  Secondly, the idea that children learn language essentially on their  own was a radical challenge to the prevailing behaviorist idea that  all learning involves reinforcement. In addition, it made clear our  need for a more ‘cognitive’ or ‘mentalistic’  conception of how language learning occurs, and vividly raised the  question — our focus in this article — of what might be  the preconditions for that process. As we will see in the  next section, Chomsky was ready with a theory addressing each of  these points.