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1 Candidates must attempt all the questions. 2 I simply must tell you what happened. 3 We must make an early start tomorrow. 4 You must see the film if you get a chance. <1> As we can see from these sentences, must varies in meaning from (1) the expression of an instruction or of what is obligatory, to (2) the expression of a sense of inner compulsion, and then to (3) the expression of what is necessary or inevitable in the speaker's opinion. In sentence 4, must expresses little more than pressing advice, and represents a 'stronger' form of should. In every sentence, however, must express the authority of the speaker, or a decision of firm opinion on the speaker's part. If obligation or necessity is imposed by a person other than the speaker, or by force of circumstance, we use have to: 1a You have to answer all the questions. (The teacher explains to students the requirements of the examiners.) 2a I have to tell you what happened. (Those are the instructions I've been given) 3a We have to make an early start tomorrow. (Circumstances or arrangements make it necessary) 4a You'll have to see the film tomorrow if you don't want to miss it. (It won't be showing any longer) <2> Must can be used with adverbs having a present or future time reference: We must discuss that question (e.g.) now, later, next week. However, the obligation or necessity is felt by the speaker to exist now, and it is the actibity denoted by the main verb (discuss) that lies in the future. In cases where the obligation or necessity will exist only eventually, or where it is dependent on some other event, we use have to with will ('ll) or shall: 5 If we miss the last bus, we shall have to walk. We use the simple present tense of have to to indicate (6) what is habitual, or (7) what is already planned or arranged for the future: 6 I have to get up at seven every morning. 7 We have to be there at ten tomorrow. A more colloquial form, have got to, is commonly used as alternative in sentences like 7, and reinforces the idea of external authority: We've got to be there at ten tomorrow. <3> The interrogative form in the present tense is generally formed with do: 6a What time do you have to get up? (rather than: what time have you to get up?) 7a What time do we have to be there? (rather than: What time have we to be there?) or What time have we got to be there? <4> Must can be left unchanged in reported speech. You must tell me how to do it.' = I said He must tell me how to do it. Must cannot, however, be used to refer to obligation or necessity existing before the time of speaking. Instead, we use had to: I had to shout to make myself heard above the noise. ( I tell you this now) <5> We also use forms of have to in the may situation where must lacks the necessary verb forms: I'm having to read this very carefully. (present progressive) I've had to give up the idea.(present perfect) I told him I'd had to give up the idea. (past perfect) We may have to change our plans. (infinitive without to) It's a pity to have to give up the idea. (Infinitive) No one likes having to pay taxes. (gerund) You'd have to do it if he insisted. ( conditional) You'd have had to do it if he'd insisted. (onditional perfect) <6> In view of the fact that forms of have to are sometimes the only ones available, it is hardly surprising that a distinction in meaning between must and have to is not always rigidly maintained in those cases where both verbs are possible grammatically. But generally speaking, students will find that English usage bears out the distinction mentioned earlier, and that the choice of one form rather than another reflects a difference in attitude on the part of the speaker. <7> One other verb phrase needs to be considered here: am/is/are to. This sometimes expresses a command or instruction issuing from the speaker, or imposed on the speaker by external authority: You are to give this letter to the manager. (Those are the instructions I'm giving you, or the instructions I'm passing on from some other authority.) We are to be there by ten o'clock. (Those are the instructions we have received.) Such sentences always have a future time reference, and the form will be to is never used. In reported speech, and to refer to past time, we use was/were to: I told him he was to give the letter to the manager. We left at eight o'clock - we were to be there by ten. Was/were to + perfect infinitive, generally implies that instructions were not carried out: You were to have given the letter to the manager. (implying but you didn't) <8> If must is followed by a perfect infinitive, it nearly always indicates an inference on the part of the speaker. It must have been a great shock to him. (= It was a great shock., I feel sure.) Students will, however, find occasional examples where must + perfect infinitive is equivalent in meaning to 'It is essential that this should already have been done': To be eligible for a full pension, an employee must have contributed to the fund for at least twenty years. <9> In all the examples so far, must, have to, etc., express the necessity for positive action on the part of the subject. To express the necessity for non-action, we use mustn't or am/is/are not to: You mustn't say anything about it. (= You must say nothing about it.) You are not to say anything about it. (= You are to say nothing about it.) |