Copenhagen Interpretation

The measurement problem is commonly taken to indicate a fundamental conflict between the linear, unitary dynamics of quantum mechanics and the definite outcomes observed in measurement processes. Standard responses typically resolve this tension by modifying the dynamics, enriching the ontology, or revising the interpretation of the quantum state. -/- In this paper, we analyze the measurement problem from a projection-based perspective in which quantum evolution and measurement outcomes are associated with ontologically distinct effective descriptions, defined by incompatible invariance requirements. Within (...) this framework, quantum mechanics is characterized by unitary invariance and coherent superposition, whereas measurement records are defined by definiteness, stability, and reproducibility. The measurement problem arises when these distinct projection structures are implicitly identified or required to coexist within a single effective description. -/- By analyzing measurement as a transition between such projections, we show that the appearance of wavefunction collapse does not require a physical dynamical process. Instead, collapse emerges as a necessary structural consequence of projecting a quantum description onto a measurement domain that enforces different invariance constraints. This account preserves the formal structure and empirical success of quantum mechanics while motivating a restrained ontological reading of its elements. -/- More broadly, the analysis situates the measurement problem within a general pattern in which foundational paradoxes arise at the boundaries between effective descriptions. In this sense, the resolution proposed here does not introduce new physics, but clarifies the ontological scope and limits of quantum-mechanical description. (shrink)

It is well-known that, historically, there is no unique interpretation, which might be named the Copenhagen interpretation. At best, it seems to be the case that there is a plethora of related interpretations that, for simplicity, are named as such. Here, a more heterodox possibility is presented. Has this interpretation ever been used/taken into account by physicists? It is a fact that historians, philosophers of science, and a handful of physicists interested in the interpretation of quantum theory have considered, discussed, (...) and, some, endorsed, in different degrees, a Copenhagen interpretation. So, as a "by-product" of academics and their disputations, there is, evidently, a Copenhagen interpretation. But as a community, have physicists ever used/taken into account this interpretation (throughout the decades)? That some "big" names did it does not imply that, as a community, there has ever been a "living tradition" that uses, in any meaningful way, this interpretation (i.e., a community for which the interpretation existed in any practical sense). Here, we propose that this has never been the case (besides some "toy versions" of the interpretation used for educational purposes in universities). (shrink)

This paper provides a detailed historical account of early debates over wave-function realism, the modern term for the view that the wave function of quantum theory is physically real. As this paper will show, the idea of physical waves associated with particles had its roots in work by Einstein and de Broglie, who both originally thought of these waves as propagating in three-dimensional physical space. De Broglie quickly turned this wave-particle duality into an early pilot-wave theory, on which a particle's (...) associated “phase wave” piloted or guided the particle along its trajectory. Schrödinger built on de Broglie's phase-wave hypothesis to provide a comprehensive account of the nascent quantum theory. However, Schrödinger's new “undulatory mechanics” came at the cost of replacing de Broglie's phase waves propagating in physical space with a wave function propagating in a system's abstract configuration space. The present work will argue that this move from three-dimensional physical space to a many-dimensional configuration space was a key reason why the founders of quantum theory uniformly abandoned the physical reality of the wave function. This paper will further clarify that de Broglie introduced two distinct pilot-wave theories, and will then argue that it was Bohm's rediscovery of the second of these two pilot-wave theories over two decades later, as well as Bohm's vociferous defense of wave-function realism, that were responsible for resurrecting the idea of an ontological wave function. This idea ended up playing a central role in Everett's development of the many-worlds interpretation. (shrink)

We introduce Quantum Holographic Consciousness Theory (QHCT), a framework that places interference, rather than collapse or causal power, at the center of conscious experience. In this view, the universe behaves like a vibrating holographic screen, carrying patterns that exist prior to observation. Consciousness does not inject energy into these patterns, but acts as a frequency-sensitive reader that selects and stabilizes them into lived experience. We tested this idea at two scales. Cosmologically, Planck 2018 data reveal node-like regularities and phase linearity, (...) signatures of holographic interference. Physiologically, heart-rate variability records display few-mode concentration, selective phase entrainment with respiration, and low-dimensional reconstructions. These findings jointly suggest that both cosmic background radiation and human physiology can be interpreted as mode-limited interference structures. QHCT thus offers a falsifiable cross-domain framework, tested on both cosmological and physiological data, that bridges physics, neuroscience, and philosophy of mind in a coherent account of consciousness. (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)

