Recent challenges to scientific authority in relation to the COVID pandemic, climate change, and the proliferation of conspiracy theories raise questions about the nature of knowledge and conviction. This article considers problems of social epistemology that are central to current predicaments about popular or public knowledge and the status of science. From the perspective of social epistemology, knowing and believing are not simply individual cognitive processes but based on participation in social systems, networks, and niches. As such, knowledge and conviction can be understood in terms of the dynamics of epistemic communities, which create specific forms of authority, norms, and practices that include styles of reasoning, habits of thought and modes of legitimation. Efforts to understand the dynamics of delusion and pathological conviction have something useful to teach us about our vulnerability as knowers and believers. However, this individual psychological account needs to be supplemented with a broader social view of the politics of knowledge that can inform efforts to create a healthy information ecology and strengthen the civil institutions that allow us to ground our action in well-informed picture of the world oriented toward mutual recognition, respect, diversity, and coexistence.