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

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