Shifty semantics and slippery slopes: essays on semantic plasticity and the epistemic theory of vagueness

Our words have meaning. What meanings they possess is determined by meaning-fixing factors, e.g. usage. Large changes in the meaning-fixing facts produce large shifts in meaning. It’s natural to conjecture that even the tiniest changes in usage produce tiny shifts in meaning - after all, any large change can be broken down into a series of small changes. This conjecture is known as semantic plasticity.
Semantic plasticity is the central component of the epistemicist theory of vagueness. Furthermore, several puzzling consequences of semantic plasticity have recently been identified. This thesis is the first sustained examination of semantic plasticity that articulates its motivation, refines its characterization, and answers this battery of recent puzzles. This work is essential if Williamsonian epistemicism (Williamson 1994) is to be tenable. But everyone needs to square the arguments for semantic plasticity with the puzzles it engenders, and so the work has wide relevance.
The aim of the thesis is threefold. Firstly, it sums up and clears up the debate engendered by the publication of 'Vagueness' in 1994. Secondly, it refines the epistemicist account in the areas that were shown to be lacking in the literature. Thirdly, it answers some recent puzzles generated by semantic plasticity.
The first chapter sums up the debate about epistemicism and semantic plasticity over the last 30 years. Later chapters are divided into three parts. Part I defends and refines epistemicist metasemantics, including the metasemantics of moral terms. Part II develops the technical details of the theory, providing an account of the definiteness operator, a model for ignorance due to semantic plasticity (and other factors) and an account of the restrictions on metalinguistic vocabulary like ‘truth’ imposed by epistemicism. Part III presents an account of metalinguistic comparatives using some elements of the epistemicist machinery, and answers a recent puzzle generated by semantic plasticity.