According to the Gottesman–Knill theorem, quantum algorithms that utilize only the operations belonging to a certain restricted set are efficiently simulable classically. Since some of the operations in this set generate entangled states, it is commonly concluded that entanglement is insufficient to enable quantum computers to outperform classical computers. I argue in this article that this conclusion is misleading. First, the statement of the theorem is, on reflection, already evident when we consider Bell’s and related inequalities in the context of (...) a discussion of computational machines. This, in turn, helps us to understand that the appropriate conclusion to draw from the Gottesman–Knill theorem is not that entanglement is insufficient to enable a quantum performance advantage, but rather that if we limit ourselves to the operations referred to in the Gottesman–Knill theorem, we will not have used the resources provided by an entangled quantum system to their full potential. (shrink)

A primary goal of quantum computer science is to find an explanation for the fact that quantum computers are more powerful than classical computers. In this paper I argue that to answer this question is to compare algorithmic processes of various kinds and to describe the possibility spaces associated with these processes. By doing this, we explain how it is possible for one process to outperform its rival. Further, in this and similar examples little is gained in subsequently asking a (...) how-actually question. Once one has explained how-possibly, there is little left to do. (shrink)

There is a deeply entrenched view in philosophy and physics, the closed systems view, according to which isolated systems are conceived of as fundamental. On this view, when a system is under the influence of its environment this is described in terms of a coupling between it and a separate system which taken together are isolated. We argue against this view, and in favor of the alternative open systems view, for which systems interacting with their environment are conceived of as (...) fundamental, and the environment's influence is represented via the dynamical equations that govern the system's evolution. Taking quantum theories of closed and open systems as our case study, and considering three alternative notions of fundamentality: (i) ontic fundamentality, (ii) epistemic fundamentality, and (iii) explanatory fundamentality, we argue that the open systems view is fundamental, and that this has important implications for the philosophy of physics, the philosophy of science, and for metaphysics. (shrink)

Although computation and the science of physical systems would appear to be unrelated, there are a number of ways in which computational and physical concepts can be brought together in ways that illuminate both. This volume examines fundamental questions which connect scholars from both disciplines: is the universe a computer? Can a universal computing machine simulate every physical process? What is the source of the computational power of quantum computers? Are computational approaches to solving physical problems and paradoxes always fruitful? (...) Contributors from multiple perspectives reflecting the diversity of thought regarding these interconnections address many of the most important developments and debates within this exciting area of research. Both a reference to the state of the art and a valuable and accessible entry to interdisciplinary work, the volume will interest researchers and students working in physics, computer science, and philosophy of science and mathematics. (shrink)

It is argued that those who defend the Everett, or ‘many-worlds’, interpretation of quantum mechanics should embrace what we call the general quantum theory of open systems (GT) as the proper framework in which to conduct foundational and philosophical investigations in quantum physics. GT is a wider dynamical framework than its alternative, standard quantum theory (ST). This is true even though GT makes no modifications to the quantum formalism. GT rather takes a different view, what we call the open systems (...) view, of the formalism; i.e., in GT, the dynamics of systems whose physical states are fundamentally represented by density operators are represented as fundamentally open as specified by an in general non-unitary dynamical map. This includes, in principle, the dynamics of the universe as a whole. We argue that the more general dynamics describable in GT can be physically motivated, that there is as much prima facie empirical support for GT as there is for ST, and that GT could be fully in the spirit of the Everett interpretation—that there might, in short, be little reason for an Everettian not to embrace the more general theoretical landscape that GT allows one to explore. (shrink)

From the philosopher’s perspective, the interest in quantum computation stems primarily from the way that it combines fundamental concepts from two distinct sciences: Physics, in particular Quantum Mechanics, and Computer Science, each long a subject of philosophical speculation and analysis in its own right. Quantum computing combines both of these more traditional areas of inquiry into one wholly new, if not quite independent, science. Over the course of this chapter we will be discussing some of the most important philosophical questions (...) that arise from this merger and philosophical lessons to be learned. (shrink)

