A conceptual integration and review are presented of three separate research programmes informed by the theory of lay epistemics (Kruglanski, 1989). They respectively address the “why”, “how”, and “who” questions about human knowledge formation. The “why” question is treated in work on the need for cognitive closure that propels epistemic behaviour and affects individual, interpersonal, and group phenomena. The “how” question is addressed in work on the unimodel (Kruglanski, Pierro, Mannetti, Erb, & Chun, 2007) depicting the process of drawing conclusions from the “information given”. The “who” question is addressed in work on “epistemic authority” highlighting the centrality of source effects (including oneself as a source) in human epistemic behaviour. These separate research paradigms explore facets of epistemic behaviour that jointly produce human knowledge, of essential significance to people's' individual and social functioning.