The mechanism-realist paradigm in the philosophy of science, championed by Mario Bunge and Roy Bhaskar, sets certain expectations for the substantive social-scientific application of the paradigm. To evaluate the application of the paradigm in accomplished substantive research, as well as the potential for future research, I examine the work of Charles Tilly, the exemplary substantive work in the mechanism-realist tradition. Based on this examination, I argue for the usefulness of explanatory mechanisms, provided that they are couched in terms of a (...) heuristic. Such a position is the most reasonable one to adopt given the expectations set by the paradigm in relation to complexity stemming from mechanism interaction and to a notion of causality that is deeper than that acknowledged by empiricism and positivism. (shrink)