薩德（Marquis de Sade）的著作影響法國文壇至深，他對變態行為的描述無疑也是佛洛依德（Sigmund Freud）的先驅。然而，薩德的變態幻想並不止於想像，而是背後有著某種堅定的意志所支持。而拉岡（Jacques Lacan）對薩德的閱讀則試圖找出這個晦澀力量背後的「理性」根據。在拉岡眼中，薩德的《寢室裡的哲學》（La philosophie dans le boudoir）不僅符合康德（Immanuel Kant）《實踐理性批判》（Kritik der praktischen Vernunft）的理性精神，甚至補充並道出了其中的真理，因而彰顯出其顛覆性的精華。於是，在精神分析所開啟的慾望向度中，拉岡讓薩德和康德一起走在佛洛依德的前面，讓薩德繼承了代表傳統倫理學之轉捩點的康德，繼而開啟了精神分析的倫理學顛覆。而在拉岡之前，薩德這個人的經驗以及其著作的重要性從來沒有以其倫理學面貌被發掘。本文隨著拉岡的閱讀，一一檢視薩德與康德彼此依存的一體性、道德律法與「絕爽」（jouissance）的關係，以及薩德的「二度死亡」（seconde mort）與佛洛依德的「死亡欲力」玄想。

In the literary world of France, the impact of Marquis de Sade’s works has long held sway. Sade is undeniably the pioneer in the writings on perverse behavior, and only much later did Sigmund Freud appear. Sade’s perverse fantasy is something beyond imaginary: an unfaltering willpower seems to stand behind the fantasy. Jacques Lacan’s reading of Sade, however, is an attempt to probe for the “rational” base behind such obscure force. For Lacan, Sade’s La philosophie dans le boudoir is itself a rational assertion written in response to Immanuel Kant’s Critique of Practical Reason. Sade goes even further to supplement and illustrate the truth of rationality, thus making his book completely and innovatively subversive. Thus, in his psychoanalytic study of “desire,” Lacan puts Sade and Kant together instead of Freud. His assigning Sade as the successor of Kant as well as the critical turning point of traditional ethics has led psychoanalysis, as a result, on the road to a subversion of ethics. Before Lacan, the experiences and works of Sade were never weighed and considered in an ethical light. This paper traces Lacan’s reading of Sade together with Kant by inspecting their symbiotic relationship, the connection between moral principles and jouissance, and finally the mystic analogy between Sade’s “second death” and Freud’s “death drive.”