Sense and Meaning

Consider the following familiar and seemingly cogent anti-Fregean argument. Take a pair of strict synonyms in English, such as (presumably) 'ketchup' and 'catsup'. As these terms have the same meaning in all respects, it seems indubitable that they have the same propositional value or semantic content with respect to every possible context of use. Now consider a speaker, Sasha, whose mother tongue is not English and who learns the meanings of 'ketchup' and 'catsup' by means of ostensive definitions in the following way, not being told at the outset that they are straightforward synonyms. Sasha acquires the words by reading the labels on the bottles in which ketchup (or catsup) is served during meals. It happens that the same condiment is regularly served to him in bottles labelled 'catsup' at breakfast, when it is eaten with eggs and hash browns, and in bottles labelled 'ketchup' at lunch, when it is eaten with hamburgers. And such a situation induces Sasha to think that he is consuming a different condiment in each case (though one which is similar in taste, colour and consistency). Therefore, whereas 'Ketchup is ketchup' is uninformative to Sasha, 'Ketchup is catsup' would be quite informative to him: his knowledge would be substantially extended if he came to know that the condiment is one and the same in both cases. Hence, by the sort of strategy labelled by Nathan Salmon “the generalized Frege's Puzzle”, one would come to the conclusion that the information value of 'ketchup'