on which + 不定式理解

FEMALE PROFESSOR: Foundationalism is the view that our "knowledge claims"-what we think we know, that is-they need to have a base.

FEMALE PROFESSOR: Um, think of knowledge as a house. You need a solid foundation on which to build your house, and if you have a strong foundation, your

FEMALE PROFESSOR: Well, foundationalists think the same thing is true of knowledge-if you have a solid base for your knowledge claims, then your knowledge structure is more likely to be strong... valid... true.

请问老师，这里的on which 是否多余？或者不定式应该改为一个完整的句子。

我见得句子不多，通常的句子中（例如下句）， prep +which后面一般加一个完整的句子，为什么这里是不定式结构？

But note that porosity is not the same as permeability, which measures the ease with which water can flow through a material;

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分类：不定式

最佳答案 2019-09-06 18:29

介词+which+to do不定式，语法上称为带有关系代词which的不定式。这种结构为正式用法，在句子中作定语。

本质上，这种结构是某种特定的定语从句的简略形式。

我以网友问题中的句子为例作以说明。

You need a solid foundation on which to build your house.

这个句子对应的定语从句为：

You need a solid foundation on which you can build your house.

注意在这个定语从句中，关系代词which作介词on的宾语，on which 在从句中作build的定语。定语从句的主语you在主句中已经出现，从句谓语can build的动作在主句谓语need的时候还没有发生，即从句的谓语是后于主句谓语的将来动作。这种定语从句就可以省略和主句相同的主语，同时删去情态动词，并将情态动词后的不带to的不定式改为to do不定式，就得到了作定语的带有关系代词which的不定式。为了更好的说明从句谓语动词为将来才会发生的动作，我们可以用be to do表示定语从句的谓语。

这个定语从句的主语和主句主语相同，就可以省略主语和be, 剩下on which to build your house作定语。

再看一个例句：

I need a chair on which I am to sit. (这是很正式的说法）

定语从句的主语与主句主语相同，谓语动作是将来的动作。于是可以省略主语和be:

I need a chair on which to sit. 正式语体

I need a chair that I am to sit on. 非正式语体

改为不定式作定语：省略that，I，am, 得到：

I need a chair to sit on.

有时虽然定语从句的主语没有在句中出现，但主语是泛指意义的人或人们，如people 或 one. 也可以省略定语从句的主语和be。例如：

This is a comfortable chair on which one is to sit. 正式

= This is a comfortable chair on which to sit. 正式

This is a comfortable chair (that) one is to sit on. 非正式

= This is a comfortable chair to sit on. 非正式

我们知道，关系代词在定语从句中作介词宾语，而介词位于定语从句之首，这种用法是很正式的结构。此时关系代词只能用which，不能用that，介词必须谓语which之前。只有这种定语从句，在满足一下二个条件的情况下，可以简略为带关系代词which的不定式结构。1）从句谓语动作在主句谓语动作时间还没有发生，为将来动作；2）从句主语在主句出现，或从句主语为泛指的人们。

非正式语体通常不用介词+which引导定语从句。通常介词留在原处，仅仅关系代词提前或省略关系代词。非正式的定语从句改为不定式结构，是不能带关系代词的。例如：

You need a solid foundation (that) you are to build your house on.

改为不定式结构时，将关系代词、主语和be同时省略，得到：

You need a solid foundation to build your house on.