18세기 조선에서 진취적으로 한역 서학서를 읽고 서학을 연구한 성호 이익의 문집이다. 『천주실의』, 『직방외기』 등 서학서에 관한 발문이 담겨 있다. 「천주실의발」은 『천주실의』를 유학적 관점에서 분석하고 비판한 논평이다. 이익은 유학을 기반으로 서양 학문과 문화는 긍정적으로 수용하는 자세였으나 종교적 측면의 천주교에는 비판적이었다.

This is a collection of writings by Yi Ik (pen name Seongho), who proactively read and studied books on Western Learning translated into classical Chinese during 18th-century Joseon. It contains epilogues for books on Western Learning, such as Tianzhu shiyi (The True Meaning of the Lord of Heaven) and Zhifang waiji (Geography of Countries Non-tributary to China). The “Epilogue for Tianzhu shiyi” offers a critical analysis of the text from a Confucian perspective. Yi Ik demonstrated a positive attitude towards Western studies and culture, rooted in his understanding of Confucianism. However, he maintained a critical stance towards Catholicism in terms of religion.