用ｏｆ還是ｆｏｒ

在以某些形容詞作表語時，句子的真正主語是一個動詞不定式，我們常用代詞it作句子的形式主語，而將其真正的主語動詞不定式移到表語形容詞后面。這時，不定式前常用介詞引出不定式的邏輯主語。例如：

1．It is wise for him to get away.他走開是明智的。

2．It is wise of，him to get away.他很明智，他走開了。

不少同學不知如何選擇of和for，對這兩個介詞所引導的邏輯主語在意義上有何差異感到很難理解。本文想就這～問題作一點探討，僅供參考。

一、分清兩類不同的形容詞

第一類：easy，hard，difficult，import-ant，necessary，possible，impossible等。這類形容詞只反映不定式動詞的行為性質，不反映行為者的特征。

第二類：kind，good，nice，brave，cour-ageous，wise，clever，foolish，unvclse，crud，polite，impolite，right，wrong，careful，careless，crazy，selfish，stupid，silly等。這類形容詞既可以反映不定式動詞的行為性質，也可以反映行為者的特征。它們通常是表示“真假、善惡、美丑”的內涵，被用來評價、鑒定他人的道德、品性或行為規范。 在“It is(was)...”句型中，第一類形容詞只能與for搭配；而第二類形容詞既可與of搭配，又可與for搭配，不過含義有所不同。例如：

1．It was important for him to speak atthe meeting.

句中for不可換成of。for短語說明不定式表示的動作是誰做的，形容詞著重說明行為的特征。意為：It was important that heshould speak at the meeting.不可說成：Hewas important to speak at the meeting.

2．It is kind of you to help us．

句中of可以換成for，不過含義不同。用of時說明不定式指的是誰的情況，即某人怎么樣，形容詞著重說明行為者的特征。其意思相當于：You are kind to help us．而用for時其含義側重為：It is kind that you shouldhelp us．

二、分清泛指和特指

如果不定式前的邏輯主語是泛指不是特指，介詞就該用for，因為，泛指的行為者不是形容詞著重要說明的對象。例如：

1．It is not polite for a person to speakwith his mouth full of food.

2．I don’t think it's right for people tomarry only for money.

3．It's necessary for man to protect na-ture.

注意：在邏輯主語是泛指的情況下，for可以和兩類形容詞搭配，如上例。

如果不定式前的邏輯主語是特指的、明確限定的，這時就可根據說話者的側重點來選擇of或for。比較例句：

1．It was clever for Edison to inventthe electric light.

2．It was clever of Edison to invent theelectric light．

1句用for短語，側重指動作的性質，指“愛迪生發明電燈”一事是聰明的行為。而愛迪生本人聰明與否不是說明的主要對象。2句則主要指愛迪生是聰明的，側重于對他的贊揚，因為他發明了電燈。

注意：在這種情況下，仍要遵循兩類形容詞與of和for的搭配習慣。如上例2句中clever不可換成第一類形容詞，不可說成：Itwas important of Edison to Invent the dec-tric light.

又如：

正：It is wrong for my son to take sucha small house.

正：It is wrong of my son to take such asmall house.

誤：It is difficult of my son to take sucha small house.

正：It is difficult for my son to takesuch a small house.

再引用幾個詞典和教材中的例句：

1．It was not right for the South tobreak away from the Union.

2．It was silly for you to conceal it.

3．It was silly of him to take offence atwhat she had said.

4．You think it's right for people tomarry for money.

5．It's considered impolite for a man towear a hat indoors.

6．Do you think it's normal for a childto get so tired?