Niels Bohr was one of the central figures in the emergence of quantum mechanics and a paradigmatic example of a scientist who engaged reflectively with his own practice. For several decades, he was also a leading voice in the philosophical interpretation of the theory. Yet toward the end of the twentieth century his influence declined sharply, and his views came to be widely dismissed as obscure or irrelevant. To assess Bohr's contributions fairly, we need to resist the analytic philosopher's idealization (...) that ontological questions can be separated from action---to treat questions about what there is as detachable from the concrete practices through which physical descriptions are articulated and assessed. This ontology-first approach fits uneasily with Bohr's philosophical sensibility, shaped by a Danish tradition that emphasized reflection on meaning, practice, and normative standards rather than the construction of metaphysical systems. Seen from this perspective, we see that Bohr's focus was not the limits of knowledge, but how knowledge gained in experimental contexts that are far beyond ordinary human experience can be communicated unambiguously. (shrink)

We use Bub's (2016) correlation arrays and Pitowksy's (1989b) correlation polytopes to analyze an experimental setup due to Mermin (1981) for measurements on the singlet state of a pair of spin-12 particles. The class of correlations allowed by quantum mechanics in this setup is represented by an elliptope inscribed in a non-signaling cube. The class of correlations allowed by local hidden-variable theories is represented by a tetrahedron inscribed in this elliptope. We extend this analysis to pairs of particles of arbitrary (...) spin. The class of correlations allowed by quantum mechanics is still represented by the elliptope; the subclass of those allowed by local hidden-variable theories by polyhedra with increasing numbers of vertices and facets that get closer and closer to the elliptope. We use these results to advocate for an interpretation of quantum mechanics like Bub's. Probabilities and expectation values are primary in this interpretation. They are determined by inner products of vectors in Hilbert space. Such vectors do not themselves represent what is real in the quantum world. They encode families of probability distributions over values of different sets of observables. As in classical theory, these values ultimately represent what is real in the quantum world. Hilbert space puts constraints on possible combinations of such values, just as Minkowski space-time puts constraints on possible spatio-temporal constellations of events. Illustrating how generic such constraints are, the equation for the elliptope derived in this paper is a general constraint on correlation coefficients that can be found in older literature on statistics and probability theory. Yule (1896) already stated the constraint. De Finetti (1937) already gave it a geometrical interpretation. (shrink)

In his ‘Participatory Universe’, John Archibald Wheeler envisioned the universe as a kind of ‘self-excited circuit’, in which acts of observation on the earliest universe have “a part in bringing that universe into being”. This paper proposes that several anomalies in the cosmic microwave background (CMB) may be explainable within a Participatory model. Specifically, peculiar alignments between the CMB and our own solar system appear, if confirmed, to challenge the Copernican Principle, while raising a temporal paradox given the vast interval (...) between CMB photon decoupling and the present observer. It is proposed that this paradox could be mitigated if detector-based measurement itself ‘participates’ in the release histories of registered CMB photons. A strict Bohr and Wheeler-inspired notion of measurement as ‘irreversible amplification’ is employed, treated as distinct from environmental decoherence. Through this approach, the measured CMB is posited not as a static fossil background, but instead as a ‘reference frame’ always relative to an observer, which becomes skewed to their state and motion. It is explained how this Participatory frameshift could offer a unified means of approaching multiple measured cosmological tensions, including alignment anomalies, the low-power anomaly on the largest angular scales, and discrepancies between CMB and matter-based dipoles. The paper first reviews Wheeler’s Participatory model, before exploring broad conceptual implications encompassing the initial conditions of the universe, CMB anomalies, the genesis of physical reality, and the role of measurement itself, motivating a new overarching conceptual framework labelled the ‘Measureverse’. The proposal is exploratory, being intended to stimulate interdisciplinary dialogue. (shrink)

