1. Past modals of deduction,
speculation and regret
Intermediate 2

2. Do you remember how to form the past with modal
verbs?
These are the modal verbs we need:
• Could
• Can / can’t
• May / might
• Must
• Should / shouldn’t have

3. You only need to add…
• He could have passed his driving test, but he was too nervous.
• Lidia must have done something to her hair; she looks different.
• I should have apologized when I had the chance. Now John won’t
speak to me.
Could / couldn’t
Can / can’t
May / might
Must
Should / shouldn’t
have
have Past participle

4. Expressing speculation or deduction
Depending on the modal verb we use, we’ll express different ideas. To express
speculation / deduction, we use: could, may, might, must and can’t.
There are differences between them; depending on the one we use we are more
sure or less sure about what we say.
Could; may;
might have
+ past part.
Must have
+ past part.
Can’t have
+ past part.
Possible past
actions.
Almost certain
past actions.
Impossible past
actions. Always
negative.

5. • I’m not sure where Jake has gone today. He said he wanted to go to the movies,
but his brother wanted to go for a beer… He might have gone with his
brother at the end.
• (We’re not very sure of this because we have mixed information, but we
are guessing).
We could also say: …he may have gone / could have gone…

6. • John and Sarah must have gone back together; I saw them
holding hands this morning.
• (We are almost sure about this, because we have
evidence).

7. • My neighbours can’t have gone out! I definitely saw Mrs
Thompson through the window today!
• (We are certain that the neighbours were at home, so it is
impossible that they went out)

8. Expressing regret: should / shouldn’t have
• Sometimes people make mistakes that regret. So when they look at
the past, they express this idea with should / shouldn’t have + past
participle.
• I shouldn’t have eaten so much cake… now I feel bloaty.
• I should have been less impulsive. I’ve spent too much, and I don’t even
need most of these things!

9. Let’s practice!
1. I’m sure you dropped your wallet at the bus stop.
You must have dropped your wallet at the bust stop.
2. Maybe Joanna missed the last bus.
Joanna …………………… the last bus.
3. Emma was wrong not to tell you the answer.
Emma ……………………………. you the answer.
4. I'm sure Diana didn’t take your books.
Diana …………………………………. your books.
5. Perhaps David didn’t notice you.
David ……………………………………….. noticed you.
6. It was a bad idea for us to be rude to the policeman!
We ………………………………………. been rude to the
policeman!
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.

10. Let’s practice!
2. Maybe Joanna missed the last bus.
Joanna could / might / may have missed the last bus.
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.

11. Let’s practice!
3. Emma was wrong not to tell you the answer.
Emma should have told you the answer.
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.

12. Let’s practice!
4. I'm sure Diana didn’t take your books.
Diana can’t have taken your books.
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.

13. Let’s practice!
5. Perhaps David didn’t notice you.
David may / might not have noticed you.
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.

14. Let’s practice!
6. It was a bad idea for us to be rude to the policeman!
We shouldn’t have been rude to the policeman!
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.

15. Let’s practice!
2. Maybe Joanna missed the last bus.
Joanna could / might / may have missed the last bus.
3. Emma was wrong not to tell you the answer.
Emma should have told you the answer.
4. I'm sure Diana didn’t take your books.
Diana can’t have taken your books.
5. Perhaps David didn’t notice you.
David may / might not have noticed you.
6. It was a bad idea for us to be rude to the policeman!
We shouldn’t have been rude to the policeman!
Complete the second sentence so
that it means the same as the first.
Use no more than three words.
Contractions count as one word.