Korea has produced movable metal type before Sejong, but in 1420 he had his craftsmen produce an improved font which could be more firmly attached to the printing plate and thus could be used to produce dozens of sheets a day. With this new metal type, and with the addition of a hangul font in 1447, Sejong was able to publish a number of important works in wide variety of fields, from agriculture, medicine and geography to history, calendrical mathematics, and the Confucian Classics. A more virtuous life in Sejong's Neo-Confucian world meant a life lived in harmony with the existing social order. To encourage his subjects to act according to their appropriate positions in this natural social order, Sejong published Samgang Haengsil , a collection of biographical sketches of filial sons and daughters, loyal subjects, and chaste widows for his subjects to model their lives after. The arts cultivate receptivity to the normative pattern within.
Astronomy focuses attention on the cosmic pattern without.
Sejong served as his people's link between heaven and earth. If they were to coordinate their activities on earth with movements in the heavens, and if they were to be able to imitate the unselfish harmonious cooperation of celestial bodies, they had to know as accurately as possible exactly what those celestial movements were. For that reason, Sejong had his technicians improve the astronomical instruments they had inherited from China and assemble even more accurate water clocks, armillary spheres, sundials, and rain gauges. Sejong ordered those instruments assembled for the same reason that he ordered ritual music reformed, type cast, books published, and hangul created. Sejong wanted his subjects to know the way universe worked, to recognize the normative pattern of appropriate inter-relationships which governed both the human community and the natural world, so that they could coordinate their actions with it.