The purpose of this book is to show that the prevalent view of personal characteristics, which has been influenced to a large extent by factor analysis, may not be the soundest or the most useful. Structural equation modelling entails a more comprehensive approach to modelling relationships between variables than factor analysis and enables one to test alternative models to the factor model in accounting for these relationships. This proposition is demonstrated by drawing on the research the authors have conducted in three important domains of personal characteristics - abilities, personality disorders and self-attitudes. The authors' discoveries in these areas have implications not only for psychological and psychosocial theory but also for applied areas such as teaching, psychotherapy, and communication.