Nijman’s concise introduction provides one of the clearest disciplinary statements of comparative urbanism. He defines the field as the systematic study of similarity and difference among cities and urban processes, operating between propositions true of all cities and descriptions true only of one city at a particular moment. The theoretical contribution lies in refusing both universalism and absolute place uniqueness: similarity and difference are mutually constitutive problems requiring explicit explanation. Nijman situates the renewed comparative impulse against an earlier retreat associated with postmodern scepticism toward scientism and developmentalism. His methodological operation is therefore reflexive. Comparative researchers must make clear what is being compared, how categories are constructed and where cities are bounded in time and space. The essay bridges comparative-historical social science and urban geography while anticipating later relational and postcolonial revisions of comparison. Its enduring value is to make comparison an epistemological problem rather than a routine research design, demanding conceptual clarity before generalisation can begin.