Some modern cosmological models predict the appearance of Boltzmann Brains: observers who randomly fluctuate out of a thermal bath rather than naturally evolving from a low-entropy Big Bang. A theory in which most observers are of the Boltzmann Brain type is generally thought to be unacceptable, although opinions differ. I argue that such theories are indeed unacceptable: the real problem is with fluctuations into observers who are locally identical to ordinary observers, and their existence cannot be swept (...) under the rug by a choice of probability distributions over observers. The issue is not that the existence of such observers is ruled out by data, but that the theories that predict them are cognitively unstable: they cannot simultaneously be true and justifiably believed. (shrink)

We give a Bayesian argument showing that, even if your total empirical evidence confirms that you have zillions of duplicate Boltzmann Brains, that evidence does not confirm that you are a Boltzmann Brain. We also try to explain what goes wrong with several of the sources of the temptation for thinking that such evidence does have skeptical implications.

Leading cosmological theories engender a controversial puzzle which has prompted philosophers to propose competing epistemological solutions and physicists to propose methodological changes to cosmology. The puzzle arises from the prediction that every brain on Earth will eventually be vastly outnumbered by physical duplicates formed by random collisions of particles in outer space. Supposing that this prediction is correct, shouldn't you believe that your brain is probably one of these vastly more typical extraterrestrial brains, since you cannot infer your brain's (...) origin from your experiential state? But supposing that your brain is one of these extraterrestrial brains, why be confident in the cosmological theories, since you never actually received testimony supporting these theories? Proposals in the literature either deny the rationality of believing theories that make the prediction or deny the typicality of your brain among its duplicates. This paper argues that these proposals are not entirely satisfactory. Instead, one should be confident in theories making the prediction on the supposition that your brain is one of the extraterrestrial brains. The upshots include that it may be rational to believe that your brain is probably an extraterrestrial brain and that cosmologists should not alter their methodology in response to the puzzle. (shrink)

Sean Carroll has recently argued that theories predicting that observations are dominated by Boltzmann Brains should be rejected because they are cognitively unstable: “they cannot simultaneously be true and justifiably believed.” While such Boltzmann Brain theories are indeed cognitively unstable, one does not need to appeal to this argumentation to reject them. Instead, they may be ruled out by conventional Bayesian reasoning, which is sufficient to keep Boltzmann Brains at bay.

Some physical theories predict that almost all brains in the universe are Boltzmann brains, i.e. short-lived disembodied brains that are accidentally assembled as a result of thermodynamic or quantum fluctuations. Physicists and philosophers of physics widely regard this proliferation as unacceptable, and so take its prediction as a basis for rejecting these theories. But the putatively unacceptable consequences of this prediction follow only given certain philosophical assumptions. This paper develops a strategy for shielding physical theorizing from (...) the threat of Boltzmann brains. The strategy appeals to a form of phenomenal externalism about the physical basis of consciousness. Given that form of phenomenal externalism, the proliferation of Boltzmann brains turns out to be benign. While the strategy faces a psychophysical fine-tuning problem, it both alleviates cosmological fine-tuning concerns that attend physics-based solutions to Boltzmann brain problems and pays explanatory dividends in connection with time’s arrow. (shrink)

A Boltzmann Brain, haphazardly formed through the unlikely but still possible random assembly of physical particles, is a conscious brain having experiences just like an ordinary person. The skeptical possibility of being a Boltzmann Brain is an especially gripping one: scientific evidence suggests our actual universe’s full history may ultimately contain countless short-lived Boltzmann Brains with experiences just like yours or mine. I propose a solution to the skeptical challenge posed by these countless actual Boltzmann (...) Brains. My key idea is roughly this: the skeptical argument that you’re one of the Boltzmann Brains requires you to make a statistical inference, but the Principle of Total Evidence blocks us from making the inference. I discuss how my solution contrasts with a recent suggestion, made by Sean Carroll and David Chalmers, for how to address the skeptical challenge posed by Boltzmann Brains. And I discuss how my solution handles certain relevant concerns about what to do when we have higher-order evidence indicating that our first-order evidence is misleading. (shrink)

