The logical operations involved in theory-building case studies include deduction (logical consistency and interconnection), induction (applying observations to theory), and abduction (creating, refining, and elaborating theory). The product of theory-building research is an account of a phenomenon in the form of words and other signs. Scientific quality control on theory is accomplished by comparing theoretical statements with observations. In case studies, detailed case observations are compared to detailed clinical theories. Stable meanings of terms and logical (deductive) interconnection allow empirical (inductive) observations on one tenet of a theory to affect confidence in other tenets. Researchers creatively modify their theories by (abductively) adding to them or altering them so that they correspond to accumulating observations. In this way, observations on cases permeate the theories, so that the words of the theory convey the accumulated experience of previous researchers.