When discussing quantum ontology, the debate has recently focused on comparing and contrasting wavefunction realism and its rivals. Among them one finds the primitive ontology approach, which is often conflated with the local beables program. In this paper I wish to clarify what I take to be the distinction between the notion of primitive ontology and the one of local beable. I argue that the primitive ontology is the local beable which allows for a dynamical, constructive explanation which preserves (...) symmetries. (shrink)

The centerpiece of Jeffrey Bub's book Interpreting the Quantum World is a theorem (Bub and Clifton 1996) which correlates each member of a large class of no-collapse interpretations with some 'privileged observable'. In particular, the Bub-Clifton theorem determines the unique maximal sublattice L(R,e) of propositions such that (a) elements of L(R,e) can be simultaneously determinate in state e, (b) L(R,e) contains the spectral projections of the privileged observable R, and (c) L(R,e) is picked out by R and e alone. In (...) this paper, we explore the issue of maximal determinate sets of observables using the tools provided by the algebraic approach to quantum theory; and we call the resulting algebras of determinate observables, "maximal *beable* subalgebras". The capstone of our exploration is a generalized version of Bub and Clifton's theorem that applies to arbitrary (i.e., both mixed and pure) quantum states, to Hilbert spaces of arbitrary (i.e., both finite and infinite) dimension, and to arbitrary observables (including those with a continuous spectrum). Moreover, in the special case covered by the original Bub-Clifton theorem, our theorem reproduces their result under strictly weaker assumptions. This added level of generality permits us to treat several topics that were beyond the reach of the original Bub-Clifton result. In particular: (a) We show explicitly that a (non-dynamical) version of the Bohm theory can be obtained by granting privileged status to the position observable. (b) We show that Clifton's (1995) characterization of the Kochen-Dieks modal interpretation is a corollary of our theorem in the special case when the density operator is taken as the privileged observable. (c) We show that the 'uniqueness' demonstrated by Bub and Clifton is only guaranteed in certain special cases -- viz., when the quantum state is pure, or if the privileged observable is compatible with the density operator. We also use our results to articulate a solid mathematical foundation for certain tenets of the orthodox Copenhagen interpretation of quantum theory. For example, the uncertainty principle asserts that there are strict limits on the precision with which we can know, simultaneously, the position and momentum of a quantum-mechanical particle. However, the Copenhagen interpretation of this fact is not simply that a precision momentum measurement necessarily and uncontrollably disturbs the value of position, and vice-versa; but that position and momentum can never in reality be thought of as simultaneously determinate. We provide warrant for this stronger 'indeterminacy principle' by showing that there is no quantum state that assigns a sharp value to both position and momentum; and, a fortiori, that it is mathematically impossible to construct a beable algebra that contains both the position observable and the momentum observable. We also prove a generalized version of the Bub-Clifton theorem that applies to "singular" states (i.e., states that arise from non-countably-additive probability measures, such as Dirac delta functions). This result allows us to provide a mathematically rigorous reconstruction of Bohr's response to the original EPR argument -- which makes use of a singular state. In particular, we show that if the position of the first particle is privileged (e.g., as Bohr would do in a position measuring context), the position of the second particle acquires a definite value by virtue of lying in the corresponding maximal beable subalgebra. But then (by the indeterminacy principle) the momentum of the second particle is not a beable; and EPR's argument for the simultaneous reality of both position and momentum is undercut. (shrink)

Summarya) Bell tries to formulate more explicitly a notion of “local causality”: correlations between physical events in different space‐time regions should be explicable in terms of physical events in the overlap of the backward light cones. It is shown that ordinary relativistic quantum field theory is not locally causal in this sense, and cannot be embedded in a locally causal theory.b) Clauser, Home and Shimony criticize several steps in Bell's argument that any theory of local “beables” is incompatible with (...) quantum mechanics. It is contended that the Clauser‐Horne derivation of a Bell‐type inequality circumvents his weak steps. The Clauser‐Horne derivation must assume that there are no undetected correlations between choices of controllable variables in two space‐like separated regions. Methodological considerations support this assumption.c) In response to criticism by Shimony, Home, and Clauser, Bell tries to clarify the argument of “The theory of local beables”, and to defend as permissible the hypothesis of free variables.d) Bell's reply to an earlier criticism by Shimony, Clauser, and Home is answered. The convergence of Bell's position towards theirs is noted. (shrink)

Is the quantum state part of the furniture of the world? Einstein found such a position indigestible, but here I present a different understanding of the wavefunction that is easy to stomach. First, I develop the idea that the wavefunction is nomological in nature, showing how the quantum It or Bit debate gets subsumed by the corresponding It or Bit debate about laws of nature. Second, I motivate the nomological view by casting quantum mechanics in a “classical” formalism (Hamilton–Jacobi theory) (...) and classical mechanics in a “quantum” formalism (Koopman–von Neumann theory) and then comparing and contrasting classical and quantum wave functions. I argue that Humeans about laws can treat classical and quantum wave functions on a par and that doing so yields many benefits. (shrink)

I discuss the interpretation of spontaneous collapse theories, with particular reference to Bell's suggestion that the stochastic jumps in the evolution of the wave function should be considered as local beables of the theory. I develop this analogy in some detail for the case of non-relativistic GRW-type theories, using a generalisation of Bell's notion of beables to POV measures. In the context of CSL-type theories, this strategy appears to fail, and I discuss instead Ghirardi and co-workers' mass-density interpretation (...) and its relation to Schrödinger's original charge-density interpretation. This discussion is extended to relativistic CSL-type theories. A few remarks on Everett's interpretation conclude the paper. (shrink)

