King Sejong's Confucian Humanism
Joseon's fourth king, King Sejong the Great (r.1418-1450), was noted for his mastery of Confucian learning. In addition to his embrace of Confucian values, he showed himself able to successfully deal with the yangban scholars. His rule in the mid-15th century was marked by progressive ideas in administration, phonetics, national script, economics, science, music, medical science and humanistic studies. He established the Jiphyeonjeon (Hall of Worthies) in order to promote research in institutional traditions and politico-economics.

King Sejong showed great concern for the livelihood of the peasants, providing relief in time of drought and flood. He had Jeong Cho compile the Nongsa jikseol (Straight Talk on Farming), a volume replete with information collected from experienced elder peasants throughout the country. The first of its kind in Korea, this became the classic work on Korean agriculture. He also put into effect a sliding tax scale which eased the peasants' burden. King Sejong ordered the development of the pluviometer in 1441 and distributed duplicates to the Office of Astronomy in Hanyang as well as to local magistrates to record precipitation. This preceded Gastelli's pluviometer of 1639 by almost 200 years.

One of his most celebrated achievements was the creation of the Korean alphabet, Hangeul. Aware that his people must have a writing system designed to express the language of their everyday speech, and desirous that all his subjects be able to learn and use it, King Sejong impelled scholars of the Hall of Worthies to devise the alphabet. The Korean alphabet, which consists of 11 vowels and 17 consonants, possesses geometric beauty, simplicity and scientific accuracy, and as such, can be learned by an uneducated man in a matter of hours.

Confucian scholars raised considerable opposition and protested that the use of Korean script would retard Confucian studies. King Sejong persisted in his determination to promote Hangeul for the benefit of the people, and Hunmin Jeongeum, or "The Correct Sounds for the Instruction of the People," was distributed in 1446.

The official written language continued to be Chinese, as was Latin in Europe, but now the Korean people had at their disposal a means of writing in their own language. A bilingual poetic eulogy on the foundings of the dynasty Yongbieocheonga (Songs of Flying Dragons) was composed in Korean as well as in Chinese, and the Seokbo sangjeol (Episodes From the Life of the Buddha) was translated into Korean. These works laid the foundation for the practical use of the Korean script.

King Sejong also showed his concern for the health of the people by ordering the compilation of medical books. A 365-chapter compendium on Chinese medicine as well as the Hyangyak jipseongbang (A Compilation of Native Korean Prescriptions) in 85 chapters, was completed in 1433. This latter included 959 entries on disease diagnoses, 10,706 prescriptions, and 1,477 items on acupuncture therapy. Another book on how to collect local medicinal material was also published in the vernacular language.

King Sejong's interest in astronomical science was comprehensive and sun dials, water clocks, orreries of the solar system, celestial globes, astronomical maps, and atlases of the seven planets were produced at his instigation. He had a notation system for Korean as well as Chinese music devised or revised, and had one of his talented subjects, Bak Yeon, improve Korea's musical instruments as well as commissioned the writing of music for Korean musicians.

In foreign relations, King Sejong took strong measures against the Jurchen tribes. The territory in the northeastern frontier area was restored, and six fortresses were established after General Kim Jongseo quelled the Jurchen invaders in 1434. In 1443 King Sejong installed four counties on the northern border, and opened three ports to the Japanese to help trade. King Sejong's land tax reform, health policy and invention of the Korean alphabet all contributed to the improvement of life of the people.

King Sejong was able to realize the Confucian state in the true sense of the word. He also engendered a modern national consciousness in the minds of the people. Although he had earlier confiscated temple lands and bondsmen and otherwise restricted Buddhism, he later became especially devoted to that faith after the death of his beloved Queen. His health declined during that period, and he abdicated the throne to his son King Munjong (r. 1450 - 1452). Unfortunately, his legacy of stability and prosperity was not sustained by his short-lived successors.