In his 1975 paper “The Meaning of ‘Meaning’”, Hilary Putnam famously argued for semantic externalism. Little attention has been paid, however, to the fact that already in 1973, Putnam had presented the idea of the linguistic division of labor and the Twin Earth thought experiment in his comment on Wilfrid Sellars’s “Meaning as Functional Classification” at a conference, and Sellars had replied to Putnam from a broadly inferentialist perspective. The first half of this paper aims to trace the development of (...) Putnam’s semantic externalism, situate his debate with Sellars in it, and reconstruct the two arguments he presented against Sellars. The second half of this paper aims to reconstruct how Sellars replied to Putnam. I argue that Sellars not only accepts the social character of language but also suggests how inferentialists can accommodate the contribution of the world. Sellars’s key idea is that substance terms have a “promissory note aspect” which is to be cashed out in a successor conceptual framework. I reconstruct Sellars’s position as ideal successor externalism, and compare it with temporal externalism. (shrink)