This study develops a new theory of personality, its development and psychopathology, rooted in evolutionary biology. The book draws on the thinking of the physical and biological sciences to create a new personology - a model of how personality originates, develops and can go astray. This innovative conceptual structure has its foundations in the natural sciences and sees personality structure and function related to three basic polarities: pleasure-pain, passivity-activity, and self-other. After developing his theoretical model, Millon relates it to psychopathology and shows how the model can be applied to nosology, assessment and intervention.