161. The infinitive may be used as the object of a preposition; as,
- He is about to go.
- They will do anything for the cause except to live for it.
162. The infinitive may be used as an adjective to modify a noun. For example:
- He showed me the way to go.
- We must have food to eat and clothes to wear.
- The question to be decided is before us.
- Claim your right to live.
163. The infinitive may also be used as an adverb to modify the meaning of a verb, adjective or adverb, thus:
- He was forced to go.
- They are slow to learn.
- The fruit was not ripe enough to eat.
Note that the infinitives in these sentences may all be changed into adverb phrases. As for example in the first sentence, He was forced to go, the infinitive to go, which modifies the verb forced, may be changed to the adverb phrase, into going, thus, He was forced into going. In the second sentence, They are slow to learn, the infinitive to learn may be changed into the adverb phrase in learning, thus, They are slow in learning. In the last sentence, The fruit is not ripe enough to eat, the infinitive to eat, which modifies the adverb enough, may be changed into the adverb phrase, for eating, as for example, The fruit was not ripe enough for eating.
164. The infinitive is quite a useful form of the verb, and we will find that we use it very frequently in expressing our ideas. While it is not the asserting word in the sentence, it retains the nature of a verb and may have both an object and an adverb modifier. As for example, in the sentence:
- I wish to learn my lesson quickly.
To learn is the infinitive, used as a noun, the object of the verb wish. The infinitive also has an object, to learn—what? My lesson is the object of the infinitive to learn. We also have an adverb modifier in the adverb quickly, which tells how I wish to learn my lesson. So the infinitive retains its verb nature, in that it may have an object and it may be modified by an adverb.