A laboratory-testable, solid-state Maxwell demon is proposed that utilizes the electric field energy of an open-gap p-n junction. Numerical results from a commercial semiconductor device simulator (Silvaco International–Atlas) verify primary results from a 1-D analytic model. Present day fabrication techniques appear adequate for laboratory tests of principle.

In 1885, during initial discussions of J. C. Maxwell's celebrated thermodynamic demon, Whiting (1) observed that the demon-like velocity selection of molecules can occur in a gravitationally bound gas. Recently, a gravitational Maxwell demon has been proposed which makes use of this observation [D. P. Sheehan, J. Glick, and J. D. Means, Found. Phys. 30, 1227 (2000)]. Here we report on numerical simulations that detail its microscopic phase space structure. Results verify the previously hypothesized mechanism (...) of its paradoxical behavior. This system appears to be the only example of a fully classical mechanical Maxwell demon that has not been resolved in favor of the second law of thermodynamics. (shrink)

It is demonstrated that Maxwell’s demon can be used to allow a machine to extract energy from a heat bath by use of information that is processed by the demon at a remote location. The model proposed here effectively replaces transmission of energy by transmission of information. For that we use a feedback protocol that enables a net gain by stimulating emission in selected fluctuations around thermal equilibrium. We estimate the down conversion rate and the efficiency of (...) energy extraction from the heat bath. (shrink)

Since 2002, at least two kinds of laboratory-testable, solid-state Maxwell demons have been proposed that utilize the electric field energy of an open-gap n-p junction and that seem to challenge the validity of the Second Law of Thermodynamics. In the present paper we present some arguments against the alleged functioning of such devices.

The Latin language is uncharacteristically rich when it comes to describing witches. A witch may be called acantatrixorpraecantrix, asacerdosorvates. She may bedocta,divina,saga, andmaga, avenefica,malefica,lamia,lupula,strix, orstriga. She may be simplyquaedam anus. The available terms are copious and diverse, and the presence of such an abundant differential vocabulary might suggest that Latin made clear linguistic distinctions between various witch types. It would seem a reasonable expectation thatpraecantrices, a word evocative of those who sing of events before they happen, would be concerned with (...) divinatory practices, whileveneficae, given the term's close relationship to the word for poison, would deal in potions or philtres, leaving thelamiae orstriges to function as quasi-demonic bogeys posing threats to the lives of small children. However, this expectation of semantic and morphological concordance remains unfulfilled following any concerted attempt to correlate a witch's title with her function. Because of this disjuncture, this paper proposes to demonstrate not only the inaccuracy of the Latin vocabulary in articulating the functional differences between various witches, but also to assert the essential uniformity of witch characters in so far as each witch is, in essence, a blank canvas onto which a myriad of fears and anxieties may be mapped. (shrink)

In this paper we propose a theoretical model of protein folding and protein evolution in which a polypeptide (sequence/structure) is assumed to behave as a Maxwell Demon or Information Gathering and Using System (IGUS) that performs measurements aiming at the construction of the native structure. Our model proposes that a physical meaning to Shannon information (H) and Chaitin's algorithmic information (K) parameters can be both defined and referred from the IGUS standpoint. Our hypothesis accounts for the interdependence of (...) protein folding and protein evolution through mutual influencing relationships mediated by the IGUS. In brief, IGUS activity in protein folding determines long term tendencies that emerge at the evolutionary time-scale.Thus, protein evolution is a consequence of measurements executed by proteins at the cellular level, where the IGUS imposes a tendency to attain a highly unique stable native form that promotes the updating of the information content. The folding kinetics observed is, thus, the outcome of an evolutionary process where the polypeptide-IGUS drives the evolution of its linear sequence. Finally, we describe protein evolution as an entropic process that tends to increase the content of mutual algorithmic information between the sequence and the structure. This model enables one: 1. To comprehend that full determination of the three-dimensional structure by the linear sequence is a tendency where satisfaction is only possible at thermodynamic equilibrium .2. To account for the observed randomness of the amino acid sequences. 3. To predict an alternation of periods of selection and neutral diffusion during protein evolutionary time. (shrink)

