Present and Past Speculation

REQUEST

DEDUCTION - ASSUMPTION

PROHIBITION

SPECULATING ABOUT THE PAST

OBLIGATION

SUGGESTIONS

MODALS and PRESENT AND PAST SPECULATION

Can I go to the cinema tonight?

Could you lend me a book?

It couldn't have been John because he's in London.

He drives a Ferrari. He must be rich.

You can't eat more chocolate.

You should never repeat what you've just said.

When speculating about a present situation, we use a modal verb + infinitive. We use:

• must, to express a strong belief that something is true:

• might, may and could, when we think that it’s possible that something is true:

• can’t, to express a strong belief that something isn’t true:

When speculating about a past situation, we use a modal verb + have + a past participle verb. We use:

• must have, to express a strong belief that something happened:
• might have, may have and could have, when we think that it's possible that something happened:
• can’t have and couldn’t have, to express a strong belief that something didn’t happen:

Lions can be dangerous.

This vase could be very valuable.

He may be waiting for us at the airport.

You must / have to study harder!

I should be studying but I'm tired.

You could give Mary some flowers.

Shall we buy her a hat?

Speculating about the present

POSSIBILITY

ABILITY - CAPABILITY

May I leave the room?

Would you please close the door?

I can swim.

I could swim when I was 5.

John might come to your party.

Would John come with us if we asked him?

PERMISSIONS

You can go to the cinema.

In the evenings we could watch TV.

ADVICE

You should go to the doctor!

NECESSITY

We must buy some more vegetables.

GRAMMAR

GRAMMAR

John must be happy working at the zoo.

The lions might / may / could be hungry now.

It can’t be a domestic cat. It’s too big.

Lucy might / may / could have missed the train.

Peter can’t/couldn’t have gone home.

You must have lost your mobile at the zoo.

MAY vs MIGHT: MAY:

• Used when you're talking about a possible event
• Present tense form

• Used when you're talking about events that are hypothetical or possible but very unlikely
• Past tense of MAY
• Best to use in the past tense