Modals: deductions about the past

Do you know how to use modal verbs to express certainty or uncertainty about past events? Enhance your knowledge with a lesson given below and the grammar explanation to guide you better.

Check out these examples to see how must, might, may, could, can't, and couldn't are used for past situations:

• A thunderstorm? That must have been quite an experience!

• We’re not sure if Sarah missed the meeting. She may have been stuck in traffic.

• How could he have lost the keys? He couldn’t have been paying attention.

Grammar explanation - Modals: deductions about the past

We use modal verbs for deduction, which means making a guess about what happened based on the information we have. The modal verb we choose shows how confident we are about the likelihood. This explanation focuses on making deductions about past events.

1. must have

We use must have + past participle when we are certain about what happened.

• Who spilled the coffee on the desk? It must have been someone who was in the office this morning.

• The power must have gone out during the night. The clock is flashing the wrong time.

• Ah, we’ve got fresh bread! Claire must have picked some up earlier.

2. might have / may have

We use might have or may have + past participle when we think there’s a possibility that something happened.

• I think I might have forgotten to lock the door. Can you check?

• They may have missed the train if they left the house late.

May have sounds more formal than might have. Could have can also be used in this context but is less common.

3. can’t have / couldn’t have

We use can’t have and couldn’t have + past participle when we believe something was impossible.

• She can’t have finished all that work in just two hours.

• I thought I saw Mark at the store, but it couldn’t have been him. He’s out of town.

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