Maxwell’s Demon is a thought experiment devised by J. C. Maxwell in 1867 in order to show that the Second Law of thermodynamics is not universal, since it has a counter-example. Since the Second Law is taken by many to provide an arrow of time, the threat to its universality threatens the account of temporal directionality as well. Various attempts to “exorcise” the Demon, by proving that it is impossible for one reason or another, have been (...) made throughout the years, but none of them were successful. We have shown (in a number of publications) by a general state-space argument that Maxwell’s Demon is compatible with classical mechanics, and that the most recent solutions, based on Landauer’s thesis, are not general. In this paper we demonstrate that Maxwell’s Demon is also compatible with quantum mechanics. We do so by analyzing a particular (but highly idealized) experimental setup and proving that it violates the Second Law. Our discussion is in the framework of standard quantum mechanics; we give two separate arguments in the framework of quantum mechanics with and without the projection postulate. We address in our analysis the connection between measurement and erasure interactions and we show how these notions are applicable in the microscopic quantum mechanical structure. We discuss what might be the quantum mechanical counterpart of the classical notion of “macrostates”, thus explaining why our Quantum Demon setup works not only at the micro level but also at the macro level, properly understood. One implication of our analysis is that the Second Law cannot provide a universal lawlike basis for an account of the arrow of time; this account has to be sought elsewhere. (shrink)

In this paper I will defend an approach to the thought experiment known as ‘Maxwell’s Demon’ based on a Maxwellian conception of statistical mechanics. Instead of assuming that thermodynamic descriptions depend reductively on the dynamics of molecular components, I will adopt a conception of thermophysics as a ‘resource theory’ in the Maxwellian line recently defended by Myrvold (2011) and Wallace (2017). From this interpretative stance, Maxwell’s demon would not lead directly to the plausibility of violating the (...) second law of thermodynamics, but to show the pragmatic impossibility of knowing deterministically the exact microscopic of thermal systems. (shrink)

Must a Maxwell demon must fail to reverse the second law of thermodynamics? Standard attempts to show it must fail make use of notions of information and computation. None of these attempts have succeeded. Worse they have distracted both supporters and opponents of these attempts from a much simpler demonstration of the necessary failure of a Maxwell's demon that employs no notions of information or computation. It requires only Liouville's theorem and its quantum analog.

This paper proves that Maxwell's Demon is compatible with classical mechanics. In particular it shows how the cycle of operation - including measurement and erasure - can be carried out with no entropy cost, contrary to the Landauer-Bennett thesis (according to which memory erasure costs kln2 of entropy increase per bit). The Landauer-Bennet thesis is thus proven to be mistaken.

We study a model proposed by Liboff (Found. Phys. Lett. 10:89, 1997) to violate the second law of thermodynamics. Discs are moving without friction in three connected channels inclined by π/3 with respect to each other. Based on the geometry considerations, it was argued that eventually all the discs end up in the middle channel regardless of their initial positions. This would mean a decrease of the entropy of the system and violation of the second law. We argue that no (...) such anomalous behavior occurs in the system. (shrink)

In this paper we show how a form of Maxwellian Demon can be interpreted as a computing automaton. We then point out some ways in which the Demon systems can be generalized, and briefly describe and discuss the properties of some of the corresponding automata. It is shown that a generalized Maxwell Demon system can carry out arbitrary Turing computations. Finally, the association developed between classes of thermodynamic systems and classes of computational systems is employed to (...) suggest approaches to some fundamental problems of the relationships between computation, the information obtained by computation, and energy. (shrink)

Boltzmann's gas model representing the second law of thermodynamics is based on the improbability of certain molecular distributions in space. Maxwell argued that a hypothetical ‘being’ with the faculty of seeing individual molecules could bring about such improbable distributions, thus violating the law of entropy. However, it appears that to render the molecules visible for any observer would increase the entropy more than the demon could decrease it, hence ‘Maxwell's Demon cannot operate’ . In the study (...) presented here Maxwell's Demon is interpreted in a general way as a biological observer system within systems which can upset thermodynamic probabilities provided that the relative magnitudes between observer system and observed system are appropriate.Maxwell's Demon within Boltzmann's Gas Model thus appears only as a special case of inappropriate, relative magnitude between the two systems. (shrink)

This paper argues that the idea of a Maxwellian Demon presupposes a notion of non-physical free will. The author has changed her mind in this point later on and now thinks that Mawellian Demons are compatible with mechanics; see her paper on this from 2010 and book from 2012.

