Quantum Mechanics Without Indeterminacy

Harvey R. Brown, Michael L. G. Redhead

Cristian Mariani

Abstract Many features of quantum mechanics (QM) suggest that, at the microscopic level, objects sometimes fail to determinately instantiate their properties. In recent years, many have argued that this phenomenon indicates the existence of an ontological kind of indeterminacy, often called metaphysical indeterminacy , which is supposed to affect the ontology of QM. As insisted by Glick ('Against Quantum Indeterminacy, 2017, Thought), however, once we look at the major realist approaches to QM we learn that the indeterminacy disappears from the description of the world at its most fundamental level. This absence might be taken as a good reason for adopting some form of eliminativism towards quantum mechanical indeterminacy. The aim of this paper is to distinguish three ways of defending eliminativism, and to argue that none of them eventually succeeds. The upshot is that QM does in fact suggest the existence of metaphysical indeterminacy, although only as an emergent phenomenon.

Peter J. Lewis

Abstract It is often claimed that quantum mechanics entails that there is indeterminacy in the world, in the sense that physical systems can lack a precise value for a property. Indeed, a radical form of indeterminacy, in which systems have almost none of the properties we normally attribute to them, can be shown to follow from a particular interpretation of quantum mechanics—the bare theory. However, the bare theory is shown to be incoherent. Still, a more limited form of indeterminacy can be located in spontaneous collapse, hidden variables, and many-worlds theories. This indeterminacy is unlike that which arises classically, having nothing to do with ordinary forms of vagueness or the composition of large objects out of smaller parts. Indeterminacy in quantum mechanics can perhaps be avoided, but there seems little reason to do so.

Niall Shanks

George Darby

There has been recent interest in formulating theories of non-representational indeterminacy. The aim of this paper is to clarify the relevance of quantum mechanics to this project. Quantum-mechanical examples of vague objects have been offered by various authors, displaying indeterminate identity, in the face of the famous Evans argument that such an idea is incoherent. It has also been suggested that the quantum-mechanical treatment of state-dependent properties exhibits metaphysical indeterminacy. In both cases it is important to consider the details of the metaphysical account and the way in which the quantum phenomenon is captured within it. Indeed if we adopt a familiar way of thinking about indeterminacy and apply it in a natural way to quantum mechanics, we run into illuminating difficulties and see that the case is far less straightforward than might be hoped.