Quine

Quine's polemic against the 'dogmas of empiricism' centers around the issue of what exactly it means to say that a statement is analytic.  Certain statements, like tautologies, are tautologies because the signs used are the same.  E.g, "All unmarried men are unmarried."  But a statement like "All bachelors are unmarried" is supposed to be analytic even though the signs differ.  So how is it that the statement is analytic?  Some appeal to the notion of synonymity.  Since 'bachelor' and 'unmarried man' are synonyms, then the sentence is analytic.  But how can we define synonymity without an appeal to a definition of analyticity?  If we say that two words are synonymous because they can be exchanged in every case with the same truth value preserved, this does not work for sentences like ""Bachelor"" has less than ten letters" and ""An unmarried man" has less than ten letters.  In order to know what really makes words synonymous, we need to first define analyticity.

Quine offers a holistic notion of language, according to which no statements are analytic.  All statements are subject to revision based on new empirical knowledge.  Some statements will be more integrated into systems of knowledge, but even those that are very foundational will be subject to revision.