A particle of molecular dimensions which can exist in two states is associated with a membrane pore through which molecules of a gas can pass. The gas molecules from two identical phases on either side of the membrane may pass only when the particle is in one particular state. If certain restrictions are imposed on the system, then the particle appears to act like a Maxwell's Demon(1) which “handles” the gas molecules during their passage through the pore.

This paper defends an internalist perspective of selection based on the hypothesis that considers living evolutionary units as Maxwell's demons (MD) or Zurek's Information Gathering and Using Systems (IGUS). Individuals are considered as IGUS that extract work by means of measuring and recording processes. Interactions or measurements convert uncertainty about the environment (Shannon's information, H) into internalized information in the form of a compressed record (Chaitin's algorithmic complexity, K). The requirements of the model and the limitations inherent to its (...) formalization are discussed. This approach offers an alternative view to the causes of evolutionary variations which goes beyond the classical Lamarckian-Darwinian controversy. I argue that random variations only apply near-to-equilibrium at the time organisms have attained structural closure, and that a speed up of mutation rates that facilitates the production of directed variations occurs far-from-equilibrium due to organisms' openness to the surrounding conditions. However, real organisms are located somewhere between the above two cases and thus, operate at an intermediate stage where there is a maximum efficiency of H/K conversion. In consequence, IGUS keep their autonomy and evolving capacity by compromising between external circumstances and inner constraints. This compromise is made possible by closure regulation. Likewise, this model explains why nature has favored the selection of agents capable of selectively recording a partial description of their environment. (shrink)

The development of synthetic biology calls for accurate understanding of the critical functions that allow construction and operation of a living cell. Besides coding for ubiquitous structures, minimal genomes encode a wealth of functions that dissipate energy in an unanticipated way. Analysis of these functions shows that they are meant to manage information under conditions when discrimination of substrates in a noisy background is preferred over a simple recognition process. We show here that many of these functions, including transporters and (...) the ribosome construction machinery, behave as would behave a material implementation of the informationmanaging agent theorized by Maxwell almost 150 years ago and commonly known as Maxwell’s demon (MxD). A core gene set encoding these functions belongs to the minimal genome required to allow the construction of an autonomous cell. These MxDs allow the cell to perform computations in an energy-efficient way that is vastly better than our contemporary computers. (shrink)

We present an analysis of Szilard's one-molecule Maxwell's demon, including a detailed entropy accounting, that suggests a general theory of the entropy cost of information. It is shown that the entropy of the demon increases during the expansion step, due to the decoupling of the molecule from the measurement information. It is also shown that there is an entropy symmetry between the measurement and erasure steps, whereby the two steps additivelv share a constant entropy change, but the (...) proportion that occurs during each of the two steps is arbitrary. Therefore the measurement step may be accompanied by an entropy increase, a decrease, or no change at all, and likewise for the erasure step. Generalizing beyond the demon, decorrelation between a physical system and information about that system always causes an entropy increase in the joint system comprised of both the original system and the information. Decorrelation causes a net entropy increase in the universe unless, as in the Szilard demon, the information is used to decrease entropy elsewhere before the correlation is lost. Thus, information is thermodynamically costly precisely to the extent that it is not used to obtain work from the measured system. (shrink)

It is generally accepted, following Landauer and Bennett, that the process of measurement involves no minimum entropy cost, but the erasure of information in resetting the memory register of a computer to zero requires dissipating heat into the environment. This thesis has been challenged recently in a two-part article by Earman and Norton. I review some relevant observations in the thermodynamics of computation and argue that Earman and Norton are mistaken: there is in principle no entropy cost to the acquisition (...) of information, but the destruction of information does involve an irreducible entropy cost. (shrink)

This book provides a conceptual foundation for statistical mechanics, which is - more generally - a conceptual framework for understanding natural kinds, which later became the conceptual framework for our reductive-physicalist view of the mind called Flat Physicalism.

