Whilst urbanisation reached an unprecedented dimension, in a not so distant future half of the urban population will live in `informal¿ settlements. Often subsumed under the pejorative term slum, these habitats account for the majority of the future urban growth. Incremental urban development was once accepted as a viable means of addressing housing needs for large parts of the urban population. However, these approaches were largely abandoned in the 1990s in favour of mass housing provided through public private partnerships. While these largely failed in providing the required quantities and produced poor urban spaces, the scale of the phenomenon is such that incremental urban development needs reconsidering. However, in contrast to the well-documented experiences of the 1970s and 1980s, there is a lack of knowledge about the actual functioning of incremental development in contemporary regimes of urbanisation. Adopting an approach informed by French pragmatist sociology (Boltanski and Thévenot 2006), particularly the sociology of convention (Thévenot 1984), this research inquires into the production of slums at two levels: the intricate reality of housing production in Mumbai¿s slums and the contemporary controversies revolving around urban development. Building on fieldwork in a `self-built¿ resettlement colony in Mumbai forty years after it was established, this research examines how incrementally developing settlements are made, maintained, and transformed through everyday practices of local actors. Standing at the crossroads of the market, the political, and the social the so-called contractors are key figures engaged in the processes of construction and house making. As mediators in and of incremental urbanism they produce not only built-up space but also social space. Focusing on contractors as hitherto under-examined figures reveals that self-help housing in Mumbai, in contrast to conventional believes about housing practices of the urban poor, is by and large a professionalised mode of urban production. This research offers a refined account of the intricate reality of housing production and the ambiguous nature of incremental urbanism. Regarding urban planning, this research analyses the on-going revision of the Mumbai Development Plan 2014-2034 and the controversies accompanying it, which brings to the forefront the interplay of powers and arguments that otherwise are disguised in the dispersed and detached everyday making of the city. To better understand the discourse on current planning practices and struggles over conflicting approaches towards slums, this research examines the arguments and legitimization principles that underpin four major positions advocated in the controversies as the `good¿ way to urbanisation. Considering them as equally valid positions allows drawing comparisons between the different conceptualisations of urban planning and development, and the role and legitimacy they confer to modes of incremental urbanism. Reading the two moments in the production of Mumbai¿s slums together sheds light on the challenges to incorporate incremental urbanism into planning processes. It is argued that these challenges lie not solely with the conflicting rationalities ¿ or cosmos ¿ of how to create a just city, which clash in the controversies, but also with the ambiguity of incremental urbanism itself. Both of which contribute to complex processes of invisibilisation, or subalternisation, of incremental urbanism.