Tuesday, February 11, 2020

Spoken English study material.

Modals: can't have/ must have / might have


Introduction

We use the modal verbs "must have", "can't have" and "might have" to make guesses or deductions about an action in the past that we believe has definitely happened, has definitely not happened or possibly happened, based on our knowledge, information or evidence, or lack of it.

We use "must have", "can't have" and "might have" in the same way as the present perfect - the action we are describing happened, or did not happen, in the past and is still true in the present.

  • "must have": we believe the action definitely happened.
    • "She must have left the house by now; it’s nearly 11 o'clock."
    • She usually leaves her house before 11 o’clock so I deduce that she has definitely left the house.

  • "can't have": we believe the action definitely did not happen (the opposite of "must have").
    • "She can’t have left the house yet because her car is still outside."
    • She usually takes her car so I deduce that she has definitely not left the house because her car is outside (the opposite of "must have").

  • "might have": we believe it's possible that the action happened, but we don't know.
    • "She might have gone to the shops."
    • It is possible that she has gone to the shops, but it is also possible that she has gone somewhere else.

  • "might not have": we believe it's possible that the action did not happen, but we don't know.
    • "He might not have finished his exams yet."
    • It is possible that he has not finished his exams, but it is also possible that he has finished them.

  • "might have" / "might not have" in the third conditional structure: to imagine the possible result of an unreal situation in the past.
    • "If I had known about the traffic problems, I might have taken a different route."
    • The clause with might have describes the possible result of the unreal situation described by the "if" clause. The real situation and result: I didn’t know about the traffic problem so I am imagining the possibility of taking a different route if I had known.

Form

We use "must have", "can't have" and "might have" with the past participle of the main verb:
  • subject + "must have" + past participle
  • subject + "can't have" + past participle
  • subject + "might (not) have" + past participle


likelihood of the deductionsubjectmodalmain verb (past participle)
definiteI
You
We
They
He / She / It
must havebeen
seen
taken
spoken
to France.
the movie.
the medicine.
to the manager.
definitely notcan't have
possiblemight (not) have

Positive and negative forms

We use "must have" in the positive form only: we believe that the action definitely happened.

We use "can't have" in the negative form only: we believe that the action definitely did not happen (the opposite of "must have").

We can make a negative form of "might have" with "not": we believe it is possible that the action did not happen, but it is also possible that it did. "might not" can be contracted to "mightn't".

Using "by now" and "yet"

We can use "by now" with positive forms e.g.
  • "He must have done it by now."
  • "She might have done it by now."

We can use "yet" with negative forms e.g.
  • "He can't have done it yet."
  • "He might not have done it yet."

Question form

We don't use "must have" or "can't have" in question form because we use them for definite beliefs. We use "might have" for question forms:

Positive question form

modalsubject"have"main verb (past participle)
MightI
you
we
they
he / she / it
havebeento France?

Practice

Complete the sentences with "can't have", "must have" or "might (not) have" using the verb in brackets:

  • He  hard for his exams because his results were very good. (study)
     
  • They  the instructions because they looked confused. (not understand)
     
  •  home late last night because she was very tired this morning. (get)
     
  •  they  to the wrong place? (go)
     

No comments:

Post a Comment

Workshop on Research Methodology,Academic Writing and Publishing

Research Methodology, Academic Writing and Publishing in English –  A One Month Online Workshop-cum-Certificate Course As part of a slew of ...