Deriving Null Subject Parameter From Predicate Licensing Condition

This thesis attempts to account for the null subject parameter by incorporating the notion of LF subject and PF/LF hybrid parameter.First, a predicate licensing condition is proposed, according to which a subject is required to combine with T head as predicate formation. Because the effect of the condition on semantic interpretation, it requires only a LF subject which can be null spelled out.Secondly, we examine how a subject combines with T in inflectional and non-inflectional languages in the light of the relativized X'-schema (Fukui 1995). It is concluded that the subjects of inflectional languages are raised to Spec-TP capitalizing on feature checking whereas the subjects of non-inflectional languages adjoin to T'. The clause projections of two types of languages are also suggested.Thirdly, by examining the distribution of overt subjects in inflectional languages, it is claimed that the morphological system of non-pro-drop languages like English, which is not rich enough to fully manifest theΦ-feature of T, triggers a PF compensation mechanism, to manifest the subject in Spec-TP. This enables us to account for the obligatory occurrence of overt subjects in English, and to attribute the obligatory overtness of subject to a PF mechanism. Accordingly the obligatorily overt subject in English is required not only by semantic mechanism but also by PF mechanism, hence being a LF/PF hybrid subject, in contrast to subjects in Chinese and Italian to which the PF compensation mechanism is not applied, hence being LF subjects. As a result, the null subject parameter can be derived from the parameter in the property of subject: the pro-drop languages like Chinese and Italian share LF subjects in common, while the non-pro-drop languages like English possess LF/PF hybrid subjects.