It is argued that the measurement problem reduces to the problem of modeling quasi-classical systems in a modified quantum mechanics with superselection rules. A measurement theorem is proved, demonstrating, on the basis of a principle for selecting the quantities of a system that are determinate (i.e., have values) in a given state, that after a suitable interaction between a systemS and a quasi-classical systemM, essentially only the quantity measured in the interaction and the indicator quantity ofM are determinate. The theorem (...) justifies interpreting the noncommutative algebra of observables of a quantum mechanical system as an algebra of “beables,” in Bell's sense. (shrink)

The call to supplement the quantum wave function with local beables is almost as old as quantum mechanics. But what exactly is the problem with the wave function as the representation of a quantum system? I canvass three potential problems with the wave function: the well-known problems of incompleteness and dimensionality, and the lesser known problem of non-locality introduced recently by Myrvold. Building on Myrvold's insight, I show that the standard ways of introducing local beables into quantum mechanics (...) are unsuccessful. I consider whether we really need local beables, and assess the prospects for a new theory of local beables. (shrink)

Bell introduces local beables in contrast to quantum mechanical observables. The present article emphasizes the importance and necessity of introducing local beables in quantum mechanics from the ontological and epistemological points of view. We argue that suggesting beables in the ontology of quantum mechanics is necessary to give an adequate account of its testability.

It is shown how, starting with the de Broglie–Bohm pilot-wave theory, one can construct a new theory of the sort envisioned by several of QM’s founders: a Theory of Exclusively Local Beables (TELB). In particular, the usual quantum mechanical wave function (a function on a high-dimensional configuration space) is not among the beables posited by the new theory. Instead, each particle has an associated “pilot-wave” field (living in physical space). A number of additional fields (also fields on physical (...) space) maintain what is described, in ordinary quantum theory, as “entanglement.” The theory allows some interesting new perspective on the kind of causation involved in pilot-wave theories in general. And it provides also a concrete example of an empirically viable quantum theory in whose formulation the wave function (on configuration space) does not appear—i.e., it is a theory according to which nothing corresponding to the configuration space wave function need actually exist. That is the theory’s raison d’etre and perhaps its only virtue. Its vices include the fact that it only reproduces the empirical predictions of the ordinary pilot-wave theory (equivalent, of course, to the predictions of ordinary quantum theory) for spinless non-relativistic particles, and only then for wave functions that are everywhere analytic. The goal is thus not to recommend the TELB proposed here as a replacement for ordinary pilot-wave theory (or ordinary quantum theory), but is rather to illustrate (with a crude first stab) that it might be possible to construct a plausible, empirically viable TELB, and to recommend this as an interesting and perhaps-fruitful program for future research. (shrink)

We discuss the question of the relativistic invariance of a quantum theory based on beables, and we suggest the general outlines of one possible form of such a theory.

John S. Bell is known, among other things, for the introduction of the notion of beable. The development of this notion inspired the so-called primitive ontology (PO) approach to the foundations of quantum mechanics, proposed for the first time by Detlef Dürr, Sheldon Goldstein and Nino Zanghì in 1992. It is not very well known, however, that the Bell theory of beables had an early formulation, in which Bell curiously adopts some Bohr-reminiscent insights to attack exactly the standard Copenhagen (...) version of quantum mechanics. Here I reconstruct the two stages of the Bell theory of beables, showing that the first stage is in fact unable to adequately confront the foundational problem it was designed to address. Only the second stage of the Bell theory could represent a motivation for the PO approach: in this respect, it may be of some interest to compare the two-stage reconstruction of the Bell theory with recent analyses of the PO approach in terms of beables. I dedicate this paper to the dear memory of Detlef Dürr, a leading figure of the international community of the foundations of physics and a lovely man. He will be long remembered for his inspiring contributions: it was a privilege to enjoy his company and his doctrine. (shrink)

I defend the idea that objects and events in three-dimensional space are part of the derivative ontology of quantum mechanics, rather than its fundamental ontology. The main objection to this idea stems from the question of how it can endow local beables with physical salience, as opposed to mere mathematical definability. I show that the responses to this objection in the previous literature are insufficient, and I provide the necessary arguments to render them successful. This includes demonstrating the legitimacy (...) of dynamical considerations in the derivation of local beables and responding to the threat stemming from the availability of different sets of local beables in the context of the GRW theory. (shrink)

Do theories of quantum mechanics and quantum gravity require spacetime to be a basic, ground level feature, or can spacetime be seen as an emergent element of these theories? While several commentators have raised serious doubts about the prospects of forgoing the standard spacetime backdrop, it will be argued that a defense of these emergent spacetime interpretations of quantum mechanics and quantum gravity hypotheses can be made, whether as an inference to the best explanation or using another strategy. Furthermore, the (...) idea that space and time can arise from a quite different, non-spatiotemporal level of reality will be shown to have various historical precedents, especially in the seventeenth and eighteenth centuries, a realization that may help dispel some of the mystery associated with these types of hypotheses. (shrink)

A field-theoretic version of Wigner’s friend (1961) illustrates how the quantum measurement problem arises for field theory. Similarly, considering spacelike separate measurements of entangled fields by observers akin to Wigner’s friend shows the sense in which relativistic constraints make the measurement problem particularly difficult to resolve in the context of a relativistic field theory. We will consider proposals by Wigner (1961), Bloch (1967), Helwig and Kraus (1970), and Bell (1984) for resolving the measurement problem for quantum field theory. We will (...) conclude by considering the possibility of giving up rich dynamical explanation in the context of a many-maps formulation of relativistic quantum field theory. (shrink)

