knowing the laws of physics. The Boltzmann brain argument dovetails in some respects with Alvin Plantinga’s evolutionary argument against naturalism. Materialism fatally undercuts the reliability of our perceptions and concepts if we are indeed merely material evolved beings.

If you are an isolated Boltzmann brain floating in chaotic soup, you have no way of really knowing that you are (or are not) a Boltzmann brain. Quantum mechanics won’t get you out of the jam, because if you a Boltzmann brain, you are deluded about nature and you have no reason to trust your conception of quantum mechanics. Materialistic explanations for man are always, in the final analysis, self-refuting.

Dr. Sean “only atoms and the void” Carroll gives us a disturbingly clear glimpse of an intellectual void. He garners great respect from New Atheists, for reasons obscure — perhaps in the land of the blind the one-eyed man really is king. Such is the dead end of materialism and atheism, and Carroll is so lost in his materialist musings that he doesn’t see the obvious contradiction in his witless philosophical error.

Image credit: FotoEmotions via Pixabay.

Michael Egnor

Senior Fellow, Center for Natural & Artificial Intelligence
Michael R. Egnor, MD, is a Professor of Neurosurgery and Pediatrics at State University of New York, Stony Brook, has served as the Director of Pediatric Neurosurgery, and award-winning brain surgeon. He was named one of New York’s best doctors by the New York Magazine in 2005. He received his medical education at Columbia University College of Physicians and Surgeons and completed his residency at Jackson Memorial Hospital. His research on hydrocephalus has been published in journals including Journal of Neurosurgery, Pediatrics, and Cerebrospinal Fluid Research. He is on the Scientific Advisory Board of the Hydrocephalus Association in the United States and has lectured extensively throughout the United States and Europe.



Boltzmann brainsCaltechcosmologyeternal inflationJason PollackKim BoddyLudwig BoltzmannmaterialismNew Atheistsphilosophyphysicsquantum mechanicsSean Carrollthermodynamics