The body of theory on speech production and speech disorder developed prior to Descartes has been so neglected by historians that its very existence is practically unknown today. Yet it provides a framework for understanding the speech process which is not only comprehensive and coherent, but of great relevance to current debates on issues of language performance and applied linguistics. This is because, the author contends, current theoretical difficulties stem largely from initial errors of Descartes; whereas earlier theoretical formulations, while outlining a bio-mechanics of speech, retain the central role of the human agent. The discussions explicated in this book come mainly from the natural- philosophic and medical literature of Greco-Roman Antiquity, the Middle Ages, and the Renaissance and early 17th century. This uncharted territory is mapped for the first time by tracing its textual history and diffusion as well as explaining the theory on its own terms but in language that will be clear and comprehensible to non-specialists. Interdisciplinary in perspective, the book encompasses topics of interest not only to the language sciences, but also to the biosciences, medicine, philosophy of human movement, psychology and behavioral sciences, neurosciences, speech pathology, experimental phonetics, speech and rhetoric, and the history of science in general.