This book addresses the question: why do sound changes happen, when and where they do? Jeremy Smith discusses the origins of a series of sound changes in English. He relates his arguments to larger questions about the nature of explanation in history and historical linguistics, and examines the interplay between sound change and social change. Drawing on the latest research in linguistics and history he shows how insights in one field illuminate the other. After the opening chapter describing the book's approach and a general theoretical framework for the study of sound-change, the author discusses problems of evidence and considers the nature of phonological processes. He then presents detailed investigations of major sound-changes from three transitional periods: first, when English emerged as a language distinct from the other West Germanic varieties; secondly, during the transition from Old to Middle English; and thirdly during the time when Middle English evolved into Early Modern English. The book is written with minimal use of jargon and offers clear definitions of complex notions. It will appeal to all serious students of English historical linguistics, from advanced undergraduate to researcher.