This text explores the invention of sodomy in medieval Christendom, examining its conceptual foundations in theology and gauging its impact on Christian sexual ethics both then and now. It traces the historical genealogy of this enduring cultural construct through many of the idiosyncratic worldviews of the Middle Ages - worldviews at war with themselves in their attitudes toward sex, love and eroticism. Moving from poetic conceit through medieval treatise to confessor's manual and scholastic summa, the text demonstrates that the medieval notion of sodomy was fashioned out of conceptual instabilities and tensions.