Christianity in Korea
Hangul, a phonemic Korean alphabet invented around 1446 by scholars in the court of Sejong the Great, was little used for several centuries because of the perceived cultural superiority of Classical Chinese (a position similar to that of Latin in Europe). However, the Catholic Church became the first Korean religious organization to officially adopt Hangul as its primary script. Bishop Siméon-François Berneux mandated that all Catholic children be taught to read it. Christian literature printed for use in Korea, including that used by the network of schools established by Christian missionaries, mostly used the Korean language and the easily learned Hangul script. This combination of factors resulted in a rise in the overall literacy rate, and enabled Christian teachings to spread beyond the elite, who mostly used Chinese. As early as the 1780s, portions of the Gospels were published in Hangul; doctrinal books such as the "Jugyo Yoji" (주교요지) appeared in the 1790s and a Catholic hymnal was printed around 1800.
Origin of Hangul
Of these seven vowel sounds, three could not be iotized (preceded by a "y-" sound). These three were written with a single stroke: ㅡ "ɨ," ㆍ "ʌ," ㅣ "i." (The letter ㆍ "ʌ" is now obsolete except in Jeju dialect.) The "Hunmin Jeong-eum" states that the shapes of the strokes were chosen to represent the Confucian 三才 "sāncái" "three realms" of 天 heaven, a "yang" concept, represented with a dot for the sun, ; 地 earth, a "yin" concept, represented with a flat line, ; and 人 man, represented with an upright line, , who mediates between the two. The other four vowels, which could be iotized, were written as a dot next to a line: yin ㅓ "ə" and yang ㅏ "a" (which alternate under vowel harmony), yin ㅜ "u" and yang ㅗ "o" (which also alternate). Iotation was then indicated by doubling this dot: ㅕ "yə," ㅑ "ya," ㅠ "yu," ㅛ "yo."
There was presumably a third parameter in designing the vowel letters, not mentioned in the "Haerye," namely choosing horizontal ㅡ "ɨ" as the graphic base of "closed" (rounded) ㅜ "u" and ㅗ "o," and vertical ㅣ "i" as the base of "open" (unrounded) ㅓ "ə" and ㅏ "a." The horizontal letters ㅡㅜㅗ "ɨ u o" represented back vowels in the fifteenth century, as they do today, whereas the fifteenth-century sound values of ㅣㅓㅏ "i ə a" are uncertain. Some linguists reconstruct them as , respectively (and reconstruct obsolete ㆍ "ʌ" as ); others as (with ㆍ "ʌ" as ). In the latter case, the vertical letters would have represented front vowels, the dot the sole central vowel, and the vowel harmony, described as "shallow" vs "deep", would have been one of vowel height, with the "yang" vowels lower than their "yin" counterparts.