shall
shall和will，should和would的种种用法很复杂。一般说来，should相当于shall，would相当于will。下面的一切规则都是根据英格兰的习惯。有两点该注意：（1）所说的错误也许在美国和苏格兰不被看作错误。（2）一切错误可以说都是在该用shall或should的场合用will或would，不是在该用will或would的场合用shall或should。
现在先讲简单句和主句：
（1）shall在第一人称的陈述句里表示将来。例如：I shall be twenty next Sunday. 和I shall be glad if you will call tomorrow afternoon. 用will而不用shall在英格兰通常被当作错误，但在美国和苏格兰很普通。比较下面两句：
I shall go tomorrow. （在英国是正常的英语，在美国往往被看作允诺或保证。）
I shall be twenty next Sunday. （在英国是正常的英语，在美国几乎不用。）
shall hope作“希望将…”解，不作“将希望…”解，“将来”的意思属于后面的不定式。例如：I shall hope to see him next week. ＝I hope to see him next week.
（2）shall在第一人称的陈述句里有时表示意向或允诺。例如：I shall tell you this evening. 和I shall never do it again. 用shall而不用will，含有“当然”的意思。
（3）shall在第一人称的疑问句里有时表示将来，有时问对方的意志。例如：Shall I be too old to work at eighty? （表示将来）和Shall I post the letter for you? （问对方的意志）这句可以改作Would you like me to post the letter for you? 或Do you want me to post the letter for you? 在爱尔兰和苏格兰往往说Will I post the letter for you?
（4）shall在第二人称和第三人称的陈述句里表示自己（指说话或作文者）的意向、命令、允诺、恫吓等。例如：
- You（或He）shall never see her again. （意向）
- You（或He）shall go at once. （命令）
- You（或He）shall have a reward. （允诺）
- You（或He）shall be punished. （恫吓）
第三句在口语里现在不普通。
比较下面各句：
- You（或He）shall go at once. （表示自己的意向，语气最强）
- You（或He）must go at once. （比较婉转）
- You（或He）have to go at once. （比较婉转）
- You（或He）have got to go at once. （比较婉转，口语）
- You are（或He is）to go at once. （最婉转）
（5）shall在第二人称的疑问句里表示将来。例如：Shall you be away for long? 但用will也很普通。例如：Will you be away for long? 在美国几乎不用Shall you...? 在修辞疑问句里总用will，不用shall，如假使Will you be away for long? 含有“你当然不会离开好久”的意思，will不可改作shall。
（6）shall在第三人称的疑问句里问对方的意志：例如：Shall he be paid? （你以为该给他钱吗？）
（7）will在第一人称的陈述句里表示自己的意向、命令、允诺、恫吓等。例如：
- I will work hard. （意向）
- I will be obeyed. （命令）
- I will help you as much as I can. （允诺）
- I will punish you. （恫吓）
（8）will通常不用在第一人称的疑问句里。Will I? 或Will we? 往往有“我（们）当然要”或“我（们）当然不要”的含意。但Will I do? 有一个特别的意思：“（你以为做那件事）我行吗？”
（9）will在第二人称和第三人称的陈述句里表示将来。例如：You will be better tomorrow. 和It will be fine very soon.
（10）will在第二人称和第三人称的陈述句里有时表示自己（指说话或作文者）的命令。例如：You will send in your report on Thursday. 和All the members will send in their reports on Thursday. 用will比用shall婉转些，主要用在公文里。
（11）will在第三人称的陈述句里有时表示必然性（certainty）或不可避免性（inevitability）。例如：Whatever you may say, things of this kind will go on. 有时有“偏偏”的意思。例如：He will ask me all sorts of questions when I am busy writing. 这句里的will该重读。有时有“或然”（probable）的意思。例如：This will be the book you're looking for. 和It is about five, he will have gone back home. （现在大约5点钟，他大概已经回家去了。）
（12）will在第二人称的疑问句里问对方的意志，尤其用在请求句（request）里。例如：Will you tell me more about him? Will you help me? 和Help me, will you? （参见（5））Will you tell me more about him? 也可能是“你能多告诉我一些关于他的事吗？”也可能是“我请求你多告诉我一些关于他的事”。用在第一解，有人以为该用shall而不用will，或改用Are you going to...? 用在第二解，句尾的问号可以改作句号。
（13）will在第三人称的疑问句里表示将来。例如：Will they be here tomorrow?