In another essay, I’ve argued by means of a formal analogy between (i) the incompleteness of Principia Mathematica-style systems of mathematical logic (logico-mathematical incompleteness) and (ii) the incompleteness of the Standard Models in contemporary physics (physico-mechanical incompleteness), that (iii) just as the fact of logico-mathematical incompleteness entails the existence of mathematical creativity, so too the fact of physico-mechanical incompleteness entails the existence of natural creativity. Building on that line of thought, in this essay I present a new and empirically-testable strategy (...) for completing quantum mechanics. More precisely, I argue that if we assume that the Standard Models in contemporary physics are incomplete, and if we also assume that all rational human animals are primitive sources of natural creativity via their free agency, then, by means of an appeal to Bohmian mechanics, together with the thesis that all rational human animals are primitive sources of natural creativity via their free agency, we can complete quantum mechanics. (shrink)

Les théories de la mécanique quantique et de la gravité quantique exigent-elles que l’espace-temps soit un trait fondamental de bas niveau, ou l’espace-temps peut-il être conçu comme un élément émergent de ces théories? Tandis que plusieurs commentateurs ont émis de sérieux doutes sur l’idée de se dispenser de l’arrière-plan d’un espace-temps standard, nous ferons valoir qu’une défense de ces interprétations de l’espace-temps émergeant des hypothèses de la mécanique et de la gravité quantiques peut être conduite soit par inférence à la (...) meilleure explication, soit en mobilisant une autre stratégie. De plus, on montrera que l’idée que l’espace et le temps peuvent émerger d’un niveau du réel tout à fait différent et non spatiotemporel a des précédents historiques variés, en particulier aux xviie et xviiie siècles. Cette prise de conscience peut aider à dissiper une partie du mystère associé à ces types d’hypothèses. (shrink)

This paper defends wave function realism against the charge that the view is empirically incoherent because our evidence for quantum theory involves facts about objects in three-dimensional space or space-time . It also criticizes previous attempts to defend wave function realism against this charge by claiming that the wave function is capable of grounding local beables as elements of a derivative ontology.

Any empirical physical theory must have implications for observable events at the scale of everyday life, even though that scale plays no special role in the basic ontology of the theory itself. The fundamental physical scales are microscopic for the “local beables” of the theory and universal scale for the non-local beables. This situation creates strong demands for any precise quantum theory. This paper examines those constraints, and illustrates some ways in which they can be met.

This chapter contains sections titled: The GRW Theory Local Beables for GRW The Flash Ontology Relativistic Flashy GRW The Role of Local Beables The Logical Situation The Methodological Situation.

Because it fails to solve the wave-particle problem, orthodox quantum theory is obliged to be about observables and not quantum beables. As a result the theory is imprecise, ambiguous, ad hoc, lacking in explanatory power, restricted in scope and resistant to unification. A new version of quantum theory is needed that is about quantum beables.

The ontology of Bohmian mechanics includes both the universal wave function and particles. Proposals for understanding the physical significance of the wave function in this theory have included the idea of regarding it as a physically-real field in its 3N-dimensional space, as well as the idea of regarding it as a law of nature. Here we introduce and explore a third possibility in which the configuration space wave function is simply eliminated—replaced by a set of single-particle pilot-wave fields living in (...) ordinary physical space. Such a re-formulation of the Bohmian pilot-wave theory can exactly reproduce the statistical predictions of ordinary quantum theory. But this comes at the rather high ontological price of introducing an infinite network of interacting potential fields which influence the particles’ motion through the pilot-wave fields. We thus introduce an alternative approach which aims at achieving empirical adequacy with a more modest ontological complexity, and provide some preliminary evidence for optimism regarding the program of trying to replace the configuration space wave function with a set of fields in ordinary physical space. (shrink)

This book is an introduction to the foundation of quantum mechanics. As such, this book is perfect: it is the book that my former, physics undergraduate, self would have wanted to read. At the time, like typical physics undergraduates around the globe, I was taught to give up hope of ever understanding what quantum theory claims: at best, the theory is an instrument to predict experimental results. No matter how much we might dislike it, we have to accept it; there (...) is no way out. It was my refusal to give in that led me to become a philosopher of physics. And I was right in being persistent because I later discovered that, as Maudlin clearly explains, there is no reason to be pessimistic: all the quantum mysteries and paradoxes have a solution. Actually, more than one. To have Maudlin’s book at the time would have saved me a lot of time and pain. I am sure it will be a life-saver for many other rightfully puzzled undergraduate physics students wondering if the questions they ask are wrongheaded, as too many of their teachers claim: How can the Schrödinger cat really be dead and alive at the same time? Is reality created by an act of observation or a measurement? How is a measurement not a physical process like any other? Because these are not bad questions at all, and they have straightforward answers: the Schrödinger cat cannot be both alive and dead; reality is not created by observation; a measurement is just a type of interaction between two physical systems. However, the book is also not perfect (becoming, ironically, a superposition). While Maudlin defends his own position on how to make sense of quantum theory, his book is also potentially misleading about the state of the art in terms of the philosophical foundations of the theory. Maudlin omits to mention (or cite, or give reference to) the majority of the literature generated in the last two decades around the problems he discusses. Although this book may be intended as an introductory textbook to the field, I am disappointed that it skirts so much of the work of the past few decades on the foundations of quantum theory. To be fair, there is a habit in philosophy of physics at large of failing to sufficiently acknowledge other work, but this is why the failure to do much to rectify this trend in even a short introductory textbook like this one troubles me as much as it does. Indeed, this can mislead students who are new to the material, in the same way that I felt misled by my undergraduate physics instructors about the nature of quantum theory. This is also puzzling because, as I will discuss below, the lack of contextualization of his view within the actual literature makes Maudlin’s arguments weaker than they could have been. (shrink)

