Chapter 7 虚拟语气
7.8 跳层虚拟
7.8 跳层虚拟
请看下面这个“脑筋急转弯”：
The Taxi Driver Mystery
Rebecca was in a taxi on her way home. Max, the taxi driver, knew she was a well-known chatterbox and didn’t want to engage in conversation with her. So he pretended to be deaf and dumb. He pointed to his ears and mouth to indicate to her that he couldn’t hear or speak. This ruse seemed to work. The journey was peacefully silent.
When they arrived and Rebecca had got out of the taxi, Max pointed to his meter so she would read how much she owed. Rebecca looked at the meter, read what she owed him, paid him and walked off.
But she almost immediately realized that Max couldn’t have been a deaf mute.
How did she know this?
这个问题的答案很简单，就是：
He must have heard her initial instructions or he would not have known where to take her.
我们看到，这个句子的谓语比较复杂，一个是must have heard，另一个是would not have known，即两个都带有情态动词。读者要注意的是，这里的must have heard不是虚拟语气，而是must表示推测的用法（详见第八章）。在英文中，“must+have done”结构表示对过去的推测。也就是说，这里谈论的是一个过去的情形。接下来有一个关键词or，表示“否则”，其后面接的就是虚拟语气。此时我们要搞清楚两点：一是虚拟的时间。由or前面的句子我们知道，这里是表示对过去的虚拟；二是句子的谓语采用虚拟主句的谓语形式还是从句的谓语形式。因为or后面的句子相当于一个虚拟主句，所以其谓语自然要采用虚拟主句的谓语形式。搞清楚这两点，就知道为什么要说would not have known了，因为这正是一个过去虚拟的主句谓语结构形式。
由此可见，这是一类较为特殊的虚拟语气。这类虚拟句一般分为两部分，两部分在语气上截然相反，一部分虚拟，另一部分不虚拟，而用的是陈述语气，用以陈述一个事实。比如上面这个句子就是“陈述句or+虚拟句”这样的结构。它们二者之间往往有but，or，or else或otherwise来连接。正是因为这种虚拟与不虚拟兼而有之，一部分虚拟，一部分又跳出虚拟的圈子，故我称之为“跳层虚拟句”。
7.8.1 陈述句+or+虚拟主句
这里的连接词除了or，还可以用or else和otherwise。需要注意的是，or前面的句子是陈述语气，而后面的句子用的是虚拟语气，而且是虚拟主句。具体的谓语搭配结构是：
1. 主语一般现在时的谓语形式, or+主语+would do→表示对现在事实的虚拟；
2. 主语+一般过去时的谓语形式, or+主语+would have done→表示对过去事实的虚拟。
请看下面的对话：
1 Jo: You look tired. What have you been doing?
Emily: I’ve been burning the midnight oil. Been writing my mid-term essay.
Jo: Oh no! I feel sorry for you. I thought you’d finished it already?
Emily: Yes, I did. But my teacher wasn’t happy with it. She told me to do it all again!
Jo: No way! Your teacher is mean.
Emily: Well, I had to do it. Otherwise, she would have given me a low score.
Jo: I suppose if you look at it like that, then your teacher is not mean at all. After all she gave you a second chance.
Emily: Yeah, and I have to admit that my essay is better now. I really need to do well so that I can get a scholarship.
Jo: Well, good luck then.
Emily: Thanks, and I’m going to sleep like a log tonight!
妙语点睛 这里前面的had to do it表示过去的时间，otherwise后面要接一个过去虚拟的主句形式，所以谓语是would have given。
埃米莉：谢谢！我今晚得好好睡一觉！
2 We didn’t know his telephone number, otherwise we would have telephoned him.
=We would have telephoned him if we had known his telephone number.
