Based upon his reading of the books on modern Western science translated into Chinese, a late nineteenth-century Korean intellectual Ji Seokyoung compiled a book in Korean, titled Sinhak sinseol 身學新說. With this book, Ji aimed to construct a new theory of bosin 保身. He built his theory upon the knowledge of light, heat, air, water, food, and bodily exercise, which he drew mostly from five books on modern Western medicine and science published in China and then introduced to Korea. Ji also inserted into the book his knowledge in traditional East Asian medicine. This article examines the relationship between Sinhak sinseol and the books on Western science that Ji read, with the aim to shed light on the way in which Korean intellectuals in the period of “enlightenment” (gaehwa 開化) understood and used modern Western science and medicine. By compiling the book, this paper argues, Ji attempted to criticize traditional yangsaeng 養生 and then to construct a hybrid between modern western hygiene and traditional East Asian medicine, a new theory that he called bosin jihak 保身之學.