Quantum Discontents, or What Is Wrong with Our Science Practice

In defence of Copenhagenism

Relational Quantum Mechanics (RQM) claims to be an interpretation of quantum theory \cite{Rovelli.21}. However, there are significant departures from quantum theory: (i) in RQM measurement outcomes arise from interactions which entangle a system S and an observer A without decoherence, and (ii) such an outcome is a "fact" relative to the observer A, but it is not a fact relative to another observer B who has not interacted with S or A during the foregoing measurement process. For B the system S⊗A remains entangled. We derive a GHZ-like contradiction showing that relative facts described by these statements are incompatible with quantum theory. Hence Relational Quantum Mechanics should not be considered an interpretation of quantum theory, according to a criterion for interpretations that we have introduced. The criterion states that whenever an interpretation introduces a notion of outcomes, these outcomes, whatever they are, must follow the probability distribution specified by the Born rule.

The aim of the article is to analyze the ontological foundations of quantum mechanics and the relationship of various interpretations of quantum mechanics with the question of truth in scientific knowledge. The theoretical material (various interpretations of quantum mechanics) was analyzed. The research methods were analysis, comparative-historical and institutional approaches. On the basis of the study, it can be concluded that physicists are only able to predict the probabilities of physical phenomena or processes, without any knowledge of the structure of entity in itself. The study helps to complement the theoretical picture of the ontology of quantum mechanics and to get an idea about the development prospects of the methodology of physical sciences. We should not ascribe properties that are unobservable in experience to the entity because science can truly interpret only the representation of entity in itself in experience and the ways of dealing with it, not future events or possible states of the entity. Otherwise, science “slides” down to the level of dialectical (rhetorical) exercises based not on true premises, but on generally accepted or “authoritative” biases, which gives room to extreme forms of relativism and takes natural scientists away from studying nature to inventing empirically unsupported hypotheses. When, in accordance with the Cartesian ontology, the scientist assumes that the entity is as the “subject” observes it (that is, the “reflection” of the entity in consciousness is identified with entity in itself), this assumption leads the scientist to attempts to “scientifically” describe the future events or the possible states of the entity. The criterion for the truth of a scientific theory put forward by Einstein in his dispute with Bohr remains a fundamentally unattainable ideal. Cognition of nature is probabilistically and fundamentally incomplete since a person can consciously comprehend natural phenomena only within the framework of their representation in the existing being. The probabilistic nature of quantum mechanics is due to the impossibility of knowing things as they exist by themselves, that is, as they exist outside of representation in the mind of the observer. This does not mean that physical entities did not exist before their knowledge: they existed potentially, but were not valid for the observer, that is, conscious. Quantum physics is as incomplete as any other physical theory when compared with an unattainable ideal, but this fact does not negate its truth for modern scientists since quantum theory is based on the results of verified experiments.

As always, Albert Einstein was ahead of his time. Quantum theory was still in its infancy, its formalism a mere sketch, and its implications only beginning to be realized. Yet Einstein, in 1917, already spotted what would trouble him throughout his lifetime. He concluded that the nascent theory, which he had helped initiate, seemed to leave “time and direction of elementary processes,” such as the spontaneous emission of radiation from a molecule, “to chance” [1]. Einstein’s conclusion was visionary. It was also incredibly bold, for it suggested a radical departure from the powerful, centuries-old deterministic and causal worldview of classical physics. But Einstein also immediately expressed his discomfort with the idea of fundamental chance. In fact, his worries were just the seed of what would turn into one of the longest and most heated debates in the history of physics. What does quantum theory mean, and what does it tell us about the nature of reality? Some of the brightest minds in physics locked horns over these issues. Besides Einstein, there were Niels Bohr, Erwin Schrodinger, Werner Heisenberg, Pascual Jordan, Carl Friedrich von Weizsacker, Wolfgang Pauli, and Richard Feynman, just to name a few. Ask anyone today working on foundational questions in quantum theory and you are likely to hear that there is still no consensus on many of these questions—all the while, of course, everybody seems to be in perfect agreement on how to apply the quantum formalism when it comes to making experimental predictions. Remarkably, there has never been any serious attempt to find out what the current opinions of the community really are and how

