The Left Periphery of the Clause.

The primary role of the complementizer system is the expression of Force (distinguishing various clause types: declarative, interrogative, exclamative, relative, comparative, different types of adverbial clauses, etc.) and Finiteness (the specification distinguishing at least between finite and non finite clauses). We may think of Force and Finiteness as two distinct heads closing off the complementizer system upward and downward, respectively (and perhaps coalescing into a single head in the simple cases). The need for two distinct positions becomes apparent when the Topic/Focus field is activated. Consider for instance the following paradigm (adapted from Rizzi 1997), involving a Topic and complementizers che (“that”) and di (“of”), which occur in Italian finite and infinitive declaratives, respectively:

(1)a   Maria crede che potrà leggere il tuo libro

          ‘Maria believes that (she) will be able to read your book’

    b   Maria crede di poter leggere il tuo libro

          ‘Maria believes of to be able to read your book’

(2)a * Maria crede, il tuo libro, che lo potrà leggere

           ‘Maria believes, your book, that (she) will be able to read it’

     b   Maria crede che, il tuo libro, lo potrà leggere

           ‘Maria believes that, your book, she will be able to read it’

(3)a   Maria crede, il tuo libro, di poterlo leggere

          ‘Maria believes, your book, of to be able to read it’

     b * Maria crede di, il tuo libro, poterlo leggere

           ‘Maria believes of, your book, to be able to read it’

I will assume, on the basis of the evidence presented in  Kayne(1983),  Rizzi (1982), that di  is the infinitival complementizer. Given the single layer approach to the C system, che and di then  occupy the same position, and  indeed this is the traditional assumption. On the other hand, the multiple layer approach opens up the possibility that che and di, while both being elements of the C system, occupy distinct positions. This possibility  is straightforwardly supported by the ordering of the two elements with respect to other structural positions:   che must precede the topic phrase in the Clitic Left Dislocation Construction (Cinque 1990), as in (2), whereas di must follow the topic, as in (3). This and other analogous types of evidence  lead to the conclusion that che occupies the highest C position, Force, while di occupies the lowest position, Finiteness. On the basis of similar kinds of positional evidence, Rizzi (1997) arrives at the conclusion that the C system has the following structure:

(4)         FORCE      (TOP*)    FOC     (TOP*)     FIN     IP

The different kinds of positions are overtly manifested in sentences like the following:

(5)            Credo  che      ieri,  QUESTO, a Gianni, i tuoi amici avrebbero dovuto dirgli

                 FORCE   TOP     FOC        TOP

‘I believe that yesterday, THIS, to Gianni, your friends should have said to him

More precisely, che expresses the FORCE head, ieri and a Gianni fill Spec positions of two TOP heads, QUESTO fills the Spec position of the FOC head, while the FIN layer is not overtly realized in this kind of sentence.