unattached infinitive(无依附动词不定式)

英语里确实有一个依附原则(ATTACHMENT RULE): 当充当状语的分词或动词不定式里没有主语时, 通常把句子的主语看作是它的主语:

1. To do good work, one must have the proper tools. (MD) 要想把工作干好, 必须有适当的工具(工欲善其事, 必先利其器)。

2. For nearly three hours we waited for the decision, only to be told to come again the next day. 我们等待决定等待了大约三个小时，结果却被告知第二天再来。

但是,有时候这个依附原则是可以打破的,于是便出现了 unattached infinitive。这大致有三种情况:

A. 动词不定式是个评注性状语, 隐含的主语是说话人 I 或 we:

1. To put it mildly, she's just inquisitive. (Snow) 说得委婉些，她有点儿爱管闲事。

2. To put it another way, do you like him? 换个说法,你喜欢他吗?

3. To be honest, I don't know anything about it. (McArthur) 老实说,对于这件事我什么也不知道。

B. 隐含的主语是不定代词 one:

1. To prevent cavities, dental floss should be used daily after brushing one's teeth. 为了防止齿窝，在刷牙之后应当每天使用牙线。

2. To borrow books from this library, it is necessary to register as a member of the library. “For one to borrow . . .” 要从本图书馆借书,必须登记为本图书馆成员。

C. 在科学著作中, 动词不定式隐含的主语是作者(I, we)或读者(you):

To check on the reliability of the first experiment, the experiment was replicated with a second set of subjects. 为了核查第一次试验的可靠性，我们用第二套试验对象重复进行了试验。