1.固定用语，连词，可用于句首。in so far as=so far as, as far as在…范围内;就……而论（来说，而言），在……程度上；请看：
That's the truth, in so far as I know it.
就我所知，那是真实情况。《牛津高阶英汉双解词典》
I’ll help you in so far as I can.
我将尽力帮助你。
In so fa as we can believe these facts we will use them.
我们将在我们所能相信的范围之内来利用这些事实。
He is a Russian in so far as he was born in Russia, but he became a French citizen in 1920.
就他出身于俄国而言他是俄国人，但他在1920年入了法国籍。
2.in so far as= in that = because 因为
Our protest was successful, in so far as/in that the Minister agreed to reconsider the matter.
我们的抗议取得了胜利，因为部长同意重新考虑这件事。
Looking back helps insofar as it helps you learn from your mistakes.
审视过去的作用是能帮你从错误中吸取教训。《柯林斯高阶英汉双解学习词典》
In so far as any inquiry is a secret one, it naturally limits all those engaged in carrying it out from effective contact with their fellow scientists either in other countries or in universities, or even, often enough, in other departments of the same firm.
由于研究是保密的,所以这就必然会限制所有从事研究工作的人员同其它国家或大学的、甚至常常在本公司其他部门的同行科学家进行有效的接触。（新概念4，P58）
Man has rights only in so far as they are a correlative of duty.
只有承担义务才能享受权利。《柯林斯高阶英汉双解学习词典》
试译：唯一因为承担义务，所以享受权利。
3. in so far as=insofar as, insofar as是美国英语写法。请看：
Looking back helps insofar as it helps you learn from your mistakes.
审视过去的作用是能帮你从错误中吸取教训。
《柯林斯高阶英汉双解学习词典》
Insofar as I can say now, I shall come.
目前我只能说来。
Insofar as schools teach perceptual patterns they tend to destroy creativity and genius.
由于学校教的是感性的模式，它们往往会摧残学生的创造性和才能。