The focus of this paper is to propose that the question of standardized versus individualized therapy is part of a more general debate regarding the nature of inquiry, the use of empirical knowledge in practice, and the evaluation of professional activities--what collectively might be called clinical science. Exclusive reliance on traditional experimental research design, with its demand for procedural standardization, promotes a model of clinical behavior therapy as a technology. Such a perspective runs counter to the development of the special relationship between theory (generality) and practice (specificity) that represents one of behavior therapy's unique contributions and long term legacies. If behavior therapists treating individual clients are to adapt general principles to individual need, there must be a broader view of relevant sources of individual differences.