Quantum Objects: Parts and Wholes

Abstract

The notion of object appropriate to quantum theory is discussed in the context of the analysis of the notion of quantum particle and in light of results in quantum field theory. The whole-part relationship and the question of the applicability of Leibniz’s Principle of the identity of indiscernibles in quantum theory are considered together with recent arguments against its applicability in the quantum realm. After the discussion of a range of alternative prescriptions for a quantum principle of individuation, one is advocated that helps clarify the relationship between the individual and ensemble interpretations of quantum mechanics and allows for a well-defined and adequate ontology of individual objects that includes subatomic particles. As a culmination of the foregoing, the prospects for physical reductionism, both explanatory and ontological, are analyzed through the discussion of a wide range of examples, including the reduction of classical physics to quantum theory and the reduction of structural chemistry to quantum theory both when approximations are allowed and not allowed.