The problem of the irreversibility's origin in thermodynamic processes occupies a distinguished place among many and lasting attempts by researchers to derive irreversibility from molecular-mechanical principles. However, this problem is still open and no universally accepted solution may be given during any course. In this paper, I shall try to show that the examining of Maxwell's demon thought experiment may provide insight into the difficulties that emerge, looking for this origin because: it is connected with the notion of (...) irreversibility, and one of its functions is that of the "reversibility objection." In order to illustrate this point, I study Boltzmann's approach to the problem of a molecular-mechanical interpretation of irreversibility and I show that an auxiliary assumption is responsible for producing irreversibility. But this result is accordant with the predictions of Maxwell's demon thought experiment: the assumptions of this kind are not dictated by molecular-mechanical principles but are separate input in the model-systems used. (shrink)

demon thought experiment remains ambiguous even today. One of the most delightful thought It seems that Maxwell originally invoked experiments in the history of physical science is..

In 1866 J.C. Maxwell thought he had discovered a Maxwellian demon—though not under that description, of course [1]. He thought that the temperature of a gas under gravity would vary inversely with the height of the column. From this he saw that it would then be possible to obtain energy for work from a cooling gas, a clear violation of Thompson’s statement of the second law of thermodynamics. This upsetting conclusion made him worry that “there remains as far (...) as I can see a collision between Dynamics and thermodynamics.” Later, he derived the Maxwell-Boltzmann distribution law that made the temperature the same throughout the column. However, he continued to think about the relationship between dynamics and thermodynamics, and in 1867, he sent Tait a note with a puzzle for him to ponder. The puzzle was his famous “neat-fingered being” who could make a hot system hotter and a cold system colder without any work being done. Thompson in 1874 christened this being a “demon”; Maxwell unsuccessfully tried to rename it “valve.” However named, the demon’s point was to “show that the second law of thermodynamics has only a statistical validity.” Since that time a large physics literature has arisen that asks a question similar to that asked in theology, namely, does the devil exist? Beginning with Popper, philosophers examining the literature on Maxwell’s demon are typically surprised—even horrified [2,3,4,5,6,7]. As a philosopher speaking at a physics conference exactly 100 yrs after Popper’s birth, I want to explain why this is so. The organizers of this conference instructed me to offend everyone, believers and non-believers in demons. Thus my talk, apart from an agnostic middle section, contains a section offending those who believe they have exorcized the demon and a section offending those who summon demons. Throughout the central idea will be to clearly distinguish the various second laws and the various demons.. (shrink)

Recently Albert and Hemmo and Shenker have argued that, contrary to what is sometimes suggested, Liouville's theorem does not prohibit a Maxwellian demon from operating but merely places certain restrictions on its ability to operate. There are two main claims made in this article. First, that the restrictions Liouville's theorem places on Maxwell's demon's ability to operate depend on which notion of entropy one adopts. Second, that when one operates with the definition of entropy that is usual (...) in this debate, the restrictions put on Maxwell's demon are not even as severe as Albert and Hemmo and Shenker argue. (shrink)

Norton describes how a Maxwell’s demon can be exorcised merely by considerations of the conservation of phase volume in classical physics. This exorcism is generalized here to quantum physics.

This chapter contains section titled: Discussion.

