Family systems theory's contribution to the world of psychotherapy was its move away from lineal causality toward a view of human relationships as not merely multi-determined, but unavoidably and inextricably inter-related and inter-dependent. Circular causation allows the therapist to assume enormous flexibility. The rise of family therapy in post World War II America is consistent with the "Protean man" described by Lifton and the alienated individual described by Mead. Family theorists incorporated into their theorizing, as do all theorists, the experiences of their own lives, which in this case included the discontinuity of World War II. This is the essence of circular causation, and a concept used by a variety of contemporary therapists influenced by family systems thinking. To move to the structural level, the "aesthetics" versus "pragmatics" debate eventually faded. It was an expression of "sociological ambivalence." Its effect was to crystallize but to mislabel the fundamental conflicts of family therapy; opportunism versus idealism, and conservatism versus radical social criticism. By mislabeling the issue, it helped to obscure it, and finally guaranteed that the "mystery-mastery" complex remain intact, that the forces influencing family dynamics remain obscure and impenetrable, while allowing and encouraging the development of sophisticated methods of behavioral control and mystification. (ABL)