如果逻辑和语法梳理清楚了,按照自己正确理解用符合中文语言逻辑和表达习惯写出来就可以了。

Social science【主语】// is 【系动词】 //that branch of intellectual inquiry 【表语】//which seeks to study humans and their endeavors in the same reasoned, orderly, systematic, and dispassionate manner【定语从句(1)】// that natural scientists use for the study of natural phenomena【定语从句(2)】. 

参考译文：社会科学是一个知识探索的分支，它试图以同样理性的、有序的、系统的和冷静的方式来研究人类和他们的行为，为了研究自然现象，自然科学家使用了这种方式。

备注：定语从句(1)修饰前面名词短语that branch of intellectual inquiry. 定语从句(2)修饰前面名词 manner.

表语从句语法结构分析

that branch of intellectual inquiry【名词短语】// which seeks to study humans and their endeavors in the same reasoned, orderly, systematic, and dispassionate manner【修饰表语的定语从句(1)】// that natural scientists use for the study of natural phenomena【修饰 manner定语从句(2)】//

定语从句语法结构分析

 which 【主语】// seeks【谓语动词】//  to study humans and their endeavors in the same reasoned, orderly, systematic, and dispassionate manner【宾语】// 

不定式语法结构分析

to study 【不定式】// humans and their endeavors【不定式的宾语】//  in the same reasoned, orderly, systematic, and dispassionate manner【不定式方式状语】// 

第2个定语从句语法结构分析

manner【名词】//  that natural scientists use for the study of natural phenomena【定语从句】//

that 【定语从句宾语】// natural scientists【定语从句主语】//  use【定语从句谓语动词】// //  for the study of natural phenomena【定语从句目的状语】//