The model for a Confucian welfare state was conceived and implemented by King Sejong in the 15th century, but it was Yi Sugwang who implemented welfare policies during the period following the Hideyoshi invasions. His efforts were inspired by the idea that the “Way of Heaven” was found among the people, and that its noblest realization was to feed and clothe the masses.
 
The commentaries of other social activists and scholars echo Yi Sugwang’s ideas. Bak Sedang advocated going to the country to engage in manual labor, noting that Confucius had endured labor more onerous than farming. Yi Ik stated that knowledge should not be sought unless it could benefit the lives of the common people. His clear-cut analysis of the causes of factionalism stemmed from a deep-seated concern for the welfare of the people.
 
Kim Yuk, known for enacting the Daedongbeop (rank-based land law), recommended the increased use of vehicles. Hong Daeyong and Bak Jiwon also saw increased vehicular traffic as promising great advantage for the national economy. Bak made a far-sighted statement: "Rulers will be blamed by future generations for not having learned from pragmatic studies."
 
Jeong Yak-yong
Cheonjusilui (Book on Catholicism)
 Jeong Yak-yong was an outstanding scholar who criticized the evils of society, and made positive proposals for reform. He advocated a system of land distribution based on egalitarian principles, and placement of people in professions based on their ability.

Exploitation continued, however, and the distressed sought salvation. Catholicism met the needs of many, since its tenets not only offered the promise of eternal
life, but matched the new egalitarian principles. Some scholars were converted to Catholicism, and others benefited from the scientific learning that accompanied the religion. The number of Catholics in Korea gradually increased.
 
Since Catholicism was opposed to both Confucian ancestral rituals and rigid social stratification, believers were termed criminals by the state. Many, including prominent scholars Jong Yak-yong and his brothers, were severely punished and sometimes executed.
 
Catholicism nonetheless grew more popular, especially among artisans. Confucian-oriented yangban officials did not understand how Koreans could choose this foreign religion over traditional values, and they resorted to various means to suppress it.
 
As for welfare, efforts were mobilized in the field of medical jurisprudence to ensure more equitable medical treatment for the common people. Other significant studies related to public welfare included research in therapeutic medicine based on individual physical characteristics. Yi Jema (1838-1900), among the pioneers of modern Eastern medicine, developed the theory of Sasang (Theory of Four Constitutions). According to his treatise, Dongeuisusebowon, humans are one of four constitutional types, taeyangin, taeumin, soyangin and soeumin based on their innate visceral functions, anatomical proportions, personality and temperament. Yi Jema developed various therapeutic treatments for each type.
 
Human dignity, opportunity, public welfare, and the advancement of the national economy thus emerged as major philosophical principles in the 17th-18th centuries, reminiscent of the Renaissance period of Western Europe.
 
On the popular literary scene, romantic novels sold well. Since books printed from metal type were far too costly for commoners, popular demand was met by using cheaper, clay-engraved plates in addition to wood-type printing.
 
At this time, classic poetry experienced a renaissance of its own. There was renewed interest in learning ancient sijo (traditionally, three-lines of 14-16 syllables each) and in writing new verse. Noteworthy were two sijo anthologies: Kim Cheontaek compiled 580 poems written since the Goryeo Period, entitled Cheonggu yeongeon (Enduring Poetry of Korea). Kim Sujang (b.1690 d?) produced a similar anthology entitled Haedong gayo (Songs of Korea). Talented yangban poets, Jeong Cheol (Songgang, 1534-1593) and Yun Seondo (Gosan, 1587-1671) also published their work.
Cheongguyeongeon (Poetry of Korea)
 
White Celadon Jar with blue flower
 Paintings of Korean themes also came into vogue. Jeong Seon (known as Gyeomjae, 1676-1759) painted Korean landscapes rather than copying Chinese paintings, while Kim Hongdo and Sin Yunbok concentrated on genre scenes of Korean life. In the area of ceramics, white porcelain decorated with underglaze blue line-drawings, was mass-produced to meet public demand. Amidst the rise of culture and art, modern thought was developing throughout 18th century Korea.