请有兴趣的网友剖析此句语法结构，for这里又是什么使用方法？
该句中的is有些是不及物动词，意为存在，有些是系动词。为了便于剖析，大家先把不及物动词is用exists替换，结构就了解了。
For to say that what exists doesn't exist or that what doesn't exist exists, is false, but to say that what exists exists and what doesn't exist doesn't exist, is true, so that the one who says that something exists or doesn't exist is either right or wrong.
1 for为并列连词，用作句首表示本句和前面一句话为因果关系，本句是前面那句话是什么原因。
2 to say that what exists doesn't exist or that what doesn't exist exists, is false 这是主句中的并列分句1，为主系表结构 to do sth is false. 主语为不定式短语 to say A or B。A和B均为to say的宾语从句。A=that what exists doesn't exist，what exists为that从句的主语，doesn't exist为谓语动词。B=that what doesn't exist exists, what doesn't exist为that从句的主语，exists为谓语动词。
3 but to say that what exists exists and what doesn't exist doesn't exist, is true 这是主句中的并列分句2，为主系表结构 to do sth is true. 主语为不定式短语to say that C and D。C和D均为to say的that宾语从句中并列的二个分句。C=what exists exists, what exists为主语，exists为谓语动词。D=what doesn't exist doesn't exist，what doesn't exist为主语，doesn't exist为谓语动词。
4 so that the one who says that something exists or doesn't exist is either right or wrong. 这是主句中的结果状语从句。这个结果状语从句相对简单，就不需要剖析了。
句子大意：
这是由于，说存在的东西没有，或者说没有的东西存在，都是错的；而说存在的东西存在，没有的东西没有，就是正确的。因此，一个人说某个东西存在或没有，他要么说对了，要么说错了。
