THE THEORETICAL FRAMEWORK
The ultimate aim of any adequate theory of language is to account for two basic problems. The first is how languages, despite superficial differences, are identical at some deep and abstract level. The second is to define the range of possible variation among languages in a principled way. In the Principles and Parameters framework (cf. Chomsky (1981), (1982), (1986a), (1986b), (1991), (1992)), the first issue is dealt with by assuming the existence of a set of predetermined principles called Universal Grammar (UG). These principles govern the structural and grammatical properties of all languages of the world by virtue of biological necessity. The fact that languages exhibit fundamental similarities therefore follows from the assumption that they share a common set of grammatical principles, i.e. UG.