Modal Verbs - Deductions about the past

Modal Verbs Deductions about the past

Do you know how to use modal verbs to show how certain you are about past events? Let's look at some examples to see how must, might, may, could, can't, and couldn't are used in the past.

An earthquake? That must have been terrifying!

We don't know for sure that Alex broke the coffee table. It might have been the dog.

How did she fail that exam? She can't have studied very much.

Grammar explanation

We can use modal verbs for deduction – guessing if something is true using the available information. The modal verb we choose shows how certain we are about the possibility. This page focuses on making deductions about the past.

Lorem ipsum dolor sit amet

might have / may have

can't have / couldn't have

must have

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

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

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

Grammar explanation

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

must have

The thief must have had a key. The door was locked and nothing was broken.

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

Oh, good! We've got milk. Mo must have bought some yesterday.

Lorem ipsum dolor sit amet

might have / may have

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

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

Police think the suspect may have left the country using a fake passport.

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

Lorem ipsum dolor sit amet

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.

I thought I saw Adnan this morning but it couldn't have been him – he's in Greece this week.

Andrés Orlando Blanco Marín

Teacher

Visit my website

My name is Andrés Blanco and my work experience includes 15 years as an English Professor in ESP (English for Specific Purposes) at Universidad del Valle, a short time at SENA and Uniminuto and 5 years as a full-time teacher at Universidad Cooperativa de Colombia (UCC) with the communicative approach. Also, at the UCC, I was in charge of more than 20 online English courses, using LMS like BlackBoard and BrigthSpace. I earned a degree as a Specialist in Translation and I'm studying a master's degree at UNIR related to the use of ICTs in education. Currently, I'm working in the B.A in teaching English as a Foreign Language at UNAD.

Education

Experience

English teacher

Universidad del ValleCali, Colombia