Must, to Have to and to Be to Compared

I. The verbs ‘must’, ‘to have to’ and ‘to be to’ have one meaning in common, that of obligation.

a) In the present tense verbs come very close to each other in their use though they preserve their specific shades of meaning.

Thus ‘must’ indicates obligation or necessity from the speaker’s point of view, i.e. it expresses obligation imposed by the speaker: I must do it. (I want to do it.)

‘To have to’ expresses obligation or necessity imposed by circumstances: What a pity you have to go now. (It’s time for you to catch your train.)

‘To be to’ expresses obligation or necessity resulting from an arrangement: We are to wait for them at the entrance. (We have arranged to meet there.)

 

b) In the past tense, however, the difference in the use of the three verbs is quite considerable. ‘Must’ has no past tense. It is used in past-time contexts only in reported speech: He said he must do it himself.

‘Had + infinitive’ is generally used to denote an action which was realized in the past as a result of obligation or necessity imposed by circumstances: I had to sell my car. (It was necessary for me to do it because I needed money.)

‘Was / were + infinitive’ is used to denote an action planned for the future which is viewed from the past. The action is not realized in the past and the question remains open as to whether it is going to take place or not: We were to meet him at the station. (It is not clear from the sentence if the action will take place or not.)

If the speaker wishes to make it clear at once that the plan was not fulfilled, the perfect infinitive is used to show that: We were to have met him at the station. (That means that we failed to meet him.)

 

Need

We can use ‘need’ as an ordinary verb or as a modal verb (followed by a bare infinitive). As a modal verb it doesn’t change its tense and doesn’t add ‘-s’ for the third person singular. Compare: I needed to leave early. You needn’t speak so loudly. She’s thirsty. She needs a drink.

When it is a modal verb ‘need’ is most commonly used in negative sentences, often with verbs like ‘bother’, ‘concern’, ‘fear’, ‘panic’, ‘worry’: I’ve already cleaned the car so you needn’t bother to do it. Judges in England need not retire until they are 75.

It is sometimes used in questions, but we prefer to use ‘need’ as an ordinary verb or ‘have to’: Need you go so soon? Do you need to go so soon? Do you have to go so soon?

In formal written English ‘need’ as a modal verb is used with negative words such as ‘hardly’, ‘never’, ‘nobody’, ‘no one’, and ‘only’: The changes need only be small to make the proposals acceptable. (less formally The changes only need to be … )

To give permission not to do something we can use either ‘needn’t’ or ‘don’t need to’: You needn’t cut the grass, I’ll do it later. (You don’t need to cut the grass …)

To talk about a general necessity, we prefer ‘don’t need to’: You don’t need to be over 18 to get into a disco.

We can use either ‘needn’t’ or don’t have to’ with little difference in meaning to say that it is necessary to do something: You needn’t whisper. Nobody can hear us. You don’t have to whisper …

Some people prefer ‘needn’t’ when it is the speaker who decides the lack of necessity, and ‘don’t have to’ when external rules or somebody else’s actions make something unnecessary. Compare: As you worked late yesterday you needn’t come in until 10.00 tomorrow morning (speaker’s decision). We’ve been told that we don’t have to be at work until 10.00 tomorrow (someone else’s decision).

We can use ‘needn’t’ (or ‘don’t have to’) to say that something is not necessarily true. We don’t use ‘mustn’t’ in this way: Volcanoes needn’t erupt constantly to be classified as ‘active’. Volcanoes don’t have to erupt …

 

Needn’t have (done)

Study this example situation:

George had to go out. He thought it was going to rain, so he decided to take the umbrella. But it didn’t rain, so the umbrella was not necessary. So he needn’t have taken the umbrella.

‘He needn’t have taken the umbrella’ = He took the umbrella but this was not necessary. Of course, he didn’t know this when he went out.

 

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