In this use the infinitive is practically equivalent to a participle. Compare “I heard him shout” with “I heard him shouting.” Hence the substantive may be regarded as an object, and the infinitive as its modifier. But the construction closely approaches that of an infinitive clause ([§§ 324–325]).
323. An infinitive may modify a verb (1) by completing its meaning, or (2) by expressing the purpose of the action.
I. Complementary Infinitive
- The ship began to roll.
- The rain continued to fall heavily.
- Every boy desires to succeed.
- The officer neglected to watch his men.
- The prisoners attempted to escape.
- You promised to come to-night.
After dare, the complementary infinitive may or may not have to. Thus,—“I dare not do it”; “Who will dare to speak?”
II. Infinitive of Purpose
- He went to New York to study medicine.
- He opened his lips to speak.
- She closed her eyes to shut out the sight.
- Elsa lifted the cover to see what was inside.
- The conductor signalled to stop the train.
- Harold waited to assist his teacher.
Both the complementary infinitive and the infinitive of purpose may be regarded as adverbial phrases modifying the verb.
Note. After some verbs the infinitive approaches the construction of a pure noun and is often regarded as an object. Thus,—“I desire to see you” (compare “I desire a sight of you”). It is simpler, however, to regard all such infinitives as complementary and to treat them as adverbial modifiers. For it is impossible to distinguish the construction of the infinitive after certain adjectives (as in “I am eager to see you”) from its construction after such verbs as wish and desire.