  The Principle of Tolerance requires the analytic-synthetic distinction. It requires that we can, in all cases, distinguish between theoretical changes which involve a change of meaning, and hence, strictly speaking, a change of language, and those which do not. The former kind of change involves analytic sentences, and is a matter for Tolerance; the latter involves only synthetic sentences, and Tolerance does not apply. The use of the Principle of Tolerance thus presupposes a clear distinction between the analytic sentences of the language and its synthetic sentences.