In this Counterpoint to Durand and Paolella, we argue that prior work on categories has neglected processes of category emergence and dissolution. In response, we call for studies of categories that focus on how they emerge and fall out of use and on what they come to mean. We call this an ontological turn in categories research because systems of categorization and their associated meanings capture and reflect what societies view as social realities, or ontologies. As a guide to this broad topic, we develop a framework that relates the effects of categories to the familiarity of (1) occasions and motivations for their usage and (2) meanings and ontologies they carry, and we use this framework to elaborate two paths by which previously unfamiliar categories become accepted as elements of common knowledge. These paths jointly inform the recognition front of the emergence question, an understudied problem in organization studies. Finally, we outline two methodologies – set theoretic analysis and network-based analysis – that offer particular promise for analysing processes of category emergence and dissolution.