This paper explores the nature of self-knowledge of beliefs by investigating the relationship between self-knowledge of beliefs and one's knowledge of other people's beliefs. It introduces and defends a new account of self-knowledge of beliefs according to which this type of knowledge is developmentally interconnected with and dependent on resources already used for acquiring knowledge of other people's beliefs, which is inferential in nature. But when these resources are applied to oneself, one attains and subsequently frequently uses a method for (...) acquiring knowledge of beliefs that is non-inferential in nature. The paper argues that this account is preferable to some of the most common empirically motivated theories of self-knowledge of beliefs and explains the origin of the widely discussed phenomenon that our own beliefs are often transparent to us in that we can determine whether we believe that p simply by settling whether p is the case. (shrink)