 Several important debates feature talk of languages that are more idiolectal than social. Some are considered in detail in other entries (see the entries on  the language of thought hypothesis,  private language, and  externalism about mental content).  This entry will concentrate instead on one extremely influential non-idiolectal view (Lewis’s account of languages as conventions, Section 2, which also discusses Davidson’s anti-conventionalism) and one extremely influential idiolectal view (Chomsky’s notion of an I-language, Section 3). The entry begins in Section 1 with some general remarks about the ontology of languages.