This chapter aims to place the discussion of holism in quantum theory generally and of the problem of identical particles and quantum statistics specifically in the context of general philosophy. Various debates in metaphysics, both historical and current, broach related subjects and involve analyses of concepts currently used in the philosophy of quantum mechanics. These include concepts of identity, individuation, essence, form, necessity, possibility, modality, contingency, and universality. But this chapter also extends the previous one by introducing Fock space and the transition from elementary quantum mechanics to quantum field theory via 'second quantization’. For this formalism relates clearly to certain ’anti‐essentialist’ approaches in the metaphysics of modality. Finally, in keeping with the empiricism pursued in this book, the general enterprise of metaphysics pertaining to those topics is viewed here within an anti‐metaphysical stance, as having as its value the display of a plurality of interpretations whose very diversity enhances our understanding of the theory.
This chapter aims to place the discussion of holism in quantum theory generally and of the problem of identical particles and quantum statistics specifically in the context of general philosophy. Various debates in metaphysics, both historical and current, broach related subjects and involve analyses of concepts currently used in the philosophy of quantum mechanics. These include concepts of identity, individuation, essence, form, necessity, possibility, modality, contingency, and universality. But this chapter also extends the previous one by introducing Fock space and the transition from elementary quantum mechanics to quantum field theory via 'second quantization’. For this formalism relates clearly to certain ’anti‐essentialist’ approaches in the metaphysics of modality. Finally, in keeping with the empiricism pursued in this book, the general enterprise of metaphysics pertaining to those topics is viewed here within an anti‐metaphysical stance, as having as its value the display of a plurality of interpretations whose very diversity enhances our understanding of the theory.
The notion of an individual and the related issues on individuation are topics that appear in the philosophical discussion ever since the antiquity. The idea of an individual thing is intuitively clear: an individual is something of a specific kind that is a unity, having its own identity, and being so that it is possible at least in principle to discern it from any other individual, even of similar species. But when we try to leave the intuitive realm and push this idea to a logical analysis, we find a cluster of problems that are difficult to overcome within standard logico-mathematical contexts. In this work, we shall be concerned with some aspects of this intuitive concept of an individual and on some related facts about individuation taken from recent discussions that arose ever since the inception of quantum theory, pushing the discussion to a “logical” view, which in our opinion is still lacking in the usual debates on such issues. In the final part of the paper, we propose a metaphysics where the notion of identity is substituted, for some objects, by a weaker notion of indiscernibility, and we try to justify such a move. In most of the uses of the expression “quantum theory”, we shall not make explicit the distinction between the non-relativistic and the relativistic approaches, although they of course are quite different, for we think that the problems as we shall present them appear in both versions. But, as the text goes, the context will distinguish between them and these questions will become clear to the reader.
One recent debate in philosophy of physics has centered whether quantum particles are individuals or not. The received view is that particles are not individuals and the standard methodology is to approach the question via the structure of quantum theory. I challenge both the received view and the standard methodology. I contend not only that the structure of quantum theory is not the right place to look for conditions of individuality that quantum particles may or may not satisfy, but also that there is an important role for traditional metaphysics to play. Consequently, my work brings together the philosophy of physics and traditional metaphysics literatures to shed new light on the debate over the individuality of quantum particles. I defend a set of conditions of individuality and argue that quantum particles satisfy these conditions thereby defending the view that particles are individuals in opposition to the received view. I also challenge a second feature of the standard methodology insofar as I challenge the significance of the Principle of the Identity of Indiscernibles in terms of which much discussion in the philosophy of physics literature is framed. My work is significant in a number of additional ways as well. My work implies that the dominant explanation for quantum statistics in terms of non-individuality is incorrect and it also undermines the ontic-structural realists metaphysical underdetermination challenge to the scientific realist.
Abstract This chapter discusses the concepts of indistinguishability, individuality, and non-individuality in the quantum context. It is argued that the above view of particles as non-individuals is not a necessary consequence of the physics, and that quantum particles can be taken to be individuals, subject to certain constraints. However, the sense of individuality here cannot be understood in terms of the Identity of Indiscernibles, since on a standard interpretation of quantum theory, Leibniz’s Principle is violated by both fermions and bosons. Criticisms of this argument are reviewed, as is Saunders’ recent attempt to defend a Quinean form of the Principle. The consequences of regarding quantum particles as individuals are considered in detail, and Teller’s account of entanglement in terms of non-supervenient relations is developed in this context. The conclusion is reached that quantum physics supports two alternative metaphysical packages of individuality and non-individuality, yielding a stronger form of underdetermination, which can be used to support a form of structuralism.
Abstract Metaphysicians should pay attention to quantum mechanics, but not because it provides definitive answers to many metaphysical questions. The theory itself is remarkably silent on the nature of the physical world, and the various interpretations of the theory on offer present conflicting ontological pictures. Rather, quantum mechanics is essential to the metaphysician because it reshapes standard metaphysical debates and opens up unforeseen new metaphysical possibilities. Even if quantum mechanics provides few clear answers, there are good reasons to think that any adequate understanding of the quantum world will result in a radical reshaping of our classical worldview in some way or other. Whatever the world is like at the atomic scale, it is almost certainly not the swarm of particles pushed around by forces that is often presupposed. This book guides readers through the theory of quantum mechanics and its implications for metaphysics in a clear and accessible way. The theory and its various interpretations are presented with a minimum of technicality. The consequences of these interpretations for metaphysical debates concerning realism, indeterminacy, causation, determinism, holism, and individuality (among other topics) are explored in detail, stressing the novel form that the debates take given the empirical facts in the quantum domain. While quantum mechanics may not deliver unconditional pronouncements on these issues, the range of possibilities consistent with our knowledge of the empirical world is relatively small—and each possibility is metaphysically revisionary in some way.
Abstract Drawing on philosophical accounts of identity and individuality, as well as the histories of both classical and quantum physics, this book explores two alternative metaphysical approaches to quantum particles. It asks if quantum particles can be regarded as individuals, just like books, tables, and people. Taking the first approach, the book argues that if quantum particles are regarded as individuals, then Leibniz’s famous Principle of the Identity of Indiscernibles is in fact violated. Recent discussions of this conclusion are analysed in detail and the costs involved in saving the Principle are carefully considered. For the second approach, the book considers recent work in non-standard logic and set theory to indicate how we can make sense of the idea that objects can be non-individuals. The concluding chapter suggests how these results might then be extended to quantum field theory.
This chapter, along with the next two chapters, sets the basic context for the readers to go into the topic of this book. Physicists, mathematicians, and philosophers struggle to clarify the foundations of quantum mechanics and debate on the interpretations of quantum mechanics. What is the foundation of quantum mechanics and how to interpret the formalism of quantum mechanics are the core issues of concern in the philosophy of physics. These two questions also involve fundamental issues in the general philosophy of science and even metaphysics and epistemology. This chapter introduces the original thoughts, historical developments, and current status of the interpretation of quantum mechanics, as well as its connection with the philosophy of science and metaphysics; it also analyzes the classifications by Bell, Leifer, and Cabello on the spectrum of interpretations of quantum mechanics, which can be regarded as a sort of “navigation map”. On this basis, the main object of discussion in this book is introduced – the quantum histories interpretation.