（14）will有时表示习惯，通常用在第二人称和第三人称。例如：You（或He）will sit here for hours saying nothing. 这用法在口语里几乎没有。
（15）should是shall的过去式，但很少用来指过去，如I should never know。远不及I was never to know或I was not going to know普通，在文字里也逐渐少用，通常用现在陈述语气就可以表示习惯。
（16）should用在第一人称的条件陈述句里表示将来，那条件从句往往省去。例如：I should be glad to see you if you would call tomorrow morning. 和I should be glad to see you. 用would而不用should在英格兰通常被当作错误，但在美国和苏格兰很普通。
I should like（或I would like）里可以说并没有省去的条件从句，它不过是比I shall like婉转些的说法。同样地，I should think和I should say 比I think和I say婉转。
（17）should用在第二人称的条件疑问句里表示将来，那条件从句往往省去，如Should you like to see him if he should call on you this evening? 和Should you like to see him? 但事实上用would普通得多，如Would you like to see him if he should call on you this evening? 和Would you like to see him? 在修辞疑问句里总用would，不用should，如假使Would you like to see him? 含有“你当然不会喜欢见他”的意思，would不可改作should。
（18）should在任何人称表示义务或责任，如I（或You，或He）Should study hard和I（或You，或He）should not leave any of these questions unanswered。这样用法的should语气比ought to…轻些。
（19）should有时在疑问句里表示情感（emotion）。例如：Why should you call him a fool?
（20）would是will的过去式，但除了表示习惯、意志（volition）和或然性（probability）以外，很少用来指过去。
would用来指过去的习惯比will用来指现在的习惯普通得多。例如：I（或You，或He）would sit here for hours saying nothing. 但这用法在口语里几乎没有。
would表示意志往往有“偏偏”的意思。例如：I（或You，或He）would go out in spite of the snowstorm. （would该重读）would在否定句里表示过去的意志，例如：I（或You，或He）would not listen to her story. would表示或然性，可以用于任何人称，但事实上主要用在第三人称。
例如：
- That would be in March 1932.
- When that happened, I would be about twelve.
- When that happened, you would be about fifteen.
有时指现在而不指过去。例如：This would be the book you're looking for.
（21）would在第一人称的条件陈述句里表示自己的意向、命令、允诺、恫吓等，条件从句往往省去。例如：
- If I could, I would work hard. （意向）
- I would be obeyed. （命令）
- I would help you as much as I could. （允诺）
- I would punish you if you should do it again. （恫吓）
在没有条件从句的场合，I would不过是比I will婉转些的说法。I would不及I should like普通。参见（16）
（22）would在第二人称和第三人称的条件陈述句里表示将来，条件从句往往省去，例如If you（或he）were a bird, you（或he）would be able to fly. 和You（或He）certainly would be glad to be able to fly.
it would seem和one would think不过是比it seems和one thinks婉转些的说法。
（23）would在第二人称的条件疑问句里问对方的意志，尤其用在请求句里，条件从句通常省去，语气比用will婉转，如Would you tell me more about him? 和Would you help me? 比Will you tell me more about him? 和Will you help me? 婉转。参见（12）
（24）would在第三人称的条件疑问句里表示将来，条件从句往往省去，如If he were here, would he be sorry to hear it? 和Would he be sorry to hear it?
（25）would有时表示愿望。例如：I would rather remain here. 和I would you were with us!
