本文讲解考研英语语法之【动词不定式作主语】。语法是英语学习的基础，语法大关不过，阅读、完型、翻译和写作都会有难度，就别提过线和拿高分了。所以说，基础阶段，语法基础要打好。请关注新东方在线2020考研英语语法大全系列文章，我们一起来梳理考研英语所需的基础语法和重点语法：
动词不定式作主语
在不定式短语作主语的句子中，往往用 it 作形式主语，而不把不定式短语放在句子的后面。如：
To die like that is a terrible thing.=It is a terrible thing to die like that.
象那样死去是一件可怕的事。( it 作形式主语，把真正的主语to die like that放在后面)
To know oneself is difficult.=It’s difficult to know oneself.
有自知之明不容易。
To tell a lie is not always easy.= It’s not always easy to tell a lie.
撒谎并非总是容易。
Never to offend anyone is my principle. 永远不得罪任何人就是我的原则。
It’s against nature to remain single. 保持单身是违反自然的。
To see is to believe. 眼见为实。
For a dog to die like that is a terrible thing. = It is a terrible thing for a dog to die like that.
一条狗象那样死去是一件可怕的事。(for a dog是不定式的主语)
For one to know everything is impossible.= It’s impossible for one to know everything.
一个人什么都知道是不可能的。
For his brother John to go to sea seems natural.= It seems natural for his brother John to go to sea. 他兄弟John去当水手是很自然的事。
It’ll be a great shame for you to forget her. 你要是把她忘了，那可太不应该了。
It’s not proper for us not to accept the invitation. 我们不接受邀请不合适。(否定)
It has not yet been decided when and where to discuss her resignation. 何时何地讨论她的辞职还没定。
但是，下列形容词做表语时，不定式的逻辑主语由 of 引出：
careless粗心的，clever聪明的，cruel残忍的，foolish愚蠢的，good好的，kind好心的 ，naughty淘气的，nice好的，polite礼貌的，right正确的，rude无礼的 ，silly愚蠢的，stupid傻的，unwise不明智的，wise明智的，wrong错误的，等等。
为什么这些词要用 of 引出不定式呢?
因为这些形容词都是描写人的性格和特点的形容词。“It is + 形容词 +of sb + to do sth”这样的句型更强调某人如何如何，可以改写为：“Sb + be + 形容词 + to do sth.” 而“for sb to do sth”这一结构更强调做某事如何如何。例如：
1、 It is difficult for me to learn English. 更强调学英语很难，不能写成
I am difficult to learn English. (这句话含有逻辑错误。)
2、 It is unwise of you to go to the United States at this time. =You are unwise to go to the United States at this time. 强调你不明智。
It’s very kind of you to come to see us off. =You’re kind to come to see us off. 你来为我们送行太好了。
It’s unwise of him to drink and smoke so much.=He is unwise to drink and smoke so much. 他喝这么多酒、抽这么多烟是不明智的。
It’s extremely cruel of John to kill animals. John杀害动物真是残忍之极。
It’s rude/polite of Jack to say this to her. Jack对她说这个，很无礼/礼貌。