Building on a foundation of newly discovered primary sources and recent secondary interpretations, Professor Russell first establishes the facts and then explains the phenomenon of witchcraft in terms of its social and religious environment, particularly in relation to medieval heresies. He treats European witchcraft as a product of Christianity, grounded in heresy more than in the magic and sorcery that have existed in other societies. Skillfully blending narration with analysis, he shows how social and religious changes nourished the spread of witchcraft until large portions of medieval Europe were in its grip―"from the most illiterate peasant to the most skilled philosopher or scientist."