Expressing Certainty, Possibility, and Advisability in the Past Using Modals + Perfective

Have you ever wondered how to express certainty, possibility, or advisability about past events? In English Dialogue: Expressing Past Probability With Modals + Perfective, you have noticed the use of modals + perfective in English conversation to express certainty, possibility, and advisability in the past. Look at the following phrases:

• ... must have forgotten ....
• ... might have lost ....
• ... may have left ....
• ... should have been ....

The phrases above are great examples of how modals + perfective work. Let’s dive deeper into this topic and learn how to use them effectively!

Structure of "Modals + Perfective"

A. Affirmative / positive sentence:

Subject	Modals	have	past participle
I We You They He She It Etc.	may might ought to must could should	have	been slept arrived finished forgotten left gone Etc.

B. Interrogative sentence / question:

Question words	Modals	Subject	have	past participle
Who What How Where When Etc.	may might must could should	I we you they he she it Etc.	have	been? slept? arrived? finished? forgotten? left? gone? Etc.

C. Negative sentence:

Subject	Modals + not	have	past participle
I We You They He She It Etc.	may not might not ought not to must not (mustn't) could not (couldn't) should not (shouldn't) needn't	have	been slept arrived finished forgotten left gone Etc.

Usage of "Modals + Perfective"

• May have + past participle ➡️ expresses less than 50% certainty.
  Example: I may have left my umbrella in the coffee lounge.
• Might have + past participle ➡️ expresses less than 50% certainty.
  Example: I might have lost it anywhere.
• Ought to have + past participle ➡️ expresses:
  • advisability
    Example: You ought to have talked to your manager, but you didn't.
  • 90% certainty/expectation
    Example: She ought to have done well in the test because she was well prepared.
• Must have + past participle ➡️ expresses 95% certainty/logical conclusion
  Example: You must have lost your umbrella, not your briefcase.
• Could have + past participle ➡️ expresses:
  • less than 50% certainty
    Example: I suppose someone could have picked it up before I rang.
  • unfulfilled suggestion (positive sentence only)
    Example: You could have talked to me before making the decision.
  • impossibility (negative only)
    Example: He couldn't have done such a silly thing.
• Should have + past participle ➡️ expresses:
  • advisability/unfulfilled expectation
    Example: He should have worked harder for the test, but he didn't.
  • 90% certainty/expectation
    Example: She should have done well in the test because she was well prepared.
• Needn't have + past participle ➡️ expresses lack of necessity.
  Example: You needn't have worried all day.

Examples Sentences in Context

Practice this dialogue and pay attention to what modal + perfective structures imply.

Barbara: Yesterday I walked home from work, because I had no money for the bus.
Bill: You needn't have walked home yesterday. I could have lent you some money.
Barbara: I didn't like to borrow money from you.
Bill: Oh, but you should have asked me.

Practice Exercises

D.1. Select the correct modal + perfective form to complete the dialogues below.

1. Tom: Where was Mary yesterday? She wasn't at work.
   Bob: She ... sick yesterday.
   1. must have been
   2. needn't have been
2. Lucy: Betty isn't home.
   Ann: She ... to the shops.
   1. may have gone
   2. needn't have gone
3. Andy: Bob hasn't arrived yet.
   Bill: He ... in a traffic jam at this busy hour.
   1. ought to have been caught
   2. could have been caught
4. Lisa: I didn't know that the meeting would be postponed to next week.
   Mary: Yes. You ... the room today.
   1. might not have prepared
   2. needn't have prepared
5. Hadi: I think I've lost my key. I put it in my pocket after locking the room.
   Mary: You ... it anywhere.
   1. must have dropped
   2. should have dropped
6. Betty: He hasn't arrived yet. I assume he's lost his way.
   Rosa: I think so. He ... his way.
   1. must have lost
   2. needn't have lost
7. Jim: Nancy hasn't received the email.
   Bill: Really? It ... to the wrong address.
   1. ought to have gone
   2. may have gone
8. Dave: Bella didn't call her office when she was away from work yesterday.
   Gary: That was bad. She ... her boss.
   1. must have informed
   2. should have informed
9. Sam: I worked until late last night.
   Greg: You ... so hard. The report is due next week.
   1. could have worked
   2. needn't have worked
10. Rea: Did she phone the police?
    Lori: No. She ..., but she didn't.
    1. must have phoned
    2. should have phoned

D.2. Change the verbs

Rewrite the following sentences in the past using the modal + perfective form (modal + have + past participle). The first one has been done for you.

1. That must be a very interesting play.
   That must have been a very interesting play.
Now, rewrite the following sentences:
2. Joan may not remember the number.
3. John might forget to do the shopping.
4. He needn't do that job.
5. You could borrow my laptop.
6. She should get to work on time.
7. They ought to tell me.
8. You needn't shout so loudly.
9. He should knock at the door before coming in.
10. She may know the answer.

^{Prev: BSE SMK Kelas XII, 7/3/11, 10:34 AM, PV 2042}