Landauer's principle, often regarded as the basic principle of the thermodynamics of information processing, holds that any logically irreversible manipulation of information, such as the erasure of a bit or the merging of two computation paths, must be accompanied by a corresponding entropy increase in non-information-bearing degrees of freedom of the information-processing apparatus or its environment. Conversely, it is generally accepted that any logically reversible transformation of information can in principle be accomplished by an appropriate physical mechanism operating in a (...) thermodynamically reversible fashion. These notions have sometimes been criticized either as being false, or as being trivial and obvious, and therefore unhelpful for purposes such as explaining why Maxwell's Demon cannot violate the second law of thermodynamics. Here I attempt to refute some of the arguments against Landauer's principle, while arguing that although in a sense it is indeed a straightforward consequence or restatement of the Second Law, it still has considerable pedagogic and explanatory power, especially in the context of other influential ideas in nineteenth and twentieth century physics. Similar arguments have been given by Jeffrey Bub. (shrink)

Landauer’s principle is the loosely formulated notion that the erasure of n bits of information must always incur a cost of k ln n in thermodynamic entropy. It can be formulated as a precise result in statistical mechanics, but for a restricted class of erasure processes that use a thermodynamically irreversible phase space expansion, which is the real origin of the law’s entropy cost and whose necessity has not been demonstrated. General arguments that purport to establish the unconditional validity of (...) the law fail. They turn out to depend on the illicit formation of a canonical ensemble from memory devices holding random data. To exorcise Maxwell’s demon one must show that all candidate devices—the ordinary and the extraordinary—must fail to reverse the second law of thermodynamics. The theorizing surrounding Landauer’s principle is too fragile and too tied to a few specific examples to support such general exorcism. Charles Bennett’s recent extension of Landauer’s principle to the merging of computational paths fails for the same reasons as trouble the original principle. (shrink)

In this first part of a two-part paper, we describe efforts in the early decades of this century to restrict the extent of violations of the Second Law of thermodynamics that were brought to light by the rise of the kinetic theory and the identification of fluctuation phenomena. We show how these efforts mutated into Szilard’s proposal that Maxwell’s Demon is exorcised by proper attention to the entropy costs associated with the Demon’s memory and information acquisition. In (...) the second part we will argue that the information theoretic exorcisms of the Demon provide largely illusory benefits. According to the case, they either return a presupposition that can be had without information theoretic consideration or they postulate a broader connection between information and entropy than can be sustained. (shrink)

In this second part of our two-part paper we review and analyse attempts since 1950 to use information theoretic notions to exorcise Maxwell’s Demon. We argue through a simple dilemma that these attempted exorcisms are ineffective, whether they follow Szilard in seeking a compensating entropy cost in information acquisition or Landauer in seeking that cost in memory erasure. In so far as the Demon is a thermodynamic system already governed by the Second Law, no further supposition about (...) information and entropy is needed to save the Second Law. In so far as the Demon fails to be such a system, no supposition about the entropy cost of information acquisition and processing can save the Second Law from the Demon. (shrink)

This paper examines some common measures of complexity, structure, and information, with an eye toward understanding the extent to which complexity or information‐content may be regarded as objective properties of individual objects. A form of contextual objectivity is proposed which renders the measures objective, and which largely resolves the puzzle of Maxwell's Demon.

We propose a new way of looking at the quantum Maxwell’s demon problem in terms of conditional action. A “conditional action” on a system is a unitary time evolution, selected according to the result of a previous measurement, which can reduce the entropy of the system. However, any conditional action can be realized by an unitary time evolution of a larger system and a subsequent Lüders measurement, whereby the entropy of the entire system is either increased or remains (...) constant. We give some examples that illustrate and confirm our proposal, including the erasure of N qubits and the Szilard engine, thus relating the present approach to the Szilard principle and the Landauer principle that have been discussed as possible solutions of the Maxwell’s demon problem. (shrink)

Landauer’s principle is the loosely formulated notion that the erasure of n bits of information must always incur a cost of k ln n in thermodynamic entropy. It can be formulated as a precise result in statistical mechanics, but for a restricted class of erasure processes that use a thermodynamically irreversible phase space expansion, which is the real origin of the law’s entropy cost and whose necessity has not been demonstrated. General arguments that purport to establish the unconditional validity of (...) the law fail. They turn out to depend on the illicit formation of a canonical ensemble from memory devices holding random data. To exorcise Maxwell’s demon one must show that all candidate devices—the ordinary and the extraordinary—must fail to reverse the second law of thermodynamics. The theorizing surrounding Landauer’s principle is too fragile and too tied to a few specific examples to support such general exorcism. Charles Bennett’s recent extension of Landauer’s principle to the merging of computational paths fails for the same reasons as trouble the original principle. (shrink)

