Theories of Vagueness (review)

A concise survey of theories of vagueness and a defense of the supervaluationism theory, this book is carefully organized into eight chapters that can be grouped into three distinct parts.

The first part, consisting of Chs. 1 and 2, covers the fundamentals of vagueness and the central features of vague expressions. It offers a concise description of the different types of vague expressions, a classification of vagueness theories according to their logic of vagueness and semantics of vagueness, and according to their position with respect to the sorites paradox. In addition, this part also offers a discussion of various methodological principles and perspectives used in the analyses of the vagueness theories.

The second part, made up of the next four chapters, is dedicated to the nonsuperevaluationist theories. Ch. 3 is intended as an attack against the epistemic theory, as represented by Timothy Williamson’s version. Chs. 4 and 5 question the area of many-valued logics. Keefe uses Michael Tye’s three-valued logic theory and Kenton Machina’s degree theory as models of degree of truth theories for an analysis of the semantics of connectives and of validity in many valued logics. Ch.5 examines the measurement theory and the representation and uniqueness theorems, with the declared aim to ‘undermine the prospects for degree theories of vagueness’ (125). K concludes that degree theories work only if they deny important features of different classes of vague expressions. Ch. 6 examines the pragmatic approach that defines vagueness as a feature of the relation between users and language. K investigates David Lewis’s philosophy of language and considers his two alternative approaches of vagueness within the cluster of precise languages. She argues that either the pragmatic view is wrong or it becomes identical with superevaluationism, depending upon how ‘the proposal is understood’.

The last part, the remaining two chapters, is a thorough analysis of superevaluationism and a defense of K’s own version of it. Ch. 7 provides a historical perspective of superevaluationism and answers to a series of objections against this theory. It also includes a discussion of Kit Fine’s theory and of Lewis’s semantic approach and an analysis of the role of classical logic within superevaluationism. The book concludes with Ch. 8 offering K’s own version of superevaluationism.

Overall, the book is concise and well presented. K offers strong and persuasive arguments for her own theory within the broad range of vagueness theories analyzed in the book. The philosophical contribution of the book is a valuable addition to the study of the linguistic implications of vagueness.