857 虚拟语气用法中，有18项特殊的问题值得注意。现在分别加以讨论。
858（a）虚拟条件中的谓语有时可用进行时，表示“如果……正在（进行）……”等。主句中谓语可用一般时、进行时或完成时，仍由should，would，might，could等构成。
If she were living happily，I should be very much astonished．
If human beings were not killing each other，we would be living a happier life．
If you had been wandering about while they were working，you might have been fired．
859（b）除用if外，还可用一些其他词或短语引起条件状语从句，如suppose，supposing（that），provided（that），providing，in case，on condition that，unless（=if not）等。
All my property would be yours on condition that you would marry me.
I could accompany you provided I had finished my work．
In case a friend should call，please ask him to go to the Diamond Restaurant．
Unless he had studied the theory very carefully，it would have been dangerous to publish it．
I should have called on you，but（that）I was（=if I had not been）too busy．
He would have died only（that）the doctor saved him（=if the doctor had not saved him）.
860（c）如果条件从句中包含were，had，should，could，连词有时可以省略，这时条件从句要用倒装语序，即把谓语动词或其中的一部分（如助动词、系动词be等）移到主语前面，这种结构主要用于书面语。
Were I（=If I were）in your place，I wouldn't do it．
Had you（=If you had）seen it，you would have believed．
Should anyone（=Suppose anyone should）come，say I am gone.
Were they to get married（=If they were to get married），they would not be happy．
Could they raise sufficient fund，they would start the project．
861（d）条件从句不仅可以放在句首，也可放在主句后面，偶尔也可插在主句的主语与谓语中间。
If he should eat so much fat，John would not live long．
John would not live long if he should eat so much fat．
John，if he should eat so much fat，would not live long．
If my father had been ill a few more weeks，my family would have been starved．
My family would have been starved if my father had been ill a few more weeks．
My family，if my father had been ill a few more weeks，would have been starved．
862（e）条件从句的谓语可以包含一个助动词（包括would，could，might，had to等），但语法上不一定需要。
If you would，you could．
If I could help anyone，I would do it．
If I might say anything，I would inform her of the danger.
但：If he knew it（无助动词），he would，tell me．
863（f）在虚拟条件句的主句中，谓语通常都必须包含would，should，could，might这类助动词。
If you needed assistance，I could do something．
If it were necessary，I might leave the office for a few minutes．
If they treated me as a slave，I had to resign．
If you had informed me earlier，I needn't have made this contract．
If you had not encouraged me．I daren't have started（在口语中代替wouldn't have dared to start）the project．
864（g）虚拟条件句的主句可以是陈述句、疑问句、感叹句、祈使句。
①陈述句：If I knew，I would tell you．If he decided to study，I could teach him.
②疑问句：If he should fail again，what else could I do? If you would like to work，when could you start?
③感叹句：If you knew the reason，how simple it would appear! If we had not known any war，how happy we should have been!