The number of independent messages a physical system can carry is limited by the number of its adjustable properties. In particular, systems that have only one adjustable property cannot carry more than a single message at a time. We demonstrate this is the case for the single photons in the double-slit experiment, and the root of the fundamental limit on measuring the complementary aspect of the photons. Next, we analyze the other ‘quantal’ behavior of the systems with a single adjustable (...) property, such as noncommutativity and no-cloning. Finally, we formulate a mathematical theory to describe the dynamics of such systems and derive the standard Hilbert-space formalism of quantum mechanics. Our derivation demonstrates the physical foundation of the quantum theory. (shrink)

In the following we will investigate whether von Mises’ frequency interpretation of probability can be modified to make it philosophically acceptable. We will reject certain elements of von Mises’ theory, but retain others. In the interpretation we propose we do not use von Mises’ often criticized ‘infinite collectives’ but we retain two essential claims of his interpretation, stating that probability can only be defined for events that can be repeated in similar conditions, and that exhibit frequency stabilization. The central idea (...) of the present article is that the mentioned ‘conditions’ should be well-defined and ‘partitioned’. More precisely, we will divide probabilistic systems into object, initializing, and probing subsystem, and show that such partitioning allows to solve problems. Moreover we will argue that a key idea of the Copenhagen interpretation of quantum mechanics (the determinant role of the observing system) can be seen as deriving from an analytic definition of probability as frequency. Thus a secondary aim of the article is to illustrate the virtues of analytic definition of concepts, consisting of making explicit what is implicit. (shrink)

In this paper I present and critically discuss the main strategies that Bohr used and could have used to fend off the charge that his interpretation does not provide a clear-cut distinction between the classical and the quantum domain. In particular, in the first part of the paper I reassess the main arguments used by Bohr to advocate the indispensability of a classical framework to refer to quantum phenomena. In this respect, by using a distinction coming from an apparently unrelated (...) philosophical corner, we could say that Bohr is not a revisionist philosopher of physics but rather a descriptivist one in the sense of Strawson. I will then go on discussing the nature of the holistic link between classical measurement apparatuses and observed system that he also advocated. The oft-repeated conclusion that Bohr’s interpretation of the quantum formalism is untenable can only be established by giving his arguments as much force as possible, which is what I will try to do in the following by remaining as faithful as possible to his published work. (shrink)

This book consists in seventeen chapters devoted to physical, metaphysical, and methodological questions concerning open systems. The chapters in the volume address questions such as: Are (theories of) open systems more fundamental than (theories of) closed systems? How have concepts of open and closed systems have been used throughout the history of physics, and how should we understand their use in contemporary physical theories? Must the universe be a closed system? Must there be a such thing as the universe at (...) all? -/- Contributors: Emily Adlam, Luis C. Barbado, Caslav Brukner, Eddy Keming Chen, Michael E. Cuffaro, Gemma De les Coves, George Ellis, Doreen Fraser, Henrique Gomes, Sean Gryb, William L. Harper, Stephan Hartmann, Molly Kao, Adam Koberinski, James Ladyman, Simon Langenscheidt, Olimpia Lombardi, Jorn Klovfjell Mjelva, Wayne C. Myrvold, Daniele Oriti, Josh Quirke, David Sloan, Karim P. Y. Thebault, Lev Vaidman, David Wallace, and Alastair Wilson. (shrink)

I argue here that progress in understanding the lessons of quantum physics has been hindered by the tendency to cast Niels Bohr as a villain. Building on the work of Favrholdt, Faye, and Howard, I present a more accurate view of Bohr's proposal for the "epistemological lesson" of quantum physics. I then argue that several interpretive programs -- often presented as alternatives to Copenhagen -- are, after substantial conceptual work, arriving at a view that is notably similar to Bohr's. -/- (...) Using Maudlin’s formulation of the measurement problem as a foil, I argue that it relies on a notion of wave-function completeness that is inappropriate for a genuinely indeterministic theory, and one that Bohr consistently rejected. On Bohr's view, quantum theory permits concrete agents, situated within specific experimental contexts, to make objective descriptions, while refusing the demand for a single, context-free "description from nowhere". (shrink)