In his 1939 Lectures, the prominent Soviet physicist L. I. Mandelstam proposed an interpretation of quantum mechanics that was understood in different ways. To assess Mandelstam's interpretation, we classify contemporary interpretations of quantum mechanics and compare his interpretation with others developed in the 1930s (the Copenhagen interpretation and the statistical interpretations proposed by K. R. Popper, H. Margenau, and E. C. Kemble). We conclude that Mandelstam's interpretation belongs to the family of minimal statistical interpretations and has much in common with interpretations developed by American physicists. Mandelstam's characteristic message was his theory of indirect measurement, which influenced his discussion of the “reduction of the wave packet” and the Einstein, Podolsky, and Rosen argument. This article also reconstructs what lay behind Mandelstam's interpretation of quantum mechanics. This was his operationalism, by virtue of which his interpretation resembled Kemble's, in which the statistical and Copenhagen views had been combined. Like Popper and Margenau, Mandelstam followed R. von Mises's empirical conception of probability. Mandelstam, like the other proponents of the statistical approach to quantum mechanics, was affected by the culture of macroscopic experimentation with its emphasis on statistical (collective) measurement.

The articles provides a phenomenological reading of the Many-Worlds Interpretation (MWI) of quantum mechanics and its answer to the measurement problem, or the question of “why only one of a wave function’s probable values is observed when the system is measured.” Transcendental-phenomenological and hermeneutic-phenomenological approaches are employed. The project comprises four parts. Parts one and two review MWI and the standard (Copenhagen) interpretation of quantum mechanics. Part three reviews the phenomenologies. Part four deconstructs the hermeneutics of MWI. It agrees with the confidence the theory derives from its (1) unforgiving appropriation of the Schrödinger equation and (2) association of branching universes with the evolution of the wave function insofar as that understanding comes from the formalism itself. Part four also reveals the hermeneutical shortcomings of the standard interpretation.

I argue that philosophical reflection can contribute to a better understanding of physical theories by performing conceptual clarification, epistemological analysis and ontological exploration. I begin by reconstructing early ontological interpretations of quantum theory, i.e., by explaining Copenhagen instrumentalism and the shift toward a quantum realism. I turn to entanglement, whose chief philosophical challenge is to understand which deeper property of nature it reveals. The trouble is that the EPR-correlations it gives rise to are not produced by common causation. Conceptual analysis shows that this failure is due to the violation of separability in quantum theory. In entangled states, it is the composite state that is primary since it cannot be neatly divided into two states that unambiguously pertain to the partial systems. As a result, total states are not produced by an interaction among the parts. This feature can be interpreted in ontological terms as suggesting a holist picture of nature. Another question of philosophical import concerns the quantum measurement problem and the contribution decoherence makes to its solution. The conceptual point is what, precisely, this problem amounts to and what we require considering it settled. The issue that divides the philosophical factions is whether a solution needs to show that superpositions are actually destroyed or whether it suffices to demonstrate that superpositions become unobservable.

Interpretations of quantum theory have traditionally assumed a “Galilean” observer, a bare “point of view” implemented physically by a quantum system. This paper investigates the consequences of replacing such an informationally-impoverished observer with an observer that satisfies the requirements of classical automata theory, i.e., an observer that encodes sufficient prior information to identify the system being observed and recognize its acceptable states. It shows that with reasonable assumptions about the physical dynamics of information channels, the observations recorded by such an observer will display the typical characteristics predicted by quantum theory, without requiring any specific assumptions about the observer’s physical implementation.

