Tu Mu’s conjecture seems to be based on a passage which states: "Wei Wu Ti strung together Sun Wu’s _Art of War_," which in turn may have resulted from a misunderstanding of the final words of Ts’ao King’s preface. This, as Sun Hsing-yen points out, is only a modest way of saying that he made an explanatory paraphrase, or in other words, wrote a commentary on it. On the whole, this theory has met with very little acceptance. Thus, the _Ssu K’u Ch’uan Shu_ says: "The mention of the 13 chapters in the _Shih Chi_ shows that they were in existence before the _Han Chih_, and that latter accretions are not to be considered part of the original work. Tu Mu’s assertion can certainly not be taken as proof." There is every reason to suppose, then, that the 13 chapters existed in the time of Ssu-ma Ch’ien practically as we have them now. That the work was then well known he tells us in so many words. "Sun Tzŭ’s _13 Chapters_ and Wu Ch’i’s _Art of War_ are the two books that people commonly refer to on the subject of military matters. Both of them are widely distributed, so I will not discuss them here." But as we go further back, serious difficulties begin to arise. The salient fact which has to be faced is that the _Tso Chuan_, the greatest contemporary record, makes no mention whatsoever of Sun Wu, either as a general or as a writer. It is natural, in view of this awkward circumstance, that many scholars should not only cast doubt on the story of Sun Wu as given in the _Shih Chi_, but even show themselves frankly skeptical as to the existence of the man at all. The most powerful presentment of this side of the case is to be found in the following disposition by Yeh Shui-hsin: [17]— It is stated in Ssu-ma Ch’ien’s history that Sun Wu was a native of the Ch’i State, and employed by Wu; and that in the reign of Ho Lu he crushed Ch’u, entered Ying, and was a great general. But in Tso’s Commentary no Sun Wu appears at all. It is true that Tso’s Commentary need not contain absolutely everything that other histories contain. But Tso has not omitted to mention vulgar plebeians and hireling ruffians such as Ying K’ao-shu, [18] Ts’ao Kuei, [19], Chu Chih-wu and Chuan She-chu [20]. In the case of Sun Wu, whose fame and achievements were so brilliant, the omission is much more glaring. Again, details are given, in their due order, about his contemporaries Wu Yuan and the Minister P’ei. [21] Is it credible that Sun Wu alone should have been passed over? In point of literary style, Sun Tzŭ’s work belongs to the same school as _Kuan Tzŭ_, [22] _Liu T’ao_, [23] and the _Yüeh Yu_ [24] and may have been the production of some private scholar living towards the end of the "Spring and Autumn" or the beginning of the "Warring States" period. [25] The story that his precepts were actually applied by the Wu State, is merely the outcome of big talk on the part of his followers.