Page 244 - Encyclopedia of Philosophy of Language

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Russell B 1905 On denoting. Mind 14: 479-93
Seuren P A M 1977 Forme logique et forme semantique: Un argument contre M. Geach. Logique et Analyse 20: 338-
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Indexicals, expressions the interpretation of which depends on the occasion on which they are uttered (e.g., /, here, today, this...), are one of the major and most pervasive means to enhance the efficiency of natural language. However, they have posed par- ticular challenges to all semantic theories of the twen- tieth century. If, for example, indexicals do not function either as referring or as describing terms, how do they fit into a general theory of meaning? Do they have a fixed, unchanging meaning apart from their ever-changing reference, and if so, what is it? At one time their status was even considered so prob- lematic that attempts were made to eliminate them altogether; but these have not been successful. In this article only the philosophical, semantic aspects will be treated. (For an overview of more descriptively oriented approaches, see e.g., chapter 2 of Levinson 1983.) Terminology tends to be confusing: instead of 'indexicals' (this term, coined by Peirce, will be used generically here), one may encounter terms like 'deictic expressions' (preferred by the more prag- matics-oriented authors), 'egocentric particulars' (Russell), 'token-reflexive expressions' (Reichenbach), 'demonstratives' (Perry), etc., all of which deal with roughly the same phenomenon.
1. Frege
The first important treatment of indexicals in modern philosophy of language was given by Gottlob Frege, who distinguished the 'reference' of linguistic expressions from their 'sense,' i.e., their descriptive content (what he calls a 'manner of presentation'). Sense determines reference, Frege holds, but not vice versa. This explains how identity statements involving names can be informative: in a=b, 'a' and 'b' have the same referent which is presented in two different manners, unlike in a=a. Sentences, whose referent is a truth value, have for their sense a 'thought,' which for Frege is not a private representation but an un- changing, Platonic entity, so that different people can grasp the same thought. The sense of a sentence is determined by the sense of its parts, so if one term
lacks sense, then the whole sentence will have no sense either.
Now how can sentences containing indexical expressions like today, whose referent changes with the occasion of utterance, express unchanging thoughts? In his essay 'Der Gedanke' (1918; translated as 'Thoughts' 1984), Frege tackles this problem by stating, first, that a sentence containing an indexical does not yet express a 'complete thought' by itself, but requires a specification of the time of utterance to determine its truth value (in other words, an incom- plete thought is not a thought at all, as it cannot yet be said to be either true or false); therefore, the time of speaking is also part of the expression of the thought. Second, Frege claims that an indexical sentence, once it is supplemented with an indication of utterance time and other necessary contextual elements, and thus expresses a complete thought, has an unchanging truth value. If a (complete) thought is true, it is always true. In other words, sentences may contain indexical terms, but thoughts never do so.
In 'Frege on Demonstratives' (1977; repr. in Your- grau 1990), John Perry has argued against this Fre- gean treatment of indexicals. The unchanging meaning of'today' in (1):
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Indexicals M. Leezenberg
Russia and Canada quarrelled today
(1)
is what he calls a 'role,' a function that takes us from the context of utterance to a day, but this is not a Fregean sense and therefore cannot complete the thought. Senses do not carry us from context to the referent (as we would want for indexicals), but directly to the referent, regardless of the context. In this case, the referent, i.e., the day of utterance, cannot complete the sense of (1) either, for an infinite number of senses corresponds to each referent; for Frege, there is no road back from reference to sense.
So, Perry claims, one cannot, using Frege's appar- atus, get from an incomplete thought, as expressed by Russia and Canada quarrelled, an indexical like today, and a context of utterance, to a complete thought. Frege may have noticed this difficulty: in fact, he