The quantum measurement problem has resisted resolution for nearly a century, fragmenting into three seemingly independent challenges: the Born rule's probabilistic interpretation, the EPR paradox of simultaneous reality, and Bell inequality violations challenging local realism. This fragmentation has obscured a common structural origin. -/- This work demonstrates that all three problems arise from a single theoretical defect: the misapplication of commutative probability theory to non-commutative operational structures. Within the framework of Cognitional Mechanics (CM), grounded in two axioms—non-commutativity ([Ô_A, Ô_B] ≠ (...) 0) and finite operational resolution (Level of Detail)—these problems dissolve simultaneously through structural reconstruction. -/- The Born rule emerges as the unique projection measure compatible with resource conservation and tensor-product linearity under non-commutative constraints, repositioning probability as an epistemic consequence of finite resolution rather than ontological randomness. EPR correlations are resolved as constraint propagation across shared operational stacks, eliminating the apparent conflict between quantum completeness and local realism without invoking non-local signaling. Bell inequality violations follow from the logical impossibility of factorization: non-commutativity structurally excludes the simultaneous eigenstates required by the factorization condition, rendering the measure space for joint distributions undefined rather than merely violated. -/- The framework derives from Tier 1 axiomatic necessity within Cognitional Mechanics. Mathematical formalisms—Hilbert spaces, operator algebras, measure theory—serve as Tier 3 projection tools expressing this structure, not as foundational requirements for its validity. -/- This paper builds on Operational Quantum Mechanics I (DOI: 10.5281/zenodo.18649525), which resolved Schrödinger's cat through operational stack management, and forms a symmetrical counterpart to Universal Relativity (DOI: 10.5281/zenodo.18645324) within the CM framework. (shrink)

Calculus is seen as describing continuous functions through the act of breaking them down to the smallest possible parts, suggesting that the whole is only an aggregation of its parts. But modern science has demanded the creation of new kinds of measurements, where the deterministic rules of classical physics cease to exist and we can no longer see the individual member parts as sole explanations towards the continuity of the whole. There is a duality between states of dis/continuous being, and (...) we seem to be doomed to only see the measured discontinuous version grounded in our own objectivity. But can the knowledge of this duality maybe help us better understand the social consequences of our world’s massively intraconnected social order? With the infrastructure of modern trade, seemingly instant communication possibilities, and newly created tribes numbering beyond what we thought possible; we have created a world that seem to defy our preconceptions of what social groups and responsibility means. Using agential realism and its groundbreaking insights into quantum philosophy with the idea of complementarity, I think we can start to understand these new states of being, and with it bring about a better grasp of the ethics that are an intrinsic part of all. Setting a foundation for how we can understand the duality of groups and individuals across all areas of our world, seeing complementarity as the grounding state of un/certain objectivity. (shrink)

This book deals with some ontological implications of standard non-relativistic quantum mechanics, and the use of the notion of `consciousness' to solve the measurement problem.

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)

The famous EPR article of 1935 challenged the completeness of quantum mechanics and spurred decades of theoretical and experimental research into the foundations of quantum theory. A crowning achievement of this research is the demonstration that nature cannot in general consist in noncontextual pre-measurement properties that uniquely determine possible measurement outcomes, through experimental violations of Bell inequalities and Kochen-Specker theorems. In this article, I reconstruct an argument from Niels Bohr’s writings that the reality of the Einstein-Planck-de Broglie relations alone implies (...) that no such properties can exist for momentum and position measurements, show how this argument responds to the challenge of EPR on general physical grounds, and advance that this reconstruction shows that and how Bohr’s “complementarity” is a view of the objective content and logic of quantum theory. (shrink)

