  At the very least, such objections serve to equalize the burden of  proof: non-nativists certainly have work to do, but so too do  nativists. Merely positing an innate UG and a  ‘triggering’ mechanism by which it ‘grows’  into full-fledged language is insufficient. Nativists need to show  how their theory can account for the known course of language  acquisition. Merely pointing out that there is a possibility that such theories are true, and that they would, if true, explain  how language learning occurs in the face of an allegedly impoverished stimulus, is only part of the job.