What is the content of a sentence in context? A proposition, says the standard propositional view accepted in much of semantics. A set of propositions, says the hitherto little-explored view of Semantic Pluralism. The aim of this book is to motivate, develop and defend Semantic Pluralism. To achieve this aim, the book puts forward two arguments against Contextualism, the most popular propositional theory. It spells out two versions of Semantic Pluralism: Flexible Pluralism, which takes many expressions to be context-sensitive, and Strong Pluralism, which denies that context-sensitivity is widespread. And it shows how Pluralists can reply to several objections that have been lodged against non-propositional semantic theories.