 The theory of conventions used in Lewis 1975 is developed at length in his earlier book (1969). The resulting theory of language is elaborated by Bennett 1976 and criticized in Burge 1975 and Laurence 1996. Wiggins 1997 and Millikan 2005, like Lewis, see languages as essentially social in nature (Chomsky replies to a version of the latter in Antony and Hornstein 2003).