This article discusses the writings of the devout Christian physicist James Clerk Maxwell (best known for his epochal work in electromagnetism and statistical mechanics) on the concept of conscious free-will. To Maxwell a correct understanding of free will, as personified in the example of the railway pointsman, was essential to clear conceptions of both man as a religious creature and of the limits of science. Understanding human volition, then, was not an end unto itself. It was a foundation (...) on which one could build reliable theories of man and matter. (shrink)

In my master's thesis for physics and philosophy, I take a long and hard look at the debates surrounding Maxwell's Demon and the status of the second law of thermodynamics. I try to clarify the use of Maxwell's thought experiment in understanding the second law; to prove that the second law is contingent, given only classical mechanics and time asymmetry; to argue that the law only holds because of facts about the kinds of particles that exist in (...) our universe; to show that and why the attempts to banish the demon using fluctuations, measurements or information or erasure have been unsuccessful; and I conclude that Maxwell's Demon is alive and kicking. (shrink)

Book review of Meir Hemmo and Orly Shenker's book "The Road to Maxwell's Demon: Conceptual Foundations of Statistical Mechanics.".

Two decades ago, Rolf Landauer (1991) argued that “information is physical” and ought to have a role in the scientific analysis of reality comparable to that of matter, energy, space and time. This would also help to bridge the gap between biology and mathematics and physics. Although it can be argued that we are living in the ‘golden age’ of biology, both because of the great challenges posed by medicine and the environment and the significant advances that have been made—especially (...) in genetics and molecular and cell biology—we feel that information as an essential aspect of life has been neglected, or at least misunderstood. We therefore summon Maxwell’s Demon and its distant relative the ratchet, and apply these to biology. (shrink)

This book is the first all-encompassing exploration of the role of demons in philosophical and scientific thought experiments. In Part I, the author explains the importance of thought experiments in science and philosophy. Part II considers Laplace's Demon, whose claim is that the world is completely deterministic. Part III introduces Maxwell's Demon, who - by contrast - experiences a world that is probabilistic and indeterministic. Part IV explores Nietzsche's thesis of the cyclic and eternal recurrence of events. (...) In each case a number of philosophical consequences regarding determinism and indeterminism, the arrows of time, the nature of the mind and free will are said to follow from the Demons's worldviews. The book investigates what these Demons - and others - can and cannot tell us about our world. (shrink)

In this critical discussion, I examine Jimena Canales' "Bedeviled: A Shadow History of Demons in Science," which explores the historical and philosophical roles of imaginary demons in scientific thought. The book traces how conceptual figures such as Laplace’s demon—symbolizing determinism—and Maxwell’s demon—challenging the second law of thermodynamics—have shaped scientific discourse by questioning established principles and prompting paradigm shifts. While Canales primarily situates these demons within the broader history of science, I argue that her work also offers valuable (...) insights for the philosophy of scientific discovery. By illustrating how conceptual constraints, paradoxes, and thought experiments influence the emergence of new theories, she provides a deeper understanding of the conditions under which scientific breakthroughs occur. This perspective aligns with recent discussions on the epistemic and heuristic dimensions of discovery, making a compelling case for the enduring role of imaginary constructs in scientific progress. (shrink)

In their book The Road to Maxwell's Demon Hemmo & Shenker re-describe the foundations of statistical mechanics from a purely empiricist perspective. The result is refreshing, as well as intriguing, and it goes against much of the literature on the demon. Their conclusion, however, that Maxwell's demon is consistent with statistical mechanics, still leaves open the question of why such a demon hasn't yet been observed on a macroscopic scale. This essay offers a sketch (...) of what a possible answer could look like. (shrink)

