The authors have grouped the theories into three classical "families" which differ in their views relative to the prime motives underlying human nature. They show how theories are specific examples of more general points of view called paradigms. The theories chosen to represent the three paradigms (the Endogenous Paradigm, Exogenous Paradigm, and the Constructivist Paradigm) were selected because they met four criteria:importance, as judged by academic and research psychologistsfertility, as judged by the amount of research the theory has generatedscope, as judged by the variety of phenomena the various theories explainfamily resemblance, as judged by how well each theory represents its paradigmThe authors present the "paradigm case" in the lead chapter for each paradigm. This paradigm case is the "best example" for the paradigm. The authors explain why paradigm cases are important, and give them more detailed treatment than other theories in the same paradigm.