He was one of the greatest thinkers in the later Joseon period, wrote highly influential books about philosophy, science and theories of government, held significant administrative positions, and was noted as a poet.

He was a close confidant of King Jeongjo and his philosophical position is often identified with the Silhak school, and his concerns are better seen as explorations of neo-Confucian themes.

He spent 18 years in exile in Gangjin County, South Jeolla Province, from 1801 until 1818, on account of his membership of the Southerners faction, and also because of his older brother's Catholic faith.

Tasan's father's family traced their descent back to Chŏng Cha-gŭp (정자급; 丁子伋, 1423–1487) who in 1460 first took a government position under King Sejo.

In 1762, the execution of Crown Prince Sado by his father the king shocked Chŏng Chae-wŏn that he withdrew from official life and returned to his home in Mahyeon-ri.

After the promotion of Chae Je-gong in 1788, Tasan took top place in the daegwa (higher civil service exam) in 1789 and was offered a position in the Office of Royal Decrees, together with 5 other members of the Southerner faction.

This alarmed members of the opposing Old Doctrine faction, who soon realized the extent to which the Southerners were being influenced, not only by the Practical Learning introduced to China from Europe, but by Roman Catholicism itself.

His older sister was married to Yi Seung-hun, the Korean who was first baptized as a Catholic in Beijing in 1784 and played a leading role in the early years of the Church's growth.

Rome had forbidden Catholics to perform ancestral rituals and this was now being strictly applied by the Portuguese Franciscan bishop of Beijing Alexandre de Gouvea.

When his mother died in 1791, Yun therefore refused to perform the usual Confucian ceremonies; this became public knowledge, he was accused of impiety and was executed.

Tasan's most important task in 1795, the 60th anniversary of the birth of Crown Prince Sado, was to help the king decide on a new honorary title for his father.

However, he then found it prudent to send Tasan away from court for a time, appointing him to be superintendent of the post station at Geumjeong, South Pyeongan province.

Here, he provided clear proof of his rejection of Catholicism by doing everything possible to persuade the Catholics working there to renounce their faith, and in particular to perform ancestral rites.

In 1796, he was brought back to Seoul and promoted but his many enemies continued to accuse him of supporting the pro-western Catholics and he preferred to take up a position as county magistrate at Koksan in Hwanghae province.

However the Silk Letter Incident of 1801 ensured his further exile: Hwang Sa-yŏng [ko], married to one of Tasan's younger sisters, had written a letter to the bishop of Beijing, giving a detailed account of the persecutions, and asking him to bring pressure on the Korean authorities by asking for Western nations to send warships and troops to overthrow the Joseon government so that Korea would be subject to China,[6] where Catholicism was permitted.

The carrier of this letter (written on a roll of silk wrapped round his body) was caught and its contents ensured the continuing persecution of Catholics.

The newly arrived exile had little or no money and no friends, he found shelter in the back room of a poor, rundown tavern kept by a widow, outside the East Gate of the walled township of Gangjin, and there he lived until 1805.

Finally, in the spring of 1808 he was able to take up residence in a house belonging to a distant relative of his mother, on the slopes of a hill overlooking Gangjin and its bay.

This needs qualifying, since one "work" might fill nearly 50 volumes of the standard size, but he certainly wrote a vast quantity, some 14,000 pages, mainly in order to set out clearly a fundamental reform program for governing the country correctly according to Confucian ideals.

After his return from exile, Tasan published his most important works: on jurisprudence Heumheumsinseo [ko] (1819); on linguistics Aeongakbi (1819); on diplomacy Sadekoryesanbo (1820); on the art of governing Mongminsimseo and on administration Gyeongsesiryeong (1822).

He used Yeoyudang as his final pen-name: it was the name of the family home where he lived quietly, near the Han River, until he died in 1836, on his sixtieth wedding anniversary.

[8] Chŏng Yagyong had been living in Gangjin for several years when the Venerable Hyejang arrived from Daeheung-sa temple to take charge of Paengnyeon-sa.

Only a few days after, Tasan sent a poem to Hyejang requesting some tea leaves from the hill above the temple; it is dated in the 4th month of 1805, very soon after their meeting.

[11] After this, Cho-ui became especially close to Chusa Kim Jeong-hui, who visited him several times bringing him gifts of tea during his exile in Jeju Island in the 1740s.

This was not only an intellectual but also a political assertion: he argued that the gwageo examinations by which people qualified for royal service should be reformed to focus on these concerns.

A Design for Good Government), a flagship work of his which presents a blueprint of state management, was Pangnye ch'obon (방례초본; 邦禮草本; lit.

He focuses this concept on his notion of good government and later extended and branched into his works of classical studies and natural sciences.

[15] Tasan's theory of Korean-style sacrificial rites shows his socio-political concern seeking for the rule of virtue and righteous government.

He intended to motivate people into making everyday practices of the human imperatives and to revitalize effectively the traditional society of the late period of Joseon dynasty which had its basis upon Ye (禮, Confucian order).

"[citation needed]Professor Peng Lin at Qinghua University, Beijing teaches the Chinese classics and has a special interest in Tasan's study of rituals.