4. TU YU (died 812) did not publish a separate commentary on Sun Tzŭ, his notes being taken from the _T’ung Tien_, the encyclopedic treatise on the Constitution which was his life-work. They are largely repetitions of Ts’ao Kung and Meng Shih, besides which it is believed that he drew on the ancient commentaries of Wang Ling and others. Owing to the peculiar arrangement of _T’ung Tien_, he has to explain each passage on its merits, apart from the context, and sometimes his own explanation does not agree with that of Ts’ao Kung, whom he always quotes first. Though not strictly to be reckoned as one of the "Ten Commentators," he was added to their number by Chi T’ien-pao, being wrongly placed after his grandson Tu Mu. 5. TU MU (803-852) is perhaps the best known as a poet—a bright star even in the glorious galaxy of the T’ang period. We learn from Ch’ao Kung-wu that although he had no practical experience of war, he was extremely fond of discussing the subject, and was moreover well read in the military history of the _Ch’un Ch’iu_ and _Chan Kuo_ eras. His notes, therefore, are well worth attention. They are very copious, and replete with historical parallels. The gist of Sun Tzŭ’s work is thus summarized by him: "Practice benevolence and justice, but on the other hand make full use of artifice and measures of expediency." He further declared that all the military triumphs and disasters of the thousand years which had elapsed since Sun Tzŭ’s death would, upon examination, be found to uphold and corroborate, in every particular, the maxims contained in his book. Tu Mu’s somewhat spiteful charge against Ts’ao Kung has already been considered elsewhere. 6. CH’EN HAO appears to have been a contemporary of Tu Mu. Ch’ao Kung-wu says that he was impelled to write a new commentary on Sun Tzŭ because Ts’ao Kung’s on the one hand was too obscure and subtle, and that of Tu Mu on the other too long-winded and diffuse. Ou-yang Hsiu, writing in the middle of the 11th century, calls Ts’ao Kung, Tu Mu and Ch’en Hao the three chief commentators on Sun Tzŭ, and observes that Ch’en Hao is continually attacking Tu Mu’s shortcomings. His commentary, though not lacking in merit, must rank below those of his predecessors. 7. CHIA LIN is known to have lived under the T’ang dynasty, for his commentary on Sun Tzŭ is mentioned in the _T’ang Shu_ and was afterwards republished by Chi Hsieh of the same dynasty together with those of Meng Shih and Tu Yu. It is of somewhat scanty texture, and in point of quality, too, perhaps the least valuable of the eleven. 8. MEI YAO-CH’EN (1002-1060), commonly known by his "style" as Mei Sheng-yu, was, like Tu Mu, a poet of distinction. His commentary was published with a laudatory preface by the great Ou-yang Hsiu, from which we may cull the following:—