Introduction

Chomsky's Principles and Parameters (P&P) framework (1981) is an alternative to the earlier generative grammar that made use of phrase structure rules (Chomsky, 1957, 1965). This shift of paradigm was motivated by two independent lines of evidence. First, as more and more languages were subjected to generative studies, a number of universal principles emerged, ones which are not restricted to specific constructions or particular languages. Second, a great variety of sentence structures can be efficiently described by a small number of parameters; different grammars are instantiations of different operational choices in a universal engine of sentence building, much like configuring computer software.

The P&P framework, like its phrase structure predecessor, offers an important perspective on children's acquisition of grammar. The principles, which are putatively innate and universal, are not learned, and can be expected to be operative in (early) child language; this opens up a wealth of topics for empirical research. On the other hand, the parameter values, which vary crosslinguistically, must be learned on the basis of specific linguistic evidence, which also can be quantified and evaluated empirically. Thus, the commonalities and differences in children's acquisition of specific languages receive a principled and unified interpretation. Moreover, if the number of parameters is finite, then there is only a finite – albeit large, perhaps – number of grammars that forms the child's learning space; this sidesteps the well-known problem of inductive indeterminacy in an infinite hypothesis space associated with phrase structure rules (Gold, 1967; Chomsky, 1981).