Poreskoro, with three cat and four dog heads and a snake with a forked tongue as his tail, is responsible for epidemics of contagious diseases in Romany folklore. The Pishachas of Vedic mythology lurk in charnel houses and graveyards, waiting for humans to infect with madness. In Christian demonology, Pythius is known as the ruler of the eighth circle of the Inferno, bestowing heinous and unspeakable tortures on those who have committed fraud. Demons are the stuff of legends, and they (...) are everywhere in mythology and theology. These are just three of the more than thirty I counted that start with the letter P.How lucky we are for the advent of science. A rational tonic, it scatters our demons, demystifying the world for us—or so, at least, we think. As Canales brilliantly shows in this book, our assumption has been far off the mark. In physics, computer science, genetics, neuroscience, and economics, not to mention in the very foundations of rationality itself, an underworld of imaginary creatures has sustained and continues to inhabit modern science. Scientific demons appear in many guises: as atomic and subatomic particle manipulators, as feedback and parallel-processing experts, as messengers who can travel faster than the speed of light, as computer-code spies, gene and bit selectors in evolution and in informatics, as triggers of cascades from the nano level to the level of full-blown ecological and astrophysical theaters. By inventing them, we have learned that causality does not always hold at the level of atoms, that the speed of message transmission is limited, that living systems spend energy, that perpetual-motion machines are impossible, and that there are corners of the universe we have not imagined.We have all heard of Laplace's Demon, and Maxwell's, but who knew that, borrowing from physics, the historian Henry Adams considered the action of demons in geopolitics or that the economist Paul Samuelson analyzed their role in producing more efficient markets? Who knew that the generation that gave us the Internet and artificial intelligence were tasked by their teachers in graduate school to insert as many demons as possible into their programs? Who among us has heard of Darwin's Demon, or Maxwell-Szilárd-Brillouin's, or Monod's, or Loschmidt's? Who is aware of Norbert Weiner's use of demons in conceptualizing cybernetics, or of the great scholar of Kabbalah Gershom Scholem's comparison between Israel's superfast computers and the Golem?As Canales shows convincingly, it has been difficult for both historians and scientists to countenance demons in science, and so they have been written out, in many ways and many instances, of the histories of which they are part and parcel. Thomas Kuhn and even the more radical philosopher Paul Feyerabend both failed to acknowledge in their social critiques of science the extent to which an imaginary underworld of beings has been constitutive of the modern scientific imagination. Ironically, it was the man who provided a hard-and-fast criterion by which to distinguish scientific and nonscientific pursuits, Karl Popper, who ultimately saw the light. Revisiting his classic book The Logic of Scientific Discovery from 1934, he clarified in Postscript to the Logic of Scientific Discovery in 1982 the extent to which every historical era has been characterized by a particular demon. We moderns believe that science is about facts and numbers, but we are mistaken. As Canales beautifully summarizes the stakes of her project, “What first sets science on its path of discovery—then as now—is the continued use of the imagination.”Tracking the fate of demons in modern thought from Descartes to Lord Kelvin to H. G. Wells to David Bohm, and from Conrad Hal Waddington to Henry Compton to Stephen Hawking and Steven Pinker, Bedeviled assumes that the demons of the church or of paganism and the demons of science differ and resemble each other in ways that can be usefully elaborated. What is more crucial, however, is how such demons become real, how they morph from fears to hopes, and from thought experiments into real experiments, and ultimately to things in this world like computer programs, transistors, and nanorobots. From weather systems to messenger RNAs to black holes, demons emerge everywhere. The hard question is: How does the imagination actually drive discovery and understanding? How does it change our world?Perhaps it has been a sidetrack to consider whether we have or have never been modern. Clearly, what reason will not allow, it perennially recruits for a shadowland that helps us to better see our world. Rather than aiming to exorcise science, one day, of all of its methodological and epistemological ghosts, perhaps we might make peace with the notion that every culture struggles with distinguishing truth from falsehood in its own unique way. Such struggles are sensitive to their times and are accomplished through leaps of imagination. But fear not: the debunking of “Western rationality” casts no wet blanket on the project of Enlightenment. If anything, as Canales writes, “an account of science that considers how scientists themselves do science only risks adding new insights into our repertoire of knowledge.” Perhaps, therefore, there is solace to be gained from the dictum, Always choose the Devil you know. Ultimately, there may be no other way forward. (shrink)