Without facts,we can't form a worthwhile opinion,for we need
5个回答

1.upon which to base our thinking=which to base our thinking upon

翻译:for we need to have factual knowledge upon which to base our thinking

因为我们需要有能以此为基础,可建立我们思想的事实性的知识.

2.上述结构是比较常见的“疑问词+不定式”结构,此处它做后置定语,修饰knowledge.

3.“疑问词+不定式”结构的具体讲解请参看我的另一回答:

4.“疑问词+不定式”中如果是疑问代词,而且它做后面不定式中所带的某个介词的宾语时,常常会把这个介词提前至疑问词前.

如:I want to find a story on which to base my new novel.

我想找到一个可以此为基础,写出我新小说的故事.