Online research in philosophy

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.

This thesis is a systematic investigation of whether there might be conceptual room for the idea that the world itself might be vague, independently of how we describe it. This idea – the existence of so-called ontic vagueness – has generally been extremely unpopular in the literature; my thesis thus seeks to evaluate whether this ‘negative press’ is justified. I start by giving a working definition and semantics for ontic vagueness, and then attempt to show that there are no conclusive arguments that rule out vagueness of this kind. I subsequently establish what type of arguments I think would be most effective in establishing ontic vagueness and provide some arguments of this form. I then highlight a potential worry for this type of argument, but argue that it can be circumvented. Finally, I consider the main ways that the opponent of ontic vagueness would be likely resist the arguments I have offered, and argue that these strategies of response are methodologically problematic. I conclude by claiming that ontic vagueness is a perfectly plausible ontological commitment.

If the world itself is metaphysically indeterminate in a specified respect, what follows? In this paper, we develop a theory of metaphysical indeterminacy answering this question.

1. E.J. Lowe claims that quantum physics provides examples of ontic indeterminacy, of vagueness in the world. Any such claim must confront the Evans-Salmon argument to the effect that the notion of ontic indeterminacy is simply incoherent (Evans 1978, Salmon 1981: 243-46). Lowe argues that a standard version of the Evans-Salmon argument fails quite generally (Lowe 1994). Harold Noonan (1995) has outlined a non-standard version of the argument, but Lowe argues that this non-standard version fails for specifically quantum mechanical reasons (Lowe 1997). He claims that it is perfectly coherent to suppose that his quantum case is an example of ontic indeterminacy.

It is often assumed that indeterminacy in mereological relations—in particular, indeterminacy in which collections of objects have fusions—leads immediately to indeterminacy in what objects there are in the world. This assumption is generally taken as a reason for rejecting mereological vagueness. The purpose of this paper is to examine the link between mereological vagueness and existential vagueness. I hope to show that the connection between the two forms of vagueness is not nearly so clear-cut as has been supposed.

 Nature: What indefiniteness is.  Logic: How to reason in the presence of indefiniteness  Mind: How indefiniteness fits into our cognitive life.

In this paper I develop a framework for understanding ontic vagueness. The project of the paper is two-fold. I first outline a definitional account of ontic vagueness – one that I think is an improvement on previous attempts because it remains neutral on other, independent metaphysical issues. I then develop one potential manifestation of that basic definitional structure. This is a more robust (and much less neutral) account which gives a fully classical explication of ontic vagueness via modal concepts. The overarching aim is to systematically investigate the puzzling question of what exactly it could be for the world itself to be vague.

A recent theory of metaphysical indeterminacy says that metaphysical indeterminacy is multiple actuality: there is metaphysical indeterminacy when there are many ‘complete precisifications of reality’. But it is possible for there to be metaphysical indeterminacy even when it is impossible to precisify reality completely. The orthodox interpretation of quantum mechanics illustrates this possibility. So this theory of metaphysical indeterminacy is not adequate.

I argue that for those who follow Evans in finding indeterminacy of de re identity statements problematic, ontic vagueness within a three-dimensionalist metaphysics will raise some problems that are not faced by the four-dimensionalist. For the types of strategies used to avoid de re indeterminacy within the context of ontic vagueness at-at-time, that is, spatial vagueness, are problematic within a three-dimensionalist framework when put to use within the context of ontic vagueness across-time, that is temporal vagueness.