条件状语从句和虚拟语气

条件状语从句分为两大类：

• 真实条件状语从句，是指可能会发生的事情（大概率事件）。比如，如果我明天发了工资，我就请你吃饭。
• 虚拟语气，是指几乎不可能发生的事情（小概率事件）。比如，如果明天我彩票中了500万，我就请你吃饭。

在汉语中，这两类句子很好区分，然而在英语中则不然，一定要通过动词的变化，来达到不同的意思。

一、真实条件状语从句

1.1、if（如果…）

if后面可以加then，如果then省略了，也隐含在句子的意思里。if引导的条件状语从句，主要用来表示客观事实和将来可能发生的情况。

在表示客观事实时，从句用一般现在时，主句用一般现在时或现在进行时，即“主现从现”。

• If I eat too much, I feel uncomfortable.
• If you can’t beat them, join them
• If you drink and drive, you are breaking the law.

在表示将来可能发生的情况时，从句用一般现在时，主句用一般将来时，即“主将从现”。此时主句的will表示肯定或很可能发生的事情。

• If you park your car in the wrong place, a traffic policeman will soon find it.

• You will be very lucky if he lets you go without a ticket.

• If she comes, she will get a surprise.

  注：如果主句的肯定程度不是很高，就可以用别的情态助动词代替will

• Are you successful in language learning? If it is less successful, you should do well to try the above ways.

• If they are not brought to the surface soon they may lose their lives.

• If the students are interested in sports, they can join different sports clubs.

如果在条件状语从句中出现了will，不是将来时，而是表示意愿。

• If I will prepare, my chance will come someday.
• If a man will not seek knowledge, it will not seek him.

1.2、unless（除非…）

unless引导的条件状语从句，时态通常都是一般现在时，而且主句常常是否定句。

• All dreams are of no value unless they are followed by action.
• I won’t call you, unless something unexpected happens.

1.3、其它比较常用的连接副词

下面是一些比较常用的连接副词：

• suppose / supposing (that)
• on condition that
• so long as / as long as
• providing / provided (that)
• assuming
• once
• in case

例句：

• In case you fail, don’t be discouraged. Keep trying.（从句一般现在时，主句一般现在时）
• Suppose you make some mistakes, it’s not the end of the world.（从句一般现在时，主句一般现在时）
• We can do whatever we wish to do provided (that) our wish is strong.（从句一般现在时，主句一般现在时）
• Assuming you are willing to work hard, I see a great future waiting for you.（从句一般现在时，主句一般现在时）
• So long as there’s something to identify, we will give people there money back.（从句一般现在时，主句一般将来时）
• My parents don’t mind what job I do as long as I am happy.（从句一般现在时，主句一般现在时）
• You’ll like her once you get to know her.（从句一般现在时，主句一般将来时）

1.4、only if（只有…才） & if only（只要…就）

• He can continue to support himself and his family only if he produces a surplus.
• Only if I get a job will I have enough money to go to school.（only if放句首，主句要倒装）
• The Almighty has given men arms long enough to reach the stars if only they would put them out.

注：only if前可以加上but

• I’ll do that, but only if we set a few rules.

1.5、翻译练习

• 如果我熬夜（stay up）过半夜，第二天早上起来看起来就很糟。
• 如果你接受这份昂贵的礼物，就是在受贿了（take a bribe）。
• 如果明天下雨，我们将取消这个活动。
• 你们大火如果形成团队（team up），可能有助于形成一个双赢的（win-win）局面。
• 除非你加紧用功，否则你就不能通过考试。

二、虚拟语气的常规用法

在汉语中，虚拟语气是通过语境实现的。而在英语中，则是通过谓语动词的变化实现的。虚拟语气的常规构成方式如下：

• 现在虚拟：从句一般过去时（be用were），主句过去将来时（would可改成should，might，could）
• 过去虚拟：从句过去完成时，主句过去将来完成时（would可改成should，might，could）
• 将来虚拟：从句should + 动词原形，主句过去将来时（would可改为should，might，could）

2.1、现在虚拟：从句一般过去时，主句过去将来时

现在虚拟中的“现在‘，不一定是发生在现在的事情，也可能是”常态“，也就是对客观事实的虚拟。比如”如果太阳从西边出来，中国队就能打败巴西队“。

• ‘Young man,’ she answered, ‘if you ate more and tallked less, we would both enjoy our dinner!’
• The tunnel would be well-ventilated if tall chimneys were built above sea-level.
• This would solve the problem of ventilation, for if a train entered this tunnel, it would draw in fresh air behind it.
• If they knew how difficult it was to drill through the hard rock, they would lose heart.

2.2、过去虚拟：从句过去完成时，主句过去将来完成时

在描述过去时，做一个假设。比如“如果不是因为那时英国人害怕入侵，隧道早已建成了。”

• If, at the time, the British had not feared invasion, the tunnel, would have been completed.
• If the Houses of Parliament had not been burned down in 1834, the great clock would never have been erected.
• If there had not been a hard layer of rock beneth the soil, they would have completed the job in a few hours.

2.3、将来虚拟：从句should + 动词原形，主句过去将来时

表示在未来发生的事情， 表达一种可能性，比较少见的用法。

If peter should come again, I would throw him out.