妙语点睛 这是一道四级真题。这里的didn’t表示陈述过去的事实，而otherwise的后面则是对过去的虚拟，且是虚拟主句的形式，因此要用would have done。
3 He must have had an accident, or he would have been here then.
妙语点睛 这是一道四级真题。这里or的前面通过用must have had这一形式来表示对过去的推测，是属于陈述过去，而or的后面则用过去虚拟。
4 Mary couldn’t have received my letter; otherwise she would have replied before now.
妙语点睛 这里otherwise后面的句子表示对过去的虚拟，相应地，其前面的半个句子就是表示陈述过去，所以要用一般过去时。不过，这里情态动词的过去时态couldn’t have done的形式表示对过去的推测，类似于must表示推测。
7.8.2 虚拟主句+but+陈述句
与or等词不同的是，这里but的前面是虚拟主句，but的后面是陈述句。该句型的使用规律是：
1. 主语+would do, BUT+主语+一般现在时的谓语形式→表示对现在事实的虚拟；
2. 主语+would have done, BUT+主语+一般过去时的谓语形式→表示对过去事实的虚拟。
当然，句中的would可换成should, might或could。这类跳层虚拟句的关键标志词是but，随着but一转折，句子的语气也由虚拟变为不虚拟，即but将句子一分为二，but前面部分的句子用虚拟语气，but后面部分的句子用陈述语气。请看例句：
1 He would put on weight, but he doesn’t eat much.
=He would put on weight if he ate much.
妙语点睛 这里不用didn’t，而是doesn’t。因为前面的would不是表示过去时态，而是表示对现在事实的虚拟，原句相当于“If he ate much, he would put on weight.”。这就解释了为什么but前面的半句话相当于虚拟主句形式了，因为but后面的陈述句相当于一个虚拟从句。
2 He could not have bought that limousine, but he inherited a big fortune from his father.
=He could not have bought that limousine if he had not inherited a big fortune from his father.
妙语点睛 这句话相当于“If he had not inherited a big fortune from his father, he could not have bought that limousine. ”。这就解释了为什么but前面的半句话相当于虚拟主句形式了，因为but后面的陈述句相当于一个虚拟从句。
3 A: I thought you were going to call me last night about the train schedule.
B: Sorry. I would have. But Harry and Jack stopped by and stayed past midnight.
妙语点睛 这里的I would have是一个省去了called的虚拟主句，表示对过去事实的虚拟，由but后面的陈述句的谓语stopped可得知。
4 I would have gone to visit him in the hospital, had it been at all possible, but I was fully occupied the whole of last week.
妙语点睛 这里but前面的句子是过去虚拟，所以采用过去虚拟主句的谓语形式would have gone。but后面的句子是陈述过去的事实。
5 Some women could have made a good salary in a job instead of staying home, but they decided not to work for the sake of the family.
=Some women could have made a good salary in a job instead of staying home if they hadn’t decided not to work for the sake of the family.
妙语点睛 这是一道四级真题。这里but后面的句子是陈述过去的事实，but前面的句子是对过去的虚拟，所以采用过去虚拟主句的谓语形式could have made。
有时不用but来表示转折，而是用其他副词，比如下句中的unfortunately：
6 A safety analysis would have identified the target as a potential danger. Unfortunately, it was never done.
妙语点睛 这里的unfortunately在语义上相当于but，表示转折，使句子从虚拟转为不虚拟。这里的was表示过去，因此前半部分也是表示过去，所以采用过去虚拟主句的谓语形式would have identified。
思维总结
共有两类跳层虚拟句，一类是由or等引导的，具体的句型结构是：
1. 主语+一般现在时谓语形式，or+主语+would do→表示对现在事实的虚拟；
2. 主语+一般过去时谓语形式，or+主语+would have done→表示对过去事实的虚拟。
另一类是由but引导的，具体的句型结构是：
1. 主语+would do，but+主语+一般现在时谓语形式→表示对现在事实的虚拟；
2. 主语+would have done，but+主语+一般过去时谓语形式→表示对过去事实的虚拟。
注意这两类句型的前后两个分句的语气正好相反。
思维训练 7.8 Key
请选择最佳答案填空。
1. We didn’t know his telephone number, otherwise we ______ him.
A. would have telephoned
B. must have telephoned
C. would telephone
D. had telephoned
2. He must have had an accident, or he ______ then.
A. would have been here
B. should be here
C. had to be here
D. would be there
3. Mary ______ my letter; otherwise she would have replied before now.
A. has received
B. ought to have received
C. couldn’t have received
D. shouldn’t have received