The nature of these episodes has long excited the curiosity of speculative thinkers. In recent times this curiosity has evolved into a loosely defined field of sociology and social psychology known as collective behavior. Even though many thinkers in this field attempt to be objective, they frequently describe collective episodes as if they were the work of mysterious forces. Crowds, for instance, are "fickle," "irrational," or "spontaneous," and their behavior is "unanticipated" or "surprising." For all their graphic quality, such terms are unsatisfactory. They imply that collective behavior flows from sources beyond empirical explanation. The language of the field, in short, shrouds its very subject in indeterminacy.