 As theoretical posits, I-languages earn their keep through their role in this kind of enquiry. By treating states on the path to normal mature linguistic competence in humans as representational states, states of knowledge (where what is represented or known is an I-language), important empirical generalizations can be formulated and assessed. One would not even have to sit at the nativist end of the spectrum in the debate on language acquisition to accept this way of framing the question. Moreover, this conception of the brain as a representational, information processing system, or as an integrated bundle of such systems, has application beyond the specific instance of language, developmental or otherwise. Chomsky’s case against behaviorism in the study of language (1959), and his alternative vision of how it might be studied, was pivotal in the cognitive revolution across psychology and affiliated disciplines (see e.g., Glass, Holyoak, &amp; Santa 1979; Marr 1982; Pylyshyn 1984; Fodor 1987).