  That such burden-shifting is endemic to discussions of linguistic  nativism (the exchange in Ritter 2002 is illustrative) suggests to  me that neither side in this debate has as yet fulfilled its  obligations. Empiricists about language acquisition have ably  identified a number of points of weakness in the Chomskyan case, but  have only just begun to take on the demanding task of developing  develop non-nativist learning theories, whether for language or  anything much else. Nativists have rested content with hypotheses  about language acquisition and innate knowledge that are based on  plausible-seeming but largely unsubstantiated claims about what the  pld contain, and about what children do and do not know and  say.