An infinitive may be used as an adjective modifier of a noun or as an adverbial modifier of an adjective.
In this use the infinitive is said to depend on the word which it modifies.
1. With Nouns (Adjective Modifier)……With Adjectives (Adverbial Modifier)
2. An opportunity to advance came……The men are ready to advance.
3. Determination to win brings success. ……John is eager to win.
4. Willingness to oblige makes friends……..I shall be glad to oblige you.
5. I wish I had the ability to swim………We are all able to swim.
6. His anxiety to please us was laughable……….He is anxious to please everybody.
Note : This use is due to the fact that the infinitive with TO is really a prepositional phrase. Thus….DETERMINATION TO WIN is equivalent to DETERMINATION FOR VICTORY and EAGER TO WIN to EAGER FOR VICTORY. The adjective force of the infinitive comes out clearly in NOTHING TO EAT where TO EAT is practically synonymous with eatable.
In its adjective use, the present infinitive sometimes shows no distinction in voice, so that the active and the passive are interchangeable such as A HOUSE TO LET or TO BE LET and AN AXE TO GRIND or TO BE GROUND. In such expressions the active form is usually preferable.
The infinitive without TO may be used as an adjective modifier after the direct object of see, hear, feel and some other verbs of like meaning.
1. I saw the policeman arrest him.
2. Hear the sea roar!
3. Can you feel the ground tremble?
4. Ruth watched the tide come in.
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.
An infinitive may modify a verb (1) by completing its meaning or (2) by expressing the purpose of the action.
1. The ship began to roll.
2. The rain continued to fall heavily.
3. Every boy desires to succeed.
4. The officer neglected to watch his men.
5. The prisoners attempted to escape.
6. You promised to come to-night.
After dare, the complementary infinitive may or may not have TO. Thus…..I DARE NOT DO IT and WHO WILL DARE TO SPEAK?
Infinitive of Purpose
1. He went to New York to study medicine.
2. He opened his lips to speak.
3. She closed her eyes to shut out the sight.
4. Elsa lifted the cover to see what was inside.
5. The conductor signaled to stop the train.
6. 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.