  Chomskyans typically take this point, conceding that the argument  from the poverty of the stimulus is not apodeictic. Nonetheless, they claim, it's a very good argument, and the burden of proof belongs  with their critics. After all, nativists have shown the falsity of  the only non-nativist acquisition theories that are well-enough  worked out to be empirically testable, namely, Skinnerian behaviorism and Popperian conjecture and refutation. In addition, they have  proposed an alternative theory, Chomskyan nativism, which is more  than adequate to account for the phenomena. In empirical science,  this is all that they can reasonably be required to do. The fact that there might be other possible acquisition algorithms which  might account for children's ability to learn language is  neither here nor there; nativists are not required to argue against  mere possibilities.