Lesson 22 · Lesson guide
Modals of Deduction: Must, Might, Can’t
Hello, my dear student!
Hello! Doctors are detectives. They look at the evidence (a high temperature, a cough, a rash) and decide what is probably true: “It must be flu.” “It might be an allergy.” “It can’t be food poisoning.”
In this lesson you use must, might, may, could and can’t to say how sure you are. These words are everywhere in IELTS: speakers in Listening say “it might be a virus”, Reading passages say “scientists believe the cause may be biological”, and in Speaking Part 3 you will often need to guess: “Why do you think people sleep less these days?”
Be careful with one thing: the opposite of “must be” is not “mustn’t be” but “can’t be”.
See you in the exercises,Your teacher
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How sure are you?
~100%
must
The evidence is strong: you are almost certain it is true.
- He has a fever and a cough. He must have flu.
~50%
might, may, could
It is possible, but you are not sure. The three words mean almost the same.
- It might be an allergy.
- It could be a virus.
~0%
can’t
The evidence shows it is impossible. Not mustn’t: mustn’t means “not allowed”.
- She ran ten kilometres this morning. She can’t be ill.
Now
must / might / can’t + be + -ing
A guess about something happening now.
- The phone’s engaged. She must be talking to the doctor.
Remember!
must = I’m sure it’s true. might / may / could = it’s possible. can’t = I’m sure it isn’t true.
Careful language for essays
This may be because…
One reason might be that…
It could be argued that…
This cannot be the only explanation.
Common mistakes
Not: He mustn’t be a doctor. He’s only sixteen.Say: He can’t be a doctor. He’s only sixteen.
Sure it isn’t true → can’t.
Not: She might sleeping.Say: She might be sleeping.
Modal + be + -ing.
Not: It must to be a virus.Say: It must be a virus.
Modal + verb (no to).
Check yourself
“She’s just had lunch. She ___ be hungry.”
Which three words mean “it’s possible”?
Now it’s your turn!
8 short parts, each a little harder than the one before. Take your time: mistakes are how we learn.
— Your teacher