I argue that our judgements regarding the locally causal models that are compatible with a given constraint implicitly depend, in part, on the context of inquiry. It follows from this that certain quantum no-go theorems, which are particularly striking in the traditional foundational context, have no force when the context switches to a discussion of the physical systems we are capable of building with the aim of classically reproducing quantum statistics. I close with a general discussion of the possible implications (...) of this for our understanding of the limits of classical description, and for our understanding of the fundamental aim of physical investigation. _1_ Introduction _2_ No-Go Results _2.1_ The CHSH inequality _2.2_ The GHZ equality _3_ Classically Simulating Quantum Statistics _3.1_ GHZ statistics _3.2_ Singlet statistics _4_ What Is a Classical Computer Simulation? _5_ Comparing the All-or-Nothing GHZ with Statistical equalities _6_ General Discussion _7_ Conclusion. (shrink)

I flesh out the sense in which the informational approach to interpreting quantum mechanics, as defended by Pitowsky and Bub and lately by a number of other authors, is (neo-)Bohrian. I argue that on this approach, quantum mechanics represents what Bohr called a “natural generalisation of the ordinary causal description” in the sense that the idea (which philosophers of science like Stein have argued for on the grounds of practical and epistemic necessity) that understanding a theory as a theory of (...) physics requires that one be able to “schematise the observer” within it is elevated in quantum mechanics to the level of a postulate in the sense that interpreting the outcome of a measurement interaction, as providing us with information about the world, requires as a matter of principle, the specification of a schematic representation of an observer in the form of a ‘Boolean frame’—the Boolean algebra representing the yes-or-no questions associated with a given observable representative of a given experimental context. I argue that the approach’s central concern is with the methodological question of how to assign physical properties to what one takes to be a system in a given experimental context, rather than the metaphysical question of what a given state vector represents independently of any context, and I show how the quantum generalisation of the concept of an open system may be used to assuage Einstein’s complaint that the orthodox approach to quantum mechanics runs afoul of the supposedly fundamental methodological requirement to the effect that one must always be able, according to Einstein, to treat spatially separated systems as isolated from one another. (shrink)

I argue that the many worlds explanation of quantum computation is not licensed by, and in fact is conceptually inferior to, the many worlds interpretation of quantum mechanics from which it is derived. I argue that the many worlds explanation of quantum computation is incompatible with the recently developed cluster state model of quantum computation. Based on these considerations I conclude that we should reject the many worlds explanation of quantum computation.

Wittgenstein did not write very much on the topic of probability. The little we have comes from a few short pages of the Tractatus, some 'remarks' from the 1930s, and the informal conversations which went on during that decade with the Vienna Circle. Nevertheless, Wittgenstein's views were highly influential in the later development of the logical theory of probability. This paper will attempt to clarify and defend Wittgenstein's conception of probability against some oft-cited criticisms that stem from a misunderstanding of (...) his views. Max Black, for instance, criticises Wittgenstein for formulating a theory of probability that is capable of being used only against the backdrop of the ideal language of the Tractatus. I argue that on the contrary, by appealing to the 'hypothetical laws of nature', Wittgenstein is able to make sense of probability statements involving propositions that have not been completely analysed. G.H. von Wright criticises Wittgenstein's characterisation of these very hypothetical laws. He argues that by introducing them Wittgenstein makes what is distinctive about his theory superfluous, for the hypothetical laws are directly inspired by statistical observations and hence these observations indirectly determine the mechanism by which the logical theory of probability operates. I argue that this is not the case at all, and that while statistical observations play a part in the formation of the hypothetical laws, these observations are only necessary, but not sufficient conditions for the introduction of these hypotheses. (shrink)

The principle of 'information causality' can be used to derive an upper bound---known as the 'Tsirelson bound'---on the strength of quantum mechanical correlations, and has been conjectured to be a foundational principle of nature. In this paper, however, I argue that the principle has not to date been sufficiently motivated to play this role; the motivations that have so far been given are either unsatisfactorily vague or else amount to little more than an appeal to intuition. I then consider how (...) one might begin to successfully motivate the principle. I argue that a compelling way of so doing is to understand it as a generalisation of Einstein's principle of the mutually independent existence---the 'being-thus'---of spatially distant things, interpreted as a special methodological principle. More specifically: I describe an argument, due to Demopoulos, to the effect that the quantum-mechanical no-signalling condition can be viewed as a generalisation, appropriate to an irreducibly statistical theory such as quantum mechanics, of the Einsteinian principle. And I then argue that a compelling way to motivate information causality is to in turn consider it as a further generalisation of the Einsteinian principle that is appropriate to a theory of communication. I nevertheless describe important obstacles that must yet be overcome if the project of establishing information causality as a foundational principle of nature is to succeed. (shrink)