Introduction The term “scientist” lacks a universally accepted definition, reflecting the evolving, interdisciplinary nature of scientific work and posing challenges for recognition, communication, and policy. This study aims to develop consensus-based definitions of the term “scientist” by engaging experienced scholars across diverse fields. Methods This study involved 156 scholars, each with at least 1,000 citations, recruited via convenience sampling. Fourteen scientist definitions, derived from literature and expert input, were assessed using a nine-point Likert scale via a structured google forms survey. The sample size was calculated using G*power (effect size = 0.5, power = 0.95), requiring at least 80 participants. Content Validity Index (CVI) was used for analysis. Definitions scoring ≥0.78 were accepted and included for final analysis, 0.70–0.78 were revised and re-evaluated, and <0.70 were excluded. Participation was voluntary and anonymous, ensuring ethical compliance and confidentiality. Results Of the 14 proposed definitions, six (42.9%) were excluded (CVI < 0.70), seven (50.0%) were accepted (CVI > 0.78), and one (7.1%) underwent revision (CVI 0.70–0.78). The highest-rated definitions were refined into two consensus-based versions: a short definition (“A scientist is a person who conducts research”) and a detailed one emphasizing hypothesis formulation and knowledge dissemination. Final validation yielded CVIs of 0.82 and 0.84, respectively, confirming strong expert agreement on both definitions. Conclusion This study developed two validated definitions of “scientist” emphasizing systematic research and knowledge dissemination. These definitions clarify the concept of scientific identity, providing a flexible yet rigorous framework applicable across academic, interdisciplinary, and policy-making contexts. Introduction The term "scientist" has undergone significant transformation since its inception, reflecting the dynamic nature of scientific inquiry and the evolving landscape of knowledge. This lack of clarity stems from the diverse roles and contributions of individuals in scientific fields, the evolving nature of research, and the interdisciplinary scope of modern science. Historically, figures such as Galileo and Newton were regarded as natural philosophers, a reflection of an earlier framework for knowledge production that has evolved alongside modern scientific advancements. Before twentieth century, the term "scientist" was commonly referred to as a "man of science," "natural philosopher," or by various other designations [1,2]. In contemporary contexts, scientists operate across a broad spectrum of fields, including medicine, biology, chemistry, physics, and social sciences, each employing methodologies tailored to their specific inquiries. For instance, biologists may design experiments to test hypotheses about living organisms, while social scientists might use qualitative methods to explore human behavior [3]. The Science Council defines a scientist as an individual who methodically collects and applies research and evidence to develop hypotheses, performs experiments, and shares results to advance knowledge in their field [4]. While National Cancer Institute defines a scientist as an individual with a background in science, particularly someone actively engaged in a specific area of research [5]. This diversity in practices underscores the challenge of defining "scientist" in a way that captures the breadth of their contributions. The plurality of definitions extends to global organizations and frameworks. For example, the United Nations Educational, Scientific, and Cultural Organization highlights the critical role of scientists in addressing global challenges and promoting sustainable development. This definition broadens the scope to include individuals working in multidisciplinary teams or applying scientific knowledge to public policy and societal issues. Similarly, some academic discussions focus on the characteristics of a scientist, such as curiosity, skepticism, and a commitment to evidence-based conclusions, rather than formal qualifications or job titles [6]. Unlike well-defined professions such as medicine or engineering, where specific educational pathways and professional titles (e.g., "doctor" or "engineer") confer clear identities, the term "scientist" lacks a universally recognized credentialing system. This absence can lead to underrepresentation or misrepresentation of scientific expertise, especially in interdisciplinary and collaborative contexts [7]. For example, the growing integration of data science in biology or physics illustrates the importance of understanding who qualifies as a scientist to ensure effective communication and collaboration among stakeholders. The absence of a standardized definition poses practical challenges for scientific communication, policymaking, and inclusivity. This study aims to address this gap by engaging scholars across disciplines to develop a consensus-based definition of "scientist." By recognizing the diverse and interdisciplinary contributions of scientists, such a definition could enhance collaboration, improve public understanding, and inform policies that support the scientific community. Methods Study design and participants A total of 156 scholars (out of 300 invited) participated in this study. Eligibility was determined based on the scholars' substantial academic expertise, evidenced by the achievement of at least 1,000 citations within their respective fields. This criterion ensured that participants had significant research experience and were highly qualified to contribute to the formulation of a consensus-based definition of "scientist." Participants were recruited through a convenience sampling method, and data were collected via a structured survey administered through google forms. While convenience sampling was used due to the accessibility of high-citation scholars, efforts were made to ensure disciplinary diversity to mitigate potential bias. Personalized invitations were sent via email to each scholar to facilitate their inclusion in the study. Sample size determination The sample size was determined using G*power statistical software (version 3.1.9.7), employing a two-tailed goodness of fit test with an effect size of 0.5, an alpha error probability of 0.05, and a statistical power of 0.95. According to the calculations, a minimum of 80 participants were required to achieve statistically valid results. Consequently, 156 scholars were recruited to participate in the study, ensuring robust representation and adequate statistical power. Data collection Fourteen proposed definitions of "scientist," curated from existing literature and expert contributions, were presented to the enrolled scholars for evaluation (Table 1). Each definition included a Likert scale with nine response options, ranging from "strongly agree" to "strongly disagree." Responses were systematically recorded and compiled in an Excel