  In response to this kind of point, Chomskyans point out that the  innateness of UG is an empirical hypothesis supported by a perfectly  respectable inference to the best explanation. Of course there is a  logical space between the conclusion that something  constrains the acquisition mechanism and the Chomskyan view that  these constraints are inborn representations of Binding Theory, Theta theory, the ECP, the principle of Greed or Shortest Path and so on.  But the mere fact that the argument from the poverty of the stimulus  doesn't prove that UG is innately known is hardly reason to  complain. This is science, after all, and demonstrative proofs are  neither possible nor required. What the argument from the poverty of  the stimulus provides is good reason to think that there are strong  constraints on the learning mechanism. UG is at hand to supply a  theory of those constraints. Moreover, that theory has been highly  productive of research in numerous areas (linguistics,  psycholinguistics, developmental psychology, second language  research, speech pathology etc. etc.) over the last 50 years. These  successes far outstrip anything that non-nativist learning theorists  have able to achieve even in their wildest dreams, and support a  powerful inference to the best explanation in the Chomskyan's favor.