Indicating possibility

4.118 The following four sections explain the different ways in which modals are used to talk about the possibility of something happening or being done.

Paragraphs 4.119 to 4.122 explain how 'can' and 'could' are used to talk about the ability of a person or thing to do something.

Paragraphs 4.123 to 4.145 explain how modals are used to express degrees of certainty about past, present, and future situations and events.

Paragraphs 4.146 to 4.149 explain how modals are used to say that something is permissible.

Paragraphs 4.150 to 4.157 explain how modals are used to say that something is forbidden or unacceptable.

Indicating ability

4.119 'Can' is used to say that someone has a particular skill or ability.

You can sit read and write.

Some people can ski better than others.

He cannot dance.

...the girl who can't act.

'Could' is used to say that someone had a skill or ability in the past.

...the good old days when everyone could read, write and do arithmetic.

I could barely walk.

He could kick penalty goals from anywhere.

4.120 'Can' is also used to say that someone is aware of something through one of their senses.

I can see you.

I can smell it. Can't you?

'Could' is used to say that someone was aware of something through one of their senses on a particular occasion in the past.

I could see a few faint stars in a clear patch of sky.

I could feel my heart bumping.

Everyone in the village could hear her voice.

4.121 'Can' and 'could' are also used to say that something or someone is capable of having a particular effect, or of behaving in a particular way.

It can be very unpleasant.

Art can be used to communicate.

I think unions can be stupid, intransigent, pigheaded.

He could be very stiff, could Haggerty.

He could really frighten me, and yet at the same time he could be the most gentle and courteous of men.

WARNING 4.122 You cannot use 'can' or 'could' to say that someone or something will have a particular ability in the future. Instead you use 'be able to' or 'be possible to'.

'Be able to' and 'be possible to' can also be used to talk about someone's ability to do something in the present or the past.

'Be able to' and 'be possible to' are dealt with in paragraphs 4.228 to 4.235.

Indicating likelihood

4.123 The following, paragraphs explain how modals are used to express different degrees of certainty about past, present, and future situations and events.

Paragraphs 4.124 to 4.131 explain the main ways in which modals are used to express degrees of certainty.

Paragraphs 4.132 to 4.138 explain special uses of modals when talking about possible future situations.

Paragraphs 4.139 to 4.145 explain special uses of modals when talking about possible situations in the past.

assumption: 'will' and 'would' 4.124 You use 'will' when you are assuming that something is the case, and you do not think there is any reason to doubt it.

Those of you who are familiar with the game will know this.

He will be a little out of touch, although he's a rapid learner.

Most listeners will have heard of hormones.

Similarly, you use 'will not' or 'won't' when you are assuming that something is not the case.

The audience will not be aware of such exact details.

You won't know Gordon. He's our new doctor.

After 'you', you can use 'would' instead of 'will', if you want to be more polite.

You would agree that the Untied Stares should be involved in assisting these countries.

certainty: 'would' and 'should' 4.125 You also use 'would' to say that something is certain to happen in particular circumstances.

Even an illiterate person would understand that.

Few people would agree with this as a general principle.

A picnic wouldn't be any fun without you.

Alter 'I', you can use 'should' instead of 'would'.

The very first thing I should do would be to teach you how to cook.

I should be very unhappy on the continent.

belief: 'must' and 'cannot' 4.126 You use 'must' to indicate that you believe something is the case, because of particular facts or circumstances.

Oh, you must be Sylvia's husband.

Fashion must account for a small percentage of sales.

This article must have been written by a woman.

When you are indicating that something is not the case, you use 'cannot'. You do not use 'must not'. (See paragraph 4.130.)

The two conflicting messages cannot possibly both be true.

You can't have forgotten me.

He can't have said that. He just can't.

4.127 You use 'could', 'might', or 'may' to say that there is a possibility of something happening or being the case. 'May' is slightly more formal than 'could' or 'might'; otherwise there is very little difference in meaning between these modals.

Don't eat it. It could be a toadstool.

His route from the bus stop might be the same as yours.

In rare cases the jaw may be broken during extraction.

4.128 If you put 'well' after 'could', 'might', or 'may', you are indicate that it is fairly likely that something is the case.

It could well be that rich people treasure peace more highly than poor people.

You might well be right.

I think that may well have been the intention.

4.129 You use 'might not' or 'may not' to say that it is possible that something is not the case.

He might not be in England at all.

That mightn't be true.

That may not sound very imposing.

4.130 You use 'could not' or 'cannot' to say that it is impossible that something is the case.

...knowledge which could not have been gained in any other way.

It couldn't possibly be poison.

Kissinger cannot know what the situation is in the country.

You can't talk to the dead.

4.131 '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.

4.132 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.

4.133 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 4.237.

certainty: 'shall' 4.134 '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.'

certainty: 'must' and 'cannot' 4.135 You use 'must' to say that something is certain to happen because of particular facts or circumstances.

Computer interviewing and rudimentary computer diagnosis 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'.

Europe cannot hope to forge a united defence policy without first setting its internal quarrels.

The repression can't last.

expectation: 'should' and 'ought to' 4.136 You use 'should' or 'ought to' to say that you expect something to happen.

We should be at Briceland by dinner time.

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 4.219.

possibility: 'could', 'might', and 'may' 4.137 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.

4.138 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 4.139 The following paragraphs explain how you use modals when you are talking about possible situations in the past.

4.140 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.

4.141 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 talked us into staying at home.

You wouldn't have pushed him, would you?

4.142 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.

4.143 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 of not.

It is just possible that such a small creature could have preyed on dinosaur eggs.

Grandpapa might have secretly married Pepita.

I may have seemed to be overreacting.

4.144 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 pregnancy.

4.145 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 Workers' Party.