Jürgen Meisel argues that “grammatical variation. . .can be described. . .in terms of parametric variation”, and – crucially for his arguments in this paper – that “parameter settings do not change across the lifespan”. To this extent he adopts the standard generative view, but he then departs from what he calls “the literature on historical linguistics” (by which he means the generative literature only) in developing the arguments leading to his major claims: that only “transmission failure” resulting from L2 acquisition can produce parametric morphosyntactic change; that any L2 learners, children or adults, may be the agents of change; that such changes “happen less frequently than is commonly assumed”; and that, “in larger and more complex societies, situations in which L2 learners exert a major influence on a language are most likely to emerge in periods of substantial demographic changes” (his example is a plague that kills most members of a speech community). Adult L2 learners, according to Meisel, can only be agents of parametric change if they provide most or all of the input for the next generation's L1 acquisition.