I present a new thermodynamic argument for the existence of God. Naturalistic physics provides evidence for the failure of induction, because it provides evidence that the past is not at all what you think it is, and your existence is just a momentary fluctuation. The fact that you are not a momentary fluctuation thus provides evidence for the existence of God – God would ensure that the past is roughly what we think it is, and you have been in existence (...) for roughly the amount of time you think you have. I don’t have a definitive way for the atheist to refute this argument, but I give one suggestion that relies on physics-based simplicity considerations. I close with an epistemological discussion of self-undermining arguments. (shrink)

We argue that, under certain plausible assumptions, de Sitter space settles into a quiescent vacuum in which there are no dynamical quantum fluctuations. Such fluctuations require either an evolving microstate, or time-dependent histories of out-of-equilibrium recording devices, which we argue are absent in stationary states. For a massive scalar field in a fixed de Sitter background, the cosmic no-hair theorem implies that the state of the patch approaches the vacuum, where there are no fluctuations. We argue that an analogous conclusion (...) holds whenever a patch of de Sitter is embedded in a larger theory with an infinite-dimensional Hilbert space, including semiclassical quantum gravity with false vacua or complementarity in theories with at least one Minkowski vacuum. This reasoning provides an escape from the Boltzmann brain problem in such theories. It also implies that vacuum states do not uptunnel to higher-energy vacua and that perturbations do not decohere while slow-roll inflation occurs, suggesting that eternal inflation is much less common than often supposed. On the other hand, if a de Sitter patch is a closed system with a finite-dimensional Hilbert space, there will be Poincaré recurrences and dynamical Boltzmann fluctuations into lower-entropy states. Our analysis does not alter the conventional understanding of the origin of density fluctuations from primordial inflation, since reheating naturally generates a high-entropy environment and leads to decoherence, nor does it affect the existence of non-dynamical vacuum fluctuations such as those that give rise to the Casimir effect. (shrink)

The philosophy of superdeterminism is based on a single scientific fact about the universe, namely that cause and effect in physics are not real. In 2020, accomplished Swedish theoretical physicist, Dr. Johan Hansson published a physics proof using Albert Einstein’s Theory of Special Relativity that our universe is superdeterministic meaning a predetermined static block universe without cause and effect in physics. A prominent theory in cosmology is that our universe originated from a random quantum fluctuation. However, some object that such (...) a large universe creating quantum fluctuation is much less likely to occur than Boltzmann Brains or even a small universe creating quantum fluctuation. But, any quantum event can be predetermined to occur at any time by the Creator of our universe. Consequently, a large universe creating quantum fluctuation occurring at the beginning of time can be predetermined to occur before any appearance of Boltzmann Brains or small universe creating quantum fluctuations. The philosophy of superdeterminism regards our universe from quantum fluctuation to be a predetermined miraculous quantum event by a Creator God. (shrink)

I present a new argument that we are much more likely to be living in a computer simulation than in the ground-level of reality. (Similar arguments can be marshalled for the view that we are more likely to be Boltzmann brains than ordinary people, but I focus on the case of simulations.) I explain how this argument overcomes some objections to Bostrom’s classic argument for the same conclusion. I also consider to what extent the argument depends upon an (...) internalist conception of evidence, and I refute the common line of thought that finding many simulations being run—or running them ourselves—must increase the odds that we are in a simulation. (shrink)

Plausible assumptions from Cosmology and Statistical Mechanics entail that it is overwhelmingly likely that there will be exact duplicates of us in the distant future long after our deaths. Call such persons “Boltzmann duplicates,” after the great pioneer of Statistical Mechanics. In this paper, I argue that if survival of death is possible at all, then we almost surely will survive our deaths because there almost surely will be Boltzmann duplicates of us in the distant future that stand (...) in appropriate relations to us to guarantee our survival. (shrink)

In recent years, anthropic reasoning has been used to justify a number of controversial skeptical hypotheses. In this paper, we consider two prominent examples, viz. Bostrom’s ‘Simulation Argument’ and the problem of ‘Boltzmann Brains’ in big bang cosmology. We argue that these cases call into question the assumption, central to Bayesian confirmation theory, that the relation of evidential confirmation is universally symmetric. We go on to argue that the fact that these arguments appear to contradict this fundamental assumption (...) should not be taken as an immediate refutation, but should rather be seen as indicative of the peculiar role that the relevant hypotheses play in their respective epistemic frameworks. (shrink)

