The role of "believes" is identified by finding a unique and unparaphraseable use of the term that is integral to the structure of important forms of language. This role can only be roughly indicated here. Roughly, "believes" identifies someone's reasons for doing or thinking something or what he counts as success in certain activities, without committing the speaker to accepting them; and so it allows the possibility of mistake. Standard objections to dispositional accounts are reviewed and found unconvincing. The central difficulty is found to be that dispositional accounts give no satisfactory explanation of the fact what it is (part of) an explanation of action to cite the agent's beliefs. It is argued that causal accounts have the same deficiency, that the role or point of "believes" in language is not satisfactorily explained. It is concluded that neglect of this central question vitlates even the real strengths of these accounts. The relation between different questions about belief is explored, and analogous questions about other cases, especially artefacts, are considered. Explanations of actions are discussed to bring out the role of "believes." This appears in explaining the relation between the "point or purpose" of an action and the actions of which it consists at a lower level of description. "Believes" identifies what governs this relation while allowing the possibility of mistake. Ryle's claims about thinking are considered, and an interpretation of the notion of an adverbial verb is suggested. The central difficulty concerns the cases of the thinking of le Penseur or of Eucild. Although it seems important that we should be able to say what the constituents of thinking are here, we cannot do so, since the relevant vocabulary is not adapted to giving the constituents of anything. These activities have their own "objects" as well as their own criteria of success. Activities, "objects", and criteria of success are bound up together, and do not connect in any simple way with the vocabulary that we try to connect them with in asking what their constituents are. This far from unique. Music provides another relevant example. The last chapters examine various contexts in which "believes" is important. Topics considered are reasons, evaluations, assertions, belief and the will, internationality, and speech-act accounts. In each case particular doctrines are critically examined.