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.
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.
It has frequently been suggested that quantum mechanics may provide a genuine case of ontic vagueness or metaphysical indeterminacy. However, discussions of quantum theory in the vagueness literature are often cur- sory and, as I shall argue, have in some respects been mis- guided. Hitherto much of the debate over ontic vagueness and quantum theory has centered on the indeterminate construal of ontic vagueness, and whether the quantum phenomenon of entanglement produces particles whose identity is indeterminate. I argue that this way of framing the debate is mistaken. A more thorough ex- amination of quantum theory and the phenomenon of entanglement reveals that quantum mechanics is best in- terpreted as supporting what I call the property construal of ontic vagueness, where vague properties are understood in terms of determinable properties without the corresponding determinates.
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.
[FIRST PARAGRAPHS] \n \nIs vagueness a feature of the world or merely of our representations \nof the world? Of course, one might respond to this question by asserting \nthat insofar as our knowledge of the world is mediated by our \nrepresentations of it, any attribution of vagueness must attach to the latter. \nHowever, this is to trivialize the issue: even granted the point that all \nknowledge is representational, the question can be re-posed by asking \nwhether vague features of our representations are ultimately eliminable or \nnot. It is the answer to this question which distinguishes those who believe \nthat vagueness is essentially epistemic from those who believe that it is, \nequally essentially, ontic. The eliminability of vague features according to \nthe epistemic view can be expressed in terms of the supervenience of \n‘vaguely described facts’ on ‘precisely describable facts’: \n \nIf two possible situations are alike as precisely described in terms of \nphysical measurements, for example, then they are alike as vaguely \ndescribed with words like ‘thin’. It may therefore be concluded that the facts \nthemselves are not vague, for all the facts supervene on precisely \ndescribable facts. (Williamson 1994, p. 248; see also pp. 201- \n204) \n \n \nIt is the putative vagueness of certain identity statements in \nparticular that has been the central focus of claims that there is vagueness \n‘in’ the world (Parfit 1984, pp. 238-241; Kripke 1972, p. 345 n. 18). Thus, \nit may be vague as to who is identical to whom after a brain-swap, to give \na much discussed example. Such claims have been dealt a forceful blow \nby the famous Evans-Salmon argument which runs as follows: suppose for \nreductio that it is indeterminate whether a = b. Then b definitely possesses \nthe property that it is indeterminate whether it is identical with a, but a \ndefinitely does not possess this property since it is surely not \nindeterminate whether a=a. Therefore, by Leibniz’s Law, it cannot be the \ncase that a=b and so the identity cannot be indeterminate (Evans 1978; \nSalmon 1982).
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.
The question of whether Everettian quantum mechanics (EQM) justifies the existence of metaphysical indeterminacy has recently come to the fore. Metaphysical indeterminacy has been argued to emerge from three sources: coherent superpositions, the indefinite number of branches in the quantum multiverse and the nature of these branches. This paper reviews the evidence and concludes that those arguments don't rely on EQM alone and rest on metaphysical auxiliary assumptions that transcend the physics of EQM. We show how EQM can be ontologically interpreted without positing metaphysical indeterminacy by adopting a deflationary attitude towards branches. Two ways of developing the deflationary view are then proposed: one where branches are eliminated, and another where they are reduced to the universal quantum state.
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.