This book explores a single theme—that the emotions, cognitions, and behaviors of love can be understood in terms of a basic motivation to expand the self. It also provides a broad overview of the literature on interpersonal attraction and on the maintenance of close relationships—not only romantic relationships, but friendship, sibling, and parent-child relationships as well. The book's main purpose, however, is to stimulate thinking by offering a new approach to unifying this wealth of data, using the idea of self-expansion, and to illustrate this idea's theoretical and practical implications.