out that "bachelor" is defined as "unmarried man"? Clearly, a dictionary would not solve the problem, as a dictionary is a report of already known synonyms, and thus is dependent on the notion of synonymy, which Quine holds as unexplained. A second suggestion Quine considers is an explanation of synonymy in terms of interchangeability. Two linguistic forms are (according to this view) synonymous if they are interchangeable in all contexts without changing the truth-value. But consider the following example: (3) "Bachelor" has fewer than ten letters. Obviously "bachelor" and "unmarried man" are not interchangeable in that sentence. To exclude that example and some other obvious counterexamples, such as poetic quality, Quine introduces the notion of cognitive synonymy. But does interchangeability hold as an explanation of cognitive synonymy? Suppose we have a language without modal adverbs like "necessarily". Such a language would be extensional, in the way that two predicates which are true about the same objects are interchangeable again without altering the truth-value. Thus, there is no assurance that two terms that are interchangeable without the truth-value changing are interchangeable because of meaning, and not because of chance. For example, "creature with a heart" and "creature with kidneys" share extension. In a language with the modal adverb "necessarily" the problem is solved, as salva veritate holds in the following case: (4) Necessarily all and only bachelors are unmarried men while it does not hold for (5) Necessarily all and only creatures with a heart are creatures with kidneys. Presuming that 'creature with a heart' and 'creature with kidneys' have the same extension, they will be interchangeable salva veritate. But this interchangeability rests upon both empirical features of the language itself and the degree to which extension is empirically found to be identical for the two concepts, and not upon the sought for principle of cognitive synonymy. It seems that the only way to assert the synonymy is by supposing that the terms 'bachelor' and 'unmarried man' are synonymous and that the sentence "All and only all bachelors are unmarried men" is analytic. But for salva veritate to hold as a definition of something more than extensional agreement, i.e., cognitive synonymy, we need a notion of necessity and thus of analyticity. So, from the above example, it can be seen that in order for us to distinguish between analytic and synthetic we must appeal to synonymy; at the same time, we