sheet for subsequent analysis. This process facilitated the systematic capture of scholarly consensus on each definition. Table 1. Respondent Agreement on Various 'Scientist' Definitions. Proposed Definitions Options A person studying or has expert knowledge of one or more natural or physical sciences. (Oxford Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree An expert who studies or works in one of the sciences. (Cambridge Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A person learned in science and especially natural science. (Merriam-Webster Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A scientist is someone who systematically gathers and uses research and evidence, to make hypotheses and test them, to gain and share understanding and knowledge. (Science Council) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A scientist is someone who has studied science and whose job is to teach or do research in science. (Collins Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree An expert in science, especially one of the physical or natural sciences. (Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A scientist is a person with some kind of knowledge or expertise in any of the sciences. (Vocabulary dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A person who is trained in a science and whose job involves doing scientific research or solving scientific problems. (Britannica Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A person who has studied science, especially one who is active in a particular field of investigation. (National Cancer Institute) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree Someone who works or is trained in science. (Longman Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A person whose profession is investigating in one of the natural sciences. (Your Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A person who is engaged in and has expert knowledge of a science. (Free Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree Someone whose job or education is about science. (LanGeek Dictionary) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree A scientist is a person who researches to advance knowledge in an area of the natural sciences. (Wikipedia) Strongly Disagree Moderately Disagree Disagree Slightly Disagree Undecided Slightly Agree Moderately Agree Agree Strongly Agree Data analysis The Content Validity Index (CVI) was employed to assess the relevance and agreement of the definitions. Definitions with a CVI below 0.70 were excluded, as they failed to meet the minimum threshold for consensus. Definitions with a CVI between 0.70 and 0.78 underwent a second round of evaluation, with refined wording sent back to the same scholars for further review. Definitions achieving a CVI above 0.78 were deemed sufficiently valid for inclusion in the final analysis [8]. These definitions formed the foundation for the development of a unified, consensus-based definition of "scientist." Ethical considerations Participation in the study was entirely voluntary, and all responses were anonymized to preserve participant confidentiality. Results Initially, out of the 14 proposed definitions of the term "scientist," six (42.9%) received a CVI score below the threshold of 0.70 and were consequently excluded from further consideration. In contrast, seven definitions (50.0%) demonstrated strong content validity with CVI scores equal to or exceeding 0.78 and were therefore retained for subsequent synthesis and analysis. Only one definition (7.1%) fell within the intermediate range, with a CVI between 0.70 and 0.78 (Table 2). Table 2. Comparison of Agreement and CVI Across Proposed Definitions of 'Scientist'. Proposed Definition Agree Disagree Undecided CVI Status Science Council Definition 146 8 2 0.94 Accepted Britannica Dictionary Definition 136 16 4 0.87 Accepted Cambridge Dictionary 130 20 6 0.83 Accepted Wikipedia Definition 125 27 4 0.80 Accepted Free Dictionary Definition 124 25 7 0.79 Accepted National Cancer Institute Definition 124 25 7 0.79 Accepted Collins Dictionary Definition 122 31 3 0.78 Accepted Oxford Dictionary Definition 120 31 5 0.77 Revised Longman Dictionary Definition 104 42 10 0.67 Excluded Your Dictionary Definition 103 48 5 0.66 Excluded Dictionary (generic) Definition 91 52 13 0.58 Excluded Vocabulary dictionary Definition 88 58 10 0.56 Excluded Merriam-Webster Dictionary Definition 81 64 11 0.52 Excluded LanGeek Dictionary Definition 79 67 10 0.51 Excluded CVI: Content Validity Index, CVI Thresholds: Accepted: ≥ 0.78, Revised: 0.70–0.78, Excluded: < 0.70 Through a rigorous, iterative evaluation process involving expert feedback, the definitions with the highest CVI scores (those above 0.78) were integrated and refined into two distinct, consensus-based definitions of the term "scientist." The first was a concise definition: “A scientist is a person who conducts research.” The second was a more comprehensive and elaborated definition: “A scientist is someone who systematically conducts or gathers and uses research to formulate hypotheses and test them, in order to gain and disseminate understanding and knowledge.” These two final definitions were subsequently circulated among the panel of scholars for a second round of evaluation, during which they were asked to rate the definitions for content validity. The short definition received a CVI of 0.82, while the more detailed definition attained a slightly higher CVI of 0.84, reflecting strong agreement among the experts. Although no additional formal qualitative feedback was solicited at this stage; minor wording adjustments were made based on informal suggestions received during this validation round. Discussion The role of a scientist extends far beyond the stereotypical image of an individual in a white coat working exclusively in a laboratory setting. Careers grounded in scientific expertise are remarkably diverse, encompassing domains such as research, education, industry, and regulatory affairs. The Science Council categorizes scientists into 10 different types, highlighting the diversity of scientific roles beyond the stereotypical lab-based researcher. It includes types such as experimental scientists, theoretical scientists, data scientists, and more, reflecting the broad spectrum of scientific work today [9]. Definitions of the term “scientist” vary, yet they generally converge on the principles of systematic inquiry, evidence-based investigation, and the pursuit of knowledge across various disciplines. For instance, the Oxford Advanced Learner’s Dictionary and the Britannica Dictionary emphasize formal training and research functions, typically within the natural sciences such as biology, chemistry, or physics [10,11]. In contrast, contemporary perspectives, such as those discussed by the American Association for the Advancement of Science in 2024, recognize a broader spectrum of scientific engagement, encompassing both professional researchers and individuals committed