ABSTRACT: It is a familiar story that Kant’s defence of our synthetic a priori cognition in the Critique of Pure Reason suffered sharp criticism throughout the extended philosophical revolutions that established analytic philosophy, the pragmatist tradition, and the phenomenological tradition as dominant philosophical movements in the first half of the twentieth century. One of the most important positive adaptations of Kant’s outlook, however, was the combined analytic and pragmatist conceptions of the a priori that were developed by the American philosophers (...) C. I. Lewis (1883–1964) and Wilfrid Sellars (1912–1989), most notably in Lewis’s 1929 classic, Mind and the World Order, followed by Sellars’ critical reworking of Lewis’s outlook in ‘Is There a Synthetic A Priori?’ (1953) and other mid-century articles. Both Lewis and Sellars defended central aspects of Kant’s analysis of our a priori knowledge of mind-independent physical objects and necessary causal connections. But both also radically transformed Kant’s view by defending the idea that there are alternative a priori conceptual frameworks that are subject to an ongoing process of reassessment and replacement on overall pragmatic and explanatory grounds. Furthermore, while Sellars’ answer to his question, ‘Is There a Synthetic A Priori?’ thus represented a partial endorsement of Lewis’s pragmatic relativization of the a priori, I argue that Sellars’ account of meaning diverged from Lewis in ways that constituted a significant improvement upon the previous ‘analytic’ defenses of the a priori, not only in Lewis but in general. This arguably has implications for wider disputes concerning the nature and possibility of a priori knowledge in non-formal domains. (shrink)