Cai Lun (; courtesy name: Jingzhong (); – 121 CE), formerly romanized as Ts'ai Lun, was a Chinese eunuch court official of the Eastern Han dynasty. He occupies a pivotal place in the history of paper due to his addition of pulp via tree bark and hemp ends which resulted in the large-scale manufacture and worldwide spread of paper. Although Cai is traditionally regarded as the inventor of paper, earlier forms of paper have existed since the 3rd century BCE, so his contributions were an innovation, rather than an invention.
Born in (in what is now Leiyang), Cai arrived at the imperial court in Luoyang by 75 CE, where he served as a chamberlain for Emperor Ming, and then as , an imperial messenger for Emperor Zhang. To assist Lady Dou in securing her adopted son as designated heir, he interrogated Consort Song and her sister, who then killed themselves. When Emperor He ascended the throne in 88 CE, Dou awarded Cai with two positions: , a political counselor to the emperor that was the highest position for eunuchs of the time, and also as , where Cai oversaw the production of instruments and weapons at the Palace Workshop.
Despite Emperor He's successful coup d'état against the Dou family in 92 CE, Cai was undisturbed by his former ally's downfall. His position in the Palace Workshop increased in scope; he became responsible for the production of ceremonial weapons, which the reports were of exemplary craftsmanship. However, Cai's most noted innovation was in 105 CE, when he substantially improved the papermaking process with the use of tree bark, hemp waste, old rags, and fishnets. His new type of paper quickly displaced the bamboo and wooden slips used until then, and Cai received wealth and fame throughout the empire. In 110 CE, Lady Deng, who had become the empress dowager to the young Emperor An, appointed Cai to oversee 100 scholars' new edition of the Five Classics. Cai was rewarded for his imperial service in 114 CE; he received the title of marquis, and was enfeoffed lord of , a small village. When his ally Deng died in 121 CE, Cai was ordered to the Ministry of Justice because of his involvement in the death of the emperor's grandmother, Consort Song. Ashamed at his predicament and expecting to be sentenced to death, he committed suicide that year and died in the capital city in which he had spent almost his entire adult life.
Cai's improvements to paper-making are considered to have had an enormous impact on human history, and of those who created China's Four Great Inventions—the compass, gunpowder, papermaking and printing—Cai is the only early figure whose name is known. Although in China he is revered in ancestor worship, deified as the god of papermaking, and appears in Chinese folklore, he is mostly unknown outside of East Asia. His hometown in Leiyang remains an active center of paper production.
Sources The main source of information on Cai Lun is just 300 characters in volume 78 of the (; Book of the Later Han), an official history compiled by the Liu Song dynasty historian and politician Fan Ye. Tsien Tsuen-hsuin, a modern sinologist, noted that while Fan's account is the most comprehensive, it is problematic as it was written nearly 300 years after Cai's death. The primary source Fan used was the 2nd-century Dongguan Hanji (; History of the Eastern Han), in which is credited as the author of Cai's biography. Yan's brief 70-character account is near-contemporary but only survives in a reconstructed state from a lost original.: "蔡倫字敬仲桂陽人為中常侍有才學盡忠重慎每至休沐輒閉門絶賔客曝體田野典作尚方造意用樹皮及敝布魚網作紙〈案一本作倫典尚方作紙用故麻名麻紙木皮名糓紙魚紙名網紙〉元興元年奏上之帝善其能自是莫不用天下咸稱蔡侯紙": "Cai Lun, courtesy name Jingzhong, a native of , served [at the court] as . He was a man of talent and learning, loyal and careful. When he was off duty, he usually shut himself up and refused to see visitors but exposed himself to nature. When he was charged with the office of , he initiated the idea of making paper from tree bark, old rags and fishing nets. He submitted the process to the emperor in the first year of and received praise for his ability. From this time, paper has been in use and is universally called the 'paper of Cai Lun'". Another older source is a brief mention by the 3rd-century scholar Dong Ba, () who is quoted referencing Cai's papermaking accomplishments in the 10th-century leishu encyclopedia (Readings of the Taiping Era).
Later history books, such as the Song dynasty's (; Compound Source of Matters and Facts), also include Cai and his work in papermaking. However, some major history books, such as the Annals of the Later Han and (Comprehensive Mirror in Aid of Governance) do not mention Cai's papermaking achievements. Sinologist T. H. Barrett suggested this was because "Cai Lun was, after all, a palace eunuch, precisely the sort of person normally viewed with antagonism by the regular bureaucrats who controlled the writing of official (and even most unofficial) history."
Life and career Birth and background Cai Lun was born in Guiyang Commandery (; modern-day Leiyang, Hunan province): """Cai Lun's courtesy name was Jingzhong, and he was from Guiyang Commandery." in the Eastern Han dynasty (25–220 CE). His exact year of birth is unknown; estimates include , , and . Other than being born into a poor family, virtually nothing is known of his early life. Guiyang was a southern commandery, where Han Chinese had immigrated for hundreds of years to plant and cultivate rice. Legends suggest there was a pool near his home, south of which was a stone mortar that Cai would later use for papermaking.