A familiar interpretation of quantum mechanics (one of a number of views sometimes labeled the "Copenhagen interpretation'"), takes its empirical apparatus at face value, holding that the quantum wave function evolves by the Schrödinger equation except on certain occasions of measurement, when it collapses into a new state according to the Born rule. This interpretation is widely rejected, primarily because it faces the measurement problem: "measurement" is too imprecise for use in a fundamental physical theory. We argue that this is (...) a weak objection, as there may be many ways of making "measurement" precise. However, measurement-collapse interpretations face a more serious objection: a dilemma tied to the quantum Zeno effect. Is measurement itself an observable that can enter superpositions? If yes, then the standard measurement-collapse dynamics is ill-defined. If no, then (at least if measurement is an observable), measurements can never start or finish. The best way out is to deny that measurement is an observable, but this leads to strong and revisionary consequences. This reinforces the view that there is no nonrevisionary interpretation of quantum mechanics. (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)

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)

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)

In the controversy on the philosophical foundations of quantum mechanics Whitehead's philosophy of organism has an essential place. But its realistic position invalidates any attempt to relate it to the School of Copenhagen's “orthodox interpretation”. Unlike, the Eurhythmic Physics developed by the Lisbon School has notable theoretical tunings with Whitehead's philosophy. In both, the notion of passive matter disappears; entities are understood as ecstatic process of becoming arising from a continuum of potentialities; and they achieve physical persistence grace to a (...) set of synergistic interactions among their own regimes of rhythmical activity. The principle of Eurhythmy proposed by Prof. Croca then appears as the hypothesis, in contemporary theoretical physics, corresponding to the organicist vision of a universe in a developmental process of realization of the abstract potentiality of all possible worlds: a universe that, as a living organism, should be described as guided by an immanent teleological principle. (shrink)

Bohr’s work in quantum mechanics posed a challenge to philosophers of science, who struggled with the question of whether and to what degree his theories and methods could be considered rational. This paper focuses on Popper, Feyerabend, Lakatos and Kuhn, all of whom recognized some irrational, dogmatic, paradoxical or even inconsistent features in Bohr’s work. Popper, Feyerabend, and Lakatos expressed strong criticism of Bohr’s approach to quantum physics, while Kuhn argued that such criticism was unlikely to be fruitful: progress in (...) science is generally not made through philosophical reflection. Feyerabend’s criticism of Bohr gradually weakened, as he gained a more detailed understanding of the development of Bohr’s views on quantum mechanics, and this went together with an increasingly critical view of normative philosophy of science and was instrumental to his conversion to ‘anarchism’. This paper aims to show that quantum mechanics played a central role in their debates and disagreements on the rationality of science and the possibility of a normative philosophy of science. (shrink)

This chapter is about Grete Hermann, a philosopher-mathematician who productively and mutually beneficially interacted with the founders of quantum mechanics in the early period of that theory's elaboration. Hermann was a neo-Kantian philosopher. At the heart of Immanuel Kant's critical philosophy lay the question of the conditions under which we can be said to know something objectively, a question Hermann found to be particularly pressing in quantum mechanics. Hermann's own approach to Neo-Kantianism was Neo-Friesian. Jakob Friedrich Fries, like Kant, had (...) understood critical philosophy to be an essentially epistemic project. Fries departed from Kant in his account of the elements involved in our cognition. In this chapter it is discussed how, beginning from a neo-Friesian understanding of critical philosophy, Hermann is led to conclude that quantum mechanics shows us that physical knowledge is fundamentally split; that the objects of quantum mechanics are only objects from a particular perspective and in the context of a particular physical interaction. It will be seen how Hermann's solution to the problem of objectivity in quantum mechanics is a natural one from a neo-Friesian point of view, even though it disagrees with those offered by more orthodox versions of Kantian doctrine. (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)

How long does a quantum particle take to traverse a classically forbidden energy barrier? In other words, what is the correct expression for quantum tunnelling time? This seemingly simple question has inspired widespread debate in the physics literature. I argue that we should not expect the orthodox interpretation of quantum mechanics to provide a unique correct expression for quantum tunnelling time, because to do so it would have to provide a unique correct answer to a question whose assumptions are in (...) tension with its core interpretational commitments. I explain how this conclusion connects to time’s special status in quantum mechanics, the meaningfulness of classically inspired concepts in different interpretations of quantum mechanics, the prospect of constructing experimental tests to distinguish between different interpretations, and the status of weak measurement in resolving questions about the histories of subensembles. (shrink)

This three-part paper comprises: (i) a critique by Halvorson of Bell’s (1973) paper ‘Subject and Object’; (ii) a comment by Butterfield; (iii) a reply by Halvorson. An Appendix gives the passage from Bell that is the focus of Halvorson’s critique.