Information and communication technology is changing many aspects ofhuman endeavour and existence. This is beyond dispute for most. Whatare contested are the social and ethical implications of thesechanges. Possible sources of these disputes are the multiple ways inwhich one can conceptualize and interpret the informationtechnology/society interrelationship. Each of these ways ofconceptualization and interpretation enables one to see theinformation technology/society relationship differently and thereforeconstrue its social and ethical implications in a different manner. Atthe center of this technology/society interrelationship we find manycomplex (...) questions about the nature of the human, the technical,agency, autonomy, freedom and much more. This is indeed a vastintellectual landscape, which can obviously not be explored here inits fullness. This entry is about just one particular perspective onthis landscape. It is primarily concerned with the phenomenologicalapproach to interpreting information technology and its social andethical implications. It should be noted from the start that there isnot a unified phenomenological tradition or approach to informationtechnology in particular, or other phenomena more generally. Thephenomenological tradition consists of many different approaches thatshare certain characteristics but not all. We may however suggest, with Don Ihde,that they all accept that “phenomenology investigates theconditions of what makes things appear as such [as that which we takethem to be].” Differently stated, phenomenology suggests thatthere is a co-constitutive relationship between us and the phenomenawe encounter in our engagement with the world. In this sensephenomenologists would suggest that to understand thetechnology/society relationship we need to reveal how theyco-constitute each other—i.e. draw on each other for theirongoing meaning and sense. We will elaborate more precisely what thismeans in section 2 below. However, in order to understand the distinctiveness of thephenomenological approach other possible ways of interpreting thistechnology/society relationship will also be outlined brieflybelow., It can be said that information technology has become in a very realsense ubiquitous. Most everyday technologies such as elevators,automobiles, microwaves, watches, and so forth depend onmicroprocessors for their ongoing operation. Most organizations andinstitutions have become reliant on their information technologyinfrastructure to a lesser or greater degree. Indeed informationtechnology is seen by many as a cost-efficient way to solve amultitude of problems facing our complex contemporary society. One canalmost say that information technology has become construed as thedefault technology for solving a whole raft of technical and socialproblems such as health provision, security, governance, etc. Onecould also argue that it has become synonymous with society’sview of modernization and progress. For most it seems obvious thatinformation technology has made it possible for humans to continue toconstruct increasingly complex systems of coordination and socialordering—systems without which contemporary society would not beable to exist in its present form. To say the least, we, ascontemporary human beings, have our manner of being made possiblethrough a rather comprehensive entanglement with information andcommunication technology. Indeed, the economic, organizational andsocial benefit of information technology is not widely disputed. Thedispute is more often about the way information technology is changingor transforming the social domain, and in particular, the ethicaldomain. This dispute is largely centered around different ways ofconceptualizing and interpreting the nature of our entanglement withinformation technology. This debate is not merely an academic debateabout different and competing theoretical ‘models.’Rather, these different ways of conceptualizing it is central to ourunderstanding of how we go about managing our increasingly entangledrelationship with information technology. (shrink)

Recently there has been a great deal of interest in tabletop experiments intended to exhibit the quantum nature of gravity by demonstrating that it can induce entanglement. In order to evaluate these experiments, we must determine if there is any interesting class of possibilities that will be convincingly ruled out if it turns out that gravity can indeed induce entanglement. In particular, since one argument for the significance of these experiments rests on the claim that they demonstrate the existence of (...) superpositions of spacetimes, it is important to keep in mind that different interpretations of quantum mechanics may make different predictions about superpositions of spacetimes. ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-complete interpretations of quantum mechanics, like the Everett interpretation, almost universally predict the existence of superpositions of spacetimes, whereas in ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-incomplete, ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-nonphysical interpretations it seems more natural to predict that spacetime superpositions are not possible. Meanwhile ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-incomplete, ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-supplemented interpretations present us with a more complex picture where we may or may not end up predicting that spacetime superpositions are possible, depending on the particular way in which the coupling between spacetime and matter is constructed. This line of reasoning suggests that what would be ruled out by a successful result to these tabletop experiments is a class of quantum gravity models that we refer to as ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-incomplete quantum gravity —i.e. models of the interaction between quantum mechanics and gravity in which gravity is coupled to non-quantum beables rather than quantum beables. It follows that the results of tabletop experiments can also be regarded as giving us new evidence about the interpretation of quantum mechanics: roughly speaking, a positive result to these experiments should increase our confidence in ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-complete interpretations, whilst a negative result should instead increase our confidence in ψ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\psi$$\end{document}-incomplete interpretations. We introduce these ideas in Sect. 1, and then in Sect. 2 we make the reasoning more precise by presenting a set of inferences that may be made about the ontology of quantum mechanics based on the results of tabletop experiments. In Sect. 3 we discuss some existing PIQG models and consider what more needs to be done to make these sorts of approaches more appealing. There are two competing paradigms for the interpretation of these experiments, which have been dubbed the ‘Newtonian’ paradigm and the ‘tripartite’ paradigm: here we largely work within the tripartite paradigm, because the tripartite view is specifically concerned with ontological aspects of the mediating gravitational interaction and that makes it a suitable setting for enquiries about the ontology of quantum mechanics, but in Sect. 4 we consider what conclusions can be drawn if one does not presuppose the tripartite view. Finally in Sect. 5 we discuss a cosmological phenomenon which could be regarded as providing evidence for PIQG models. (shrink)

