Abstract
To correct the misconception that incommensurability implies incomparability, Kuhn lately develops a new interpretation of incommensurability. This includes a linguistic theory of scientific revolutions (the theory of kinds), a cognitive exploration of the language learning process (the analogy of bilingualism), and an epistemological discussion on the rationality of scientific development (the evolutionary epistemology). My focus in this paper is to review Kuhn's effort in eliminating relativism, highlighting both the insights and the difficulties of his new version of incommensurability . Finally I suggest that some of Kuhn's difficulties can be overcome by adopting a concept of rationality that filly appreciates the important role of instruments in the development of science.