With little or no formal teaching, human beings develop the capacity to deploy psychological concepts in predicting and explaining the actions and mental states of other members af the species. What is the basis of this capacity? Many philosophers and psychologists argue that this everyday ability reflects the fact that normal adult human beings possess a primitive or 'folk' psychological theory. Recently, however, this theory theory has come under challenge from the simulation alternative. This alternative view says that human beings are able to predict and explain each other's actions by using the resources of their own minds to simulate the psychological aetiology of the actions of others. The thirteen essays in this volume offer comprehensive coverage of the mental simulation debate, and are accompanied by an extensive new introductory essay. A companion volume, Mental Simulation, contains thirteen further essays, most of which appear there for the first time.