This book offers a thorough technical elaboration and philosophical defense of an objectivist informational interpretation of quantum mechanics according to which its novel content is located in its kinematical framework, that is, in how the theory describes systems independently of the specifics of their dynamics. -/- It will be of interest to researchers and students in the philosophy of physics and in theoretical physics with an interest in the foundations of quantum mechanics. Additionally, parts of the book may be used (...) as the basis for courses introducing non-physics majors to quantum mechanics, or for self-study by those outside of the university with an interest in quantum mechanics. (shrink)

There has been a long-standing and sometimes passionate debate between physicists over whether a dynamical framework for quantum systems should incorporate not completely positive (NCP) maps in addition to completely positive (CP) maps. Despite the reasonableness of the arguments for complete positivity, we argue that NCP maps should be allowed, with a qualification: these should be understood, not as reflecting ‘not completely positive’ evolution, but as linear extensions, to a system’s entire state space, of CP maps that are only partially (...) defined. Beyond the domain of definition of a partial-CP map, we argue, much may be permitted. (shrink)

I argue that Kant's and Frege's refutations of the ontological argument are more similar than has generally been acknowledged. As I clarify, for both Kant and Frege, to say that something exists is to assert of a concept that it is instantiated. With such an assertion one expresses that there is a particular relation between the instantiating object and a rational subject - a particular mode of presentation for the object in question. By its very nature such a relation cannot (...) be the property of an object and thus cannot be included in the concept of that object. Thus the ontological argument, which takes existence to be a part of the concept of the supreme being, cannot, according to Kant and Frege, succeed. A secondary goal of the paper is to illuminate what I take to be an important affinity between Kant's and Frege's views more generally: that Frege's fundamental distinction between the sense and the referent of a proposition echoes, in an important way, Kant's distinction between concepts and the formal principles for their application to experience. (shrink)

I argue that Immanuel Kant's critical philosophy—in particular the doctrine of transcendental idealism which grounds it—is best understood as an `epistemic' or `metaphilosophical' doctrine. As such it aims to show how one may engage in the natural sciences and in metaphysics under the restriction that certain conditions are imposed on our cognition of objects. Underlying Kant's doctrine, however, is an ontological posit, of a sort, regarding the fundamental nature of our cognition. This posit, sometimes called the `discursivity thesis', while considered (...) to be completely obvious and uncontroversial by some, has nevertheless been denied by thinkers both before and after Kant. One such thinker is Jakob Friedrich Fries, an early neo-Kantian thinker who, despite his rejection of discursivity, also advocated for a metaphilosophical understanding of critical philosophy. As I will explain, a consequence for Fries of the denial of discursivity is a radical reconceptualisation of the method of critical philosophy; whereas this method is a priori for Kant, for Fries it is in general empirical. I discuss these issues in the context of quantum theory, and I focus in particular on the views of the physicist Niels Bohr and the Neo-Friesian philosopher Grete Hermann. I argue that Bohr's understanding of quantum mechanics can be seen as a natural extension of an orthodox Kantian viewpoint in the face of the challenges posed by quantum theory, and I compare this with the extension of Friesian philosophy that is represented by Hermann's view. -/- A shorter version of this paper, focusing specifically on the views of Grete Hermann, has been published as: Cuffaro, Michael (2023). Grete Hermann, Quantum Mechanics, and the Evolution of Kantian Philosophy. In Jeanne Peijnenburg & Sander Verhaegh (eds.), Women in the History of Analytic Philosophy. Cham: Springer. pp. 114-145. (shrink)

This is an extended essay review of Tanya and Jeffrey Bub’s Totally Random: Why Nobody Understands Quantum Mechanics: A serious comic on entanglement. We review the philosophical aspects of the book, provide suggestions for instructors on how to use the book in a class setting, and evaluate the authors’ artistic choices in the context of comics theory. Although Totally Random does not defend any particular interpretation of quantum mechanics, we find that, in its mode of presentation, Totally Random is a (...) beautiful expression and illustration of the information-theoretic interpretation and its value. (shrink)

