这句话的that前面加逗号是什么意思,能帮我分析一下吗?
这个句子的主干是
You have all heard it repeated that men of sciencework by means of induction and deduction manage to extract from Nature certain natural laws and build up their theories.
作者唯恐读者不明白这些men是如何利用归纳法和演绎法manage to extract…laws和build up their theories的,就用插入的方式分别对它们进行了解释,这也是第二个和第三个that以及两个they出现的原因:
第二个that之后至natural laws的部分是对men of sciencework 如何by means of induction and deduction才manage to extract…laws的解释,其中这个that后面的they指代men of sciencework(没有这个they,这个说明句就缺少主语,此处that they manage to…=that men of sciencework manage to…);
第三个that至their theories则是对man of sciencework是如何by means of induction and deduction才build up their theories的进行的解释,此处的out of these=out of these operations.
总之,第二个和第三个that后面相应的较为凌乱的部分,都是对by means of induction and deduction做的说明,两个that和they一起构成的从句that they… manage to extract…laws和that they… build up their theories分别对应repeated后面的从句that men of sciencework by means of induction and deduction manage to extract…laws以及that men of sciencework by means of induction and deduction build up their theories.
本句中的三个that从句均是并列的宾语从句,是真正的宾语或逻辑宾语,前面第一行“...heard it repeated...”中的it则是形式宾语。代词it可以作形式主语和形式宾语。it可以作不定式、动名词和从句的形式主语和宾语。例如:
1. 形式主语:
It is necessary to do the experiment.
相当于:To do the experiment is necessary.
It is no use waiting here.
相当于:Waiting here is no use.
It is true that he won the match.
相当于: That he won the match is true.
2. 形式宾语(主要用在"动词+ it + 宾补 + 不定式短语、动名词短语、宾语从句"结构中):
I think it no use waiting here.
We find it difficult for him to deal with the problem.
We consider it necessary to do the experiment.
I think it impossible that we should give up such a good chance.