others in addition to the “13 chapters,” is good proof, Pi I-hsün thinks, that all of these were contained in the 82 _p‘ien_. Without pinning our faith to the accuracy of details supplied by the _Wu Yüeh Ch‘un Ch‘iu_, or admitting the genuineness of any of the treatises cited by Pi I-hsün, we may see in this theory a probable solution of the mystery. Between Ssŭ-ma Ch‘ien and Pan Ku there was plenty of time for a luxuriant crop of forgeries to have grown up under the magic name of Sun Tzŭ, and the 82 _p‘ien_ may very well represent a collected edition of these lumped together with the original work. It is also possible, though less likely, that some of them existed in the time of the earlier historian and were purposely ignored by him.[37] Tu Mu, after Ts‘ao Kung the most important commentator on Sun Tzŭ, composed the preface to his edition[38] about the middle of the ninth century. After a somewhat lengthy defence of the military art,[39] he comes at last to Sun Tzŭ himself, and makes one or two very startling assertions:—“The writings of Sun Wu,” he says, “originally comprised several hundred thousand words, but Ts‘ao Ts‘ao, the Emperor Wu Wei, pruned away all redundancies and wrote out the essence of the whole, so as to form a single book in 13 chapters.”[40] He goes on to remark that Ts‘ao Ts‘ao’s commentary on Sun Tzŭ leaves a certain proportion of difficulties unexplained. This, in Tu Mu’s opinion, does not necessarily imply that he was unable to furnish a complete commentary.[41] According to the _Wei Chih_, Ts‘ao himself wrote a book on war in something over 100,000 words, known as the 新書. It appears to have been of such exceptional merit that he suspects Ts‘ao to have used for it the surplus material which he had found in Sun Tzŭ. He concludes, however, by saying: “The _Hsin Shu_ is now lost, so that the truth cannot be known for certain.”[42] Tu Mu’s conjecture seems to be based on a passage in the 漢官解詁 “Wei Wu Ti strung together Sun Wu’s Art of War,”[43] which in turn may have resulted from a misunderstanding of the final words of Ts‘ao Kung’s preface: 故撰爲略解焉. This, as Sun Hsing-yen points out,[44] is only a modest way of saying that he made an explanatory paraphrase,[45] or in other words, wrote a commentary on it. On the whole, the theory has met with very little acceptance. Thus, the 四庫全書 says:[46] “The mention of the 13 chapters in the _Shih Chi_ shows that they were in existence before the _Han Chih_, and that later accretions are not to be considered part of the original work. Tu Mu’s assertion can certainly not be taken as proof.”[47]