There has, as of late, emerged a promising strand in the historical and philosophical literature on Bohr that focuses on the central importance assigned in his view to the details of the experimental context under which observations of the systems described by quantum theory are made. Perovic’s book, which I summarize in the first part of this review, belongs to this tradition. The book is not without its shortcomings, which I summarize in the second part of this review, but overall (...) it is a plausible, accessible, and illuminating presentation of Bohr’s views that should be of interest to both historians and philosophers of science. (shrink)

Combining physics, mathematics and computer science, quantum computing and its sister discipline of quantum information have developed in the past few decades from visionary ideas to two of the most fascinating areas of quantum theory. General interest and excitement in quantum computing was initially triggered by Peter Shor (1994) who showed how a quantum algorithm could exponentially “speed-up” classical computation and factor large numbers into primes far more efficiently than any (known) classical algorithm. Shor’s algorithm was soon followed by several (...) other algorithms that aimed to solve combinatorial and algebraic problems, and in the years since theoretical study of quantum systems serving as computational devices has achieved tremendous progress. Common belief has it that the implementation of Shor’s algorithm on a large scale quantum computer would have devastating consequences for current cryptography protocols which rely on the premise that all known classical worst-case algorithms for factoring take time exponential in the length of their input (see, e.g., Preskill 2005). Consequently, experimentalists around the world are engaged in attempts to tackle the technological difficulties that prevent the realisation of a large scale quantum computer. But regardless whether these technological problems can be overcome (Unruh 1995; Ekert and Jozsa 1996; Haroche and Raimond 1996), it is noteworthy that no proof exists yet for the general superiority of quantum computers over their classical counterparts. -/- The philosophical interest in quantum computing is manifold. From a social-historical perspective, quantum computing is a domain where experimentalists find themselves ahead of their fellow theorists. Indeed, quantum mysteries such as entanglement and nonlocality were historically considered a philosophical quibble, until physicists discovered that these mysteries might be harnessed to devise new efficient algorithms. But while the technology for harnessing the power of 50–100 qubits (the basic unit of information in the quantum computer) is now within reach (Preskill 2018), only a handful of quantum algorithms exist, and the question of whether these can truly outperform any conceivable classical alternative is still open. From a more philosophical perspective, advances in quantum computing may yield foundational benefits. For example, it may turn out that the technological capabilities that allow us to isolate quantum systems by shielding them from the effects of decoherence for a period of time long enough to manipulate them will also allow us to make progress in some fundamental problems in the foundations of quantum theory itself. Indeed, the development and the implementation of efficient quantum algorithms may help us understand better the border between classical and quantum physics (Cuffaro 2017, 2018a; cf. Pitowsky 1994, 100), and perhaps even illuminate fundamental concepts such as measurement and causality. Finally, the idea that abstract mathematical concepts such as computability and complexity may not only be translated into physics, but also re-written by physics bears directly on the autonomous character of computer science and the status of its theoretical entities—the so-called “computational kinds”. As such it is also relevant to the long-standing philosophical debate on the relationship between mathematics and the physical world. (shrink)

Hardy and Unruh constructed a family of non-maximally entangled states of pairs of particles giving rise to correlations that cannot be accounted for with a local hidden-variable theory. Rather than pointing to violations of some Bell inequality, however, they pointed to apparent clashes with the basic rules of logic. Specifically, they constructed these states and the associated measurement settings in such a way that the outcomes satisfy some conditionals but not an additional one entailed by them. Quantum mechanics avoids the (...) broken ‘if …then …’ arrows in such Hardy–Unruh chains, as we call them, because it cannot simultaneously assign truth values to all conditionals involved. Measurements to determine the truth value of some preclude measurements to determine the truth value of others. Hardy–Unruh chains thus nicely illustrate quantum contextuality: which variables do and do not obtain definite values depends on what measurements we decide to perform. Using a framework inspired by Bub and Pitowsky and developed in our book Understanding Quantum Raffles (co-authored with Michael E. Cuffaro), we construct and analyze Hardy–Unruh chains in terms of fictitious bananas mimicking the behavior of spin-1/2 particles. (shrink)

A précis of Michael E. Bratman, Shared Agency: A Planning Theory of Acting Together (Oxford University Press, 2014).

