This chapter re-examines how C. I. Lewis's pragmatic realism in Mind and the World Order (1929, MWO) contrasts to logical empiricism, and to Lewis's later An Analysis of Knowledge and Valuation (1946, AKV), to highlight several important philosophical points Lewis clearly understood and argued for in MWO, which we need to recover today. MWO is expressly an "Outline of a Theory of Knowledge"; nevertheless, it provides several important lessons about human knowledge, action and our worldly context. These are highlighted by contrast to some key points in Carnap's empiricist semantics (§2) and by considering a point important to scientific realism, not properly accommodated by Carnap's semantics: Reichenbach's (1920) "coordination" (Zuordnung) principles – a very important point about scientific measurement procedures, central both to Peirce and to MWO (§3). These coordinating principles for exact scientific measurements highlight the contrast between the meta-linguistic "relative a priori" admissible by empiricist semantics (Friedman 1999 2001), and Lewis's robustly realist "pragmatic a priori" in MWO. I re-examine key features of MWO (§4), including Lewis's rejection of mythical givenness and of a series of false dichotomies which still plague current discussions of epistemology, pragmatism and history and philosophy of science.