Formal epistemology is the study of crucial concepts in general or mainstream epistemology including knowledge, belief (-change), certainty, rationality, reasoning, decision, justi…cation, learning, agent interaction and information processing using a spread of di¤erent formal tools. The formal tools may be drawn from logic, probability theory, game theory, decision theory, formal learning theory, distributed computing and is thus not simply a purely philosophical province. Its practitioners include philosophers, computer scientists, social scientists, cognitive psychologists, theoretical economists, mathematicians, and theoretical linguists. Formal epistemology is a thoroughly interdisciplinary …eld with many agendas, actors and issues. What follows is a breezy overview of formal epistemology as organized around notions of agency and interaction.