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Theory is a kind of essay style, according to Yun: "Commentator, discuss also". "Selected Works of Zhaoming" said: "There are two theories. One is the theory of history, which is the judgment of good and evil made by loyal ministers at the end of biographies. For example, Tai Shigong said after Historical Records. Second, when it comes to political theory, it is fallacious for a bachelor and doctor to talk about ancient and modern figures or comment on classics and history. " For example, The Six Kingdoms and Guo Qin.