The non-relativistic quantum mechanics offers us conditions to consider at least two possible metaphysical packages, but incompatible between themselves: metaphysics of individuals, and metaphysics of non-individuals. In addition, the standard formalism is compatible with both the ontologies, without the theory being decided for either of them. From this particular kind of situation, the thesis of the underdetermination of metaphysics by physics can be established. Actually, it can be found, among scientists and philosophers, defenders of one, or another ontology, as well as those who do not address the issue, given that theory on its own does not decide. This means that if we make a choice for one of these packages, it will be happing in a metaphysical field, increasing a lot the philosophical discussions about individuality of quantic objects in quantum physics. From a naturalized methodological view, we present the issues from those defend the individuality of quantic objects, and from those, include us, defend non-individuality, focusing two approaches: (i) the ontological one, in which the fail of IIP as individuation principle is discussed; and, (ii) the logical one, in which non-reflexive logics, as well as a quasi-set theory became more suitable for representing the non-individuals. In this paper we stand for the choice of non-individuals ontology becomes more plausible, and should be taken in account seriously, opening up possibilities for ontological pluralism.
The non-relativistic quantum mechanics offers us conditions to consider at least two possible metaphysical packages, but incompatible between themselves: metaphysics of individuals, and metaphysics of non-individuals. In addition, the standard formalism is compatible with both the ontologies, without the theory being decided for either of them. From this particular kind of situation, the thesis of the underdetermination of metaphysics by physics can be established. Actually, it can be found, among scientists and philosophers, defenders of one, or another ontology, as well as those who do not address the issue, given that theory on its own does not decide. This means that if we make a choice for one of these packages, it will be happing in a metaphysical field, increasing a lot the philosophical discussions about individuality of quantic objects in quantum physics. From a naturalized methodological view, we present the issues from those defend the individuality of quantic objects, and from those, include us, defend non-individuality, focusing two approaches: (i) the ontological one, in which the fail of IIP as individuation principle is discussed; and, (ii) the logical one, in which non-reflexive logics, as well as a quasi-set theory became more suitable for representing the non-individuals. In this paper we stand for the choice of non-individuals ontology becomes more plausible, and should be taken in account seriously, opening up possibilities for ontological pluralism.
In this article, we discuss some questions about the nature of elementary particles treated by quantum mechanics, in particular related to the concepts of identity and individuality of these particles. We started briefly exposing the philosophical and formal concepts of the identity and individuality, and then show how these notions are problematic when applied to elementary particles such as electrons, protons and neutrons. In particular, we emphasize that both philosophy, logic and set theory (and thus the mathematics) admit the usual assumption that things have a ‘type’ of identity and individuality (i.e., are individuals), in the sense that objects which have all the same properties are the same object (are equal). Nevertheless, we show that in the quantum universe is possible to find objects that share all their properties, but are not just one, constituting in something like “nonindividuals” (thesis defended by many physicists and philosophers of science). In sequence, we show how classical mathematics — which, as we said, assumes an individuality to your entities — handle this situation, in particular admitting assumptions external to the physical theories. To avoid this procedure, and look for a formalism more ‘natural’ and appropriate to work with these quantum characteristics, we suggest the use of a non-classical set theory called the quasi-set theory, based on a non-reflective logics, which admits objects devoid of identity and individuality ab initio. Finally, we show another application of this theory: the search to a quasi-set mathematical structure that describes the ‘behaviour’ of non-relativistic quantum theory, and discuss some advantages of this ‘quasi-structure’ to a classical one.
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.
In this article we try to justify a way of looking for an alternative approach to quantum mechanics based on a non-classical logic. The main motivation is both to accommodate a metaphysical view according to which quantum objects are non-individuals and to introduce, so to say, these objects within the formalism, for as we know, the usual formalism treats of states of quantum systems and not (directly) of quantum systems properly speaking. We consider two specific questions related to quantum theory, namely, entanglement and the indiscernibility of quanta. Our way of looking to these concepts motivate us to construct a metaphysical view according to which quantum objects do not present identity criterion (they are ‘non-individuals’), and then we try to construct a quantum theory based on such a view, which is grounded on a non-classical logic, termed non-reflexive. From the formal point of view, the main motivation comes from the fact that in using classical logic and classical set theory (such as ZFC), we are necessarily committed to individuals, and non-individuals can be considered only by assuming ‘strong’ symmetry principles, which mask the basic idea involving non-individuality. In the core of the article, due to questions of space, only the main philosophical arguments are presented, but in two appendixes we outline, firstly, quasi-set theory, the non-reflexive mathematical framework that sustain our view, and a bottom-top construction of a quantum mechanics based on quasi-set theory.
In the non-reflexive formulation of quantum physics, attention is given to a metaphysical view of quantum objects (q-objects) as non-individuals, characterised as entities to which the standard notion of identity lacks sense. The reference to the nature of q-objects is usually omitted in other interpretations and the most we can find is some vague reference to “to each [quantum] system we associate a Hilbert space”, and nothing more is said about them; we need to infer from the theory their characteristics, and it gives us several alternatives. One of them, to be justified here in broad aspects, is the non-individual view. It is important to enlighten that we are not trying to just find a way to deal with quantum entities but to defend a possible ontology of non-individuals, which can be applied also to ‘particles’ arising from quantum fields. Our account is based on two assumptions: (i) the ‘classical theory of identity’ does not apply to q-objects, and (ii) their non-individuality must be attributed from the start, that is, as a primitive notion and not ‘made a posteriori’ say by assuming symmetry principles. The underlying logic is called non-reflexive because the reflexive law of identity ∀x(x=x) is supposed not to hold for q-objects. Since all the details demand a lot of space, here we only sketch and justify our view. The references provide a more detailed account.
Abstract Nonrelativistic quantum mechanics (QM) works perfectly well for all practical purposes. Once one admits, however, that a successful scientific theory is supposed not only to make predictions but also to tell us a story about the world in which we live, a philosophical problem emerges: in the specific case of QM, it is not possible to associate with the theory a unique scientific image of the world; there are several images. The fact that the theory may be compatible with distinct ontologies, and that those ontologies may themselves be associated with a plurality of metaphysical approaches, gives rise to the problem of metaphysical underdetermination. This paper concludes that the available metametaphysical criteria fail to deliver objectivity in theory choice, and it puts forward its own criterion based on a tension between two methods of metaphysical inquiry: one that is closely related to science and another that is not.
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.