ABSTRACT
The problem which motivated and inspired the papers in this volume, and the conference on which the volume is based, is the puzzle of transition, of change, in human development. Clearly, change is the essence of what is interesting about development; if there were no transition points or discontinuities, then our theories of human development could be much simpler than they are. The notion that change is crucial in development is the essential claim of any stage theory of development. Paradoxically, though, stage theories are best at dealing with, describing, and accounting for the plateaus of nonchange, the within-stage phenomena. Stage theories do not help explain transitions except by noting that reorganization occurs between stages. The nature and the causes of change in human development are obscure to the degree that the change is important and general.
