An exploration of the roles of metamorphosis and hybridity in the establishment of personal identity, with particular emphasis on the twelfth and thirteenth centuries. The four studies in this book center on the Western obsession with the nature of personal identity. Focusing on the twelfth and thirteenth centuries, but with an eye toward antiquity and the present, Caroline Walker Bynum explores the themes of metamorphosis and hybridity in genres ranging from poetry, folktales, and miracle collections to scholastic theology, devotional treatises, and works of natural philosophy. She argues that the obsession with boundary-crossing and otherness was an effort to delineate nature's regularities and to establish a strong sense of personal identity, extending even beyond the grave. She examines historical figures such as Marie de France, Gerald of Wales, Bernard Clairvaux, Thomas Aquinas, and Dante, as well as modern fabulists such as Angela Carter, as examples of solutions to the perennial question of how the individual can both change and remain constant. Addressing the fundamental question for historians--that of change--Bynum also explores the nature of history writing itself.