Zhuang Zi was one of the few pre-qin scholars who made important statements about language. He didn’t think language could present Dao, and that was what he meant by the uncertainty of language. The uncertainty of language resulted in infinite argument while the argument about right and wrong was the main cause why men and things are not equal. Yet to eliminate disputes, we have to deal with the causes of disputes. In this paper, we employ the philosophy of language and the set theory to re-consider this important view, in wishes to understand more about the doctrines of Zhuang Zi.