We prove a uniqueness theorem showing that, subject to certain natural constraints, all 'no collapse' interpretations of quantum mechanics can be uniquely characterized and reduced to the choice of a particular preferred observable as determine (definite, sharp). We show how certain versions of the modal interpretation, Bohm's 'causal' interpretation, Bohr's complementarity interpretation, and the orthodox (Dirac-von Neumann) interpretation without the projection postulate can be recovered from the theorem. Bohr's complementarity and Einstein's realism appear as two quite different proposals for selecting (...) the preferred determinate observable--either settled pragmatically by what we choose to observe, or fixed once and for all, as the Einsteinian realist would require, in which case the preferred observable is a 'beable' in Bell's sense, as in Bohm's interpretation (where the preferred observable is position in configuration space). (shrink)

Between 1964 and 1990, the notion of nonlocality in Bell's papers underwent a profound change as his nonlocality theorem gradually became detached from quantum mechanics, and referred to wider probabilistic theories involving correlations between separated beables. The proposition that standard quantum mechanics is itself nonlocal became divorced from the Bell theorem per se from 1976 on, although this important point is widely overlooked in the literature. In 1990, the year of his death, Bell would express serious misgivings about the (...) mathematical form of the local causality condition, and leave ill-defined the issue of the consistency between special relativity and violation of the Bell-type inequality. In our view, the significance of the Bell theorem, both in its deterministic and stochastic forms, can only be fully understood by taking into account the fact that a fully Lorentz-covariant version of quantum theory, free of action-at-a-distance, can be articulated in the Everett interpretation. (shrink)

The embedding and promotion of social change is faced with aparadoxical challenge. In order to mainstream an approach to socialchange such as responsible research and innovation and makeit into a practical reality rather than an abstract ideal, we need tohave conceptual clarity and empirical evidence. But, in order to beable to gather empirical evidence, we have to presuppose that theapproach already exists in practice. This paper proposes a social labmethodology that is suited to deal with this circularity. Themethodology combines the (...) defining features of social labs emergingfrom the literature such as agility and real-world focus withestablished theories and approaches such as action research andexperiential learning. Thereby it enables the parallel investigationand propagation of RRI. The framework thus constructed provides atheoretical embedding of sociallabs and overcomes some of theknown limitations of the constitutive approaches. (shrink)

Advocates of the Everett interpretation of quantum mechanics have long claimed that other interpretations needlessly invoke "new physics" to solve the measurement problem. Call the argument fashioned that gives voice to this claim the Redundancy Argument, or ’Redundancy’ for short. Originating right in Everett’s doctoral thesis, Redundancy has recently enjoyed much attention, having been advanced and developed by a number of commentators, as well as criticized by a few others.[1] Although versions of this argument can target collapse theories of quantum (...) mechanics, it is usually conceived with no-collapse "hidden variable" interpretations in mind, e.g., modal and Bohmian interpretations. In particular, the argument is an attack against theories committed to both realism about the quantum state and realism about entities – what Bell 1987 calls "beables" – that supplement this state. Particles, fields, value states, and more have been suggested as possible ontology to supplement the quantum state. Redundancy is the argument that this supplementation is methodologically otiose, the superfluous pomp that Newton scorned. (shrink)

It is a widespread belief that the Kochen-Specker theorem imposes a contextuality constraint on the ontology of beables in quantum hidden variables theories. On the other hand, after Bell’s influential critique, the importance of von Neumann’s wrongly called ‘impossibility proof’ has been severely questioned. However, Max Jammer, Jeffrey Bub and Dennis Dieks have proposed insightful reassessments of von Neumann’s theorem: what it really shows is that hidden variables theories cannot represent their beables by means of Hermitian operators in (...) Hilbert space. Hereby I show that i) the very same constraint can be derived from Gleason’s theorem, and that ii) if we consider the import of von Neumann’s and Gleason’s theorems, the relevance of the Kochen-Specker theorem for hidden variables theories gets substantially weakened: it does not force them to be contextual in any interesting sense of the term. (shrink)

The empirical coherence problem of quantum gravity is the worry that a theory which does not fundamentally contain local beables located in space and time—such as is arguably the case for certain approaches to quantum gravity—cannot be connected to measurements and thus has its prospects of being empirically adequate undermined. Spacetime functionalism à la Lam and Wüthrich is said to solve this empirical coherence problem as well as bridging a severe conceptual gap between spatiotemporal structures of classical spacetime theories (...) on the one hand, and the non-spatiotemporal structures in quantum gravity approaches on the other hand. The aim of this essay is to offer a deflationary account of both the empirical coherence problem and the spatiotemporal gap problem as they are claimed to arise at least prima facie for current theories of quantum gravity by Huggett and Wüthrich :276–285, 2013), Lam and Wüthrich and Le Bihan. I defend the view that spacetime functionalism is set up to address a problem which can usually be solved without it; and that it is wrongly claimed to solve another problem which for any actual account of quantum gravity is in fact currently non-existent anyway. (shrink)

