Modals of deduction and past modals
must have, can't have, might have, should have, could have.
| Structure | Meaning | Example |
|---|---|---|
| must + base | I'm sure it's true (present) | He must be tired. |
| can't + base | I'm sure it's not true (present) | That can't be true. |
| might / may / could + base | perhaps | She might be at home. |
| must have + p.p. | I'm sure it happened | He must have missed the bus. |
| can't have + p.p. | I'm sure it didn't happen | She can't have forgotten. |
| might have + p.p. | perhaps it happened | They might have left. |
| should have + p.p. | it was the right thing but didn't happen (criticism, regret) | You should have told me. |
| could have + p.p. | it was possible but didn't happen | We could have won. |
Test yourself
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Deduce: I'm sure he forgot.
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He must have forgotten. -
Criticise: You didn't help me, but it was possible.
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You could have helped me. -
Deduce: I'm sure she didn't say that.
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She can't have said that. -
Correct: I should of called you.
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I should have called you.