 Some realists reject the publicity of meaning principle as it applies to language learning. While many accept that the meaning of a word is determined by its use in a given language, not all do [e.g. Chomsky 1986; Fodor and Lepore 2002]. Realists who think of semantic understanding as a mental state reject the idea that a speaker’s understanding of meaning is exhaustively manifest in its use as an instrument of communication rather than in its internal use in expressing thought. If Dummett’s manifestation requirement is a demand for a behaviouristic reduction of semantic knowledge, they argue, it should be rejected [Burgess 1984; Chomsky 1986]. However, some sympathetic to the demand for full manifestability of semantic knowledge reject the behaviouristic construal and instead justify it on conceptual grounds [e.g. Shieh 1998, McGee  2015].[3] 