7A Past Modals
Make deductions or speculate about past actions.
Must May/Might/Could Can't/Couldn't Should/Ought to
+ have + past participle
(-ed/'3rd column')
7A Past Modals
Must
Used when we are almost sure that something happened or was true.
must + have + past participle
I must have left my phone at Anna's. I definitely remember having it there. You must have seen something. You were there when the accident happened.
7A Past Modals
Used when we think it's possible that something happened or was true.
May/Might/Could
may/might/could+ have + past participle
Somebody might have stolen your wallet when you were getting off the train. I wonder why she's not here. I suppose she could have forgotten about the meeting. He still hasn't arrived. I may not have given him the right directions.
7A Past Modals
Used when we are almost sure that something didn't happen or was impossible.
Can't/Couldn't
can't/couldn't + have + past participle
She can't have gone to work. Her car is still here. You couldn't have seen their faces very clearly. It was too dark.
7A Past Modals
Should/Ought to
Used to express regret or criticism.
should/ought to + have + past participle
We have gone the wrong way. We should have turned left at the traffic lights. It was my fault. I oughtn't to have told you a lie.