This is a highly critical review of David Lightfoots 1999 book "The development of language", which argues that there are no principles of grammatical change, so that "historicist" or deterministic approaches to diachronic change are misguided. Instead, Lightfoot argues that language change can only be understood by taking the perspective of the "growth" (i.e. acquisition) of an individual's biological grammar, which may end up with a different parameter setting from the parent's generation

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... the trigger experience changes. This review is very critical of most aspects of Lightfoot's theory: his strange notions of "language" and "social grammar", his failure to say anything meaningful about "nongrammatical changes" (i.e. apparently the great majority of changes), his unconstrained theoretical innovation of "diglossia", his complete misunderstanding of the neogrammarian revolution, and his irresponsible ignoring of much of contemporary work on language change.