Past modal verbs of deduction |
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Past modal verbs of deduction
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Past modal verbs of deduction – Grammar chart
We can use some modal verbs + infinitive to talk about how certain we are that something is or is not true. We can also use some modal verbs + have + past participle to talk about how certain we are that something was or was not true in the past. Must have doneWe use must have + past participle to say that we are quite sure that something was true or happened in the past. I can’t find my wallet! I must have dropped it in the taxi. You must have had a real scare when you saw the crocodile.Can’t have done We use can’t/couldn’t have + past participle to say that we are quite sure that something did NOT happen or was NOT true in the past. You can’t/couldn’t have seen John last night. He was in hospital. She can’t/couldn’t have passed the test. She didn’t even open the books.Note that for negative deduction we use can’t (NOT mustn’t) He can’t be that famous. (NOT He mustn’t be that famous.)Could/might/may have done We use might/may have + past participle to say that it’s possible that something was true or happened in the past. It’s been three days. They might/may have finished painting the house by now. If they left at 9, they might/may have already arrived.Note that we use might not or may not (NOT could not) to talk about a negative possibility. She might/may not have heard us. Knock again.Should/ought to have done We use should have/ought to have + past participle to talk about a situation expected to happen in the past. This form is normally used for criticism. You should/ought to have already packed your things. We’re going to be late. He should/ought to have studied more. Nobody fails if they study. |
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