Through the evaluation and integration of developmental theories, this volume proposes a new structural/behavioral model of development. Dr. Horowitz’s model helps account for both the behavioral development of children (with extensions across the life-span) and for the universal and non-universal characteristics in human behavioral development. Exploring Developmental Theories also sheds a new and different light on the nature- nurture or heredity-environment controversy and on the topic of continuity and discontinuity in development. Exploring Developmental Theories: *examines the concepts of stage, structure, and systems; organismic theory; and general system theory;*analyzes open and closed systems as well as organismic and mechanistic world views;*integrates the concepts associated with organismic and mechanist world views;*examines learning mechanisms and processes that foster the acquisition of behavior, and*discusses the strengths and weaknesses of Gessel, Piaget, and behaviorism in accounting for behavioral development.