The domain of moral behaviour has received much attention from researchers in a number of psychological fields such as the cognitive developmental, psychoanalytic, socioanalytic and social learning approaches. While valuable, these approaches have not fully described the psychology of morality and methodological difficulties appear to be built into popular measures of moral reasoning. In this book a number of approaches to the psychology of morality, including evolutionary psychology, are reviewed and evidence for a Libertarian-Communitarian dimension of moral orientation is described. A model incorporating this conceptualisation of moral orientation together with cognitive dissonance as the mechanism for moral decision making is outlined. Subsequent chapters describe the development of a measure of moral orientation and findings from several studies involving some 8,500 participants are presented.