We examined the relationship between leader behavioral integrity and leader behavioral courage using data from two studies. Results from Study 1, an online experiment, indicated that behavioral manifestations of leader behavioral integrity and situational adversity both have direct main effects on behavioral manifestations of leader courage. Results from Study 2, a multisource field study with practicing executives, indicated that leader behavioral courage fully mediates the effects of leader behavioral integrity on leader performance and leader executive image. Implications of these findings (...) and future directions are discussed. (shrink)

These are replies to the discussions by Kirk Ludwig, Elizabeth Pacherie, Björn Petersson, Abraham Roth, and Thomas Smith of Michael E. Bratman, Shared Agency: A Planning Theory of Acting Together (Oxford University Press, 2014).

This book challenges the dominant approach to problems of justice in global normative theory and offers a radical alternative designed to transform our thinking about what kind of problem injustice is and how political theorists might do better in understanding and addressing it. It argues that the dominant approach, ideal moral theory (IMT), takes a fundamentally wrong-headed approach to the problem of justice. IMT seeks to work out what an ideally just society would look like, and only then outlines our (...) moral obligations in realizing that ideal. In other words, it ignores the realities of everyday politics. As Michael Goodhart asserts, IMT postpones engagement with actually existing injustices and distorts our understanding of them, and it normalizes many problematic features of our world. On the other hand, the leading alternatives to IMT struggle to make sense of the role values play in politics. This book sees justice as an ideology and develops an innovative bifocal theoretical framework for making sense of it. This framework provides two complementary perspectives on justice: a theoretical perspective that situates competing ideological claims about justice in a broader political context and a partisan perspective that evaluates the structure and coherence of particular conceptions of justice. As opposed to IMT, it focuses on barriers to justice and advocates an activist political theory that takes sides in political struggles against injustice. Goodhart argues that theorists can help to generate the countervailing power necessary for social transformation through the work of articulation, translation, and mapping, work which contributes to a more comprehensive social science of injustice. (shrink)

Daniel, Michael E Review of: Words from the wound: selected addresses, letters and homilies of archbishop mark coleridge, by Mark Coleridge, edited by Anthony Ekpo and David Pascoe, pp. 342, $24.95.

Cases of modest sociality are cases of small scale shared intentional agency in the absence of asymmetric authority relations. I seek a conceptual framework that adequately supports our theorizing about such modest sociality. I want to understand what in the world constitutes such modest sociality. I seek an understanding of the kinds of normativity that are central to modest sociality. And throughout we need to keep track of the relations—conceptual, metaphysical, normative—between individual agency and modest sociality. In pursuit of these (...) theoretical aims, I propose that a central phenomenon is shared intention. I argue that an adequate understanding of the distinctiveness of the intentions of individuals allows us to provide a construction of attitudes of the participants, and of relevant inter-relations and contexts that constitutes shared intention. I explain how shared intention, so understood, differs from a simple equilibrium within common knowledge. And I briefly contrast my views with aspects of views of John Searle and Margaret Gilbert. (shrink)

Drawing upon selected literature from the United Kingdom, Denmark, and Canada we examine how Foucault's concepts of ‘episteme’, ‘rupture’ ‘parrhesia’ ‘care of the self’, and ‘problemitization’ have been applied to particular contexts of leadership development, pedagogy, nursing knowledge, and the relationship between caring and politics. Our aims are threefold: to give examples of how selected Foucauldian concepts have been taken up in practice; to clarify how we are positioned today as nurses; and to invite more nurses to engage critically with (...) historical inquiry and to engage in deep philosophical reflection about their relationship with nursing. We begin by examining the conditions and circumstances of Foucault's life, and conclude by posing the question in our subtitle to stimulate debate about the philosophical relevance of Foucauldian scholarship to nursing. (shrink)

