1、The Ninth Lesson: Auxiliary Verb,第九讲：助动词,助动词又分为基本助动词、情态动词和半助动词。本讲主要介绍情态助动词的用法。 英语的情态助动词共有13个，其中包括一些过去时形式，它们是：,情态助动词的语法特征是，没有非限定形式，没有词形曲折变化。句法特征是，协助主动词构成限定动词词组，无一例外地带有不带to的不定式；在限定动词词组中，只能用一个情态助动词，而且总是位居第一。情态助动词多半一词多义；在肯定句、否定句和疑问句中，往往意义不尽相同；而且其“时”的特征并不是时间区别的主要标志，也就是说，现在时情态助动词不一定表示现在时间，过去时情态助动词也不一定表示过去
2、时间，各有其用法上的特殊性。因此，情态助动词的用法有许多值得注意的地方。,9.1情态意义表示法,9.2情态助动词的推测性用法和非推测性用法,9.3半助动词,9.1 情态意义表示法,1）表示“能力”和“可能”,a）表示“能力”（Ability），可用can，could，be able to。can既能表示现在的“能力”，也能表示将来的“能力”。例如： Look! I can do it. I cant do it now, but I can do it later.,用can表示现在的“能力”，既可表示做某桩具体事情的“能力”。例如： I can climb this cliff. Is th
3、ere anything I can do for you?,He is only four, but he can read.,Fire cannot destroy gold.,can表示“能力”与be able to同义，在许多情况下可以交替使用。例如： As I have got enough money, I can / am able to help her.,也可泛指一般的“能力”：,表示将来的“能力”，通常用will / shall be able to。例如： Ill be able to speak German in another two months. If he d
4、oesnt apply fairly soon, he wont be able to get the job.,当然，要表示将来做某桩具体事情的能力也可用can： Can you go and see him tomorrow morning? If I can, I will do it.表示过去的“能力”，可用could和was / were able to，但在肯定句中，could所表示的“能力”仅是泛指过去的一般能力。例如： She could play the piano when she was only six. At that time I could still read
5、without spectacles.,如果要表示过去做某桩具体事情的“能力”，通常不用could，而用was / were able to（以及managed to）。例如： He was able to swim halfway before he collapsed. I talked a long time, and in the end I managed to make her believe me.上述could与was / were able to用法上的区别仅是就肯定句而言；在否定句中却无此限制：could既可表示过去的一般能力，也可表示过去做某桩具体事情的能力。例如： I
6、couldnt / wasnt able to play the piano when I was at school. He got so drunk that he couldnt / wasnt able to find the front door.,b）表示“可能”（Possibility），可用may，might，can，could。 may / might表示“可能”，往往可以交替使用，并无时间上的 差异，只是用might在口气上比用could更加不甚肯定，从而 比较婉转。may / might既可表示现在的“可能”： It may / might be true. He may
7、 not / might not live near the theatre.,在疑问句中表示“可能”，须用can而不用may。例如： Where can he be? He may be in the office. Can they have missed the bus? Yes, they may have.,因为在书面语中表示“不可能”常用cant。 用can / could表示现在的“可能”，在口气上could比较婉转。例如：Thats not mine. Whose can it be? It could be Johns.She cant / couldnt love him.
8、 用can表示“可能”，较多地用于否定句和疑问句，而could则不受此限。例如：If you dont have a guide, you could lose your way (= its possible for you to lose your way).It cant / couldnt be true.,在肯定陈述句中，用can表示“可能”与用may表示“可能”往往产生含义上的微妙差别：用can表示可能往往指逻辑上的可能性；而用may表示可能则指事实上的可能性。试比较：The road can be blocked. (= It is possible for the road t
9、o be blocked.)The road may be blocked. (= It is possible that the road is blocked.),表示过去的“可能“，可用“ may / might不定式完成体和不定式进行体”，在这里用may / might，也只是口气上婉转程度的差异，而没有时间上的区别。例如：He may / might have been hurt.She may / might have been expressing her true feelings at the moment.,也可用“can / could 不定式完成体”表示过去的“可能”：
10、 He cant / could have been hurt. She cant / could have missed the train. 用“might / could 不定式完成体”有时可以表示本来可能发生但没有发生，或者本来可能完成却没有完成的动作。例如：You might have killed yourself.（你本来可能送命的。）I could have reported you.（我本可以告发你。）,2）表示“许可”和“不许”,a）请求对方“许可”（Permission）可用can，could，may，might。may / might与can / could相比，前者较
11、为正式；may / can与might / could相比，后者较为婉转，更有礼貌。在口语中特别常用can表示“许可”。例如： Can / Could / May / Might I smoke in here?表示给予“许可”通常用can / may，而不用could / might。例如：Could I use your phone? Yes, of course you can.Might I trouble you for a while? You may indeed.,b）表示“不许可”用may not或者cannot。例如：Can I go out for a moment? N