Given an ontological model of a quantum system, a “genuine measurement,” as opposed to a quantum measurement, means an experiment that determines the value of a beable, i.e., of a variable that, according to the model, has an actual value in nature before the experiment. We prove a theorem showing that in every ontological model, it is impossible to measure all beables. Put differently, there is no experiment that would reliably determine the ontic state. This result shows that the (...) positivistic idea that a physical theory should only involve observable quantities is too optimistic. (shrink)

The empirical coherence problem of quantum gravity is the worry that a theory which does not fundamentally contain local beables located in space and time—such as is arguably the case for certain approaches to quantum gravity—cannot be connected to measurements and thus has its prospects of being empirically adequate undermined. Spacetime functionalism à la Lam and Wüthrich is said to solve this empirical coherence problem as well as bridging a severe conceptual gap between spatiotemporal structures of classical spacetime theories (...) on the one hand, and the non-spatiotemporal structures in quantum gravity approaches on the other hand. The aim of this essay is to offer a deflationary account of both the empirical coherence problem and the spatiotemporal gap problem as they are claimed to arise at least prima facie for current theories of quantum gravity by Huggett and Wüthrich :276–285, 2013), Lam and Wüthrich and Le Bihan. I defend the view that spacetime functionalism is set up to address a problem which can usually be solved without it; and that it is wrongly claimed to solve another problem which for any actual account of quantum gravity is in fact currently non-existent anyway. (shrink)

A new ensemble interpretation of quantum mechanics is proposed according to which the ensemble associated to a quantum state really exists: it is the ensemble of all the systems in the same quantum state in the universe. Individual systems within the ensemble have microscopic states, described by beables. The probabilities of quantum theory turn out to be just ordinary relative frequencies probabilities in these ensembles. Laws for the evolution of the beables of individual systems are given such that (...) their ensemble relative frequencies evolve in a way that reproduces the predictions of quantum mechanics.These laws are highly non-local and involve a new kind of interaction between the members of an ensemble that define a quantum state. These include a stochastic process by which individual systems copy the beables of other systems in the ensembles of which they are a member. The probabilities for these copy processes do not depend on where the systems are in space, but do depend on the distribution of beables in the ensemble.Macroscopic systems then are distinguished by being large and complex enough that they have no copies in the universe. They then cannot evolve by the copy law, and hence do not evolve stochastically according to quantum dynamics. This implies novel departures from quantum mechanics for systems in quantum states that can be expected to have few copies in the universe. At the same time, we are able to argue that the center of masses of large macroscopic systems do satisfy Newton’s laws. (shrink)

Standard quantum theory is inadequate to explain the mechanisms by which potential becomes actual. It is inadequate and therefore unable to describe generation of events. Niels Bohr emphasized long ago that the classical part of the world is necessary. John Bell stressed the same point: that “measurement≓ cannot even be defined within the standard quantum theory, and he sought a solution within hidden variable theories and his concept of “beables.≓Today it is customary to try to explain emergence of the (...) classical world through a decoherence mechanism due to “environment.≓ But, we believe, as it was with the concept of measurement, “environment≓ itself cannot be defined within the standard quantum theory.We have proposed a semiphenomenological solution to this problem by introducing explicitly, from the very beginning, classical degrees of freedom, and by coupling these degrees of freedom, through a Lindblad type coupling, to the quantum world. The resulting theory, we call “event-enhanced quantum theory.≓ EEQT allows us to describe an event-generating mechanism for individual quantum systems under continuous observation. The objections of John Bell are met and precise definitions of an “experiment≓ and of a “measurement≓ have been given within EEQT. However EEQT is, essentially, a nonrelativistic theory.In the present paper we extend the ideas of L. P. Horwitz and C. Piron and we propose a relativistic version of EEQT, with an event-generating algorithm for spin one-half particle detectors. The algorithm is based on proper time formulation of the relalivistic quantum theory. Although we use indefinite metric, all the probabilities controlling the random process of the detector clicks are nonnegative. (shrink)

In the paper the relation between the standard probabilistic characterization of the common cause and Bell's notion of local causality will be investigated. It will be shown that the probabilistic common cause follows from local causality if one accepts, as Bell did, two assumptions concerning the common cause: first, the common cause is localized in the intersection of the past of the correlating events; second, it provides a complete specification of the `beables' of this intersection. However, neither assumptions are (...) a priori requirements. In the paper the logical role of these assumptions will be studied and it will be shown that only the second assumption is necessary for the derivation of the probabilistic common cause from local causality. (shrink)

A growing number of applications of automated reasoning exhibitsthe necessity of flexible deduction systems. A deduction system should beable to execute inference rules which are appropriate to the given problem.One way to achieve this behavior is the integration of different calculi. Thisled to so called hybrid reasoning [22, 1, 10, 20] which means the integrationof a general purpose foreground reasoner with a specialized background reasoner. A typical task of a background reasoner is to perform special purposeinference rules according to a (...) built-in theory. The aim of this paper is togo a step further, i.e. to treat the background reasoner as a hybrid systemitself. The paper formulates sufficient criteria for the construction of complete calculi which enable reasoning under hybrid theories combined fromsub-theories. For this purpose we use a generic approach described in [20].This more detailed view on built-in theories is not covered by the knowngeneral approaches [1, 3, 6, 20] for building in theories into theorem provers.The approach is demonstrated by its application to the target calculi of thealgebraic translation [9] of multi-modal and extended multi-modal [7] logicto first-order logic. (shrink)

