This book collects Joseph Greenberg's most important writings on the genetic classification of the world's languages. Fifty years ago Joseph Greenberg put forward the now widely accepted classification of African languages. This book charts the progress of his subsequent work on language classification in Oceania, the Americas, and Eurasia,in which he proposed the language families Indo-Pacific, Amerind and Eurasiatic. It shows how he established and deployed three fundamental principles: that the most reliable evidence for genetic classification is the pairing of sound and meaning; that nonlinguistic evidence, such as skin colour or cultural traits, should be excluded from the analysis; and that the vocabulary and inflections of a very large number of languages should be simultaneously compared. The volume includes Joseph Greenberg's substantive contributions to the debate his work provoked and concludes with his writings on the links between genetic linguistics and human history. William Croft's introduction focuses on the substance and the development of Professor Greenberg's thought and research within the context of the discussion they stimulated. He also includes a bibliography of scholarly reactions to and developments of Joseph Greenberg's work and a comprehensive bibliography of his publications in books and journals.