The main thesis Pienemann puts forward is that while L1 acquisition and L2 acquisition of a particular language (e.g. German) exhibit non-parallel paths of development, such a difference does not entail that the processing resources claimed to be responsible for transitioning from one stage to the next are any different in the two situations. The cause of the difference in routes, he suggests, is the difference in departure points. In the German case at hand, L1 acquirers begin with an SOV grammar, while L2 acquisition, according to Pienemann, starts off SVO (“canonical order”). “Generative entrenchment” of SVO is what makes the ensuing development distinct from that of L1 German: “once a decision has been made and a new structure has been added, it is very costly, if not impossible, for the developmental process to move to a different developmental path.” I think there's something very right about this general picture – but also that part of it is “wrong-headed.”