​Concepts are critical to the functioning and evolution of social sciences. Conceptual confusion has long been a source of difficulty in the study of social science and politics. W. B. Gallie’s analysis of ‘essentially contested concepts’ stands as a notable effort to address this problem. This article examines Gallie’s framework and develops a solution to the problem of essentially contested concepts by focusing on the crucial stage in the research process: when the concepts are defined. The paper works mainly with Sartori’s classic rules of concept formation, and with reference to his “ladder of abstraction”.