Drawing on manuscript sources, this book examines how the medieval clergy developed the authority and persuasive force to attempt to govern the day-to-day speech of Western Christians. It explores, for the first time, how Chaucer, Langland, Gower and the Patience poet presented and judged these attempts to label some political, social and private speech as deviant and destructive--as lying, slander, blasphemy and other Sins of the Tongue.