Indicating importance

4.215 Modals can be used in declarative sentences to say that it is important that something is done. Different modals indicate different degrees of importance.

4.216 'Must' be used in three common ways to talk about the importance of doing something.

You use 'must' with 'you' or 'we' to urge someone to do something, because you feel it is important. 'Must not' is used to urge someone not to do something.

You must come at once.

We must accept the truth about ourselves.

You must not worry.

You mustn't let her suffer for it.

You use 'must' to say that something is required by a rule or law.

People who qualify must apply within six months.

European Community standards must be met.

You use 'must' to say that it is necessary that something happens or is done, in order that something else can happen.

Meadows must have rain.

To identify a poison you must be able either to carry out a chemical analysts or observe the poison at work on the victim.

'Have to', 'have got to', and 'need to' can be used instead of 'must' to talk about the importance of doing something. This is explained in paragraphs 4.243 and 4.249.

4.217 If you want to say that an action will be necessary in the future, you use 'will have to' or 'will need to'.

They will have to pay for the repairs.

Mr Smith will have to make the funeral arrangements.

You will need to cover it with some kind of sheeting.

Electric clocks will need to be reset.

4.218 'Shall have to' is sometimes used instead of 'will have to' after 'I' or 'we'. This is a slightly formal use.

I shall have to speak about that to Peter.

We shall have to assume that you are right.

4.219 'Should' and 'ought to' are used in three different ways when you are talking about the importance of doing something.

You use 'should' or 'ought to' when you are trying to help someone by advising them to do something.

Carton steel knives should be wiped clean after use.

You should claim your pension 3-4 months before you retire.

You ought to try a different approach.

You use 'should' or 'ought to' when you are saying that something is the right or correct thing to do.

We should send her a postcard from Eastbourne.

Whoever discovers the body should contact the family doctor.

We ought to stay with him.

You ought not to do that.

You use 'should' or 'ought to' with 'have' and a past participle to say that something was desirable in the past, although it did not in fact happen.

One sailor should have been asleep and one on watch.

We ought to have stayed in tonight.

A more junior member of staff ought to have done the work.

You also use 'should' and 'ought to' to say that you expect something to happen. This use is explained in paragraph 4.136.

Introducing what you are going to say

4.220 Sometimes you introduce what you are going to say by using a modal followed by a verb such as 'say' of 'ask' which refers to the act of saying something. You can also combine a modal with a verb such as 'think' or 'believe' which refers to the holding of an option.

You use a modal in order to sound more polite, or to indicate your feelings about what you are going to say.

In structures like these, the subject is usually 'I'. Sometimes you use an impersonal structure beginning with 'it' or 'you'. For example, instead of saying 'I ought to mention that he had never been there', you can say 'It ought to be mentioned that he had never been there'.

importance: 'must' 4.221 If you feel strongly that what you are saying is important, you use 'must'.

I must apologise to you.

I must object.

It must be said that it never really came up to expectations.

importance: 'should' and 'ought to' 4.222 If you feel that it is important or appropriate that something is said, you indicate that you are going to say it by using 'should' or 'ought to'.

I should explain at this point that there are two different sorts of microscope.

It should also be said that I learned a great deal from the experience.

I ought to stress that this was not a trial.

Perhaps I ought to conclude with a slightly more light-hearted questions.

politeness: 'can' and 'could' 4.223 If you want to say something during a discussion, you can indicate politely that you are going to say it by using 'can'.

Perhaps I can mention another possibility.

If I can just intervene for one moment.

If you want to be even more polite, you use 'could'.

Perhaps I could just illustrate this by mentioning two cases that I know of personally.

Perhaps I could just ask you this...

4.224 You also use 'can' and 'could' when you are mentioning an opinion or a way of describing something.

'Can' suggests that you approve of the opinion or description.

English can be seen as an expressive discipline.

'Could' is more neutral.

You could argue that this is irrelevant.

You could call it a political offence.

4.225 'May' and 'might' can also be used to mention an opinion or a way of describing something.

'May' suggests that you approve of the opinion or description. It is more formal than 'can'.

This, it may be added, greatly strengthened him in his resolve.

'Might' also suggests that you approve of the opinion or description. You use 'might' when you think there is a possibility that the person you are talking to will disagree with you.

You might say she's entitled to get angry.

That, one might argue, is not too terrible.

4.226 If you are stating an opinion of your own, you can indicate politely that you are going to state it by using 'should'.

I should think it would last quite a long time.

'Would' is used in a similar way, but is less common.

I would guess it may well come down to cost.