12、o, you cant.May I use our car for a few days? No, you may not. may not也可表示一般的“不许可”，即表示根据一般规定的“不许可”，而不是说话人不许可。例如：Borrowers may not take out of the library more than two books at a time.当然，表示“不许可”还可采用其他比较婉转的说法。例如：A: Could I say it in Chinese?B: No, Im afraid not.,要注意may not表示“不许可”的过去时形式并不是might not。试比
13、较： He may not go. (= I dont permit him to go.) He might not go. (= Possibly he will not go.) 若要表示过去的“不许可”，通常要说： He was not allowed to go. I didnt permit him to go.,3）表示“义务”和“必然”,a）所谓表示“义务”（Obligation），即表示“必须”、“应该”做某事。表示这些意义，可用should，ought to，must。用这三个情态助动词表示“义务”，其口气强弱略有差别。 用should / ought to表示“应该”，带
14、有表示“劝说”和“敦促”的含义。例如： We should learn from the model workers. You should do what your teachers tell you to. should与ought to同义，都能表示“应该”，往往可以交替使用。例如： You should / ought to drink less. He shouldnt / oughtnt to stay up so late.,用should口气比较肯定一些，说话人的主观信心要强烈一些，而用ought to则在口气上不是那么坚定。 “should / ought to + 不定式完
15、成体”可表示本来应该做某事却没有做或者本来不应该做某事却做了。例如：You should / ought to have asked my permission first.You shouldnt / ought not to have been resting at that time of day. 正因为should在口气上带有更多的主观信心，从而在表示强烈的劝说和敦促时，往往用should而不用ought to。例如： You should mind your own business. 用must表示“敦促”或“命令”，在口气上比should（表示“应该”）更加强烈，这意味着说话人
16、是权威的一方，对人对己都适用。例如：You must be back by ten oclock.（你必须十点以前回来。）I really must stop smoking.（我真的必须戒烟了。）,表示将来的“必须”，常用半助动词have to的一定形式（will / shall have to）。试比较： We must do it again.（表示现在） Well have to do it again.（表示将来） 表示过去的“必须”，常用have to的过去时形式had to。试比较：I must leave at six.I had to leave at six yesterd
17、ay.must有两个否定形式：第一个否定形式是must not / mustnt，表示“不许”、“禁止”，相应的半助动词是be to的否定形式be not to。例如：You mustnt talk like that.You are not to talk like that.（不许你如此讲话。）上述两句的过去时形式均为：You werent to talk like that.,must的第二个否定形式试need not / neednt，表示“不必”。例如： A: Must you leave so soon? B: No, I neednt.与neednt相当的动词形式是dont ne
18、ed to / dont have to / havent got to。例如： You must do it at once. You neednt do ii at once. You dont need to do it at once. You dont have to do it at once. You havent got to do it at once.过去时形式通常是： You didnt need to do it at once. You didnt have to do it at once.,表示“必须“，must与have to意义接近，但在用法上略有区别：用mu
19、st表示“必须”，侧重于说话人的主观意志；用have to表示“必须”，则侧重于客观的需要。试比较：He must say it in English. (I want him to do so.)He has to say it in English. (Because he doesnt know Chinese.),b）所谓表示“必然”（Necessity）就是根据说话人的判断和推测认为“必然”会有某种情况。表示这种意义，可用should，ought to和must，其中以用must口气最为肯定。,用should表示“必然”，指说话人根据一定情况作出推测或推断。例如：She should
20、 be here in a minute.（估计她马上就会到来。）That should not be a difficult problem for Mary.（估计那件事对于玛丽不会成为困难的问题。）,用out to表示“必然”也是根据一定情况作出的推测或推断。例如：These young trees ought to provide shade in ten years.（这些小树十年后定会成荫。）Bob has made a thorough study of this subject. He ought to be able to help you.（鲍勃曾对这一问题作过深入研究。他
21、一定能够帮助你的。）,用out to表示推断或推测与must同义，但口气较弱，从而也比较婉转。试比较：Mary Blake must be home by now.Mary Blake ought to be home by now.,ought to（表示“推测”）的否定形式是oughtnt to，其含义也比表示“推测”的must的否定形式cant来的婉转。试比较：You cant have any difficulty getting the tickets.You oughtnt to have any difficulty getting the tickets. 用must表示“必然
22、”，也是一种推测或推断，其口气最为肯定，一般用于表示肯定陈述句。例如：All men must die.Careless reading must give poor results. 如果事推测过去的事态，则用“must不定式完成体”。例如：You must have left your handbag in the theater. Her eyes are red. She must have been crying.,表示推测的must的否定形式是cant而不是must not。例如：He cant have been to your home. He doesnt know your
23、 adress.,4）表示“预见”和“推测”,a）表示“预见”（Prediction），即表示“单纯将来”，可用will / shall不定式，从而认为（I / We）shall和（You / He / It / They）will就是“将来时”（Future Tense）的标记。,I will be a different person when I live in England.We will have a great time if we go to the party.,shall用于第一人称主语表示“意图”和“决心”，还表示征求对方意见。例如： I shall never do t
