Debates about indoctrination raise fundamental questions about the ethics of teaching. This paper presents a philosophical analysis of indoctrination, including 1) an account of what indoctrination is and why it is harmful, and 2) a framework for understanding the responsibilities of teachers and other educational actors to avoid its negative outcomes. I respond to prominent outcomes-based accounts of indoctrination, which I argue share two limiting features--a narrow focus on the threat indoctrination poses to knowledge and on the dyadic relationship between indoctrinator and indoctrinated person. I propose a system-based account of indoctrination in which actors with authority contribute to the production or reinforcement of closed-mindedness, which threatens both knowledge and understanding. By taking a system-based approach, my account is better equipped to identify the implications of indoctrination for educational policy and practice.