龔鼎孳（1615-1673），安徽合肥人，字孝升，號芝麓，生於明萬曆四十四年，卒於清康熙十二年（1616-1673）。其生平不僅跨越明清二代，明清鼎革之際更曾分別在明、大順、清三個不同政權下任官。就政治上的表現而言，龔鼎孳無論是在明或清，皆受到君主與百姓的好評及肯定，同時還以自己的仕宦的優勢，庇護了相當多的落難漢人，在經濟上也援助許多出處立場、理念不同的士人。然而吊詭的是，乾隆四十一年（1776）時他被削除諡號，官方編輯的《貳臣傳》更指斥其道德不彰、大節有虧。此外，在龔鼎孳對遺民、舊友的交游與庇護，也被一些人士指為「好集令譽」使然。這些不同的觀點可以顯示對於龔鼎孳的政治作為的解讀上有重大的落差。 本文主要在討論龔鼎孳的仕宦生涯。首先檢視龔鼎孳家族的仕宦歷程及其在明代的仕宦狀況，以了解他政治理念的奠基與形成。接者比較龔鼎孳於易代之後的仕宦、交游情況，以呈現各時期仕宦之異同。最後則並以龔鼎孳在易代之際的遭遇，來討論其出處之選擇，並評價其之仕宦。事實上，經過對龔鼎孳仕宦之考察，不僅可深切了解到其在時代劇變中的為人、心態與仕途，並顯示學界以「出處抉擇」作為評價易代士人的侷限性。 Gong Dingzi (1616-1673), whose courtesy name was Xiaosheng and whose style name was Zhilu, was a native of Hefei, Anhui Province. He was born in the forty-fourth year of Wanli period (1616) and died in the twelfth year of the Kangxi period (1673). His life was across the Ming and the Qing dynasties and had served in three different dynasties – Ming, Shun, and Qing. As for his political performance, Gong Dingzi had won praises from his lords and also from common people. Furthermore, Kong Dingzi, as a Qing official, generously took care of many suffering Han people in the transitional period and gave aid to those who refused to cooperate with the Qing Dynasty. Yet in the forty-first year of the Qianlong period (1776), he was striped of his posthumous title and was even blamed for “poor ethics” and “error in major principles” in the official Biographies of the Two Dynasties. After his death, Kong’s assistance to the Ming loyalists had been interpreted as for collecting good reputations. These different viewpoints have shown a huge difference in interpreting his role in politics. The thesis is an analysis of Gong Dingzi’s official career. The first part is to examine Gong’s family background and his official career in the Ming Dynasty in order to understand the formation of his political thought and ideals. The following part is a comparison of his careers in different dynasties and also studies his association with friends in this transitional period. The last part is to illustrate Gong’s decisions in serving different dynasties and to evaluate his performance in officialdom. Through a thorough examination of Gong’s official career, we not only can understand his behavior, mentality, and experience, but also prove the limitation of application of the criterion of “public service or seclusion” to Chinese intellectuals in Ming-Qing transitional period.