Individuation in Quantum Mechanics

Jonas R. Becker Arenhart

One of the most famous metaphysical problems in the philosophy of quantum mechanics concerns the individuality status of quantum entities: are they individuals, or non-individuals? The typical approach to the problem consists in defending one of the options by appealing directly to features of quantum mechanics with the addition, eventually, of theoretical virtues the favoured proposal may have. In this paper, we argue that this strategy is inappropriate, because the problem of individuality is ill formulated in the case of quantum mechanics. In a nutshell, our point is that considerations exclusively from quantum mechanics are too general and generic to grant the level of particularity required for providing for a principle of individuality. Problems of individuality appear only at the level of particular applications of the theory in specific contexts, and in these cases, we shall argue, search for a metaphysical notion of individuality may be substituted by an epistemic notion of individuation. The approach also has the benefits of dissolving the problems created by metaphysical underdetermination on this front. This article is part of the theme issue 'Identity, individuality and indistinguishability in physics and mathematics'.

Elihu Lubkin, Thelma Lubkin

Bruce M. Bennett, Donald D. Hoffman, Chetan Prakash

James B. Hartle

A formulation of quantum mechanics, which begins by postulating assertions for individual physical systems, is given. The statistical predictions of quantum mechanics for infinite ensembles are then derived from its assertions for individual systems. A discussion of the meaning of the “state” of an individual quantum mechanical system is given, and an application is made to the clarification of some of the paradoxical features of the theory.

Martin Fraas, Bruno Nachtergaele, Simone Warzel +1 more

Willy De Baere

It is argued that the issue of embedding quantum mechanics in a classical frame of counterfactual reasoning in generating inconsistencies with quantum mechanics is stressed. Invoking a criterion of actualizability of hypothetical situations it is shown how a, new nonreproducibility property of individual subquantum states mag avoid the inconsistencies with QM.