请教一个关于by which的定语从句

Question

王若平考研英语难句过关中的一句话，原句：Yet members of the nation's present educational and cultural elite still cling to the notion that the United States belongs to some vaguely defined entity they refer to as "Western civilization," by which they mean, presumably, a civilization created by people of Europe, as if Europe can even be viewed as completely uninfluenced by the rest of the world.
我能看懂这句话的意思，就是有一个细节想不通，为什么要用by which引导非限制性定语从句修饰“Western civilization”，直接用which引导不可以么？我怎么觉得这个地方加个by有点多余？

Answer 1

把句子提出来
The United States belongs to some vaguely defined entity they refer to as "Western civilization," by which they mean, presumably, a civilization created by people of Europe

如若将非限定性定语从句放在句子中间，起前后都需要用逗号隔开。

去掉不相干的
The United States belongs to "Western civilization," by which they mean a civilization created by people of Europe

这个句子其实是 mean by sth～ by 提前而已 不用是不可以的哦·

如：hat do you mean by “out of the question”? 你说“不可能”，是什么意思？

句子翻译：然而，当今（美国）教育文化界的精英分子还抱有这样的观念，美国属于（某种）定义模糊的他们称之为西方文明的实体，这所谓的文明想必是指由欧洲人创造的文明，仿佛把欧洲看做完全不受世界其他地方影响似地。

希望帮到你

Answer 2

把后面的主语谓语宾语前移的话， they mean "something" 后接by which, 而不是which.

Answer 3

你好，俊狼猎英团队为您解答：
by which they mean 结构 为什么用by,

理由： 这里是mean... by 结构
比如： What do you mean by "success"? 你说success是什么意思？
What do you mean by doing that? 你那样做是什么意思？本回答被提问者采纳

Answer 4

by的意思是通过