Modals of deduction in the present
We use the modal verbs Must/could/might , may and can’t to talk about different degrees of certainty. Remember that they are followed by the infinitive without to.
could/may and might we use them to speculate or to express possibility or uncertainty.
She is very late, she might be lost
Must is used to make a logical deduction about somethin in the present and we deduce that something is true beyond all doubt.
He must be sick today, he never misses classes.
can’t is used when we deduce that something is completely impossible.
he can’t be him because he hasn’t got his driving licence.
Modals of deduction in the past
We can use modal verbs to talk about how sure or unsure we are about something in the past just as we use modals in the present with a slight change in the form.
He must be really happy about his promotion. (present deduction)
He must have been very happy when he was told about his promotion. (past deduction)
When we use a modal verb to talk about a situation where we are not expressing a fact but we are using deduction the form is MODAL + have + past participle
Might have/may have/could have + past participle
We use ‘might have/may have/could have + past participle’ when we are not sure about something but we think it was possible.
He was supposed to be here an hour ago but he could have been stuck in a traffic jam.
He may have said he was coming but I can’t really remember. I wasn’t listening.
I might have been here when I was a child but I can’t really remember.
Must have + past participle
We use ‘must have + past participle’ when we are quite sure about something.
You must have been very pleased when you received the results of your exams.
He must have forgotten his phone at home again. He’s not answering.
I must have left my keys in the car. I can’t find them.
Can’t have + past participle
We use ‘can’t have + past participle’ for things that we are sure did not happen in the past.
I can’t have left my phone at work. You phoned me when I was walking to my car. That’s it. It must be in the car.
You can’t have seen him this morning. He was with me all the time.
She can’t have liked the show. She hates musicals.
Now put the correct modal in these sentences.
- 1 – She ___ misunderstood my directions. Why else is she late?
- 2 – He ___ gone to the beach. He hates being in the sun.
- 3 – I ___ written down the number incorrectly. I’ve just called a hospital not the restaurant.
- 4 – They ___ been at the cafe but I didn’t see them.
- 5 – John ___ been very happy when he found out he was going to be a father. He’s wanted this for a long time.
- 6 – He ___ gone to the city centre. He did say he wanted to go shopping.
- exercise one exercise two exercise three exercise four
- Pictures to use the modals of deduction