According to epistemological internalism, the rationality of a belief supervenes purely on "internal facts" about the thinker's mind. But what are "internal facts"? Why does the rationality of a belief supervene on them? The standard answers are unacceptable. This paper proposes new answers. "Internal facts" are facts about the thinker's nonfactive mental states. The rationality of a belief supervenes on such internal facts because we need rules of belief revision that we can follow directly, not by means of following any (...) other rules, and the proximate explanation of any belief revision always consists of such internal facts. (shrink)