We show that the existence of a recursively enumerable set whose Turing degree is neither low nor complete cannot be proven from the basic axioms of first order arithmetic (P -) together with Σ 2 -collection (BΣ 2 ). In contrast, a high (hence, not low) incomplete recursively enumerable set can be assembled by a standard application of the infinite injury priority method. Similarly, for each n, the existence of an incomplete recursively enumerable set that is neither low n nor (...) high n - 1 , while true, cannot be established in P - + BΣ n + 1 . Consequently, no bounded fragment of first order arithmetic establishes the facts that the high n and low n jump hierarchies are proper on the recursively enumerable degrees. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:78 Discussion c:\users\kenneth\documents\type3401\rj 3401 193 red.docx 2014-05-14 8:54 PM MORE WIT IN PM Michael E. Berumen 37155 Dickerson Run Windsor, co 80550, usa [email protected] eldom does one find a piece by Bertrand Russell without a morsel of humour or wryness. Sometimes the Russellian wit is obvious. Other times it is more subtle, maybe even requiring a second look just to be sure. Headlong into some of his most (...) technical and difficult works, a delightful bon mot might suddenly punctuate the philosophical solemnity. One doesn’t ordinarily think of Principia Mathematica as a sourcebook for Russellian waggishness, but it is there, to be sure—albeit one will negotiate many pages of symbols and scant prose before finding a specimen. Perhaps the best-known witticism amongst cognoscenti is, after having proved 1 + 1 = 2 (PM ∗110.643, 2: 83), the authors observe, “The above proposition is occasionally useful.” The most complete directory for these jewels that I know is by Kenneth Blackwell.1 I thought it unlikely another would be found, so imagine my surprise when, after having dusted off my seldom-used Volume 3 to look something up, I came across a droll nugget that (to the best of my knowledge) has not been highlighted before. Something tells me Russell was biting down on his pipe stem and had a twinkle in his eye when he (I assume Russell, but they, anyway) wrote in the summary of Section A of Part vi, “Quantity”: Great difficulties are caused, in this section, by the existence-theorems and the question of types. These difficulties disappear if the axiom of infinity is assumed, but it seems improper to make the theory of (say) 2/3 depend upon the assumption that the number of objects in the universe is not finite. (PM 3: 234; italics mine) “Improper” indeed, the erstwhile Victorian says! By way of explanation, he goes on to say, We have, accordingly, taken pains not to make this assumption, except where, as in the theory of real numbers, it is really essential, and not merely convenient. Even that has a bit of Russellian sarcasm. So, accept the challenge and find another. In the meantime, take comfort in the knowledge that the sometimes controversial Axiom of Infinity is an unnecessary assumption in mixing one part soda and two parts Red Hackle. 1 “The Wit and Humour of Principia Mathematica”, Russell 31 (2011): 151–60. S... (shrink)

Misunderstandings often develop when scientists from different backgrounds use the same words (e.g., “selection”) when they mean different things by them. Theorists must therefore choose and define their terms carefully. In addition, proponents of “new” theories need to demonstrate empirically that theirs are more powerful than the existing theories they wish to supplant. Wilson & Sober have not yet done this.

Daniel, Michael E Review(s) of: Australians and the Christian god: An historical study, by Hugh Jackson, (Preston: Mosaic Press, 2013), pp.209, $37.95.

Daniel, Michael E Review of: Continental ambitions: Roman catholics in North America: The colonial experience, by Kevin Starr, pp. 605, hardback, $59.99.

Daniel, Michael E Review of: It is right and just: Responses of the Roman Missal, by John M. Cunningham, Strathfield, NSW: St Pauls, 2017, pp. 63, paperback, $9.95.

Daniel, Michael E Review of: Wehrmacht priests: Catholicism and the Nazi war of Annihilation, by Lauren Faulkner Rossi, Cambridge, MA: Harvard University Press, 2015, pp. 255, hardback, $79.00.

This is a reply to discussions by David Copp, Tamar Schapiro, and Sergio Tenenbaum of Michael E. Bratman, Shared Agency: A Planning Theory of Acting Together.

The standard reading of Kuhn's philosophy attributes to him the view that the incommensurability of rival theories and theory-ladenness of observation make rational debate about competing paradigms nearly impossible. If this reflects his real view, then he has claimed something prima facie absurd, and easily refuted with historical counter-examples. It is not the incommensurability thesis per se that is easily refutable, but Kuhn's gestelt interpretation of it. The gestalt interpretation, moreover misrepresents his more fundamental ideas on paradigms, and is in (...) itself confused. The incommensurability thesis can be explained and defended without invoking gestalts, and this reconstructed view can be used to show that familiar criticisms, such as those of Davidson and Laudan, and unwelcome endorsements, such as that of Barnes, which are based on the assumption that Kuhn must be an extreme relativist, are all directed at views that he need not, and should not, hold. (shrink)

Cramer et al. contrast two possible explanations for psychological symptoms: latent variables (i.e., specific cause) versus a network of causality between symptoms. There is a third explanation: The reason for comorbidity and the reported network structure of psychological symptoms is that the underlying biological cause is a psychoneuroimmunoendocrine information network which, when dysregulated, leads to several maladaptive psychological and somatic symptoms.