Abstract
Thomas Reid in the eighteenth century and Ludwig Wittgenstein in the twentieth made strong cases for the existence of "communication systems" that must be in place if there is to be the acquisition of any language; language in the full sense of a system of words, displaying distinctions into word classes and ordered by a grammar that is sensitive to those word classes. Although their pre-languages have something of the character of language proper, Reid and Wittgenstein offer a very different conception of the necessary conditions for the existence of language from that proposed by Chomsky, much criticized for its implausible cognitivism. In this paper we compare and contrast Reidian and Wittgensteinian conceptions of what there must be for language to be possible, and draw some morals for the vexed, but in our view, empty question of the demarcation of language from all other intentional and normative systems in use amongst people and animals.