Abstract Drawing inspiration from Ian Hacking's claim that new modes of description generate new possibilities for action, this essay explores the impact of changes to the mode of description through the 1901 Census in Ceylon. It begins by exploring the modes of description used in the censuses prior to 1901 to demonstrate that in Ceylon, the census was yet to emerge as the critical tool of colonial governance claimed by dominant scholarship around colonial census taking. This leads to an exploration of how the changes that Sir Ponnambalam Arunachalam, the first Ceylonese Census superintendent, made to the Census Ordinance, Census Manual, and Census Report impacted the function of the census as a mode of description. It then explores the possibilities for action generated by these changes in the mode of description, paying particular attention to the ways in which the census shaped elite, indigenous activism leading to the first major reforms of the colonial governance structure in Ceylon, including the introduction of limited franchise. Thus, Ceylon's 1901 Census affords a unique opportunity to examine the impact that shifts in modes of description have on possibilities for action.