In this article, I examine racial narratives of passing and their relationship to discourses of hybridity. Rather than defining passing as inherently transgressive, or as one side of identity politics or the other, I suggest that passing must be understood in relationship to forms of social antagonism. I ask the following questions: how are differences that threaten the system recuperated? How do ambiguous or hybrid bodies get read in a way which further supports the enunciative power of those who are (...) telling the difference? In what ways is `passing' implicated in the very discourse around tellable differences? Although to some extent all identities involve passing - insofar as the subject never `is' what it `images' itself to be - we still need to theorize the differences between passing as white and passing as black. I argue that passing as black as a white subject can function as a technique of knowledge which assumes `blackness' to be imageable and hence beable. However, for black subjects to refuse to pass as white - that is, for black subjects to pass as black - can make visible the violent histories concealed by the invisibility of the mark of passing. Such a process of passing as black subjects is tied to a politics of the collective - a coming together through the recognition of the lack that engenders passing in the first place. (shrink)

We propose an approach to the question of how qualia fit into the physical world, in the context of a relational and realist completion of quantum theory, called the causal theory of views\cite{views}. This is a combination of an approach to a dynamics of discrete causal structures, called energetic causal sets, developed with M. Cortes, with a realist approach to quantum foundations, called the real ensemble formulation. In this theory, the beables are the information available at each event from (...) its causal past, such as its causal predessesors and the energy and momentum they transfer to the event. We call this the view of an event. That is, we describe a causal universe that is composed of a set of partial views of itself. We propose that conscious perceptions are aspects of some views. This addresses the problem of why consciousness always involves awareness of a bundled grouping of qualia that define a momentary self. This gives a restricted form of panpsychism defined by a physically based selection principle which selects which views have experiential aspects. We further propose that only those views which are novel, in the sense that they are not duplicates of the view of any event in the event's own causal past, are the physical correlates of conscious experience. (shrink)

The procedures of canonical quantization of the gravitational field apparently lead to entities for which any interpretation in terms of spatio-temporal localization or spatio-temporal extension seems difficult. This fact is the main ground for the suggestion that can often be found in the physics literature on canonical quantum gravity according to which spacetime may not be fundamental in some sense. This paper aims to investigate this radical suggestion from an ontologically serious point of view in the cases of two standard (...) forms of canonical quantum gravity, quantum geometrodynamics and loop quantum gravity. We start by discussing the physical features of the quantum wave functional of quantum geometrodynamics and of the spin networks of loop quantum gravity that motivate the view according to which spacetime is not fundamental. We then point out that, by contrast, for any known ontologically serious understanding of quantum entanglement, the commitment to spacetime seems indispensable. Against this background, we then critically discuss the idea that spacetime may emerge from more fundamental entities. As a consequence, we finally suggest that the emergence of classical spacetime in canonical quantum gravity faces a dilemma: either spacetime ontologically emerges from more fundamental non-spatio-temporal entities or it already belongs to the fundamental quantum gravitational level and the emergence of the classical picture is merely a matter of levels of description. On the first horn of the dilemma, it is unclear how to make sense of concrete physical entities that are not in spacetime and of the notion of ontological emergence that is involved. The second horn runs into the difficulties raised by the physics of canonical quantum gravity. (shrink)

In an old paper of our group in Milano a formalism was introduced for the continuous monitoring of a system during a certain interval of time in the framework of a somewhat generalized approach to quantum mechanics. The outcome was a distribution of probability on the space of all the possible continuous histories of a set of quantities to be considered as a kind of coarse grained approximation to some ordinary quantum observables commuting or not. In fact the main aim (...) was the introduction of a classical level in the context of QM, treating formally a set of basic quantities, to be considered as beables in the sense of Bell, as continuously taken under observation. However the effect of such assumption was a permanent modification of the Liouville-von Neumann equation for the statistical operator by the introduction of a dissipative term which is in conflict with basic conservation rules in all reasonable models we had considered. Difficulties were even encountered for a relativistic extension of the formalism. In this paper I propose a modified version of the original formalism which seems to overcome both difficulties. First I study the simple models of an harmonic oscillator and a free scalar field in which a coarse grain position and a coarse grained field respectively are treated as beables. Then I consider the more realistic case of spinor electrodynamics in which only certain coarse grained electric and magnetic fields are introduced as classical variables and no matter related quantities. (shrink)

Wallace has recently argued that a number of popular approaches to the measurement problem can’t be fully extended to relativistic quantum mechanics and quantum field theory; Wallace thus contends that as things currently stand, only the unitary-only approaches to the measurement problem are viable. However, the unitary-only approaches face serious epistemic problems which may threaten their viability as solutions, and thus we consider that it remains an urgent outstanding problem to find a viable solution to the measurement problem which can (...) be extended to relativistic quantum mechanics. In this article we seek to understand in general terms what such a thing might look like. We argue that in order to avoid serious epistemic problems, the solution must be a single-world realist approach, and we further argue that any single-world realist approach which is able to reproduce the predictions of relativistic quantum mechanics will most likely have the property that our observable reality does not supervene on dynamical, precisely-defined microscopic beables. Thus we suggest three possible routes for further exploration: observable reality could be approximate and emergent, as in relational quantum mechanics with the addition of cross-perspective links, or observable reality could supervene on beables which are not microscopically defined, as in the consistent histories approach, or observable reality could supervene on beables which are not dynamical, as in Kent’s solution to the Lorentzian classical reality problem. We conclude that once all of these issues are taken into account, the options for a viable solution to the measurement problem are significantly narrowed down. (shrink)