It has been argued that measurement-induced collapses in Orthodox Quantum Mechanics generates an intrinsic (or built-in) quantum arrow of time. In this paper, I critically assess this proposal. I begin by distinguishing between an intrinsic and non-intrinsic arrow of time. After presenting the proposal of a collapse-based arrow of time in some detail, I argue, first, that any quantum arrow of time in Orthodox Quantum Mechanics is non-intrinsic since it depends on external information about the measurement context, and second, that (...) it cannot be global, but just local. I complement these arguments by assessing some criticisms and considerations about the implementation of time reversal in contexts wherein measurement-induced collapses work. I conclude that the quantum arrow of time delivered by Orthodox Quantum Mechanics is much weaker than usually thought. (shrink)

The purpose of this article is to establish a connection between modelling practices and interpretive approaches in quantum mechanics, taking as a starting point the literature on scientific representation. Different types of modalities play different roles in scientific representation. I postulate that the way theoretical structures are interpreted in this respect affects the way models are constructed. In quantum mechanics, this would be the case in particular of initial conditions and observables. I examine two formulations of quantum mechanics, the standard (...) wave-function formulation and the consistent histories formulation, and show that they correspond to opposite stances, which confirms my approach. Finally, I examine possible strategies for deciding between these stances. (shrink)

In this paper I present a new perspective for interpreting the wavefunction as a non-material, non-epistemic, non-representational entity. I endorse a functional view according to which the wavefunction is defined by its roles in the theory. I argue that this approach shares some similarities with the nomological account of the wave function as well as with the pragmatist and epistemic approaches to quantum theory, while avoiding the major objections of these alternatives.

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)

The last decade has seen an increasing number of references to quantum mechanics in the humanities and social sciences. This development has in particular been driven by Karen Barad’s agential realism: a theoretical framework that, based on Niels Bohr’s interpretation of quantum mechanics, aims to inform social theorizing. In dealing with notions such as agency, power, and embodiment as well as the relation between the material and the discursive level, the influence of agential realism in fields such as feminist science (...) studies and posthumanism has been profound. However, no one has hitherto paused to assess agential realism’s proclaimed quantum mechanical origin including its relation to the writings of Niels Bohr. This is the task taken up here. We find that many of the implications that agential realism allegedly derives from a Bohrian interpretation of quantum mechanics dissent from Bohr’s own views and are in conflict with those of other interpretations of quantum mechanics. Agential realism is at best consistent with quantum mechanics and consequently, it does not capture what quantum mechanics in any strict sense implies for social science or any other domain of inquiry. Agential realism may be interesting and thought provoking from the perspective of social theorizing, but it is neither sanctioned by quantum mechanics nor by Bohr’s authority. This conclusion not only holds for agential realism in particular, it also serves as a general warning against the other attempts to use quantum mechanics in social theorizing. (shrink)

Detailed summary of Chapters 2–5 • The interplay between principle-theoretic and constructive approaches to physics • The new kinematics of quantum theory • Examples of problems solved by the new kinematics • Measurement.

Genealogy of interpretations of quantum mechanics • Informational interpretations: objections (parochialism and anti-realism) and rejoinders • Bub and Pitowsky’s “big” and “small” measurement problems: puzzles to be solved or lessons to be learned? • Bub’s correlation arrays and Pitowsky’s correlation polytopes for Mermin’s setup to test a Bell inequality • Quantum mechanics as a general framework for handling probabilities.

Our interpretation of quantum mechanics in a nutshell • Comparison with the Everett family of interpretations.

