Emotions are central to human behavior and experience. Yet scientific theory and research ignored emotions during most of the twentieth century. This situation changed dramatically during the last 30 years of that century, which witnessed an upsurge of interest in emotions in a number of disciplines. This book arises from the 24 keynote papers presented at a symposium held in June 2001 that had the same title as this volume. The aim of that meeting was to review the state of research on emotions from a multidisciplinary perspective. Each chapter is authored by an acknowledged authority in the field. Together they provide an overview of what is being studied and thought about emotions, in disciplines ranging from neurophysiology and experimental psychology to sociology and philosophy.