Collins Cobuild English Grammar (113 page)

…knowledge which
could not
have been gained in any other way.
It
couldn’t
possibly be poison.
He
cannot
know everything that is going on.
You
can’t
talk to the dead.

strong assertion:
could not
with comparatives

5.127
   
Could
is sometimes used in negative constructions with the comparative form of an adjective. You use
could
like this to say that it is not possible for someone or something to have more of a particular quality.

I
couldn’t
be happier.
You
couldn’t
be more wrong.
The setting
couldn’t
have been lovelier.
He
could hardly
have felt more ashamed of himself.

talking about the future

5.128
   The following paragraphs explain how modals are used when you are talking about possible future situations. The uses of
must
,
cannot
,
could
,
might
, and
may
are similar to their uses when you are talking about possible situations in the present.

certainty:
will

5.129
   You use
will
to say that something is certain to happen or be the case in the future.

They
will
see everything.
The price of food
will
go up.
The service
will
have been running for a year in May.

Be going to
can also be used to say that something is certain to happen in the future. This use of
be going to
is dealt with in paragraph
5.231
.

certainty:
shall
,
must
, and
cannot

5.130
   
Shall
is also used to say that something is certain to happen. You usually use
shall
when you are talking about events and situations over which you have some control. For example, you can use
shall
when you are making a resolution or a promise.

I
shall
be leaving as soon as I am ready.
Very well, my dear. You
shall
have the coat.
Of course he
shall
have water.
‘You’ll make a lot of money.’ – ‘I
shall
one day.’

This usage is considered very formal in American English and is not often used.

You use
must
to say that something is certain to happen because of particular facts or circumstances.

This research
must
eventually lead to computer decision-making.

You use
cannot
to say that something is certain not to happen because of particular facts or circumstances. You do not use
must not
.

A team
cannot
hope to win consistently without a good coach.
The bad weather
can’t
last.

expectation:
should
and
ought to

5.131
   You use
should
or
ought to
to say that you expect something to happen.

She
should
be back any time now.
This course
should
be quite interesting for you.
The Court of Appeal
ought to
be able to help you.
It
ought to
get better as it goes along.

Should
and
ought to
are also used when you are talking about the importance of doing something. This use is explained in paragraph
5.213
.

future possibility:
could
,
might
, and
may

5.132
   You use
could
,
might
, or
may
to say that it is possible that a particular thing will happen.

England’s next fixture in Salzburg
could
be the decisive match.
The river
could
easily overflow.
They
might
be able to remember what he said.
Clerical work
may
be available for two students who want to learn about publishing.

If you put
well
after
could
,
might
, or
may
, you are indicating that it is fairly likely that something will happen or be the case.

When it is finished it
may well
be the largest cathedral in the world.
We
might well
get injured.

If you put
possibly
or
conceivably
after
could
,
might
, or
may
, you are indicating that it is possible, but fairly unlikely, that something will happen or be the case.

These conditions
could possibly
be accepted.
Rates
could conceivably
rise by as much as a whole percentage point.

talking about the past

5.133
   The following paragraphs explain how you use modals when you are talking about possible situations in the past.

expectation:
should have
,
ought to have

5.134
   You use
should
or
ought to
with
have
to say that you expect something to have happened already.

Dear Mom, you
should have
heard by now that I’m O.K.

You also use
should
or
ought to
with
have
to say that something was expected to happen, although it has not in fact happened.

Muskie
should have
won by a huge margin.
She
ought to have
been home by now.

possibility:
would have

5.135
   You use
would
with
have
to talk about actions and events that were possible in the past, although they did not in fact happen.

Denial
would have
been useless.
I
would have
said yes, but Julie persuaded us to stay at home.
You
wouldn’t have
pushed him, would you?

possibility:
could have
,
might have

5.136
   You use
could
or
might
with
have
to say that there was a possibility of something happening in the past, although it did not in fact happen.

It
could have
been awful.
I
could
easily
have
spent the whole year on it.
You
could have
got a job last year.
A lot of men died who
might have
been saved.
You
might have
found it very difficult.

uncertainty:
could have
,
might have
,
may have

5.137
   You also use
could
,
might
, or
may
with
have
to say that it is possible that something was the case, but you do not know whether it was the case or not.

It is just possible that such a small creature
could have
preyed on dinosaur eggs.
They
might have
moved house by now.
I
may have
seemed to be overreacting.

negative possibility:
might not have
,
may not have

5.138
   You use
might not
or
may not
with
have
to say that it is possible that something did not happen or was not the case.

They
might not have
considered me as their friend.
My father
mightn’t have
been to blame.
The parents
may not have
been ready for this news.

impossibility:
could have
with negative

5.139
   You use
could
with a negative and
have
to say that it is impossible that something happened or was the case.

It
couldn’t have
been wrong.
The money was not, and
never could have
been, the property of the organization.

Talking about permission

permission:
can

5.140
   
Can
is used to say that someone is allowed to do something.

You
can
drive a van up to 3-ton capacity using an ordinary driving licence.

If you are giving permission for something, you use
can
.

You
can
borrow that pen if you want to.
You
can
go off duty now.
She
can
go with you.