language from the mid-20th century, such as that of J.L. Austin and the ordinary language philosophers, has provided much of the originary inspiration for the study of indexicality and related issues in linguistic pragmatics (generally under the rubric of the term deixis), though linguists have appropriated concepts originating in philosophical work for purposes of empirical study, rather than for more strictly philosophical purposes. However, indexicality has remained an issue of interest to philosophers who work on language. In contemporary analytic philosophy, the preferred nominal form of the term is indexical (rather than index), defined as "any expression whose content varies from one context of use to another ... [for instance] pronouns such as 'I', 'you', 'he', 'she', 'it', 'this', 'that', plus adverbs such as 'now', 'then', 'today', 'yesterday', 'here', and 'actually'. This exclusive focus on linguistic expressions represents a narrower construal than is preferred in linguistic anthropology, which regards linguistic indexicality (deixis) as a special subcategory of indexicality in general, which is often nonlinguistic. Indexicals appear to represent an exception to, and thus a challenge for, the understanding of natural language as the grammatical coding of logical propositions; they thus "raise interesting technical challenges for logicians seeking to provide formal models of correct reasoning in natural language." They are also studied in relation to fundamental issues in epistemology, self-consciousness, and metaphysics, for example asking whether indexical facts are facts that do not follow from the physical facts, and thus also form a link between philosophy of language and philosophy of mind. The American logician David Kaplan is regarded as having developed "[b]y far the most influential theory of the meaning and logic of indexicals". See also Conversational scoreboard Quasi-indexical References External links Arché Bibliography of Indexicals Commens Dictionary of Peirce's Terms, consisting in Peirce's own definitions and characterizations. See "Index". Demonstratives & Indexicals at Internet Encyclopedia of Philosophy. Semantics Formal semantics (natural language) Linguistics terminology Charles Sanders Peirce