Family therapists disagree over the utility of historical reconstruction for treatment. Following either a behavioral or a psychoanalytic paradigm, theorists insist that history is irrelevant or essential to the treatment process. This paper demonstrates how a variety of family therapy concepts were used in his historical research into the life of the family of William James, the American psychologist and philosopher (1842-1910). This is offered as evidence both that family theory has a contribution to make to the writing of history and that the historical process is important to family therapy. It is suggested that clinical actuality calls forth interventions within both paradigms, often by the same therapist with the same family. The alternatives need not be mutually exclusive, though theory-building is clarified by talking as if the therapist were confronted by an either/or choice.