The Experimental Approach To Vagueness

This thesis is about philosophical theorising about vagueness, and the possibility of contributions from experimental work. I defend the view that empirical studies can inform theorising, given that the philosophical project is an essentially descriptive one, and I aim to provide a better theoretical framework to interpret empirical results than hitherto seen in the literature.
In the first half of the thesis (chapters 1-3), I introduce vagueness and make a case for the experimental approach to it, but argue that some recent studies are unsatisfactory in their methods. Following a general introduction to the phenomena of vagueness and some theories of vagueness (chapter 1), I argue that empirical work can inform theorising about vagueness, at least in theory (chapter 2). I argue that if theories of vagueness are descriptive, i.e. aim to model features of real-life language use, then there is a role for experimental work, and then argue that the debate shows that philosophers are engaged in a descriptive project. I then argue that even though experiments can be a useful philosophical tool in theory, recent studies haven’t provided significant results, and the authors of studies have failed to establish their conclusions (chapter 3). One reason for this is that the approach lacks a strong theoretical basis for the connection between any particular theory of vagueness, and particular empirical result; there isn’t a strong enough principled reason for associating one theory or another with particular patterns given by participants.
In the second half of the thesis (chapters 4-6) I aim to make progress with supplying this theoretical back drop. I first argue that logic and semantic theories, such as those that come with a theory of vagueness, restrict theories of mind; a theory of rational belief and decision making (chapter 4). This provides the initial justification for associating a theory of vagueness with patterns seen in experiments; it can be claimed that a particular theory gives a good explanation of an empirical result, based on that theory’s commitments in the theory of mind. I then go on to discuss what the particular commitments for supervaluationism (chapter 5) and degree theoretic semantics (chapter 6) look like. I argue that in each case there is more than one consistent way to work out a theory of mind, but that the best models are a suspension of judgement model for supervaluationism, and a kind of indeterminate belief for degree theoretic semantics. In chapter 7, I sum up the conclusions of the thesis, and consider some ways the experimental approach to vagueness might continue to make progress.