Typologies classify activities into similarities and differences in a semantic web of purposes, contexts, practices, organizational structures, and theoretical frameworks. Huutoniemi and Rafols (2017) contended multiple claims tend to paralyze debate on definition. Yet, Frédéric Darbellay (2015) identified two major lines of argument in current discourse about interdisciplinarity: an epistemological, theoretical orientation that transcends disciplinary boundaries and a pragmatic, participative orientation to problem solving. The epistemic approach is philosophical, raising questions about the nature of knowledge amplified by ontological questions about the nature of reality. In contrast, problem solving is oriented to instrumental needs. This chapter compares discourses of philosophy and problem solving while adding a third imperative of critique. After acknowledging differences, it then takes into account their intersections. The chapter closes by asking whose knowledge counts, weighing the relationship of generalizations and individual cases, and reflecting on how discourse shapes definition.