④祈使句：If you should meet Mr．Kim，please tell him I arrived yesterday．If anyone should come for money，tell him I am gone．If you still had the courage，do try again．
注：在祈使句中除了用加重语气的do外，不能使用其他助动词来构成谓语。
865（h）通过下表可以比较一下陈述语气和虚拟语气两种情况的差别。
I=Indicative Mood（陈述语气）
S=Subjunctive Mood（虚拟语气）
表现的情况 条件从句 主句
可能性 现在或任何时的假设 现在或任何时的结论
I．有可能性 If she loves him， she will marry him．
S．可能性不大 If she love him， she will marry him．
S．与事实相反 If she loved him， she would marry him．
可能性 过去假设 过去结论
I．有可能性 If she loved him， she would marry him．
S．与事实相反 If she had loved him， she would have married him．
可能性 将来假设 将来结论
S．可能性不大 If she should love him， she will（or would）marry him．
S．与事实相反 If she would love him， she would marry him．
S．与事实相反 If she were to love him， she would marry him．
注1：上面主句中的will也可用shall，can，may，must，ought to，need（not），dare（not）代替，意思略有变化。
注2：主句中的would可用should，could，might，must，had to，need（not），dare（not）代替，意思也略有变化。
866（i）条件从句和主句所表示时间有时并不相同，这种句子称为错综时间条件句（Conditional Sentences of Mixed Time），如过去假设配合现在结论，现在假设配合过去结论，等等。
①过去假设＋现在结论
If I had studied medicine ten years ago，I should be（代替should have been）a doctor now．
If you had bought this house before the war，you could sell（代替could have sold）it now for ten times the original price．
If I had worked hard for the last ten years，I should be living a happy life today．
②现在假设＋过去结论
If John should arrive today，he must have started five days ago from Tokyo．
If I gave a party this week，I should have let you know a week ago．
③过去假设＋将来结论
If he had started five days ago，he would arrive in three days．（But I know he did not start five days ago，nor will he arrive in three days．）
④将来假设＋过去结论
If he should arrive in three days，he would have started five days ago．
⑤现在假设＋将来结论
If I should fail this time，I would try again．
If you didn't make up your mind this moment，you might suffer in future．
867（j）一般说来，条件从句谓语若为虚拟语气，主句谓语也应是虚拟语气。在个别情况下，尽管条件从句的谓语为虚拟语气，主句的谓语却用陈述语气。
If you were in need of money，here I am．
If he had wanted to marry，there were many girls．
I shall be very happy if you could agree．
I shall be surprised if he became bankrupt．
868（k）如果条件句作宾语从句，它的动词形式不受主句谓语动词（如tell，report等）的影响。
I often tell him that
I have told him that
I told him that
I shall tell him that
if he had done good work，he would have been rewarded．
if he did good work，he would be rewarded.
if he were to do good work，he would be rewarded．
869（l）在主从两种句内，助动词有不同的意义。
①从句内，任何人称后，should无特别意思。
②从句内，任何人称后，would表示意愿。
③主句内，would在任何人称后，should在第一人称后，无特别意思。
④主句内，should在第二人称、第三人称后，表示说话者的主意。
⑤从句内，任何人称后，could，might等表示能力、许可。
⑥主句内，任何人称后，could，might等表示推测。
If we（or you，she）should（=happen to）meet John，we should（没有特别意思）（or you would，she would）not be able to recognize him．
If you（or he，I）would（=wished to，were willing to）marry her，her parents would（无特别意思）be happy．
If she went to the front，I would（=would be willing to），you would，he would，too．
If you（or he）needed it，you（or he）should have it（=I would be willing to give it to you or him）.
If he could not have travelled（=had not been able to travel）in so many countries，he could not have known（=he would not be able to have known）so many things．
If he had been educated，he could not have been（=would not have been）so silly．
If he might（=were allowed to）drink as he likes，he might（=would probably）drink too much．
870（m）条件从句有时可以缩短成介词短语、不定式短语等。
①介词短语
Without water（=If there were no water），they would die of thirst．
In his position（=If one were in his position），one would commit suicide．
What would I not give for it（=if I could get it）?
We should have died but for you（=if it had not been for you）．
②不定式短语
I should be very glad to help anybody（=if I could help anyone）．
Stones would have wept to see the scene（=if they had seen the scene）．
To hear him talk（=if you heard him talk）you would think him an American．
③分词短语
Coming yesterday（=If it had come yesterday），the rain would have spoiled our party．
Doing your best（=If you did your best），you would be criticized all the same．
Left to herself（=If she were left to herself），she would surely get into trouble．
Surrounded longer by the enemy（=If it had been surrounded longer by the enemy），the city couldn't have maintained itself and would have surrendered．
④名词或代词
Your refusal（=If you should refuse，it）would mean offence．
A gentleman（=If he had been a gentleman，he）wouldn't have done so．
I（=If I were you，I）wouldn't agree to it．
⑤连词or或otherwise
Be honest，or（=if you were not honest）nobody would trust you．
He must be crazy，otherwise he wouldn't have divorced her．
有时尽管没有条件从句或表示条件的短语，有的句子实际上也是虚拟条件句。
Heaven and earth would cry at the sad news（if they were able to hear it）.
