A practical english grammar - Vyssaja skola 1978
Complex modal verb phrases
Sound symbols
Modals are always followed by the base form of a verb. If they are followed by have or be, these auxiliary verbs may in turn be followed by other verb forms, with the result that complex verb phrases consisting of three or more words can be built up.
The modal perfect phrase. This phrase consists of modal + have + participle. Any modal studied in this chapter can be used in this pattern. The modal perfect retains the meaning of the modal, whatever it may be, in addition to the idea of past time that is inherent in the perfect structure. Study these pairs.
Possibility: What can he do with his money?
Past possibility: What can he have done with his money?
Preference: I would rather stay at home.
Past preference: I would rather have stayed at home.*
Condition: I would help you if I could.
Past condition: I would have helped you if I could have.*
Obligation: They ought to repair the roof.
Past obligation: They ought to have repaired the roof.*
* These sentences mention actions that did not occur; the combination of the modal and a past meaning results in a contrary-to-fact assertion.
The modal progressive phrase. When a modal is followed by be + ing-form, the meaning of the progressive phrase is added to that of the modal.
Statement: He is working.
Modal statement:
He may be working.
He should be working.
He will be working.
(etc.)
The modal passive phrase. When the modal is followed by be (or get) + past participle, the resulting phrase combines the meaning of the modal with the passive voice.
This can be done. This could be done.
This will be done. This ought to be done.
This may be done. This might be done.
More complex modal phrases. When have follows the modal, and been follows have, the next word can be either an ing-form or a past participle, depending on whether the construction is passive or not.
He could have been working all morning.
This could have been done yesterday.
You ought to have been studying this morning.
This work ought to have been finished already.
Interrogative and negative patterns with complex modal phrases. In the interrogative, the subject follows the first word in the phrase.
Could this have been done yesterday?
Will they have arrived tomorrow?
The negative particle n’t is attached to the first word in the phrase, the modal.
This couldn’t have been done yesterday.
You won’t be believed if you tell that story.
Couldn’t this have been done yesterday?
Echoes of complex modal phrases. The echo for a complex modal phrase may be the first word only, or it may include two or even three auxiliary verbs, omitting only the “real” verb at the end.
Tom will have left New York next Monday.
Henry will, too. or:
Henry will have, too.
This could have been finished yesterday.
Yes, it could, or:
Yes, it could have, or:
Yes, it could have been.
The echo for a predicate consisting of be + complement must contain a form of be.
Was Mary ill yesterday?
She must have been, otherwise she would have come to school.
(The echo must have would be incorrect in the preceding sentence.)
Is your father at home?
No, but he will be this afternoon. (Not will alone.)
In tag questions, only the first auxiliary verb is used, regardless of the length of the verb phrase in the main sentence.
This could have been done yesterday, couldn’t it?
You shouldn’t have been wasting your time, should you?