This article explores how new modes of writing and reading that developed in epistolary culture brought about intellectual, social, and political changes in Chosŏn society. From the sixteenth century onwards, the diverse uses of letters transformed the lifestyle and the mode of political participation of Confucian intellectuals. Letters became the main reading materials for neo-Confucian studies and self-cultivation as well as a medium for political action, especially for rural scholars, who innovated various epistolary genres to raise their political voices. New epistolary practices facilitated their collective activism, the spread of radical opinions, and the mobilization of new political groups. Toward the end of the dynasty, even nonelites emulated these practices for their activism. In this period, “spiral letters” developed in both vernacular Korean and literary Chinese letters. These new letter forms, used by both male elites and women, reflected and subverted the existing gender dynamics and power relations associated with the norms of reading and writing. The rise and fall of spiral letters demonstrate the mutual influence between the written culture and sociopolitical changes. The versatility and resourcefulness of epistolary practices characterized Chosŏn letter writers' fashionable choice of a radical lifestyle, which geared their social life to yield actual political power.