to understanding the world through observation, experimentation, and analysis [12]. In light of this diversity, the present study aimed to clarify and formalize the definition of a "scientist" through expert consensus. Two definitions were developed: a concise definition “A scientist is a person who conducts research”, and a comprehensive definition “A scientist is someone who systematically conducts or gathers and uses research to formulate hypotheses and test them, in order to gain and disseminate understanding and knowledge.” These definitions encapsulate the core activities and guiding principles of scientific inquiry, emphasizing both methodological rigor and the essential role of knowledge dissemination across disciplines. A key finding of this study lies in its recognition of the evolving tension between disciplinary specialization and the increasing importance of interdisciplinary collaboration. As highlighted in contemporary analyses of interdisciplinary research and development, scientists now frequently operate at the intersection of multiple fields, such as nanomedicine, where the diversity and dissimilarity of collaborators’ knowledge can significantly enhance research productivity [13]. The concise definition, "A scientist is a person who conducts research" captures this shift by avoiding constraints tied to specific disciplinary boundaries. In contrast, the more detailed definition explicitly incorporates the systematic formulation and testing of hypotheses, along with the dissemination of knowledge, thereby reinforcing the structured and communicative nature of scientific inquiry. These elements align closely with UNESCO’s 2019 call for stronger science-society engagement and underscore the ethical responsibilities inherent in modern scientific practice [14]. The study’s findings also contribute to ongoing debates surrounding professional identity within the scientific community. In contrast to regulated professions such as medicine, the absence of a universal credentialing system for scientists complicates formal recognition, particularly in non-academic and interdisciplinary contexts. This ambiguity is reflected in the National Cancer Institute’s pragmatic definition of a scientist, which emphasizes active participation in research rather than reliance on formal titles or qualifications [15]. By anchoring the term “scientist” in core research activities rather than occupational labels, the consensus-based definitions proposed in this study offer a more inclusive framework. This approach accommodates emerging roles in fields such as data science and applied research, thereby addressing the risk of under recognition in collaborative and cross-sector environments. The dual definitions, concise and comprehensive, offer flexibility for different contexts, a strategy aligned with the Science Council’s emphasis on methodological diversity [4]. The detailed definition’s focus on systematic inquiry and dissemination aligns with studies of interdisciplinary science, where “impassioned commitment” to shared goals drives innovation [13]. Simultaneously, the availability of a concise definition enhances clarity in public discourse and science communication, while the more detailed version provides the specificity necessary for institutional contexts such as policy development, research funding, and professional accreditation. Notably, the study’s findings also challenge enduring stereotypes of the “lone genius” scientist by highlighting the inherently collaborative and iterative nature of scientific practice. Contemporary frameworks, such as those emerging from computational biology, suggest that scientific identity is increasingly dynamic, pluralistic, and shaped by collective knowledge production [16]. The process undertaken in this study, involving successive refinement and expert validation of definitions, closely mirrors the recursive logic of the scientific method itself. This methodological alignment is particularly salient in fields like nutritional epidemiology, where the replication of findings remains a persistent challenge and iterative inquiry is essential for refining evidence [17]. Despite the methodological rigor and expert involvement, several limitations should be acknowledged. First, the study employed convenience sampling, which may introduce selection bias and limit the generalizability of the findings. Although participants were selected based on a minimum citation threshold to ensure scholarly expertise, this criterion may have inadvertently excluded emerging researchers or experts with significant practical contributions who have not yet achieved high citation metrics. Second, the use of an online survey format may have constrained participant engagement, as scholars with limited availability or preference for alternative formats may have been underrepresented. Additionally, response bias cannot be ruled out, as those with a particular interest in the topic or in defining scientific identity may have been more inclined to participate, potentially skewing the results. Future refinements of the definition should also consider voices from non-academic scientific contexts including those in industry, policy, and community-based science who are increasingly central to addressing complex global challenges. Conclusion By engaging experienced scholars across disciplines, this study establishes two validated definitions of “scientist” that emphasize systematic research activity and knowledge dissemination. These definitions offer a structured yet adaptable framework for understanding scientific identity, balancing clarity with flexibility. They help address the ambiguity surrounding the term “scientist,” providing a foundation for improved communication, interdisciplinary collaboration, and evidence-informed policy development. Importantly, they remain open to future refinement as scientific practice continues to evolve. Declarations Conflicts of interest: The authors have no conflicts of interest to disclose. Ethical approval: Not applicable. Patient consent (participation and publication): Not applicable. Funding: The present study received no financial support. Acknowledgements: None to be declared. Authors' contributions: JG, MM, SB, BS, VS, ASN, SHM, HAH, AGH, ADS, RAK, WRR, AB, GB, SS, SN, CJ, PL, MSS, ZK, MC, AM, SK, FCT, FB, FRK, MAM, AA, VK, DH, PM, VRM, MSA, EA, and RV were significant contributors to the conception of the study, voting for the items. FHK, BAA, and AMM were involved in the literature review, manuscript writing, and data analysis and interpretation. FHK and AMM Confirmation of the authenticity of all the raw data. All authors have read and approved the final version of the manuscript. Use of AI: ChatGPT-3.5 was used to assist in language editing and improving the clarity of the manuscript. All content was reviewed and verified by the authors. Authors are fully responsible for the entire content of their manuscript. Data availability statement: Not applicable.

