Choson‘s fourth king, Sejong (r. 1418-50), was noted for his mastery of Confucian learning. In addition to his internalization of Confucian values, he showed himself able to successfully deal with the yangban scholars. His rule in the mid-l5th century was marked by progressive ideas in administration, phonetics, national script, economics, science, music, medical science and humanistic studies. He established the Chiphyönjön (Hall of Worthies) in order to promote research in institutional traditions and politico-economics.
Sejong showed great concern for the livelihood of the peasants, providing relief in time of drought and flood. He had Chong Ch’o compile the Nongsa chiksol (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. Sejong ordered the development of the pluviometer in 1442 and distributed duplicates to the Office of Astronomy in Seoul and 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,
Han-gul. It was the awareness that his people must have a writing system designed to express the language of their everyday speech, and a desire that all his subjects be able to learn and use it that impelled King Sejong to have scholars of the Hall of Worthies devise the alphabet. The Korean alphabet, consisting of 11 vowels and 28 consonants possessing geometic beauty, simplicity, and scientific accuracy, is such that an uneducated man can learn it in a few hours.
Confucian scholars raised considerable opposition and protested that the use of Korean script would retard Confucian studies. Sejong persisted in his determination to promote Hangul for the benefit of the people, and Hunmin chong-um, 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 their own language. A bilingual poetic eulogy on the foundings of the dynasty Yongbioch'on ka (Songs of Flying Dragons) was
composed in Korean as well as in Chinese, and the Sokpo sangjol (Episodes from the Life of the Buddha) was translated into Korean. These works laid the foundation for practical use of the Korean script.
Sejong 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 Hyang-yak-chip-song-bang (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 published in the vernacular language.
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, Pak Yon, improve musical instruments of various kinds and compose a sort of orchestral music.
In foreign relations, 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 Chong-so quelled the Jurchen invaders in 1434. In 1443 Sejong installed four counties on the northern border, and opened three ports to the Japanese to help trade. Sejong’s land tax reform, health policy and invention of the Korean alphabet all contributed to the improvement of life and hence the awakening of the people.
Sejong was able to bring the Confucian state to realization in the true sense of the word, and to engender 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 in that period, and he abdicated the throne to his son Munjong (r. 1450- 52). Unfortunately, his legacy of stability and prosperity was not sustained by his short-lived successors.