In this important new book, Louis-Jean Calvet, one of the foremost sociolinguists working today, argues that what we call 'languages' are in fact abstractions invented by linguists as a convenient tool to label the subject-matter of their science. Languages, Calvet contends, are social practices that we need to listen to, describe, and understand in the contexts in which they are used. Languages exist only in so far as they used by the people who speak them, and linguistic situations can be understood only through fieldwork, which can then provide the basis for theory. It is on this methodological basis, and by way of numerous concrete examples, that this exceptional book proposes an approach to human communication that situates linguistic practices in their environment, analyzes the role of representations in the evolution of these practices, and tries to provide a scientific explanation for phenomena that we perceive every day without necessarily understanding what produces them. Calvet provides the reader with a pathbreaking ecological approach to the world's languages which will be of enduring value to the field of linguistics.