The theory is now the basis on which all our ideas of the un

关系代词which的用法
在非限定性定语从句中,只宜用which,不宜用that.
Beijing,which is the capital of China,is a very beautiful city.
在限定性定语从句中which和that在指代物的时候常常可以通用,但是有时只宜用which
而不用that
i.关系代词前面有介词的时候
This is the hotel in which you will stay.
ii.如果有两个定语从句,其中的一句的关系词是that,另一句宜用which.
Let me show you the novel that I borrowed from the library which was newly
open to us.
3.关系代词与介词,关系代词的省略
a) 关系代词和介词
介词放在关系代词的前面时,介词短语只能用which代物,和用whom代人
This is the hero of whom we are proud.
I want to find the very pen with which I wrote that letter.
当介词放在句子的末尾时,可用that/which代物,that/whom/who来作为介词的宾语,
且这个做介词宾语的关系代词往往忽略
This is the hero that (who/whom/忽略) we are proud of.

the theory是主语
is是系动词
now是时间副词 basis on 是基于的意思 应该是介词
which引导定语从句 all后面是修饰which的

我觉得the theory is now the basis是主句部分,on which是介词+关系代词的定语从句吧，which 指代basis

做介词on的宾语，引导宾语从句，仅供参考

on which 因为前面是basis 定语从句
on which all our ideas of the universe are built都是来修饰 basis的

on which 是一个引导词 它修饰前面的the basis