A natural language utterance, as Barwise & Perry (1983) see it, is fundamentally dependent on the context of its use. This is most clearly demonstrated by indexical expressions: if I utter I will arrive today on December 22, 1994, what I have said is that I, WDM, will arrive on December 22, 1994. As Perry (1977, 1979) showed, using arguments from Castañeda (1967), there is no way to analyse this context-dependence of natural language in the Fregean way, by replacing the indexicals by other expressions (i.a. Russellian definite descriptions) conceived as parts of the thought expressed. Indeed, even if I believe that I am John F. Kennedy and believe that today is June 27, 1958, my utterance of I will arrive today will not mean that John F. Kennedy will arrive on June 27, 1958. Moreover, I can use today even if I do not have the slightest idea of what day it is.
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