In recent years, a great deal has been written on the topic of aggression; another book on the same topic might seem superfluous at this time. However, the present volume is not just-or even primarily-about aggres- sion. It is, rather, a book on anger. Anger and aggression are closely related phenomena, and it is not possible to discuss one without the other. Yet, not all anger is aggressive, nor can all aggression be attributed to anger. Therefore, somewhat different considerations apply to each. Even more importantly, the type of theoretical generalizations one can make differs depending upon whether the primary focus is on anger or aggression. The present volume is subtitled "an essay on emotion." This indicates that the generalizations to be drawn have more to do with emotional responses (e.g., grief, love, envy, etc.) than with various forms of aggression (e.g., riots, war, crimes of violence, etc.). Stated somewhat differently, anger is here being used as a paradigm case for the study of emotion, not for the study of aggression.