This is the first exhaustive investigation of gradience in syntax, conceived of as grammatical indeterminacy. It looks at gradience in English word classes, phrases, clauses and constructions, and examines how it may be defined and differentiated. Professor Aarts addresses the tension between linguistic concepts and the continuous phenomena they describe by testing and categorizing grammatical vagueness and indeterminacy. He considers to what extent gradience is a grammatical phenomenon or a by-product of imperfect linguistic description, and makes a series of linked proposals for its theoretical formalization. Bas Aarts draws on, and reviews, work in psychology, philosophy and language from Aristotle to Chomsky, and writes clearly on a fascinating and important aspect of language and cognition. His book will appeal to scholars and graduate students of language and syntactic theory in departments of (English) linguistics, philosophy and cognitive science.