This paper argues that debates over saturation in qualitative research point to a deeper problem than conceptual ambiguity or inconsistent application. At stake is the lack of a general account of how inquiry becomes sufficient. Drawing on sociological theories of justification, evaluation, and boundary work, the paper introduces the concept of epistemic closure to describe how qualitative inquiry is rendered sufficiently complete to warrant stopping, despite the continued availability of further data and alternative interpretations. Reframing saturation in these terms shifts attention from methodological endpoints to the social processes through which claims of adequacy are rendered credible. The paper develops a typology of four distinct grammars of closure—redundancy, interpretive, procedural, and audit—and argues that contemporary alternatives to saturation are best understood as different ways of rendering inquiry sufficiently complete rather than as competing stopping criteria. In doing so, it reinterprets contemporary debates over saturation, information power, and rigor as struggles over how closure is achieved. The paper concludes by showing how this framework recasts rigor as a relational and situated accomplishment while situating epistemic closure within the broader governance of qualitative knowledge.