Public knowledge presents a persistent problem for democratic deliberation. While especially salient for public participation in technical decision-making, scholars agree that all deliberations are best informed by quality, shared information. But what kind of knowledge is required in deliberation? Can deliberative practices foster requisite learning? Through rhetorical analysis of 20 small-group, public conversations about water policy in Kansas, USA, I sought to describe cultural understandings of public knowledge to inform future research and deliberative practice. Discussants voiced three epistemologies, which I label cognitivist, sociocultural, and behaviorist, each with distinct implications for democracy. I argue that researchers and practitioners should further consider how and when to foreground epistemological assumptions in deliberation. I also question whether facts are the most critical information for community self-determination, and instead argue that deliberators be pushed to openly discuss their values.