This introduction briefly reviews the intertwinement of ‘informality’ and ‘modernization’ and their implications for the theory and practice of the city. The editors identify the importance of recognizing uneven processes of informalization, emphasizing the need to compare the quality of state–citizen–market relations more than the quantity of ‘informality.’ In the process they ask whether and how informal and formal practices can help to rethink modern concepts such as citizenship, universal infrastructural access, organized resistance, and the state itself. One way to do so is to reposition these concepts as relational processes involving various actors, spaces, and temporalities rather than as essentialized objects. Such epistemological moves will shed light on the extent to which basic social needs such as the distribution of justice, the production of authority, and the regulation of class relations are not the sole terrain of the state, but negotiated relationally. The article concludes by proposing three epistemological devices – iterative comparison, ambiguous categories, and the use of hermeneutics – that can help scholars avoid the biases associated with essentialized categories.