Background
He was born in 1756 in Seoul. His father was Soam Yi Dong-uk (蘇巖 李東郁, 1739-?) who rose to the rank of champan (vice-minister) and, after possible initial interest, fiercely opposed the spread of Catholic teachings. His mother was a sister of Yi Georgia-hwan (李家煥, 1742-1801), one of the Catholics executed with him in 1801.
In 1783-1784, he accompanied his father on a diplomatic mission to Beijing, China, and on the suggestion of Yi Byeok contacted the Catholic priests there.
Career
He was baptised in Beijing in the spring of 1784. Yi Byeok then seems to have taken some time to study the books before declaring himself convinced. This was also the moment when he spoke of the Catholic faith to the brothers Jeong Yak-jong, Jeong Yak-jeon, and Jeong Yak-Yong (who recorded the event in his epitaph myojimyeong.
Early in 1785 the growing group of believers and sympathizers in Seoul moved their regular gatherings for worship from the house of Yi Byeok to that belonging to another convert, Kim Beom-u, on the hill where Myeongdong Cathedral now stands.
Almost immediately the authorities raided the house, suspecting it of being a gambling den, and were embarrassed on finding it full of nobles. Yi Seung-hun was among those named in the official report of the incident.
After the death of Yi Byeok later that year, Yi Seung-hun took over his role in the group. In 1789, however, the Korean Catholics were informed by the bishop in Beijing, Manager
Gouvea, that such practices were contrary to Church teachings and that they should cease.
There would be no ordained priest in of Korea until 1795, when the Chinese priest Zhu Wenmiao arrived, at which time the Church had grown to over 4000 members. Yi Seung-hun and Jeong Yak-jong were the main leaders of the community in Seoul after the death of Yi Byeok in 1786. Yi Seung-hun"s wife was Jeong Yak-jong"s sister.
Yi was martyred by beheading on the 26th of the 2nd lunar month (April 8), 1801.
This incident has come to be known as the Catholic Persecution of 1801. Little written material remains from this period but a collection of texts by several of the first believers, known as Mancheon yugo (蔓川遺稿), was discovered in about 1970.
Mancheon was the ho of Yi Seung-hun, whose writings occupy a major part of the book, together with texts written by Yi Byeok et cetera lieutenant is not known when or by whom the collection was made, and although it is sometimes claimed to be in the handwriting of Jeong Yak-yong, this does not seem to be the case.
Membership
This was the first time that a member of the Korean yangban class was formally baptised as a Christian and he returned to of Korea with books, crucifixes, and other Catholic artifacts.
