  In his famous review of Skinner's book, Chomsky (1959) effectively  demolishes Skinner's theories of both language mastery and language  learning. First, Chomsky argued, mastery of a language is not merely  a matter of having one's verbal behaviors ‘controlled’ by various elements of the environment, including others' utterances.  For language use is (i) stimulus independent and (ii) historically  unbound. Language use is stimulus independent: virtually any words can be spoken in response to any environmental stimulus,  depending on one's state of mind. Language use is also  historically unbound: what we say is not determined by our  history of reinforcement, as is clear from the fact that we can and  do say things that we have not been trained to say.