 Chomsky (1986) does take an explicit position on the nature of language and its ontological building blocks. He argues that linguistics is the science of “I-languages”—i.e., internalized languages, the mental rules of grammar, phonology, and so on, that individuals use in expressing themselves or understanding the utterances of others. He rejects “E-languages”—externalized or public languages like English, Chinese, and Khosa—as unscientific fictions. Others disagree on various grounds. Katz and Postal (1991) share Chomsky’s view that each person has his or her own language, but argue that languages are abstract or mathematical entities rather than psychological ones (see also Higginbotham 1991). Wittgenstein (1953) and his successors have a more substantive disagreement: Wittgenstein denies the possibility of a “private language” altogether, arguing that language is a matter of engagement of people with one another and with the world. Other philosophers have argued for the publicity and externality of language on a variety of grounds, including the communicative basis of language, the nature of rules, and theories of semantic content (see Kripke 1972, 1982; Schiffer 1972; Lewis 1975; Putnam 1975; Burge 1979; Brandom 1994; Dummett 1989; and entries on  theories of meaning,  externalism about mental content,  names,  and  the normativity of meaning and content).