SEQUENCE OF TENSES (VERBS AND VERBALS).
Lack of logical sequence in verbs.
446. If one or more verbs depend on some leading verb, each should be in the tense that will convey the meaning intended by the writer.
In this sentence from Defoe, "I expected every wave would have swallowed us up," the verb expected looks forward to something in the future, while would have swallowed represents something completed in past time: hence the meaning intended was, "I expected every wave would swallow" etc.
Also in verbals.
In the following sentence, the infinitive also fails to express the exact thought:—
I had hoped never to have seen the statues again.—Macaulay.
The trouble is the same as in the previous sentence; to have seen should be changed to to see, for exact connection. Of course, if the purpose were to represent a prior fact or completed action, the perfect infinitive would be the very thing.
It should be remarked, however, that such sentences as those just quoted are in keeping with the older idea of the unity of the sentence. The present rule is recent.
Exercise.