§ 123. The construction consists of a noun (or a noun-pronoun) in the common case or a personal pronoun in the nominative case and an infinitive. The peculiarity of the construction is that the first element is separated from the second one by a finite verb-form which together with the infinitive forms a compound verbal predicate of double orientation, whereas the nominal part of the construction forms the subject of the sentence. Thus the construction does not function as one part of the sentence but falls into two parts each functioning separately.
Semantically of these two parts of the predicate only the second one refers to the subject, as only this part denotes either the action or the state of the person or non-person expressed by the subject. Thus in the sentence: He is said to know five languages it is the relation. He knows five languages that is important.
In between the subject and the infinitive there is a part of the predicate expressed by a finite verb which grammatically indicates subject-predicate relations. However, Semantically this finite verb cannot serve as the predicate of the subject, as it denotes some comment, or estimate, or judgment, or conclusion, or attitude to the action or state expressed by the infinitive. The comment or attitude comes from somebody not mentioned in the sentence, therefore such sentences can be transformed into complex ones with the indefinite-personal subject in the principal clause:
He is reported to have left. ————> They report (or somebody reports) that he has left.
The car was heard to turn round the corner. ——> They heard (somebody heard) that the car turned round
The subjective infinitive construction is used with a limited number of finite verbs either in the passive or in the active voice:
I. Verbs used in the passive voice fall into four groups:
1) verbs of sense perception ( hear, see, observe, watch, etc.). When used in the passive voice they are followed by a to-infinitive. They express the idea of evidence. The same idea is also rendered by some other verbs in the passive voice (such as find, discover).
He was seen to enter the building. (Somebody was a witness of this fact)
They were heard to quarrel. (Somebody heard them and therefore was a witness of their quarrel)
The boy was found to be sleeping at home. (Somebody found the boy and he was sleeping)
2) verbs of mental perception ( think, know, mean, believe, expect, consider, assume, presume, suppose) With this construction these verbs denote different shades of expectation, opinion, judgment:
Pat was supposed to come with me tonight.
The Paliament is expected to introduce some changes into the laws.
Programmed instruction is considered to have many advantages.
3) verbs of saying and reporting (say, report, declare, predict, etc). These verbs also express some judgment or opinion:
Blackberries are said to have a lot of vitamins.
A new star was reported to have appeared in the East.
4) Causative verbs (cause, make, order, allow, etc.) The verb to make when used in the passive voice is followed by a to-infinitive.
Jule was made to repeat her words.
The doctor was ordered to change his shift.
No dam was allowed to be built in this part of the country.
II. The following verbs used in the active voice:
1. Verbs expressing subjective or personal attitude to facts and their evaluation ( to seem, to appear, to happen, to chance, to turn out, etc.).
The structure seemed to have been properly designed.
Your friend turned out to be stronger than we expected.
Everybody appeared to be enjoying themselves.
He chanced to be in the park when I was there.
I was to tell you the news if I happened to run into you.
2. Modal phrases expressing different shades of probability or certainty ( to be (un)likely, to be sure, to be certain, to be bound); also adjectives or nouns with the link-verb to be expressing an estimate of a different kind (pleasant, hard, easy, difficult, terrible, apt, etc.). As probability mostly implies a future action the non-perfect infinitive is generally used after to be likely. With modal phrases expressing certainty both non-perfect and perfect infinitives are possible. The modal phrases to be apt, to be bound generally refer to habitual actions or states and are accordingly followed by the non-perfect infinitive:
We are certain to come to an agreement.
You are not likely to believe my story.
A strawberry, unless fresh-picked, is bound to exude juice.
These objects are sure to be wanted as evidence.
He is always liable to do idiotic things.
A girl is apt to be a little nervous on her wedding day.
Chrisis is apt to strike suddenly like influenza.