A study of Korea’s first significant encounter with Western civilization, this work analyzes how Koreans reacted to Catholicism imported from China at the end of the 18th century. It explores the reason most Koreans, especially Confucian scholars and government officials, reacted negatively to Catholic ideas and practices, going so far as to launch an official persecution of Catholics that cost thousands of lives. To render visible the philosophical background to the anti-Catholic movement, this work includes a complete translation of an anti-Catholic essay written before the persecution began. However, it also examines those Koreans, many of whom were also Confucian scholars, who adopted Catholic beliefs and practices even before there were missionaries on the Korean peninsula. To aid in that investigation, it includes an annotated translation of the Silk Letter of Hwang Sayŏng, a first-person account of the persecution of 1801 relating why some Koreans became Catholics, why some later apostatized, and why others remained faithful to their new faith through torture and execution. In addition, it includes a discussion of Korea attitudes toward their nation and its place in the international order before the emergence of modern nationalism.