Infinitives

The infinitive to is considered an auxiliary verb in the XTAG system, and selects the auxiliary tree in Figure 20.1. To, like do, does not interact with the other auxiliary verbs, adjoining only to main verb base forms, and carrying infinitive mode. It is used in embedded clauses, both with and without a complementizer, as in sentences ((354))-((356)). Since it cannot be inverted, it simply does not select the trees in Figure 20.4.

(353)0(353

(354)

John wants to have a backpack .  (354)0(354

(355)

John wants Mary to have a backpack .  (355)0(355

(356)

John wants for Mary to have a backpack . 

The usage of infinitival to interacts closely with the distribution of null subjects (PRO), and is described in more detail in section 8.5.