The possibility of algorithmic consciousness depends on the assumption that conscious states can be copied or repeated by sufficiently duplicating their underlying physical states, leading to a variety of paradoxes, including the problems of duplication, teleportation, simulation, self-location, the Boltzmann brain, and Wigner’s Friend. In an effort to further elucidate the physical nature of consciousness, I challenge these assumptions by analyzing the implications of special relativity on evolutions of identical copies of a mental state, particularly the divergence of these (...) evolutions due to quantum fluctuations. By assuming the supervenience of a conscious state on some sufficient underlying physical state, I show that the existence of two or more instances, whether spacelike or timelike, of the same conscious state leads to a logical contradiction, ultimately refuting the assumption that a conscious state can be physically reset to an earlier state or duplicated by any physical means. Several explanatory hypotheses and implications are addressed, particularly the relationships between consciousness, locality, physical irreversibility, and quantum no-cloning. (shrink)

Accelerating Expansion explores some of the philosophical implications of modern cosmology, focused on the significance that the discovery of the accelerating expansion of the Universe has for our understanding of time, geometry, and physics. The appearance of the cosmological constant in the equations of general relativity allows one to model universes in which space has an inherent tendency towards expansion. This constant, introduced by Einstein but subsequently abandoned by him, returned to centre stage with the discovery of the accelerating expansion. (...) This pedagogically-oriented essay begins with a study of the most basic and elegant relativistic world that involves a positive cosmological constant, de Sitter spacetime. It then turns to the relatives of de Sitter spacetime that dominate modern relativistic cosmology. Some of the topics considered include: the nature of time and simultaneity in de Sitter worlds; the sense in which de Sitter spacetime is a powerful dynamical attractor; the limited extent to which observation can give us information about the topology of space in a world undergoing accelerated expansion; and cosmologists' favourite sceptical worry about the reliability of evidence and the possibility of knowledge, the problem of Boltzmann brains. (shrink)

Many philosophers have been attracted to a restricted version of the principle of indifference in the case of self‐locating belief. Roughly speaking, this principle states that, within any given possible world, one should be indifferent between different hypotheses concerning who one is within that possible world, so long as those hypotheses are compatible with one's evidence. My first goal is to defend a more precise version of this principle. After responding to several existing criticisms of such a principle, I argue (...) that existing formulations of the principle are crucially ambiguous, and I go on to defend a particular disambiguation of the principle. According to the disambiguation I defend, how we should apply this restricted principle of indifference sensitively depends on our background metaphysical beliefs. My second goal is to apply this disambiguated principle to classical skeptical problems in epistemology. In particular, I argue that Eternalism threatens to lead us to external world skepticism, and Modal Realism threatens to lead us to inductive skepticism. (shrink)

What degrees of belief does Sleeping Beauty's evidence support? That depends.

Schulman (Entropy 7(4):221–233, 2005) has argued that Boltzmann’s intuition, that the psychological arrow of time is necessarily aligned with the thermodynamic arrow, is correct. Schulman gives an explicit physical mechanism for this connection, based on the brain being representable as a computer, together with certain thermodynamic properties of computational processes. Hawking (Physical Origins of Time Asymmetry, Cambridge University Press, Cambridge, 1994) presents similar, if briefer, arguments. The purpose of this paper is to critically examine the support for the link (...) between thermodynamics and an arrow of time for computers. The principal arguments put forward by Schulman and Hawking will be shown to fail. It will be shown that any computational process that can take place in an entropy increasing universe, can equally take place in an entropy decreasing universe. This conclusion does not automatically imply a psychological arrow can run counter to the thermodynamic arrow. Some alternative possible explanations for the alignment of the two arrows will be briefly discussed. (shrink)

