This paper analyzes the development of Kuhn's metaphilosophical position concerning the proper relationship between the history and the philosophy of science. I reconstruct Kuhn's model of scientific change presented in Structure as having the logical status of a Weberian explanatory theory; the philosophy of science and the history of science were of equal importance in its development and defense. However, Kuhn's metaphilosophical position changed in the 1990s, when he gave primacy to philosophy over the history of science in response to the challenge new sociology of science presented to his views. I analyze Kuhn's seldom discussed ‘first principles’ and argue that the locution should be understood as marking this metaphilosophical shift. Kuhn's project in his last writings was to develop epistemology and metaphysics capable of withstanding relativism and of selecting cognitive internal historiography as the appropriate historiography for the philosophy of science. I sketch the contours of this project which Kuhn was unable to complete in his lifetime.