 The most conspicuous debate about the “nature of language”—namely, the debate over innateness—does not have much to do with the metaphysics of language. Like most phenomena involving the human mind, language is causally affected by social factors. A person’s vocabulary and grammar, for instance, are affected by interactions with parents, peers, and other community members. Just how significant these causal effects are is widely debated in linguistics, with many in the Chomskian tradition favoring innate constraints on the mental structures of language and others rejecting innatism (see Chomsky 1986, 2000; Tomasello 1992, 1995; Elman, Bates et al. 1996; Kirby 1999). The question of the nature of language, however, is to a large extent independent of innatism versus anti-innatism. Interactions with other people may contribute only a bit to an individual’s mental structures, or they may fundamentally shape them—but in either case a person’s language may or may not ontologically depend only on that person’s brain states.