Knowing one’s past thoughts and attitudes is a vital sort of self-knowledge. In the absence of memorial impressions to serve as evidence, we face a pressing question of how such self-knowledge is possible. Recently, philosophers of mind have argued that self-knowledge of past attitudes supervenes on rationality. I examine two kinds of argument for this supervenience claim, one from cognitive dynamics, and one from practical rationality, and reject both. I present an alternative account, on which knowledge of past attitudes is inferential knowledge, and depends upon contingent facts of one’s rationality and consistency. Failures of self-knowledge are better explained by the inferential account.