This essay sketches a pragmatist interpretation of quantum theory and shows how to use it to explain EPR-Bell correlations consistently with relativity. Quantum theory is not a locally causal theory, not because it violates Bell’s local causality condition, but because that condition is simply inapplicable to it. Any agent can use quantum theory to show why EPR-Bell correlations are to be expected. For space-like separated measurements of vertical/horizontal polarization of each photon from a pair in Bell state Φ+, an agent’s explanation of why the distant measurement outcome matches his own appeals neither to a preferred frame nor to any direct connection or influence between these events. Here, as elsewhere, quantum theory helps one explain an initially puzzling phenomenon not by locating it in a causal net but by showing why its occurrence is just what one should have expected in the circumstances.

Far from regarding physical science as a universal model of human knowledge, Werner Heisenberg relativized the scientificity of natural science, situating this domain of knowledge in a wide range of our modes of experiencing the world. In this paper, with a focus on his critical analysis of the notion of objectivity in quantum theory and other fields, I survey Heisenberg’s view of the world as divided into six distinct areas of reality, including – but not centered on – physical science. I also seek to show how this conception of the structure of reality, specifically of the relation between different areas of reality, is mediated by his mis- or reinterpretation of Bohr’s idea of complementarity.

One of the main challenges in theoretical physics over the last five decades has been to reconcile quantum mechanics with general relativity into a theory of quantum gravity. However, such a theory has been proved to be hard to attain due to i) conceptual difficulties present in both the component theories (General Relativity (GR) and Quantum Theory); ii) lack of experimental evidence, since the regimes at which quantum gravity is expected to be applicable are far beyond the range of conceivable experiments. Despite these difficulties, various approaches for a theory of Quantum Gravity have been developed. In this thesis we focus on two such approaches: Loop Quantum Gravity and the Topos theoretic approach. The choice fell on these approaches because, although they both reject the Copenhagen interpretation of quantum theory, their underpinning philosophical approach to formulating a quantum theory of gravity are radically different. In particular LQG is a rather conservative scheme, inheriting all the formalism of both GR and Quantum Theory, as it tries to bring to its logical extreme consequences the possibility of combining the two. On the other hand, the Topos approach involves the idea that a radical change of perspective is needed in order to solve the problem of quantum gravity, especially in regard to the fundamental concepts of `space' and `time'. Given the partial successes of both approaches, the hope is that it might be possible to find a common ground in which each approach can enrich the other.

