ABSTRACT
This chapter provides one aspect of a program aimed at studying normative constraints on the evolution of language. It shows that one respect of similarity will take center stage: both the truth predicate and vague predicates support speech acts which are initially very puzzling and which admit of a uniform explanation. The chapter examines the behavior of vague predicates under increases in precision, with the upshot that philosophers's use of vague predicates requires to recognize an important class of sentences whose distinguishing feature is that they are not acceptably called false. It explains the sorites and liar paradoxes which would block the unwanted inferences. The chapter focuses on the brief remarks and propose a set of goals for a treatment of vague predicates generally. The motivation for taking the supervaluational structure to perform the second job is the penumbral intuition, which is indeed undercut by the objection from essentially vague predicates.