上面只讲简单句和主句，下面讲从句：
（26）shall和should表示加在那从句里的主语所指的人或物身上的责任。例如：
- I demand that he shall（或should）return my book by 24 May.
- My demand is that he shall（或should）return my book by 24 May.
- I demanded that he should return my book by 24 May.
- My demand was that he should return my book by 24 May.
这种以that引导的从句通常用在condition，demand，desire，insist，intend，intention，provide，provision，require等词的后面。
（27）shall用在条件从句或不定从句里现在很不普通，如现在不说if he shall come, when he shall come或whoever shall come，却说if he comes, when he comes和whoever comes。
用shall既然不普通，用will竟然是错误的，如不可说If it will be fine tomorrow, I shall go out，该把will be改作is，用will在条件从句或不定从句里只表示意志等，如If you will help me, I shall be grateful to you和I shall be grateful to whoever will help me。
（28）should用在条件从句或不定从句里表示疑惑，有“偶然”的含意。例如：
- If it should be fine tomorrow, I shall go out.
- If I should ever go to Europe, I should see such things.
- Whoever should apply for further information will have to write to the secretary.
- Whatever should happen to them would be considered something new.
第一句和第三句里的should比第二句和第四句里的should表示程度轻些的疑惑。注意第一句里用shall，第三句里用will，但第二句里用should，第四句里用would。
假使要表示意志，该用would而不用should。例如：If you would help me, I should be grateful to you. 和I should be grateful to whoever would help me.
If it should be fine, I shall go out里的should决不可改作would。If you should catch cold again, you would keep in bed for a few days more里的should也不可改作would。If you would keep in bed for a few days more, you would find it difficult to catch up里的would并不表示意志，If you would keep in bed for a few days more＝If (if you should catch cold again) you would keep in bed for a few days more。
（29）should（不是shall）有时表示情感。例如：
- It is a pity that she should be so ill.
- It is strange that you should know nothing about it.
- It is only natural that we should be left behind.
- It is odd that you should live alone in this cottage.
- I wonder why some of you should keep laughing at me.
（30）should（不是shall）用在以lest或in case引导的从句里。例如：I have to remind him lest he should forget it. 和They took their umbrellas with them in case it should rain. 在以lest引导的从句里在美国通常不用should而用虚拟现在式。例如：... lest he forget it.
（31）在间接引语里，依照语法该用在直接引语里所用的shall或will，should或would，但在必要的时候该变换时态，把shall改作should，把will改作would。例如：
- He says he shall be glad to see her. （直接引语：I shall be glad....）
- He said he should be glad to see her. （直接引语：I shall be glad ....）
- He thinks I will be glad to see her. （直接引语：He will be glad ....）
- He thought I would be glad to see her. （直接引语：He will be glad ....）
不过在事实上第一句里用will普通些，第二句里用would普通些，第三句里在英国用shall普通些，第四句里在英国用should普通些。尤其在第三句和第四句里现在很少用will和would，因为will和would在第一人称里很像表示意志，但在美国几乎总是用will和would。
像下面各句里的shall和should，will和would当然是不可改动的：
- I think I shall be glad to see her.
- I thought I should be glad to see her.
- I think you（或he）will be glad to see her.
- I thought you（或he）would be glad to see her.
- You think he will be glad to see her.
- You thought he would be glad to see her.
- He thinks you will be glad to see her.
- He thought you would be glad to see her.
- He thinks she will be glad to see you.
- He thought she would be glad to see you.
- I shall ask whether you（或he）will help me.
- I asked whether you（或he）would help me.
- You（或He）will ask whether I will help you（或him）.
- You（或He）asked whether I would help you（或him）.
- I shall tell you（或him）that you（或he）shall have a reward.
- I told you（或him）that you（或he）should have a reward.
（32）It is necessary that he should come by six o'clock和I suggest that he should come by six o'clock等句子里用should，在美国通常不用should而用虚拟现在式。例如：...he come（不用comes）by six o'clock.