The formalism of covariant quantum theory, introduced by Reisenberger and Rovelli, casts the description of quantum states and evolution into a framework compatible with the principles of general relativity. The leap to this covariant formalism, however, outstripped the standard interpretation used to connect quantum theory to experimental predictions, leaving the predictions of the theory ambiguous. In particular, the absence of a pre-defined time variable or background causal structure resulted in an ``order of projections" ambiguity, in which the usual rule for multiple-measurement probabilities (obtained by time-ordered projections) is not defined. Equally troublesome, the probability postulate of Reisenberger and Rovelli fails to reproduce the Born interpretation for the case of simple quantum mechanical systems. Here, we develop an alternative quantum measurement formalism, based on basic principles of quantum information. After reviewing how this can be done in the context of the traditional formulation of quantum mechanics and noting its implications for the quantum measurement problem, we find that this approach can be generalized to the covariant setting, where it essentially solves the correspondence problems of covariant quantum theory. We show explicit agreement with the Born interpretation of standard quantum mechanics in the context of simple systems. We also demonstrate the origin of the quantum mechanical arrow of time within our framework, and use this to solve the order of projections ambiguity. In addition to compatibility with general covariance, we show that our framework has other attractive and satisfying features - it is fully unitary, realist, and self-contained. The full unitarity of the formalism in the presence of measurements allows us to invoke time-reversal symmetry to obtain new predictions closely related to the quantum Zeno effect.

Exact predictions for most quantum systems are computationally inaccessible. This is the so-called many body problem, which is present in most common interpretations of quantum mechanics. Therefore, predictions of natural quantum phenomena have to rely on some approximations (assumptions or simplifications). In the literature, there are different types of approximations, ranging from those whose justification is basically based on theoretical developments to those whose justification lies on the agreement with experiments. This last type of approximations can convert a quantum theory into an “unfalsifiable” quantum theory, true by construction. On the practical side, converting some part of a quantum theory into an “unfalsifiable” one ensures a successful modeling (i.e. compatible with experiments) for quantum engineering applications. An example of including irreversibility and dissipation in the Bohmian modeling of open systems is presented. On the ontological level, however, the present-day foundational problems related to controversial quantum phenomena have to avoid (if possible) being contaminated by the unfalsifiability originated from the many body problem. An original attempt to show how the Bohmian theory itself (minimizing the role of many body approximations) explains the transitions from a microscopic quantum system towards a macroscopic classical one is presented.

Generally, there are two interpretative approaches to quantum theory: psi-ontic and psi-epistemic. According to the psi-ontic interpretations, quantum theory does/should describe or represent what the world is like. In contrast, according to the psi-epistemic interpretations, rather than representing the way the world is, quantum theory advises us on what to expect from the world and so helps us better navigate our surrounding world. In this paper, we will argue that Edmund Husserl’s philosophy of science especially his notion of lifeworld provides an appropriate framework for better understanding this shift from the psi-ontic to psi-epistemic interpretations of quantum theory. In particular, we analyse Richard Healey’s pragmatic approach to quantum mechanics from a phenomenological point of view.