Sufferers of eating disorders often hold false beliefs about their own body size. Such beliefs appear to violate norms of epistemic rationality, being neither grounded by nor responsive to appropriate forms of evidence. Contrary to appearances, I defend the rationality of these beliefs. I argue that they are in fact grounded in and reinforced by appropriate evidence, emanating from proprioceptive misperception of bodily boundaries. This argument has far-reaching implications for the explanation and treatment of eating disorders, as well as debates over the relationship between rationality and human psychology
