AUXILIARY VERBS WITH PERFECT INFINITIVE n The Perfect

AUXILIARY VERBS WITH PERFECT INFINITIVE

n The Perfect Infinitive is used with auxiliary verbs to express assumptions or speculations about the past action. HAVE + PAST PARTICIPLE

It is used: 1. With should, would, might and could to form the perfect conditional in the third type of conditional clauses. If I had seen her I should have invited her. 2. With should or ought to express unfulfilled obligation. He should have helped her. (but he did not) I shouldn’t have gone out. (but I did) n

3. With should/would like to express an unfulfilled wish. I should like to have seen it (but it wasn’t possible). (would is used in the second and third person) 4. With could to express past unused ability. I could have climbed the mountain (but I didn’t).

5. With needn’t to express an unnecessary past action: We needn’t have hurried. Now we are too early. 6. With may/might in speculations about past actions: He may have come. (it is possible that he came) He might have come. (the use of might increases the doubt)

7. With must to express affirmative deduction (conclusion): Someone must have been here recently; these ashes are still warm. 8. With can’t and couldn’t to express negative deduction: He can’t/couldn’t have moved the piano himself.