During the Sui dynasty

It is not known when Du Zhenglun was born, but it is known that he was from what would eventually become Xiang Prefecture (相州, in modern Handan, Hebei). During the Renshou era (601–604) of the Sui dynasty's founding emperor Emperor Wen, Du Zhenglun and his older brothers Du Zhengxuan (杜正玄) and Du Zhengzang (杜正藏) all passed the imperial examination. As Sui dynasty imperial examinations were considered unusually difficult—with only 10-odd examinees passing each year—the Du household received great acclaim for having three brothers who did so. It was said that Du Zhenglun was capable in literature, particularly in explaining meanings of passages. He later served as a military officer in the Sui imperial government.

During Emperor Gaozus reign

During the reign of the Tang dynasty's founder, Emperor Gaozu, Du Zhenglun was initially serving as the military advisor to the commandant at Qi Prefecture (齐州, roughly modern Jinan, Shandong). Emperor Gaozu's son, the major general Li Shimin the Prince of Qin became aware of Du's talents and invited him to serve as a resident scholar at Li Shimin's mansion.

During Emperor Taizongs reign

In 626, Li Shimin became emperor (as Emperor Taizong). One of his key advisors, Wei Zheng, recommended Du Zhenglun's talent and stated that there were few people as talented. Emperor Taizong then made Du an official at the ministry of defense in 627. In 628, Du was made imperial attendant and put in charge of recording Emperor Taizong's acts for imperial archives. On one occasion, Emperor Taizong stated, "Everyday, as I sit in judgment of important matter and get ready to speak, I think carefully about whether what I have to say has any benefit or harm to the people. That is why I do not speak a lot." Du responded, "Whatever an emperor says is recorded in history. As my responsibility is to record Your Imperial Majesty's acts, I have to be honest. If any of your words is improper, it will harm your reputation for a thousand years, and it is not only harmful to the people. May Your Imperial Majesty consider this carefully." Emperor Taizong was pleased with these words and gave Du an award of silk.

In 630, Du was promoted to the post of Zhongshu Shilang (中书侍郎), the deputy head of the legislative bureau of government (中书省, Zhongshu Sheng). In 632, after Du and three other officials, Wei Ting (韦挺), Yu Shinan, and Yao Silian had submitted petitions commenting on various imperial acts, Emperor Taizong invited them to a feast, where he thanked them for being honest at danger to themselves (as they risked offending the emperor). Du was soon given titles as imperial advisor and scholar, as well as a member of the staff of Emperor Taizong's crown prince Li Chengqian—with Emperor Taizong specifically asked to counsel Li Chengqian in proper behavior. In 636, he was again Zhongshu Shilang, but still served on Li Chengqian's staff; he was also created the Marquess of Nanyang. It was said that Du was known for his capability in handling the matters at both palaces (i.e., the emperor's palace and the crown prince's palace).

However, soon Du drew both the emperor's and the crown prince's ires. At that time, Li Chengqian was suffering from a foot ailment that made it difficult for him to walk, and therefore he did not see Emperor Taizong often, but instead spent his time in frivolous activities with associates that Emperor Taizong disapproved of. Emperor Taizong told Du:

Du made several suggestions to Li Chengqian, asking him to change his ways, but Li Chengqian did not do so. Du told Li Chengqian what Emperor Taizong told him—which led to Li Chengqian immediately submitting an objection to Emperor Taizong. Emperor Taizong asked Du, "Why did you let him know what I said?" Du responded, "He did not listen to me, so I wanted to scare him with your words. I hoped that he would be scared and would change his ways." Emperor Taizong was still displeased, and he demoted Du to the post of prefect of Gu Prefecture (谷州, in modern Luoyang, Henan), and later to be the commandant at Jiao Prefecture (交州, roughly modern Hanoi, Vietnam). After Li Chengqian was revealed to have plotted with the general Hou Junji to overthrow Emperor Taizong in 643, Du was accused of having received a gold belt from Hou, and he was stripped of his rank and exiled to Huan Prefecture (驩州, also in modern Vietnam). However, later he successively served as the prefect of Ying (郢州, roughly modern Wuhan, Hubei) and Shi (石州, roughly modern Lüliang, Shanxi) prefectures.

During Emperor Gaozongs reign

In 656, Du Zhenglun was serving as the deputy minister of treasury, when Emperor Taizong's son and successor Emperor Gaozong promoted him to serve as Huangmen Shilang, the deputy head of the examination bureau (门下省, Menxia Sheng). Emperor Gaozong also gave him the designation of Tong Zhongshu Menxia Sanpin, making him a chancellor de facto. Du was also created the Duke of Xiangyang. In 657, he was made Zhongshu Ling (中书令), the head of the legislative bureau and a post considered one for a chancellor. Later that year, he concurred with the official Liu Xiangdao that there were too many people made imperial officials, and Emperor Gaozong put them in charge of drafting a proposal to reduce the number of officials. However, their proposal ran into much opposition from other officials and was never carried out.

