牟宗三哲學中的「物自身」概念

The Concept of “Thing in Itself” in Mou Tsung-san’s Philosophy

在當代中國哲學中，牟宗三先生與康德哲學之密切關係是眾所周知的。早在1949年，他便已撰成大部頭的《認識心之批判》一書，對康德底《純粹理性批判》一書作了深入的探討。此書主要是順著康德對知性(Verstand)底機能所作的說明，來融攝羅素(Bertrand Russell)、維根斯坦(Ludwig Wittgenstein)等人關於邏輯及數學的理論。但此書在絕版多年之後，於1990年由臺灣學生書局重印時，牟先生在〈重印誌言〉中對此書表示了不滿，認為：「最大的失誤乃在吾那時只能了解知性之邏輯性格，並不能了解康德之『知性之存有論的性格』之系統。」《認識心之批判》撰成之後，有十五年之久，他對康德哲學未作有系統的專門討論。直到1964年，他才再譯出康德底《道德底形上學之基礎》一書。從1961年起，他開始陸續撰寫《心體與性體》中各章節，至1969年，這三冊的巨著始全部出版。在這部巨著中，他順著康德「自律倫理學」底基本義 理，來詮釋宋明儒學中的周濂溪、張橫渠、程明道、程伊川、胡五峰及朱子六 家，並且分判其義理型態。1978年他撰成《從陸象山到劉蕺山》一書，進而討 論陸象山、王陽明及劉蕺山三家，始完成關於宋明儒學的研究。但是他在這一 系列的研究中並非完全以康德為標準，而是順著康德底「自律」(Autonomie) 概念，進一步提出「道德的形上學」底概念，作為分判底標準。他在《心體與 性體》第一冊〈綜論〉底第三章「自律道德與道德的形上學」中檢討康德底倫 理學，認為康德只有「道德底形上學」(metaphysics of morals)，而無「道 德的形上學」(moral metaphysics)。簡言之，「道德底形上學」是指「道德 之形上的解析」，等於「純粹的道德哲學」；「道德的形上學」則是依道德進 路而建立的形上學，相對於「思辨的形上學」(speculative metaphysics)。依 牟先生之見，康德僅依道德進路建立了一套神學，而有「道德的神學」，卻無 「道德的形上學」，其關鍵在於康德不承認意志底自由可以在人類底意識中呈 現，而僅視之為「設準」(Postulat)。

The concept of “thing in itself” has a central position in the philosophy of Kant. But as most of his important concepts often expose their meanings only gradually in the process of the development of his thought, this concept likewise has somewhat different meanings in his different works, and thus makes its understanding more difficult than others. Most scholars refer to his Critique of Pure Reason in their discussion of this concept. In this work, the distinction between “appearance” and “thing in itself” is a transcendental distinction, and its essential meaning is epistemological. Accordingly, “thing in itself” means the foundation of human knowledge on the one hand and its limits on the other hand. For Kant, this is a “problematic” concept. He also conceives “thing in itself” as the object of a non-sensible (intellectual) intuition. But as he denies this kind of intuition for human beings, he denies our ability to know the “thing in itself”. So Kant's conclusion in this work is : the concept of “thing in itself” contains no contradiction, but transcends the bounds of our possible knowledge; and at the same time, it is a necessary idea, in order to account for the possibility of our knowledge. But in Groundwork of the Metaphysics of Morals and Critique of Practical Reason, the concept of “thing in itself” presents yet another meaning. Here he interprets “thing in itself” as a viewpoint, through which an “intelligible” world is disclosed. This is a necessary conclusion of his thesis of the primacy of practical reason over speculative reason. As Prof. Richard Kroner in his Kant's Weltanschauung puts it, “thing in itself” opens a “kingdom of freedom”. In this way, the concept of “thing in itself” achieves a more fundamental meaning, namely, its ethical meaning. But in the development of its meaning, Kant's interpretation thereof is neither sufficient nor conclusive, so that it becomes a subject for debatet in the ensuing German philosophy. In his Mind and Human Nature, Prof. Mou Tsung-san at first investigates Kant's moral philosophy, and points out that the sphere of freedom in Kant remains abstract, and lacks reality, since Kant looks upon the freedom of will only as a “postulate”. Therefore, Kant can only establish a “metaphysics of morals”，but not a “moral metaphysics”. In his Intellectual Intuition and Chinese Philosophy, Prof. Mou furthur points out that in order to establish the metaphysics of Confucianism, Taoism, and Buddhism (above all the Confucian moral metaphysics), it is necessary to admit an intellectual intuition for human beings. This implies that “thing in itself” can be represented to the moral mind of human beings, and need not lie beyond the extreme limits of practical philosophy. But this does not contradict Kant's thesis that “thing in itself” can't be an object of human knowledge.. In his Appearance and Thing in Itself, An Essay on the Highest Good, 14 Lectures on the Meeting of Chinese and Western Philosophy, and his commentary on Critique of Practical Reason, Prof. Mou examines in detail Kant's distinction between “appeaiance” and “thing in itself”，and shows its insufficiency. From this investigation he comes to the conclusion that only in the metaphysics of Confucianism, Taoism, and Buddhism, can this distinction fully establish its systematic meaning.