Even stones would rush to listen to her singing．
The uproar of the fighting might have aroused dead men．
I was so hungry．I could have eaten a whole cow．
这类句子可以称为含蓄条件句（Conditional Sentences of Implied Condition）。
871（n）有时一个定语从句起着条件从句的作用。
Anyone who（=，if he）should have insulted my dog，would have insulted me．
A nation，which（=，if it）often got into political troubles，would never make progress．
Every caress I gave you（=if I gave you any caress，every caress）would be sin．
What would people say about John，whose（=if his）wife should go with another boy?
872（o）有时整个条件从句可以不出现，但从上下文中可感觉出来，这时主句谓语可以用虚拟语气。
I might have come yesterday．（If it had not rained；but as you know，it rained yesterday．）
I would do anything for you．（If I could I...）
He would have failed．（If he had made less efforts，he...）
I should have died．
You need not have told her the secret．
I had rather（or as soon，sooner，better，best）stay here．
I had almost said she had a pretty mouth．
Who would have thought so?
I had not thought（or dreamt）that my daughter-in-law was so pretty．（说I did not think，I never thought...更普通一些）
873（p）在日常口语及书信中，would，should，could，might等助动词可用来代替will，shall，can，may等，这样可使口气显得谦逊婉转，让人觉得仿佛有一个if I might ask you，if it were...possible，if you would not mind这类条件从句省略掉似的。这类用法非常普通，也很有用，可以称为客气说法的虚拟语气（Polite Subjunctive）。
①问句
Could this be your luggage?（现在情况）
Would he return very soon?（将来情况）
Could he have said it?（过去情况）
②请求
Would you lend me your newspaper?（回答：I will.）
Could I eat it?（回答：You can．）
Might I borrow your pen?（回答：You may．）（用might时不太多）
③意愿
I should like to have some coffee．
I would have a talk with you．
④看法
I should say you are mistaken．
I should think so．
I don't think she could forget me．
I am afraid you might fail．
He would regard this as a piece of folly．
It would seem to be queer．
She could ask David，but he might refuse to answer．
That would have been risky．He might have died．（过去情况）
874（q）有时表示后果的主句（如what would happen）可以省略，只剩下条件从句。
①“What would happen”省略（可译为“……怎么办?”）
If our secret should be discovered!
If they did not like it!
If she said no!
②“How happy I should be”省略（可译为“但愿……”）
If I succeeded!
If I were young again!
If only（or but）I could see you!
If I had learned something!
Oh，if we met again!
Oh，if I had wings!
O could I but see you !
O had I not committed the crime!
Ah，had I only known it!
③“I'll be hanged（or damned，dashed）”省略
If ever I know it．（=I don not know it．）
If he has not broken the window．（=He has broken it．）
If I do not love my wife．
If you are not my good friend．
在③这类句子中多用陈述语气，现在这种用法用得也比较少。
875（r）在as if引起的从句中，谓语也常用虚拟语气，这类句子也接近虚拟条件句。
He talks as（he would talk）if he were（or was）（口语中也可说is）a professor．
He talks as（he would have talked）if he had（口语中也可说has）been a professor．
He talks as（he would talk）if he would（口语中也可用will）be a professor．
He talks as（he would talk）if he were（or was）（口语中也可用is）giving a lecture．
He talked as if he were（or had been）（口语中也可用was）a professor．
He felt as（he would have felt）if the house had been（口语中也可用was）turning round him．
She weeps as if her heart would（口语中也可用will）break．
It seems as if he knew（口语中也可用knows）everything．
It looks as if he didn't（口语中也可用doesn't）care．
It seemed（to me）as if he had done something wrong．
As if前的主句有时省略。
As if he were a professor!