Meanwhile, Du was beginning to have conflict with fellow chancellor Li Yifu, who also carried the title of Zhongshu Ling, as Du considered himself the senior official, but Li, who was an ally of Emperor Gaozong's powerful wife Empress Wu (later known as Wu Zetian), disrespected Du. They argued frequently before Emperor Gaozong, who rebuked both for not cooperating with each other. On December 6, 658, Emperor Gaozong demoted both to be prefects—in Du's case, the prefect of Heng Prefecture (横州, roughly modern Nanning, Guangxi). Du was said to have died at Heng Prefecture soon thereafter.

Notes and references

• Old Book of Tang, vol. 70.https://web.archive.org/web/20080210041809/http://ef.cdpa.nsysu.edu.tw/ccw/02/tan08.htm

• New Book of Tang, vol. 106.https://web.archive.org/web/20071011093344/http://ef.cdpa.nsysu.edu.tw/ccw/02/ntan15.htm

• Zizhi Tongjian, vols. 192, 193, 194, 197, 200.

生平

隋朝隋文帝仁寿年间，杜正伦与其兄杜正玄、杜正藏通过了科举。隋代举秀才止十馀人，杜正伦一家已有三秀才，时甚称道。杜正伦精于文学，特别精通解释经典。在隋朝为羽骑尉。唐高祖建立唐朝取代隋朝，杜正伦为齐州（今山东济南市）总管府录事参军。唐高祖的儿子秦王李世民闻其名，令他入直秦府文学馆。

626年，李世民即位为唐太宗。尚书右丞魏徵推荐杜正伦才能古今无比，唐太宗在627年以杜正伦为兵部员外郎。628年，杜正伦为给事中兼知起居注。一次，唐太宗表示：「朕每日坐朝，欲出一言，即思此言于百姓有利益否，所以不能多言。」杜正伦回答：「君举必书，言存左右史。臣职当修起居注，不敢不尽愚直。陛下若一言乖于道理，则千载累于圣德，非直当今损于百姓，愿陛下慎之。」太宗大悦，赐他二百段绢。

630年，杜正伦升迁中书侍郎，中书省的副官。632年，杜正伦和御史大夫韦挺、秘书少监虞世南、著作郎姚思廉都上封事称旨，太宗皇帝为他们设宴答谢他们的诚实与勇敢。杜正伦加官散骑常侍，行太子右庶子，兼崇贤馆学士。让他辅佐皇太子李承乾。636年，他再任中书侍郎，爵南阳县侯，仍兼太子左庶子。杜正伦出入两宫（东宫和太极宫），参典机密，以干练著称。

但不久后杜正伦就陷入了皇帝和太子之间的矛盾。当时，太子腿脚有病，不便行走。所以他不能按时朝见父亲，而经常和近侍小人在一起，做一些轻浮之事。唐太宗对杜正伦说：「我儿的疾病，只是小事。但他全无好名声，没听说他爱贤好善，他所接触的，多是小人，卿可密切观察此事。如果他不听你的劝教，须来告我。」

杜正伦多次劝说太子，建议他规范自己的行为。但太子却不改。杜正伦把皇帝给他说的话告诉了太子，太子接著上表父亲抗辩。唐太宗质问杜正伦：「何故泄露我的话？」杜正伦解释：「他不听我的，所以拿陛下的话震吓他，希望他有所畏惧，改恶从善。」唐太宗依然生气，将杜正伦贬为谷州（今河南洛阳市宜阳县）刺史，不久改任交州（今越南河内市）刺史。 在643年太子联合侯君集谋反之事泄露而被废黜时，杜正伦因为和侯君集关系好，还得到过侯君集赠送的腰带，所以被流放驩州（今越南乂安省荣市）。之后复官，做郢州（今湖北武汉市）和石州（今山西吕梁市）刺史。

656年，太宗的儿子唐高宗授杜正伦为黄门侍郎，兼崇贤馆学士，同中书门下三品。657年，兼度支尚书，仍依旧知政事。不久拜中书令，兼太子宾客、弘文馆学士，进封襄阳县公。他和中书令刘祥道认为应该精简国家官员，唐高宗让他们负责。但是，他们的阻力太大，最终无果而终。

同时，杜正伦和另一个宰相中书令李义府发生矛盾，李义府是武后的同党，诬告杜正伦结党，唐高宗在658年十二月，将杜正伦贬为横州（今广西南宁市）刺史，杜正伦不久死在了横州，当时有《杜正伦集》十卷。

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