Syntactic properties associated with the Null Subject Parameter

As I mentioned in the introductory chapter, the NSP derives from the idea that clauses in all languages have subjects (the EPP in (8), Section 1.2). Languages that apparently lack subjects actually have null versions of them (both thematic and expletive), and this parametric setting correlates with a cluster of syntactic properties. The six properties initially related to the NSP included (a) having null subjects, (b) having null resumptive pronouns, (c) having free inversion in simple sentences, (d) availability of ‘long wh-movement’ of subjects, (e) availability of empty resumptive pronouns in embedded clauses and (f) presence of overt complementizers in that-trace contexts (Perlmutter, 1971; Chomsky and Lasnik, 1977; Kayne, 1980; Taraldsen, 1980; Jaeggli, 1982; Rizzi, 1982; Safir, 1985; Jaeggli and Safir, 1989). In addition, null and overt subjects are interpreted differently in NSLs (see Montalbetti, 1984, among others). In this section, we will review and exemplify the different properties associated with the NSP.

Null subjects

As expected, NSLs have null subjects. In languages like Chamorro and Irish, subjects must be null when the verb shows person subject agreement. Thus, in the Chamorro example in (1a), the pronoun gui' cannot appear because the verb agrees with the subject in person and number, whereas in (1b), the verb agrees in number but not in person, so the subject can be overt or null (see Chung, 1998, 30–31).