[*] 561. A clause used as a noun is called a Substantive Clause. [*] a. A Substantive Clause may be used as the Subject or Object of a verb, as an Appositive, or as a Predicate Nominative or Accusative.
[*] Note 1.--Many ideas which in English take the form of an abstract noun may be rendered by a substantive clause in Latin. Thus, he demanded an investigation may be postulābat ut quaestiō habērētur . The common English expression for with the infinitive also corresponds to a Latin substantive clause: as,—it remains for me to speak of the piratic war, reliquum est ut dē bellō dīcam pīrāticō .
[*] Note 2.--When a Substantive Clause is used as subject, the verb to which it is subject is called impersonal, and the sign of the construction in English is commonly the so-called expletive IT.