The quantum reconstruction program seeks to uncover the deeper physical meaning of the quantum formalism by distilling its content into a set of physically graspable postulates. Once reconstructed, one can further elucidate the theory by reflecting philosophically upon the postulates rather than the inscrutable formalism in which the theory is couched. Quantum reconstruction thereby opens up a two-step strategy for developing a quantum conceptual framework that reflects the full physical content of quantum theory and can be used to establish precisely what aspects of the classical conceptual framework are retained, modified, or abandoned. The chapter is organized as follows. Section 11.2 describes the tripartite structure of classical physics, whose coherency I argue underlies its intelligibility. Section 11.3 discusses the lack of intelligibility of quantum physics, analyses the limitations of the main traditional elucidative approaches, and describes how reconstruction can remove the fundamental interpretative bottleneck. Section 11.4 discusses the methodology of reconstruction per se , showing that it is part of the natural life-cycle of physical theories, and summarizes its use in the elucidation of the theories of classical physics. Finally, circling back to quantum theory, Section 11.5 summarizes the reconstruction of quantum theory, and Section 11.6 describes some of the interpretative insights obtained thus far through interpretation of reconstructions of the abstract quantum formalism and the quantum symmetrization postulate.
The quantum reconstruction program seeks to uncover the deeper physical meaning of the quantum formalism by distilling its content into a set of physically graspable postulates. Once reconstructed, one can further elucidate the theory by reflecting philosophically upon the postulates rather than the inscrutable formalism in which the theory is couched. Quantum reconstruction thereby opens up a two-step strategy for developing a quantum conceptual framework that reflects the full physical content of quantum theory and can be used to establish precisely what aspects of the classical conceptual framework are retained, modified, or abandoned. The chapter is organized as follows. Section 11.2 describes the tripartite structure of classical physics, whose coherency I argue underlies its intelligibility. Section 11.3 discusses the lack of intelligibility of quantum physics, analyses the limitations of the main traditional elucidative approaches, and describes how reconstruction can remove the fundamental interpretative bottleneck. Section 11.4 discusses the methodology of reconstruction per se , showing that it is part of the natural life-cycle of physical theories, and summarizes its use in the elucidation of the theories of classical physics. Finally, circling back to quantum theory, Section 11.5 summarizes the reconstruction of quantum theory, and Section 11.6 describes some of the interpretative insights obtained thus far through interpretation of reconstructions of the abstract quantum formalism and the quantum symmetrization postulate.
One hundred years after the creation of quantum theory, there is no consensus on the kind of reality that is described by the theory. Here, I attribute the lack of progress to the prevailing interpretative methodology, which invariably takes the quantum formalism as the starting point for philosophical reflection and analysis. I argue that this methodology is particularly inappropriate, for it invariably marginalizes much of the theory's content, both that implicit in modelling heuristics and experimental practices, and that encapsulated in the mathematical structures of its formalism. In addition, the prevailing methodology offers little protection against undue influence by metaphysically-laden language which invariably accompanies the formalism.
Here, I summarize an alternative methodology whose goal is to ensure that an interpretational project take into account all forms of theoretic content. The methodology harnesses the recent results of the quantum reconstruction program. These results distil the mathematical content of the quantum formalism into physical principles and assumptions, which are more readily philosophically digestible than the formalism itself, and bracket much of its metaphysically-laden language.
As a case study of reconstruction-based interpretation, I describe the reconstruction of the identical particle formalism, and its step-by-step interpretation, highlighting the key questions that drive the interpretation forwards and the techniques and stances that are employed in each step. The interpretation yields a novel metaphysical profile for systems of identical particles as potential parts of a whole, which can be traced step-by-step to elementary experimental data and the reconstruction's physical postulates and assumptions. I also describe some of the pitfalls that one faces in any attempt to directly interpret the identical particle formalism.
For a century, quantum theory has posed a fundamental challenge to philosophical thinking. On its face, it repudiates many of the key features of the mechanical conception of physical reality. However, the challenge of developing a precise, coherent alternative to that conception has yet to be met. Here, I argue that a major hindrance to the project of quantum interpretation is its existing interpretative methodologies, which suffer from a lack of systematicity in their judgements about what aspects of the theory are interpretational relevant. In particular, I argue that current interpretations tend to marginalize the informal part of the theory in favour of its formal part, and place inappropriate emphasis on the natural language component of the formalism over its detailed mathematical structure. To counterbalance these biases, I propose that an interpretation-free zone be constructed around the theory, wherein an interpreter initially adopt a descriptive stance which considers all parts of the theory, and that the results of this deliberation~(and the judgements about what facts are interpretationally relevant) are reported as part of their interpretation.
