Speakers, in their everyday conversations, use language to talk about language. They may wonder about what words mean, to whom a name refers, whether a sentence is true. They may worry whether they have been clear, or correctly expressed what they meant to say. That speakers can make such inquiries implies a degree of access to the complex array of knowledge and skills underlying our ability to speak, and though this access is incomplete, we nevertheless can form on this basis beliefs about linguistic matters of considerable subtlety, about ourselves and others.
Under what conditions are expressions of a language the same; when are they different? Indices and Identity focuses on this question in the context of the theory of anaphora and on the role of indices in characterizing syntactic and semantic identity of expressions.