The question of how we deploy logic in developing and justifying scientific theories of any sort is an important one. In this commentary, I consider William Stiles' (2009) arguments about the logical operations that are deployed especially in theory-building case-study research in psychotherapy. My commentary contains three sections, defined by three sets of distinctions: (a) the distinction between description and explanation in theory building, (b) the distinction between theory building and theory justification, and (c) the distinction between nomothetic and idiographic approaches to theory building in case-study methodology.Key words: descriptive theory; explanatory theory; causal explanation; theory justification; objectivist epistemology; perspectival epistemology; relativism; theoretical generalization ___________________________________________________________________________ The question of how we deploy logic in developing and justifying scientific theories of any sort is an important one, and so I am pleased to have this opportunity to comment on William Stiles' (2009) article. That Stiles addresses deduction, induction, and abduction in the context of "theory-building case studies" in psychotherapy is no small undertaking; he is therefore to be commended on that ambitious basis alone. In this commentary, I present my understanding of his central arguments, and I raise questions about some of those arguments. I structure my response by way of three sections that comprise this commentary: (a) the distinction between description and explanation in theory building, (b) the distinction between theory building and theory justification, and (c) the distinction between nomothetic and idiographic approaches to theory building in case-study methodology.