Judgments about the validity of at least some elementary inferential patterns(say modus ponens) are a priori if anything is. Yet a number of empirical conditions mustin each case be satisfied in order for a particular inference to instantiate this or that inferentialpattern. We may on occasion be entitled to presuppose that such conditions aresatisfied (and the entitlement may even be a priori), yet only experience could tell us thatsuch was indeed the case. Current discussion about a perceived incompatibility betweencontent externalism (...) and first-person authority exemplifies how damaging the neglect ofsuch empirical presuppositions of correct reasoning can be. An externalistic view of mentalcontent is ostensibly incompatible with the assumption that a rational subject should beable to avoid inconsistency no matter what the state of her empirical knowledge may be.That fact, however, needs not be taken (as it often is) as a reductio of externalism: alternatively,we may reject that assumption, adding to the agenda of a philosophical investigationof rationality an examination of the vicissitudes of logical luck. I offer an illustrationand defense of that alternative. (shrink)

If some sort of dynamical collapse theory is correct, what might the world be like? Can a theory of that sort be a quantum state monist theory, or must such theories supplement the quantum state ontology with additional beables? In a previous work, I defended quantum state monism, with a distributional ontology along the lines advocated by Philip Pearle. In this chapter the account is extended to collapse theories in relativistic spacetimes.

Since the analysis by John Bell in 1965, the consensus in the literature is that von Neumann’s ‘no hidden variables’ proof fails to exclude any significant class of hidden variables. Bell raised the question whether it could be shown that any hidden variable theory would have to be nonlocal, and in this sense ‘like Bohm’s theory.’ His seminal result provides a positive answer to the question. I argue that Bell’s analysis misconstrues von Neumann’s argument. What von Neumann proved was the (...) impossibility of recovering the quantum probabilities from a hidden variable theory of dispersion free (deterministic) states in which the quantum observables are represented as the ‘beables’ of the theory, to use Bell’s term. That is, the quantum probabilities could not reflect the distribution of pre-measurement values of beables, but would have to be derived in some other way, e.g., as in Bohm’s theory, where the probabilities are an artefact of a dynamical process that is not in fact a measurement of any beable of the system. (shrink)

We describe the picture of physical processes suggested by Edward Nelson’s stochastic mechanics when generalized to quantum field theory regularized on a lattice, after an introductory review of his theory applied to the hydrogen atom. By performing numerical simulations of the relevant stochastic processes, we observe that Nelson’s theory provides a means of generating typical field configurations for any given quantum state. In particular, an intuitive picture is given of the field “beable”—to use a phrase of John Stewart Bell—corresponding to (...) the Fock vacuum, and an explanation is suggested for how particle-like features can be exhibited by excited states. We then argue that the picture looks qualitatively similar when generalized to interacting scalar field theory. Lastly, we compare the Nelsonian framework to various other proposed ontologies for QFT, and remark upon their relative merits in light of the effective field theory paradigm. Links to animations of the corresponding beables are provided throughout. (shrink)

On Two Types of Realism in Quantum Theory. Current realist approaches to the foundations of quantum theory emphasize the dichotomy between (Copenhagen) positivism and ‘beable’-realism. Recently it was even attempted to turn this picture into two (equally possible) histories in order to legitimate Bohmian Mechanics as a viable alternative. This paper argues that this dichotomy is philosophically inadequate and historically questionable by embedding it into the philosophical discussion on positivism and realism that has taken place since the 1920s. Logical Empiricists (...) back then advocated empirical realism and contrasted it to absolutistic metaphysical realism. From this viewpoint David Bohm's ‘beable’-realism combines elements of Mach's sensualism with a pre-Kantian metaphysics. As Wesley Salmon's position shows, empirical realism can become quite pronounced without relapsing into Bohmian philosophy. Instead it arrives close to the GRWP-interpretation. Hence, when Bernard d'Espagnat binds both together as ‘ontological interpretations’, he blurs the borderline between empirical and metaphysical realism that his Veiled Reality has set out to draw, quite in concordance with Logical Empiricism. (shrink)

We critically examine the role and status probabilities, as they enter via the Quantum Equilibrium Hypothesis, play in the standard, deterministic interpretation of deBroglie’s and Bohm’s Pilot Wave Theory (dBBT), by considering interpretations of probabilities in terms of ignorance, typicality and Humean Best Systems, respectively. We argue that there is an inherent conflict between dBBT and probabilities, thus construed. The conflict originates in dBBT’s deterministic nature, rooted in the Guidance Equation. Inquiring into the latter’s role within dBBT, we find it (...) explanatorily redundant (in particular for dBBT’s solution of the Measurement Problem, which only requires that the corpuscles possess definite positions), and subject to a number of difficulties. Following a suggestion from Bell, we propose to abandon the Guidance Equation, whilst retaining dBBT’s point particle-based Primitive Ontology, with positions as local beables. The resultant theory, which we identify as a stochastic, minimally deBroglie-Bohmian theory, describes a random walk through configuration space. Its probabilities, we propose, are best understood as dispositions of possible corpuscle configurations to manifest themselves. We subsequently evaluate the merits of sdBBT vis-à-vis dBBT, such as the justification of the Symmetrisation Postulate and the violation of the Action-Reaction Principle. Not only is sdBBT an attractive Bohmian theory that, whilst retaining dBBT's virtues, overcomes many of its shortcomings; it also sparks off a number of exciting follow-up questions, such as a comparison between sdBBT and other stochastic hidden-variable theories, e.g. Nelson Stochastics, or between sdBBT and the Everett interpretation. (shrink)