Early imperial court service
It is not known how Cai came to be in the service of the imperial court in Luoyang (modern-day Luoyang, Henan province), which was distant from his birthplace. The reports that he was first employed during the end of the era (58–75) of Emperor Ming.: """He began serving in the palace at the end of the era".: At the close of the reign of , Cai Lun was employed at the court". The site of modern Guiyang Commandery was known to have had various iron mines at the time, so the former director of the Paper Museum in Tokyo, Kiyofusa Narita, suggested that "through the assistance of some who were in charge of the iron foundry, he found opportunity to go to the capital city". Narita cited Cai's future court appointment to oversee the production of weapons, especially swords, as evidence that he must have learned the skills to do so earlier in his life, likely from the iron foundry. Alternatively, if there is any truth to the various folktales about Cai, his supposed habits of trickery may have helped him receive a court appointment.
Cai is known to have been a eunuch in 75 CE, although it is possible he was employed somewhat earlier in the era; sinologist Rafe de Crespigny suggested this was in the early 70s. In the Han dynasty, eunuchs were employed in imperial service and were the only people eligible for certain specialized tasks, such as watching over the imperial harem and the imperial household; there were also certain promotions available exclusively for them. Cai's position was probably as a liaison between the privy council and the emperor, and likely involved duties akin to a chamberlain for the imperial family. Narita notes Cai's role meant he would have had many chances to become acquainted with the most powerful people in the empire. Around 80 CE, during the subsequent era (76–84) under Emperor Zhang, Cai was promoted to a Xiao Huangmen (; "Attendant at the Yellow Gates").: """At the beginning of the era, he served as ".: "During the period (76–84), Cai Lun formed part of the Imperial Guard." The positions, with a salary-rank of 600 shi or dan, involved delivering and receiving messages between the imperial palace apartments and the outside court.
Palace intrigue and workshop In 79 CE, Liu Qing, Zhang's son from his concubine Consort Song, had been the designated heir, secured by the favor of Empress Ma. However, Ma's death later in 79 CE made Lady Dou the empress, and—aiming to develop her family's power—she adopted Prince Zhao with the intention of installing him as heir. As a result, when Song became ill in 82 and asked for herbs, Dou falsely accused her of planning to use the herbs for witchcraft against Zhang. Dou then ordered Cai to interrogate Consort Song and her sister, another imperial consort, to force a confession; they both killed themselves. Believing Dou's accusation, Zhang replaced Liu Qing with Prince Zhao as heir.
Prince Zhao, ruling as Emperor He, was 10 years old at his accession in 88 CE, so Dou took control as empress dowager and secured her authority by giving various positions to her four brothers, particularly Dou Xian, who promoted Cai to (; "Regular Attendant") for his loyalty. Cai served as a private counselor to He in political matters;: """After Emperor He took the throne, he became , and he participated in key strategic decisions.": "The Emperor He, on coming to the throne, knowing that Cai Lun was a man full of talent and zeal, appointed him a privy counsellor.": "The Emperor He, upon his accession, learning of Cai Lun's superior qualities and talents, named him private counsellor". this post gave Cai a salary-rank of 2000 shi, and was the highest eunuch-exclusive position, which also made him a chief eunuch of the palace. In the , Cai was characterized as, in the words of de Crespigny, "honest, cautious and a good judge of policy".: """Cai Lun was talented and learned. He used his full effort and was careful. He often was willing to correct the wrongs, even when it offended the stern faced [those in power]. When he had vacation days, he would close his door and not entertain guests, but spent time in the field." Cai was also designated (; "Prefect of the Palace Workshop" or "Prefect of the Masters of Techniques") later in 88 or 89 CE.: """He was later given the additional post of Shangfangling." While in this eunuch-only position, he would have been responsible for the production of instruments and weapons for imperial use. The role had a salary-rank of 600 shi—though this was in addition to the 2000 shi from his continued post.
When Emperor He came of age in 92 CE he led various officials, especially Zheng Zhong, in a coup d'état to overthrow the Dou family. Cai was not involved in their removal, and though he was previously allied with the family, he was undisturbed by the Emperor's coup. In 97 CE, his position as expanded in scope, as he became responsible for ceremonial swords and other items. The describes his craftsmanship as high-quality and a model for later generations.: """In the 9th year of the era , he oversaw the manufacturing of imperial swords and other equipment, which were all made carefully and well, and he became an example for later generations.": "In the ninth year of the period (97) Cai Lun became inspector of public works. By his plans and according to his arrangements, engineers and workmen made, always with the best of materials, swords and arms of various sorts. Later generations could do no better than imitate his methods of work.": "In the ninth year of the reign of (97), Cai Lun was made inspector of works and through his efforts the engineers and workmen by the use of fine materials and skill produced swords and arms that served as models for future generations."
Development of paper