2.4、翻译练习

• 如果当时你帮助我的话，我就可以完成任务了。
• 要是我是你，我会坐地铁去那儿。
• 如果我有100万美元，我就会买一套豪华别墅。
• 万一火山爆发了，有可能造成一场可怕的灾难。

三、条件状语从句转化为分词短语

当分词短语表条件时，但从分词短语本身，是看不出真实和虚拟的，只有从句的时态才能看出来。

• Cooked in wine, snails are a great luxury in various parts of the world.（因为主句是一般现在时，所以本句的分词短语是真实条件，相当于真实条件状语从句If snails are cooked in wine, …）
• Weather permitting, we’ll go fishing.（因为主句是一般将来时，所以本句的分词独立主格结构是真实条件，相当于真实条件状语从句If weather permits, we’ll go fishing.）
• Added to steel, chromium increases the metal’s hardness.（相当于真实条件状语从句If chromium is added to steel, it increases the metal’s hardness.）
• Given more time, I would be able to complete it.（相当于虚拟条件状语从句If I were given more time, I would be able to complete it.）
• Given the right kind of training, these teenage soccer players may one day grew the international stars.

四、虚拟语气的特殊用法

与客观真理相反的强烈虚拟语气，从句用were to + 动词原形，主句用过去将来时（would可改为should，might，could）

• If I were to live my life over again, I would have you as my wife.
• If the sun were to rise in the west, I would marry you.

主观意志动词之后的宾语从句，要使用助动词should（可省略）。这类动词主要有3大类：“建议（suggest，advise，propose）”，“要求（demand，require，request，insist）”，“命令（order，command）”

• He suggested that a double railway tunnel (should) be built.
• In life, your goals may require that you (should) try different approaches and persevere.

should (ought to) have + 过去分词，表示与过去事实相反的推测，译为“早应，本应该…”

• He should have known that the police would never allow this sort of thing.

• Those who failed to get in need not have felt disappointed as many of the artistes who should have appeared did not come.

• A policeman approached Jimmy and told him he ought to have gone along a side-street as Jumbo was holding up the traffic.

  注：这里绝对不能说he ought to go along，它的意思是“只是他做某件事情”。

whether引导的让步状语从句，可用虚拟语气

• Whether it be bird, fish or beast, the porpoise is intrigued with anything that is alive.

• After all, all living creatures live by feeding on something else, whether it be plant or animal, dead or alive.

  注：这种句型也可倒装，即去掉whether，把be放到从句句首。

• Be it bird, fish or beast, the porpoise is intrigued with anything that is alive.

• Be it a rock or a grain of sand, they sink as the same in water.

• All students of English, be they native speakers or those who are studying English as a second language, will profit from this book.

wish后面的宾语从句，必须使用虚拟语气

• I wish he were here.（现在虚拟，用一般过去时）
• I wish I had kept faithful to my childhood dreams.（过去虚拟，用过去完成时）
• I wish you would keep on trying to improve your English.（将来虚拟，用过去将来时。would可改为should，might，could）

if only用于虚拟，表示“要是…该多好啊！”（时态变化同wish一样）

• If only he were here.
• If only I had known it earlier.
• If only I would make a lot of money.

as if / as though用于虚拟，表示“就像…一样”（时态变化同wish一样）

• He acted as if he had never lived in England before.
• I do not turn for protection to dreary cliches about respect of elders – as if mere age were a reason for respect.
• I felt as if I had stumbled into a nightmare country, as you sometimes do in dreams.
• It looks as if there would be an exciting race across the Channel.

would rather / would sooner用于虚拟，表示”宁可…“。现在和将来虚拟，均用一般过去时。过去虚拟，用过去完成时。

• I would rather you had more health than wealth.（过去虚拟）
• I would rather my father kept his mind and body active after he retires in three years.（将来虚拟）
• I would rather my son had become a doctor, but he became a teacher after graduating.（过去虚拟）

lest / in case / for fear的虚拟，表示“以防…”，谓语均要使用should（可省略） + 动词原形

• Weigh well your words lest they (should) be swords.
• Take time when time comes, in case it (should) steal away.
• We must not promise what we should not, for fear that we (should) be called on to perform what we cannot.

what if …？如果…会怎么样呢？

• What if he doesn’t agree?
• But what if your data do not support your hypothesis? Perhaps different experiments are needed.

翻译练习：

• 你若中了一亿美元，你可能会做什么？
• 如果我五年前遇到她，今天她可能就是我的妻子了。
• 我建议你把这篇作文撕掉，再从头开始写。
• 我们几个月前就该预见到这一困难。
• 既然已完成了工作，你本就应该好好休息一下。
• 所有物质，不论是气体、液体、或固体，都是由原子构成的。
• 我希望我能改掉吸烟的习惯。
• 我倒希望你当初别把这一切都告诉我。
• 我多么希望你妹妹能在这儿。
• 太疲倦了。如果明天能不上班多好。
• 玛丽对着我微笑，仿佛他已经了解我想要什么。
• 我们小声说话以免吵醒婴儿。
• 我要是没有买这栋房子又会怎么样呢？