《圓善論》是牟宗三先生晚年的重要哲學著作，涉及儒釋道三教的基本義理，其主要的構想在藉由儒釋道（最後以儒家為主）的義理解決「圓善」問題。由於他使用的概念並不容易理解，故容易讓人對牟先生的《圓善論》產生誤解。大陸學者楊澤波教授於其《貢獻與終結——牟宗三儒學思想研究：第四卷‧圓善論》向牟先生提出了挑戰：「牟宗三未能解決康德意義的圓善問題」。然而，若細讀可發現，楊澤波教授的挑戰一來起因於他誤解（誤讀）康德與牟先生論述中的「幸福」概念；二來是他誤認為「道德幸福」適用於儒家，並以之詮釋牟先生──藉由儒家圓教所解決——的「圓善」中之「幸福」概念。而這很大的原因是他誤解孟子「性善說」的核心概念（例如「性分」、「良心」）、未注意孟子對道德與幸福的基本區分，以致於他未能掌握孔孟一脈儒家如何回應「為什麼要實踐道德」（why be moral）的問題。本文雖未能處理「圓善」如何可能的問題，但釐清上述問題是探討「圓善」如何可能的先決條件。因此，我將依序說明：（1）造成楊澤波教授詮釋不當的原因：（1-1）誤解康德道德哲學中「自然」與「經驗」概念；（1-2）誤讀康德論及幸福的文本；（1-3）以偏概全的邏輯謬誤。（2）康德的兩重幸福觀，並順此線索提出第一人稱與第三人稱的幸福觀；（3）說明牟宗三先生論述下之德行與幸福的關係。

Yuan Shan Lun [《圓善論》, On the Perfect Good], related to respective theory of Confucian, Buddhism, and Daoism, is an important philosophical work in/from Mou Zhongsan’s later years. This work attempts to resolve the problem of the “perfect good” based on teachings of Confucian, Buddhism, and Daoism. Since Mr. Mou’s philosophical terminology in Yuan Shan Lun is difficult to comprehend, this sometimes leads to incorrect interpretation from his readers. For example, Professor Yang Zebo points out/states: “Mou Zhongsan is unable to resolve the problem of the ‘perfect good’.” However, if we examine his arguments thoroughly, we will find that his challenge to Mr. Mou is caused from two of his incorrect understandings. First, Yang incorrectly interprets the meaning of “happiness” in Mr. Mou’s sayings and Kant’s. Second, Yang misunderstood that the concept, “moral happiness”, is appropriately applicable to Confucian. He then uses “moral happiness” to describe Mr. Mou’s usage of “happiness” of the “perfect good”. His misunderstanding comes from not grasping Mencius’s two core concepts, xingfen (性分) and lianxin (良心) in the “theory of the goodness of human nature”. Furthermore, Professor Yang does not notice Mencius’ fundamental distinction between virtue and happiness so that Yang fails to grasp how Mencius responds to the question of “why be moral”. Although resolving how the “perfect good” is possible is not the main task in this paper, to clarify the meanings of the foregoing concepts is a prerequisite to respond how the “perfect good” is possible. Therefore, I seek to, step by step, respond to the following issues. (1) What causes professor Yang’s incorrect interpretations: (1-1) his incorrect reading of the concepts, “nature” and “experience” in Kant’s philosophy; (1-2) his incorrect understanding of the context of “happiness”; (1-3) hasty generalization. (2) There are actually two dimensions of “happiness” in Kant’s moral theory, and based on this I will discuss the meanings between the first-person-perspective happiness and third-person-perspective happiness. (3) How does Mr. Mou draw a distinction between virtue and happiness?