Contemporary diagnostic criteria for anorexia nervosa explicitly refer to affective states of fear and anxiety regarding weight gain, as well as a fixed and very strong attachment to the pursuit of thinness as an overarching personal goal. Yet current treatments for that condition often have a decidedly cognitive orientation and the exact nature of the contribution of affective states and processes to anorexia nervosa remains largely uncharted theoretically. Taking our inspiration from the history of psychiatry, we argue that conceptualizing anorexia nervosa as a passion is a promising way forward in both our understanding and treatment of that condition. Building on the theory of the passions elaborated by Théodule Ribot, the founder of scientific psychology in France, we argue that there is convincing empirical evidence in defense of the empirical hypothesis that anorexia nervosa is a passion in Ribot’s specific, technical sense. We then explore the implications of this finding for current approaches to treatment, including cognitive–behavioral therapy, and clinical and ethical issues associated with treatment refusals.