Who was Sejong the Great?
Sejong (1397–1450), fourth king of Korea's Joseon dynasty, is remembered principally for commissioning Hangul — a writing system designed deliberately and from first principles, which is extraordinarily rare.
The problem he addressed. Korean was written using Chinese characters, which represent meaning rather than Korean sounds and require years of study. Literacy was therefore confined to an elite with the leisure to learn thousands of characters, and ordinary Koreans could not record their own language — including, as Sejong noted, being unable to express grievances in writing.
What was created. Hangul, promulgated in 1446 in a document explaining the system and its reasoning. Its features are unusual:
It was designed, not evolved. Almost every writing system developed gradually; Hangul was created by a deliberate project with stated principles.
The consonant shapes represent the articulation — the shape of the letter depicts the position of the tongue, lips or throat when making the sound. This is featural design, and it is essentially unique among writing systems in wide use.
Vowels are built from three elements representing heaven, earth and humanity, combined systematically.
Letters are grouped into syllable blocks, so the writing is alphabetic but visually organised by syllable.
It was designed to be learnable quickly, and the promulgating document claims a wise man could learn it in a morning and a fool in ten days — a claim closer to true than such statements usually are.
The resistance it met. The scholarly elite opposed it, partly from attachment to Chinese learning and partly because widespread literacy threatened their position. It was suppressed at points, and did not fully displace Chinese characters until the twentieth century.
His other work. Sejong's reign produced substantial achievement in astronomy, including instruments for measuring time and celestial positions; agriculture, with a handbook gathering practical knowledge from farmers rather than from Chinese texts; music and its notation; and printing.
He is regarded as Korea's most significant historical figure, and Hangul Day is a public holiday.