Concepts and Theories of Human Development is the most comprehensive and in-depth overview of the foundational theoretical contributions to understanding human development and the influence of these contributions for contemporary research and application in developmental science. Since its initial publication in 1976, it has been an essential resource for students and professionals alike, and has become the go-to book for graduate students studying for their comprehensive exam on human development. In this new Fourth Edition, Richard M. Lerner concentrates his focus on advanced students and scholars already familiar with the basic elements of major psychological theories. The book discusses the assumptions involved in such topics as stage theories, the nature-nurture issue, the issue of continuity-discontinuity, and the important role of philosophical ideas about theories – in particular, metatheories – in understanding the links between theory and research. It particularly focuses on relational developmental systems (RDS) metatheory, exploring its roots in the 1930s, following its development into the present day, and contrasting it with the fundamentally flawed genetic reductionist models that continue to be circulated by scientists, the media, and the general public. It discusses implications of theory for research methods and for applications aimed at the promotion of health, positive development, and social justice among diverse people across the life span.