As if the house were turning!
As if he had done something important
另外，在than后面也可跟一个由if引起的虚拟条件句。
He feels happier than（he would feel）if he were on his wedding day．
The room looked prettier in its simplicity than（it would have looked）if he had put many decorations in it．
I can learn more from these books than（I could learn）if I had travelled in fifty countries．
b．在让步状语从句中的用法
876 虚拟语气也可在让步从句中使用，用法和条件从句中的用法很相近，常用的连词为though，although，if（=though），even if，even though，whether，whatever，wherever，however，whoever。
Though he be shy，he can be courageous．（I DOUBT whether he is shy．）
Even if he have everything，he remains unsatisfied．
Whether the rumour be true or not，we must take precaution．
（虚拟现在时be和have等多用于书面材料中，在现代口语中多用may be或is，may have或has）
Even though I were guilty，I would not confess．（I know I AM NOT guilty．）
Although he killed me，I should remain firm．
I should not wonder（or be surprised）if（=though）he did not fail（=failed）again．
Wherever you might go，you would see nothing but misery．
However dangerous it might be，I would try it once．
Even if I had known his plan，I could not have prevented it．（But I DID NOT know it．）
Even though I had done my best，I should not have met any encouragement．
Though I were to study ten years more．I could not be wiser．（But I know I SHALL NOT study more．）
Even though I should be jilted ten times more，I would not commit suicide．
877 有时连词可以省略，这时从句要用倒装语序（可参阅860节）。
Be it（=Though it be）never so（=ever so）easy，nobody will try．
Were she（=Though she were）ever so gentle，I could not marry her．
Had you（=Though you had）advised him a hundred times，he would have remained stubborn．
Were I（=Though I were）to try a hundred times，as many times I should fail．
Should he（=Though he should）eat more than usual，he would remain skinny．
c．在后果状语从句中的用法
878 虚拟语气也可用在由lest（书面语）引起的从句中，表示“唯恐……”，谓语动词多由should构成。
I always speak slowly lest I should be misunderstood．（should可以省略）
He works hard lest his family should be starved．
We kept quiet lest we should disturb our parents．
We ran as fast as possible lest we should be too late（for fear that we should be too late）.
We trembled
We were in great fear
I was afraid（or suspicious）
I felt some apprehensions
lest he should
（or might）discover
our secret.
在表示目的的状语从句中，谓语多由may，can构成，间或也可以用shall，will，若主句为过去时，从句谓语则由might，could等构成。
He works hard that（or so that，in order that）he may（or can，will，shall）maintain this family．
He worked hard that（or so that，in order that）he might（or could）maintain his family．
在以in case引起的状语从句中，谓语也多由should构成，should有时可以省略。
Take some medicine in case she get（or should get）ill on the way．（用陈述语气gets时比用get时更普通一些）
I will put down your address in case I forget（or should forget）it．
He carried an umbrella in case it should rain．
d．在时间状语从句中的用法
879 偶尔在时间状语从句中可以使用虚拟语气，但在现代英语中多用陈述语气。
I must pause till my breath come（or shall come）back．
We leave bed before the cock crow（or shall crow）.
We love each other as long as the earth last（or shall last）.
He did it when he were（or should be）in the mood．
2．That引起的名词从句中的虚拟语气
880 虚拟语气有时可用在主句后由that引起的从句中。主要有下面几种情况。
(1)在wish或would that后的从句中使用（that有时可以省略），谓语多用虚拟过去时（谈现在情况）或虚拟过去完成时（谈过去情况）。
I wish he might recover soon．
I wish he would not trouble us again．
但是：I wish（or hope）he may（or will）come no more．（间或用陈述语气）
God（or Heaven）grant it（may）be so．
I wish I could fly．
