This document discusses the use of modal verbs to express different degrees of certainty in English. It explains that: 1) Modals like "must have" and "had to have" express near certainty about past events, while modals like "might" and "may" express less certainty. 2) When speculating about present situations, modals take the base verb form, like "they should be very happy." 3) When speculating about past events, modals take the past participle verb form, like "she could have won the lottery." 4) Modals like "should" and "ought to" express near certainty about future events, using the base verb form, while

1. Modals to Express
Degrees of Certainty
Nosy Neighbors
2
Focus on Grammar 5
Part II, Unit 6
By Ruth Luman, Gabriele Steiner, and BJ Wells
Copyright © 2006. Pearson Education, Inc. All rights reserved.

2. Nosy Neighbors 1
Honey, how can
Mrs. Carson afford
a Ferrari? Isn’t she
a teacher?
I suppose. Or she
could have won
the lottery.
Who knows?
She may have
gotten a big
raise at work.
Well, she might
have inherited
some money from
her family.
I doubt it. She
had to have
robbed a bank!
You could
be right.

3. Nosy Neighbors 2
I haven’t
seen the
Chins for a
month.
They may
have been
abducted by
aliens.
Or they
might be
staying with
their son for
a while.
Well, they
couldn’t have
gone on
vacation. The
dog is still there.
Hmmm. They
must have
moved to an
exotic island.
Then they
should be
very happy.

4. Speculating about the Present
Modals speculating about the present are
followed by a base form verb.
Then they should be very happy.
base form verb
You could be right.

5. Speculating about the Past
Modals speculating about the past are
followed by the past participle.
past
participle
She could have won the lottery.
She may have gotten a big raise.

6. Review
Modals and modal-like expressions express
degrees of certainty.
Degree of Certainty
certain near
certainty
near
impossibility
less
certain
no
modal
must
have to
have got to
can’t
couldn’t
may
might
could

7. Certainty
Modals and modal-like expressions express degrees
of certainty. Don’t use a modal for 100% certainty.
Mrs. Carson got a raise.
The Chins went on vacation.

8. He had to have robbed a
bank.
They must have moved to
an exotic island.
Near Certainty
There are several modals that express near certainty,
including must have and had to have.

9. Near Impossibility
There are several modals that express near certainty
that something is impossible, including couldn’t have
and can’t.
They just
moved here.
They left all the
lights on!
They couldn’t have moved away.
They can’t be out of town.

10. Less Certainty
There are several modals that express less certainty,
including may, and might.
They may have been abducted
by aliens.
They might be staying with their
son.

11. Practice 1
Use modals to suggest reasons for
these classroom situations. Speculate
on what might have happened.
Example: One of your classmates is late.
She must have gotten stuck in traffic.
There was a big accident.
1. You smell smoke.
2. The teacher is angry.
3. The desks are shaking.
4. You can’t find your textbook.
5. The lights go out.

12. She ought to take us for a drive soon.
Modals speculating about the future are also followed
by a base form verb. The modals should and ought
to express near certainty.
Speculating about the Future 1
That Ferrari should last a lifetime.

13. Speculating about the Future 2
Use may, might, and could when you are
less certain.
The Chins may not return.
The house might get sold.
They could move next month.

14. Practice 2
Use modals to express future
possibilities about these
present situations.
Example: We shop for food at grocery stores.
‘Smart’ kitchens might calculate what we need and
order it electronically. In the future, household
computers may do all our shopping.
1. Ordinary people don’t travel in space.
2. Houses are made of wood.
3. People pay for products with cash or credit cards.
4. Our fingerprints provide identification.

15. References
Copyright © 2006 Pearson Education and
its licensors. All rights reserved.