This book presents a critical comparison of the two leading theories of linguistic change. After introducing the aims and methods of historical linguistics, Olga Fischer provides an exposition of the main theories used to describe morphosyntactic change and a full account of the causes and mechanisms by which their leading exponents seek to explain it. She measures the effectiveness of rival theories and methods in different contexts and in the process throws fresh light on the balance of factors influencing linguistic change. Professor Fischer emphazises the unity of form and meaning in the linguistic sign and examines the role played by analogy. She looks at how changes in discourse, lexicon, semantics, pragmatics, and sound interact with changes in morphosyntax, and explores the relationship between external and internal causes of change. She considers whether morphosyntactic change is gradual or abrupt and discusses how far rates of change reflect the degree to which grammar is innate or learned. She uses detailed case studies to illustrate different types of morphosyntactic change, and to show how each theory fares when put into practice. The author's clear style and her balanced approach to this fascinating and complex subject combine to make this a book that will be of central interest and value to scholars and students of linguistic change, at graduate level and above.