Abstract: This book argues that an adequate account of vagueness must involve degrees of truth. The basic idea of degrees of truth is that while some sentences are true and some are false, others possess intermediate truth values: they are truer than the false sentences, but not as true as the true ones. This idea is immediately appealing in the context of vagueness — yet it has fallen on hard times in the philosophical literature, with existing degree-theoretic treatments of vagueness facing apparently insuperable objections. The book seeks to turn the tide in favour of a degree-theoretic treatment of vagueness, by motivating and defending the basic idea that truth can come in degrees, by arguing that no theory of vagueness that does not countenance degrees of truth can be correct, and by developing a new degree-theoretic treatment of vagueness — fuzzy plurivaluationism — that solves the problems plaguing earlier degree theories.

Keywords: truth, truth values, false sentences, degree-theoretic treatment, degrees, fuzzy plurivaluationism