Editing Clause (section)

===''to''-infinitive clauses===
Some modern theories of syntax take many ''to''-infinitives to be constitutive of non-finite clauses.<ref>For an example of a grammar that acknowledges non-finite ''to''-infinitive clauses, see Radford (2004:23).</ref> This stance is supported by the clear predicate status of many ''to''-infinitives. It is challenged, however, by the fact that ''to''-infinitives do not take an overt subject, e.g.

::a. She refuses <u>to consider the issue</u>.
::a. He attempted <u>to explain his concerns</u>.

The ''to''-infinitives ''to consider'' and ''to explain'' clearly qualify as predicates (because they can be negated). They do not, however, take overt subjects. The subjects ''she'' and ''he'' are dependents of the matrix verbs ''refuses'' and ''attempted'', respectively, not of the ''to''-infinitives. Data like these are often addressed in terms of [[Control (linguistics)|control]]. The matrix predicates ''refuses'' and ''attempted'' are control verbs; they control the embedded predicates ''consider'' and ''explain'', which means they determine which of their arguments serves as the subject argument of the embedded predicate. Some theories of syntax posit the null subject [[PRO (linguistics)|PRO]] (i.e. pronoun) to help address the facts of control constructions, e.g.

::b. She refuses <u>PRO to consider the issue</u>.
::b. He attempted <u>PRO to explain his concerns</u>.

With the presence of PRO as a null subject, ''to''-infinitives can be construed as complete clauses, since both subject and predicate are present.

PRO-theory is particular to one tradition in the study of syntax and grammar ([[Government and Binding Theory]], [[Minimalist Program]]). Other theories of syntax and grammar (e.g. [[Head-Driven Phrase Structure Grammar]], [[Construction Grammar]], [[dependency grammar]]) reject the presence of null elements such as PRO, which means they are likely to reject the stance that ''to''-infinitives constitute clauses.