24、hat again. Shall we go?,b）表示“推测”（Predictability），除用should，ought to和must外，还可用will / would。用will表示“推测”，其口气的肯定程度仅次于must，若用would，则口气的肯定程度又次于will。试比较：They should / ought to be home by now.（他们现在该到家了。）They would be home by now.（他们现在大概到家了。）They will be home by now.（我估计他们现在一定到家了。）They must be home by now.（他们
25、现在一定到家了。） 用will / would表示“推测”可有三种情况：第一种是对待事态的推测。例如：A: Theres someone coming upstairs.B: That will be Mary.（估计一定是玛丽。）,若用would则口气不够肯定，但仍指现在时间。试比较：A: Whos that man over there?B: That will be George, no doubt.（一定是乔治。）B: That would be George, I expect.（我想，大概是乔治。）,第二种是对某些习惯性事态的推测，用will指现在习惯；用would则指过去习惯，均
26、不重读。例如：A lion will attack a man only when hungry.（狮子饿了就会攻击人。）Every day shell sit there for hours doing nothing.（每天她总是在那里坐几个小时无所事事。）,第三种是对某些不受时限的客观过程的推测，通常只用will， 表示现在时间，可与一般现在时的类似用法交替使用。例如：Oil will float on water.（油总是浮于水面。） Oil floats on water.Pigs will eat anything.（猪什么都吃。） Pigs eat anything.,5）表示“
27、意愿”、“意图”和“决心”,a）表示“意愿”（Willingness），即愿意做某事，可用will，would，shall。用will表示“意愿”，可用于一切人称的主语。例如：My sister will help you with the luggage.You can help me if you will. 在以上诸例中，will相当于be willing to。当will用于第二、三人称主语疑问句时，时询问别人是否愿意做某事。例如：Will you sing at the party tomorrow evening?,当will用于第二人称主语请求句时，为了缓和可能含有的命令口气，可
28、在Will you之后增添礼貌性词语。例如： Will you please open the door for me? Will you kindly help me with the luggage?,还可用Would you，Would you please，Would you be good enough to，Would you like to，Would you be so kind as to: Would you pass me the salt, please? Would you kindly drive me home? Would you be good enough
29、to send me some books? Would you be so kind as to look after my luggage when I am away? 表示客气的请求，用Would you?但表示接受请求时，要用will，而不用would。例如： Would you lend me your pen a minute? Certainly, I will. Would you write to me as soon as you arrive? Yes, I will.,表示“不愿意”，用will not / wont。例如：I will not do anything
30、 solely for money.I sent Alice the invitation, but she wont accept it.表示过去的意愿或过去不愿意做某事，可用would和would not / wouldnt，这种用法常见于间接引语中和过去时间语境中。例如：I asked him if he would help with my writing.When I was at college, I wouldnt read any books solely for pleasure.用shall表示“意愿”一般适用于第二、三人称主语。这时，shall所表示的“意愿”不是句子主语
31、的“意愿”，而是说话人的“意愿”。例如：You shall stay with us as long as you like. = Im willing to let you stay with us as long asHe shall be praised if he works hard for the people. = Ill see that he is praise,用shall表示“意愿”，在疑问句中是征询听话人的“意愿”。例如： Shall you take a holiday this summer? Shall my daughter do the shopping fo
32、r you? b）表示“意图”（Intention），即“打算”做某事，也可用will，would，shall。用will表示“意图”，并可用于一切人称主语。例如： I will (= am going to) write to her tomorrow. He wont help me unless I accept his offer.,shall表示“意图”用于疑问句中（Shall I / we?）是征询说话人的意见或意图。例如： Shall I carry the suitcase for you? = Do you want me to carry your suitcase? Sh
33、all we have dinner? = Lets have dinner, shall we? / Do you agree with my intention to have dinner? 在美国英语中，shall不管是表示“预见”（即表示“将来”）、“愿意”或“意图”，都常为will所取代，即使在征询听话人“意图”的疑问句中，Shall I / we也常为Should I / we所取代。例如： Shall I turn off the light? What should we do now?,c）表示“决心”（Determination），即坚持要做某事，也可用will，woul
34、d，shall，均须重读，且不能用缩略形式。用will表示“决心”或“坚持”（Insistence），可用于一切人称的主语。例如： I will (= am determined to) take the job and no one is going to stop me. I wont go back on my words. 如果表示过去的“决心”，即过去坚持做某事，便可用would。例如： She would marry him (= insisted on marrying him) in spite of my warning that it was unwise. He woul
