According to our commonsense view of the matter, beliefs, desires, intentions and the like are special kinds of internal states the possession of which by a given cr- ture potentially explains its behavior and otherwise renders the creature intelligible to us. So-called folk psychology provides us with a rough-and-ready network of counterfactuals delimiting the role supposedly played by these internal states v- à-vis perceptual input, inference, and behavioral output in a normal member of our species. The exact empirical details of this network do not matter here, for we are not undertaking further re nement or systematization of the relevant counterfac- als. Instead, our topic is the ontological analysis of the internal states that occupy the nodes of this complex network and the bearing of that analysis on the truth conditions of the sentences we use to ascribe beliefs and related states. The relevant counterfactuals canonically describe particular belief-, desire-, and intention-states as states of believing, desiring, and intending that such-a- such. The use of in nitival clauses to describe desires and intentions is not really an exception, for desiring or intending to do A (or to be F) is just having a self-regarding desire or intention that oneself does A (or that oneself is F). By the lights of our commonsense psychology, then, to be in a particular belief-, desire-, or intention-state is to bear the corresponding attitudinal relation― believing, desiring, or intending―to a certain content.
This book provides a formal ontology of senses and the belief-relation that grounds the distinction between de dicto, de re, and de se beliefs as well as the opacity of belief reports. According to this ontology, the relata of the belief-relation are an agent and a special sort of object-dependent sense (a "thought-content"), the latter being an "abstract" property encoding various syntactic and semantic constraints on sentences of a language of thought.
One bears the belief-relation to a thought-content T just in case one (is disposed as one who) inwardly affirms a certain sentence S of one’s language of thought that satisfies what T encodes, which in turn requires that S’s non-logical parts stand in appropriate semantical relations to items specified by T. Since these items may include other senses as well as ordinary objects, beliefs of arbitrary complexity are automatically accommodated. Within the framework of the formal ontology, a context-dependent compositional semantics is then provided for a fragment of regimented English capable of formulating ascriptions of belief―a semantics that treats substitutional opacity as a genuine semantic datum.
Finally, the resulting picture of belief and its attribution is defended by showing how it solves standard puzzles, avoids objections to rival accounts, and satisfies certain adequacy conditions not fulfilled by traditional theories. Along the way, clarification and defense is offered for the ingredient conception of object-dependent senses, and it is shown how adoption of the language of thought hypothesis permits Bertrand Russell’s obscure doctrine of logical forms to be understood in a way that not only vindicates his Multiple Relation theory of de re belief but also reveals the connection between these logical forms and thought-contents.
