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This chapter develops and defends a new account of essentially indexical, de se, or self-locating belief with the aim of using it in later chapters to clarify the analogy between self-locating information and phenomenal information. The account is a modified version of David Lewis's analysis of self-locating information in terms of centered possible worlds, which are abstract objects consisting of a possible world plus a designated person and time in the world. It is argued that the modified analysis is better able than Lewis's to account for the way knowledge and belief change over time, and for one person's knowledge and belief about the knowledge and belief of others. The analysis is applied to two famous examples from the literature on essentially self-locating belief — David Lewis's case of the two omniscient gods, and Adam Elga's Sleeping Beauty puzzle. The chapter concludes with an appendix that sketches some of the formal details.

The main constructive task of this chapter is to provide a way of modeling self-locating or essentially indexical information in a way that allows for the communication of this kind of information, and for a representation of common ground that includes information about where and when in the world the participants in a conversation locate themselves and each other. The model uses the resources introduced in David Lewis’s theory of self-locating belief, which models belief with centered worlds, but modifies his account in a way that allows for the explanation of the interaction of the self-locating attitudes of different agents, and of the change of propositional attitudes over time.

A defense of a thesis about self-locating attitudes that Clas Weber has labeled “Propositionalism”: to be ignorant of where in the world one is, what time it is, or who one is is always to be ignorant of what possible world is actual. The thesis is articulated in the context of David Lewis’s “centered worlds” model of self-locating or indexical attitudes. It is argued that the underlying issue concerns, not just the analysis of a distinctive kind of self-locating attitude, but the nature of intentionality. It is argued that in a sense all attitudes are self-locating since their content is explained in terms of the way the agent is situated in his or her environment.

It is argued, following David Lewis, that we should model a cognitive state by a set of centered possible worlds, since this is required to represent the believer’s self-locating or indexical knowledge and belief. But it is also argued, contra Lewis, that we should take the contents of belief to be propositions, represented by sets of uncentered possible worlds, since this is required to give a perspicuous account of agreement and disagreement of different agents, and of change of belief over time. Reconciling these two thoughts requires a defense of Propositionality: roughly, the thesis that any ignorance of where one is in the world is also ignorance about what the world in itself is like. This thesis is defended against some criticisms, and motivated by an externalist picture of knowledge and intentionality.

This chapter discusses the intuitive idea of context, and two contrasting theoretical representations of context: first, a notion of context as a representation of the concrete situation at a point in time at which a discourse is taking place, modeled by a centered possible world (a representation that contains all of the information that might be relevant to the interpretation of any context-dependent expressions); second, the notion of context as common ground: a body of information that is presumed to be shared (at a particular time) by the participants in a discourse. The chapter considers the relation between the two notions of context, and some tensions between them.