I argue that the interpretation of quantum theory poses special challenges and difficulties which necessitate this interpretation-free zone, and that existing interpretative methodologies are insufficient to address them. Further, I argue that a reconstructive interpretative methodology, which harnesses the recent results of the quantum reconstruction program, provides a powerful means to identify almost all facts that could be interpretationally relevant, and naturally meets these challenges and difficulties. Moreover, I argue that the quantum reconstruction program offers a powerful way to discover new physical principles, and offers a systematic pathway to build a rich, coherent conception of quantum reality.
Quantum theory poses deep challenges to the mechanical conception of reality that underlies classical physics. Yet today, over eighty years after its creation, its implications for our picture of reality remain enshrouded in uncertainty. In view of the current search for a more comprehensive theory of physics (a so-called theory of everything), it is vital that these implications be clearly elucidated. In this article, I describe the nature of the challenge posed by quantum theory, and outline efforts that have been made to better understand its nonclassical features, such as non-locality. In particular, I discuss the informational perspective, which, through the study of quantum information processing, has provided deep insights into the nature of quantum reality, and has also revitalized the long-standing quest to reconstruct the content of the rather mysterious mathematical formalism of quantum theory from a set of crisp physical principles. Finally, I indicate some implications of recent reconstructive work for the search for a theory of quantum gravity, and, more broadly, for our picture of physical reality.
Although, the main objective of this book has been to expose the facts that underpin formal description of quantum mechanics and to make quantum mechanics seem natural, in going about this process we have tried to provide the young student with a guideline on how to approach learning a new theory. Thus, somewhat unconventionally, we start the discourse with a discussion on the meaning of theory and its formal description. This allows us to demonstrate, in concrete terms, how quantum mechanics is just another theoretical framework that conforms to the standard definition of a theory in the natural sciences. In this first chapter, we start with a nontechnical discussion of what one means by a theoretical framework and its formal description. We clarify what qualifies as a theory, and list the questions whose answers one must seek in trying to learn it. A notion of what amounts to understanding a theory is thus conveyed. The meaning of law, axiom, postulate, theorem, falsifiability etc., are thus discussed. We try to draw out the purpose of constructing a formal description of a theory. We also outline the role of abstraction and generalization in its construction. Finally, we discuss the sense in which the terms “philosophy” and “fundamental theorem” are used in the construction of a theoretical framework.
Abstract The reconstruction of quantum physics has been connected with the interpretation of the quantum formalism, and has continued to be so with the recent deeper consideration of the relation of information to quantum states and processes. This recent form of reconstruction has mainly involved conceiving quantum theory on the basis of informational principles, providing new perspectives on physical correlations and entanglement that can be used to encode information. By contrast to the traditional, interpretational approach to the foundations of quantum mechanics, which attempts directly to establish the meaning of the elements of the theory and often touches on metaphysical issues, the newer, more purely reconstructive approach sometimes defers this task, focusing instead on the mathematical derivation of the theoretical apparatus from simple principles or axioms. In its most pure form, this sort of theory reconstruction is fundamentally the mathematical derivation of the elements of theory from explicitly presented, often operational principles involving a minimum of extra‐mathematical content. Here, a representative series of specifically information‐based treatments—from partial reconstructions that make connections with information to rigorous axiomatizations, including those involving the theories of generalized probability and abstract systems—is reviewed.
Abstract In quantum foundations, there is growing interest in the program of reconstructing the quantum formalism from clear physical principles. These reconstructions are formulated in an operational framework, deriving the formalism from information-theoretic principles. It has been recognized that this project is in tension with standard ψ-ontic interpretations. This paper presupposes that the quantum reconstruction program (QRP) (i) is a worthwhile project and (ii) puts pressure on ψ-ontic interpretations. Where does this leave us? Prima facie, it seems that ψ-epistemic interpretations perfectly fit the spirit of information-based reconstructions. However, ψ-epistemic interpretations, understood as saying that the wave functions represents one’s knowledge about a physical system, recently have been challenged on technical and conceptual grounds. More importantly, for some researchers working on reconstructions, the lesson of successful reconstructions is that the wave function does not represent objective facts about the world. Since knowledge is a factive concept, this speaks against epistemic interpretations. In this paper, I discuss whether ψ-doxastic interpretations constitute a reasonable alternative. My thesis is that if we want to engage QRP with ψ-doxastic interpretations, then we should aim at a reconstruction that is spelled out in non-factive experiential terms.