過去學界討論鄭觀應的角色定位，著重在兩方面：一是買辦商人的經歷，一是主張「中本西末論」的變法思想家，兩者皆從中國現代化的論述脈絡來定位這位開明的思想家，然而鄭氏的內心世界裡，道教實佔據重要的位置。本文試圖論證，鄭觀應始終兼有長生與濟世的思想，同時他認為，仙學與西學都足以救世。甚者，鄭氏所欲成就的人生典範──道教聖王，成為其晚年救世的主要憑藉。事實上，人們熟悉的「中本西末論者」之形象，無法與鄭氏的內心世界接軌；相對而言，「成道濟世」一詞，更能充分地描述他的想像世界，並點出他畢生精神生活的主體性。一旦我們關注思想家個人的意義脈絡，不僅挑戰只從近代思潮發展定位趨新思想家既有的取徑，同時也為近現代思想史的多元性，提供一鮮明的個案研究。

In the past, academic discussions on Zheng Guanying’s role in late Qing history have emphasized two aspects: as a Chinese comprador, and as a reformist thinker who advocated the doctrine of “Chinese learning as the primary and Western learning as the secondary” (zhongben ximo lun). Both of these factors orient this open-minded thinker within the context of discourse on China’s modernization. However, within Zheng’s inner world, Daoism occupied an important position. This paper discusses the connection between Zheng’s desire for eternal life and his ambition to better the world; it also explains the subtle changes in his ideology on saving the country and bettering the world in his later years, from the viewpoint of his Daoist beliefs.This essay argues that Zheng Guanying, at heart, always had a view both to attain immortality and to better the world. At the same time, he also believed that xianxue, “learning to attain eternal life,” and Western learning provided sufficient means to better the world. Zheng’s public image as a reformist emerged from his propagation of Western learning, which involved remolding social communities. The Daoist beliefs that occupied his mind were for the most part manifest in activities he engaged in as an individual, and thus were easily overlooked. In fact, the familiar image of the man who promoted the idea of “Chinese learning as the primary and Western learning as the secondary” does not correlate at all with Zheng’s inner world. Conversely, the expression “to achieve the Dao and better the world,” (chengdao jishi) captures more completely the interaction between his beliefs and ideology and better resonates with the melody of his spiritual life throughout his days. Once we turn our attention to the significant train of thought of the intellectual himself as a man, we not only challenge the well-laid path that determines the role of innovative thinkers within the development of ideological trends, we also provide a distinctive case study for research in the pluralistic intellectual and cultural history of the modern age.