非谓语动词逻辑主语可以不表示出来的情况

一般说来，非谓语动词的逻辑主语必定能在所在句中找到，否则被视为有语法错误。但是，下列的非谓语动词形式逻辑主语却允许不表示出来。

一、不定式短语在下列情况下，逻辑主语可不表示出来。

1.不定式作主语或表语时泛指一个动作，并无具体实施者，其隐含主语是one。例如：

To borrow books from this library, it is necessary to register as a member of the library. [For one to borrow...]要从这个图书馆借书，在图书馆做登记是必要的。

To take such an attitude is to seek truth from facts.这种态度就是实事求是的态度。

2.不定式短语作插入语表示说话人的态度，其隐含的主语是I或we。例如：

To sum up, we have to work still harder.总之，我们还得更加努力地工作。

To tell the truth, I don't agree with you.老实说，我不同意你的意见。

3.不定式短语的逻辑主语可在上下文中找到。例如：

Well, I put on weight again. To take it off would be no easy job.嗯，我又发胖了。再要减肥可不容易。

4.在一些科学论著中，隐含的不定式短语的逻辑主语是I, we, you(即作者或读者)。例如：

To increase the rate of reaction, a catalyst is used.要加快反应速度就得使用催化剂。

This medicine should be taken before meals to get the best result.这种药应在饭前服用以获得最佳疗效。

二、-ing分词短语在下列情况下，其逻辑主语可不表示出来。

1.-ing分词短语的逻辑主语泛指人，其隐含的逻辑主语是one。例如：

Seeing is believing.(作主语和表语)眼见为实。

There is no stopping him.根本不可能阻止他。

2.有时-ing分词短语强调动作，逻辑主语one常被隐含，一般作宾语或介词宾语；若作定语时，-ing分词表示用途。例如：

I don't think it worthwhile going to such a place.(作动词宾语)我认为到这种地方去不值得。

His plan is about expanding the business.(作介词宾语)他的计划是关于扩大企业的。

This is a printing house.(作定语)这是个印刷厂。

3.-ing分词短语转变成介词或连词表示说话的态度。隐含的逻辑主语一般是one(including等例外)。例如：

Considering her dislike of Martin, it was surprising that she invited him.由于她不喜欢马丁，所以她邀请他是很令人惊讶的。

Owing to our hard work, the task was fulfilled ahead of time.由于我们努力工作，任务提前完成。

Supposing he can't come, who will do the work?假如他不来了，谁干这项工作呢？

Seeing (that) she's legally old enough to get married, I don't see how you can stop her.鉴于她已到了法定结婚年龄，我想象不出你怎么能阻止她。

4.有些-ing分词短语、固定词组作插入语，表示说话人的态度、看法，此时其隐含的逻辑主语一般是说话人。例如：

Judging from his appearance, he is over fifty.从外表看，他有五十多岁。

Putting it mildly, you have caused us some inconvenience.说温和些，你给我们造成了一些不便。

5.-ing分词短语作结果状语时有时隐含的主语是整个句子，-ing分词短语的作用相当于which引导的非限制性定语从句。例如：

This siren sounded, indicating that the air raid was over.[..., which indicated that...]警报响起

来了，表明空袭结束了。

6.在被动句中，-ing分词短语的主语是被省略的主句中的动作执行者。例如：

All the work in the factory is done (by the workers) sitting down.这工厂所有工作都是坐着做的。

Ideas can be expressed (by us) accurately and effectively using simple sentences.可以用简单的语句把意思表达得精确有效。

7.以it作为形式主语的句子中，不论其真正的主语是不定式短语、-ing分词短语，还是that从句，作状语的-ing分词短语是泛指的。隐含的主语为one。例如：

Studying science, it is important combining theory with practice. [When one studies science...]学习科学时，理论联系实际很重要。

Threshing grain, it is dangerous playing with fire.打场时，玩火是危险的。

8.-ing分词短语所隐含的主语是一个表示时间、天气、距离等的it。例如：

Being Christmas, the government offices were closed. [Since it was Christmas...]因为是圣诞节，政府办公室不办公。

9.-ing分词短作状语时，隐含的主语是泛指的one。例如：

When dinning in the restaurant, a jacket and tie are required. [When one dines...]

10.-ing分词的逻辑主语在句中或-ing分词本身所在短语中找，一般是从物主代词等中可看出。例如：

Walking or sleeping, this subject was always in my mind.不论走路或睡觉，我总是想着这个问题。(通过my可看出逻辑主语是I)

Eating our dinner, the sky cleared up.我们吃饭时，天转晴了。

[注]10中的-ing分词短语表达方式尽管有人使用，但是语法学家们还是认为违反了语法规则，是不正确的或不严格的，只有在不会被误会的情况下才可使用。

三、-ed分词短语在句中逻辑主语不表示出来的情况。

1.given(考虑到), granted(即使), provided(如果/只有……才)等-ed分词具有介词或连词性质时。例如：

Given their inexperience, they have done a good job.考虑到他们缺乏经验，这工作他们算是做得不错了。

Granted that you've made some progress, you should not be conceited.即使取得了一些进步，你也不该骄傲自满。

I will go, provided that you go too.只有你也去，我才去。

2.-ed分词短语作插入语，表示说话人的一种态度，隐含的逻辑主语应为I或we。例如：

Taken as a whole, there's nothing wrong with the book.总的来说，这本书没问题。

3.有些谚语中，-ed分词逻辑主语one隐含掉了。例如：

Forewarned is forearmed.凡事预则立。

Easier said than done.说起来容易做起来难。

4.-ed分词隐含的主语是整个主句。例如：

Unknown to his closest advisers, he had secretly negotiated with an enemy

emissary. [It was unknown to his closest advisers that...]连他最亲密的顾问们也不知道，他就跟一个敌人使者秘密谈判。