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)

During his intellectual life, Karl Popper blamed Niels Bohr for defending subjectivist theses about Quantum Mechanics and for introducing the concept of subject in physics. But Popper’s accusation contradicts Bohr’s texts. The goal of this article is to show that Popper did not take seriously a central point of Bohr’s position : the contextuality of quantum phenomena. Quantum contextuality has strong consequences on the nature of measurement and on the constitution of the object in Quantum Mechanics. I try to show (...) that this misunderstanding is the reason why Popper accused Bohr for being a subjectivist. (shrink)

Heisenberg is one of the founders of quantum mechanics, and one of the pioneers and intellectual leaders of the Copenhagen interpretation of quantum mechanics. He proposed in two seminal papers in 1925 and 1927, the fundamentals of matrix mechanics (1925) as the first formalism of quantum mechanics, and then the uncertainty relations (1927) as one of the essential components of the Copenhagen interpretation. The purpose of this paper is to formulate Heisenberg's philosophical approaches during the formation of quantum mechanics and (...) its Copenhagen interpretation. The main question of the paper is whether philosophical approaches can be formulated in the development of quantum mechanics through Heisenberg's works? To answer this question, two seminal papers by Heisenberg (1925 and 1927) are examined. The research method of the paper is based on the content analysis of the text (physics) of Heisenberg's papers. The findings of this study show that three crucial principles - observability, correspondence, and analogy-can be formulated from Heisenberg's 1925 paper, which has played a key role in the formation of the fundamentals of matrix mechanics. Moreover, from his 1927 paper, some issues are addressed including interpretation, understanding and classical-quantum relation, the role of experience and measurement, the subject of causality, as well as reality. Finally, it is concluded that through these works of Heisenberg, four philosophical approaches can be formulated including empiricism, Unificationism, indeterminism, and anti-causality, as well as anti-realism, which themselves include other sub-approaches. (shrink)

Privileged-perspective realism (PPR) is a version of metaphysical realism that takes certain irreducibly perspectival facts to be partly constitutive of reality. PPR asserts that there is a single metaphysically privileged standpoint from which these perspectival facts obtain. This chapter discusses several views that fall under the category of privileged-perspective realism. These include presentism, which is PPR about tensed facts, and non-multiverse interpretations of quantum mechanics, which the chapter argues, constitute PPR about world-indexed facts. Using the framework of the bird perspective (...) and the frog perspective, it argues that PPR views methodologically treat the frog perspective as metaphysically primary. This chapter considers case studies of metaphysical interpretations of special relativity and quantum mechanics in order to demonstrate that such motivations for PPR are non-naturalistic. Further, it considers psychological factors that motivate the appeal of PPR views and offers naturalistic explanations of why we should not expect them to produce an adequate metaphysics of science. (shrink)

Tous les chercheurs intéressés aux fondements de la théorie quantique s’entendent sur le fait que celle-ci a profondément modifié notre conception de la réalité. Là s’arrête, toutefois, le consensus. Le formalisme de la théorie, non problématique, donne lieu à plusieurs interprétations très différentes, qui ont chacune des conséquences sur la notion de réalité. Cet article analyse comment l’interprétation de Copenhague, l’effondrement du vecteur d’état de von Neumann, l’onde pilote de Bohm et de Broglie et les mondes multiples d’Everett modifient, chacun (...) à sa manière, la conception classique de la réalité, dont le caractère local, en particulier, requiert une révision. (shrink)

This publication is an appreciation of the natural philosophy and epistemology of the philosopher Grete (Henry-)Hermann. A student of the mathematician Emmy Noether and the philosopher Leonard Nelson, she was one of the early interpreters of quantum mechanics. Werner Heisenberg memorialized her in his book "The Part and the Whole". For the first time, her writings on natural philosophy and epistemology are collected in one volume. An extensive introduction by various authors introduces the work of Grete Henry-Hermann. This edition is (...) supplemented by excerpts from correspondence on natural philosophical and epistemological topics, including correspondence with Carl Friedrich von Weizsäcker, Werner Heisenberg, and Gustav Heckmann. Contents ● Grete Henry-Hermann's contribution to the interpretation of quantum mechanics ● Grete Henry-Hermann's work on the relationship between modern physics and transcendental philosophy ● Grete Hermann's dissertation: The Question of the Finitely Many Steps in the Theory of Polynomial Ideals (1925) ● Discussions on the question of free will and the significance of behavioral research for the critique of reason ● Excerpts from correspondence from 1925 to 1982. (shrink)

