ABSTRACT
This chapter considers three main points. The first is that, with respect to null subjects in young children's speech, the data collected thus far indicate no point at which the grammar of US children speaking Standard English clearly licenses null subjects, and no point at which IP and complementizer phrase are clearly absent. The second point is that, in order to account for the diversity as well as the commonalities in acquisition within and across languages, theories must specifically include both a competence component and a performance component, and a model of how the two interact. The third point is that children's initial state is, with respect to parameters, unset. The obvious dilemma created by the parsing constraint can be solved by allowing both values of a parameter to feed the child's parser simultaneously. Some parameters, such as the head-direction and SPEC-direction parameters, must be set in order for the child to produce any speech at all.
