Generative grammar addressed for the first time acquisition as a central issue in the study of grammar. This perspective has given rise over the years to a considerable body of work, mainly on first language acquisition, but also on second language acquistion, bilingual acquisition, and the acquisition by children affected by SLI. If we assume continuity, i.e. that all stages in acquisition reflect possible natural languages, we must posit a mutual dependency between grammatical theory and the facts of acquisition. On the one hand, theories about particular languages should pass the proof against data from acquisition. On the other hand, acquisition data may provide a source of evidence for deciding among alternative theories of language