The contrast between the past-future symmetry of mechanical theories and the time-arrow observed in the behaviour of real complex systems doesn’t have nowadays a fully satisfactory explanation. If one confides in the Laplace-dream that everything be exactly and completely describable by the known mechanical differential equations, the whole experimental evidence of the irreversibility of real complex processes can only be interpreted as an illusion due to the limits of human brain and shortness of human history. In this work it is (...) surmised that in the description of real events it would be more reasonable to renounce exactness and completeness of mechanical differential equations, assuming that also further effects exist in nature, governed by different kinds of rules, in spite of being so weak to be directly unobservable in single motions. This surmise can explain not only the time-arrow, but also why, in particular cases, it can happen that approximate and/or statistical models represent an improvement of mechanical theories instead of an approximation: this happened for Boltzmann gas-model and also for the famous work of Max Planck on blackbody-radiation. And it also appears as a more promising “working hypothesis”, stimulating and guiding us to learn more about limits and origin of the basic equations, and also about the nature of chance and the meaning of probability, which is nowadays not clear in spite of the fundamental role it plays in physics. Particularly that kind of probability which gives the connection between quantum–mechanical differential equations and observable events. (shrink)

It is necessary to distinguish between Boltzmann’s original lecture notes, his extemporaneous lectures, the fair copy of philosophy lectures 3 to 18 by an unknown hand which are mostly on mathematics, and the multi-published versions which only include lectures 1 and 2. There is a difference between his real thought in his notes (or “honne” in Japanese) and what seems to have survived in lectures 1 and 2 for public consumption (“tatamae”). We have stuck with honne, but where it (...) is too abbreviated to make initial sense, we have put it in grammatical and intelligible form as what we think he most probably intended or believed. It was precisely his linguistic philosophy and the relativistic and pragmatic way of presenting it which was largely suppressed or at least toned-down in the fair copy and published versions. Listeners remembered how witty he was when speaking, and the shortened published accounts are also interesting, but his first thoughts, his honne, before prudence set in will interest most readers, though alas as happens with notes there is also some extraneous material. In translating most of the notes for the first three lectures we have ended where mathematics begins to predominate. (shrink)

Pothos & Busemeyer's (P&B's) query about whether quantum probability can provide a foundation for the cognitive modeling embodies so many underlying implications that the subject is far from exhausted. In this brief commentary, however, I suggest that the conceptual thresholds of the meaningful learning give rise to a typical Boltzmann's weighting measure, which indicates astatistical verisimilitudeof quantum behavior in the human cognitive ensemble.

This study discusses the mind-body problem, arguing that the human person is best understood as an animal who is also spirit. Braine suggests that human beings should be described holistically, in the tradition of Aristotle and Thomas Aquinas. His final chapter explores a doctrine of immortality.

Galatea, or the Future of Darwinism W Russell Brain Originally published in 1927 "A brilliant exposition…of the evolutionary hypothesis." The Guardian "Should prove invaluable…" Literary Guide This non-technical but closely-reasoned book is a challenge to the orthodox teaching on evolution known as Neo-Darwinism. The author claims that although Neo-Darwinian theories can possibly account for the evolution of forms, they are quite inadequate to explain the evolution of functions. 88pp ************** Daedalus or Science and the Future J B S Haldane Originally (...) published in 1924. "The essay is brilliant. Sparkling with wit and bristling with challenges." British Medical Journal "Predicts the most startling changes." Morning Post This volume examines the future of scientific research from religious, philosophical social and economic standpoints. 94pp Automaton, or the Future of Mechanical Man H Stafford Hatfield Originally published in 1928 "It is impossible to do justice to his volume in a brief review…"Daily Herald At the time of original publication mankind’s chief inventions had been extensions of his senses or limbs. This work prophesies the dawn of an era in which substitutes will gradually be found even for the human brain. 96pp Gallio or the Tyranny of Science J W N Sullivan Originally published in 1927 "So packed with ideas it is not possible to give any adequate résumé of its contents." Times Literary Supplement "Remarkable monograph…devastating summary of materialism…" Spectator An attack on the values which science is so successfully imposing upon civilization. 90pp. (shrink)

David Braine; III*—The Nature of Knowledge, Proceedings of the Aristotelian Society, Volume 72, Issue 1, 1 June 1972, Pages 41–64, https://doi.org/10.1093/arist.