For consider: The fact (i) that the pld are finite whereas natural languages are infinite shows that children must be generalizing beyond the data when they are learning their language's grammar: they must be proposing rules that cover as-yet unheard utterances. This, however, opens up room for error. In order to recover from particular sorts of error, children would need access to particular kinds of data. If those data don't exist, as (ii) asserts, then children would not be able to corre