Beliefs are a species of propositional attitude distinguished by their having the mind-to-world direction of fit.

Propositional attitudes are psychological states characterized by a psychological mode, Ψ, and a propositional content, P, schematically: Ψ(P). My belief that the earth moves has belief as its psychological mode, and that the earth moves as its propositional content. A desire that the earth move has the same propositional content, but a different psychological mode, desire. Within a psychological mode, propositional attitudes are distinguished by their contents. I could not have two beliefs with the content that the earth moves. Many, though not all, propositional attitudes admit of a bivalent evaluation. Beliefs are true or false. Desires are satisfied or unsatisfied. Intentions are carried out or not carried out. Propositional attitudes with a bivalent evaluation have either the mind-to-world direction of fit or the world-to-mind direction of fit (Searle 1983, chapter 1). Its direction of...