35、d climb the mountain regardless of danger.,shall（表“决心”）主要用于第二、三人称主语，表示说话人的强烈意志和决心。例如：You shall obey my orders. = I insist that you obey my orders.They shall do what I told them to. = Im determined to make them do it.shall作这一用法的否定形式shall not / shant则表示说话人“禁止”或“威胁”。例如：No one shall stop me. = I dont al
36、low anybody to stop me.Foreign countries shall not interfere in our internal affairs. = We are determined not to allow any foreign country to interfere in our internal affairs.,6）其他情态意义,a）should可在某些语境中表示惋惜、忧虑、欢欣、惊讶等感情色彩。例如在某些that-分句： Its a pity that he should leave so soon. They were amazed that she
37、 should have done so much in so short a time. 又例如在某些习惯用的疑问句和感叹句中：How should I know? （我怎么会知道？）That he should dare to attack me! （想不到他竟敢攻击我！）Who should come in but the mayor himself? （你道是谁进来了，是市长自己呀！）,还可用在某些语境中并不表示具体的情态意义，例如在某些结构中与be-型虚拟式交替使用： I insisted that he go / should go with me. The order that
38、all civilians（平民）be evacuated / should be evacuated was soon carried out. 在下列状语分句中也不带具体的情态意义： They got warmly dressed for fare that they should catch cold. He ran away or he should be found by people. 此外，should还可以和say，think搭配表示婉转口气。例如： I should say he is just the right man for the job. I should thin
39、k your approach is correct.,b）作为情态助动词表示“胆敢”，dare通常只用于否定陈述句和疑问句中。例如：I dare not go there.How dare he say such rude things about me?注意：I dare say这一惯用语除外。 I dare say也可以写成I daresay，意为“我想”、“我恐怕”。例如： I dare say you are right.（我想你是对的。） Itll rain tomorrow, I daresay.（明天恐怕要下雨。） dare作为情态助动词没有过去时形式，但它既可指现在时间，也可
40、指过去时间。例如： The president was so hot-tempered that no one dare tell him the bad news.,dare的否定形式（darent）也可指过去时间。例如： Tom wanted to come, but he darent.dare还可用作主动词。作为主动词，dare也常用于否定句和疑问句，随后的不定式可带to，也可不带to。例如： She didnt dare (to) say anything about it. He does not dare (to) answer. Does she dare (to) go th
41、ere alone?c）need也是既可作情态助动词，也可作主动词，作“必须”、“需要”解。作为情态助动词，need也只用于否定句和疑问句。例如： He neednt worry about it. Need I collect the parcel（取包裹）myself?,以need作情态助动词提问，其答语如果是肯定的，须用must；如果答语是否定的，则用neednt。例如：Need we work late today? No, but we must tomorrow.Need I tell Elizabeth at once? No, you neednt tell her just
42、yet.询问对方是否“需要”、“必须”做某事，既可用need，也可用must。如前所述，对于这类问题的答语如果是否定的，都得用neednt或dont have to，而不是用mustnt。例如：A: Must I see a doctor at once?B: No, you neednt / dont have to see a doctor for the time being.“neednt不定式完成体”表示过去本来不必做某事却做了。例如：You neednt have bought that house.She neednt have been worrying about it.,由
43、此可见，didnt need to与neednt have + -ed的含义是有区别。试比较：I didnt need to go to the station.I neednt have gone to the station.d）used to（只有过去时形式，没有现在时形式）表示过去习惯动作或状态，这种情况现在已经不复存在。例如：There used to be an old temple at the corner of the street, but it was destroyed in the war and has never been rebuilt.He used to s
44、moke a lot, but he has long given up smoking.,used to的否定形式一般是used not to。例如： He used to live in Shanghai, used not he? 在否定陈述句或否定疑问句中，用didnt use to或used not to均可： He didnt use to smoke cigarettes. He used not to smoke cigarettes. used to与would均可表示过去习惯，因此往往可以交替使用。例如：When we were children, we used to /
45、 would go skating every winter. 所不同的是：would只可与动态动词连用，而used to则既可与动态动词也可与静态动词连用；would表示过去习惯通常用于正式语体，而used to则不受此限。,Exercises9.1,她可能忘了给我回电。（may）She may have forgotten to call me back.我不知道现在是否可以离开。（could）I wonder if I could leave now.他竟出了事故，真使我吃惊。（should）Im surprised that he should have an accident.你不可以再违反交通规则了。（must）You mustnt violate the traffic regulations again.你本应该帮他一把。（should）You should have helped her.,
