This book discusses the ethics of belief that Locke developed in the last book of his Essay: how we ought to govern our opinions, especially on matters of religion and morality. Wolterstorff shows that this concern was instigated by the collapse of a once-unified moral and religious tradition in Europe into warring factions. After presenting Hume's powerful attack on Locke's recommended practice, Wolterstorff argues for Locke's originality and emphasizes his contribution to the "modernity" of post-sixteenth-century philosophy.