Modals of speculation (past, present, future)

Modals of speculation (past, present, future)

Modals of speculation-deduction

• We can use modal verbs for deduction – guessing if something is true using the available information.

• It shows how certain we are about the possibility.

must have

• We use must have + past participle when we feel SURE about what happened.

• Example: Who told the newspapers about the prime minister's plans? It must have been someone close to him.

• 
  

might have / may have

• We can use might have or may have + past participle when we think it's possible that something happened. 

• Example: I think I might have left the air conditioning on. Please can you check?

• May have is more formal than might have. Could have is also possible in this context but less common.

can't have / couldn't have 

• We use can't have and couldn't have + past participle when we think it's not possible that something happened.

• She can't have driven there. Her car keys are still here.

• 
  

Multiple Choice

Where's Clare? Her bag's here and her computer's still on so she _____ gone home.

• must have

• might have

• can't have

Multiple Choice

I can't remember my password! But I _____ written it in my notebook as sometimes I do that.

• must have

• may have

• couldn't have

Multiple Choice

3. Sorry, I don't know if she's here or not. She was feeling ill so she _____ gone home.

• must have

• might have

• can't have

Fill in the Blanks

She

cleaned the whole house on her own in two hours. She must have had some help.

Fill in the Blanks

Wow! Have you finished all that already? You

been hungry!

Must, might, may, can, and 

could can also be used to speculate about the present or future. Modals for deduction – guessing if something is true using the available information - show how certain we are about the possibility.

Look at the following examples.

• That must be the main entrance. I can see people queuing to get in.

• I've lost my keys. They might be at work or they could be in the car.

• You can't be bored already! You've only been here five minutes. 

Must

• Use must when we feel sure that something is true or it's the only realistic possibility.

• Example: This must be her house. I can see her car in the garage.

might, may, could

• Use might, may or could to say that we think something is possible but we're not sure. 

• She's not here yet. She might be stuck in traffic.

• Note: They all have the same meaning, but may is more formal than might and could.

can't

• Use can't when we feel sure that something is not possible.

• It can't be far now. We've been driving for hours.

Multiple Select

Do you remember my birthday party last year? You _____ remember! It was the same day as your graduation.

• can

• could

• must

Multiple Select

Whose is this coat? It _____ be Paul's. It's way too small for him.

• must

• may

• can't

Multiple Select

Come in and sit down. You _____ be tired after the journey.

• must

• might

• can

Multiple Select

The exam results will be out soon. It _____ be this week or possibly next week.

• must

• might

• can't

Multiple Select

The house isn't hard to find. It's the red one at the end. You _____ miss it!

• must

• might

• can't