What is called ``orthodox'' quantum mechanics, as presented in standard foundational discussions, relies on two substantive assumptions --- the projection postulate and the eigenvalue-eigenvector link --- that do not in fact play any part in practical applications of quantum mechanics. I argue for this conclusion on a number of grounds, but primarily on the grounds that the projection postulate fails correctly to account for repeated, continuous and unsharp measurements and that the eigenvalue-eigenvector link implies that virtually all interesting properties are (...) maximally indefinite pretty much always. I present an alternative way of conceptualising quantum mechanics that does a better job of representing quantum mechanics as it is actually used, and in particular that eliminates use of either the projection postulate or the eigenvalue-eigenvector link, and I reformulate the measurement problem within this new presentation of orthodoxy. (shrink)

This book explores the prospects of rivaling ontological and epistemic interpretations of quantum mechanics (QM). It concludes with a suggestion for how to interpret QM from an epistemological point of view and with a Kantian touch. It thus refines, extends, and combines existing approaches in a similar direction. The author first looks at current, hotly debated ontological interpretations. These include hidden variables-approaches, Bohmian mechanics, collapse interpretations, and the many worlds interpretation. He demonstrates why none of these ontological interpretations can claim (...) to be the clear winner amongst its rivals. Next, coverage explores the possibility of interpreting QM in terms of knowledge but without the assumption of hidden variables. It examines QBism as well as Healey’s pragmatist view. The author finds both interpretations or programs wanting in certain respects. As a result, he then goes on to advance a genuine proposal as to how to interpret QM from the perspective of an internal realism in the sense of Putnam and Kant. The book also includes two philosophical interludes. One details the notions of probability and realism. The other highlights the connections between the notions of locality, causality, and reality in the context of violations of Bell-type inequalities. (shrink)

What are quantum entities? Is the quantum domain deterministic or probabilistic? Orthodox quantum theory (OQT) fails to answer these two fundamental questions. As a result of failing to answer the first question, OQT is very seriously defective: it is imprecise, ambiguous, ad hoc, non-explanatory, inapplicable to the early universe, inapplicable to the cosmos as a whole, and such that it is inherently incapable of being unified with general relativity. It is argued that probabilism provides a very natural solution to the (...) quantum wave/particle dilemma and promises to lead to a fully micro-realistic, testable version of quantum theory that is free of the defects of OQT. It is suggested that inelastic interactions may induce quantum probabilistic transitions. (shrink)

Simon Friederich’s Therapeutic Approach to quantum theory (QT) sheds new light on the status of the quantum state. In particular, Friederich presents revisionary ideas on how to exactly differentiate objective from subjective elements of the theory and thereby improves upon previous stabs at an epistemic interpretation of quantum states. The book not only provides interesting perspectives for the cognoscenti but is also written with sufficient care and free of unnecessary technicalities so as to be accessible and worth reading for the (...) physical layman interested in the foundations of QT. The main achievement of the book is an innovative outline for interpreting quantum states epistemically while avoiding many problems of previous attempts. (shrink)

Niels Bohr and Philosophy of Physics: Twenty-First Century Perspectives examines the work, influences and legacy of the Nobel Prize physicist and philosopher of experiment Niels Bohr. While covering Bohr's groundbreaking contribution to quantum mechanics, this collection reveals the philosophers who influenced his work. Linking him to the pragmatist C.I. Lewis and the Danish philosopher Harald Høffding, it draws strong similarities between Bohr's philosophy and the Kantian way of thinking. Addressing the importance of Bohr's views of classical concepts, it discusses how (...) his interpretation of quantum mechanics now compares with a variety of issues that have arisen only since his lifetime, including decoherence and other non-collapse arguments. Balancing historical themes with contemporary ideas, Niels Bohrs and Philosophy of Physics reveals Bohr's on-going contribution to the philosophy of science and confirms his place in the history of philosophy. (shrink)