康德对道德法则(moralisches Gesetz)的演绎和证明无疑在其道德哲学中占有重要的地位。道德法则以及相关的自由概念若不具有客观实在性,则道德将会成为一种“虚构的观念”和“头脑的产物”。然而不幸的是,在其代表作《道德形而上学原理》和《实践理性批判》中,康德的思想发生了很大的转变,甚至是巨大的颠倒。在前书中试图从自由来确立和演绎出道德法则,后者则是明确反对有任何关于道德法则的演绎,并同时从道德法则演绎出自由。在此背景下,文章首先分析和评价这两种不同的演绎,然后通过比较来解释这种转变的原因以及意义。 Kant’s deduction and proof of moralisches Gesetz undoubtedly occupy an important position in his moral philosophy. Without the objective reality of moral law and related concepts of freedom, morality will become a “fictional concept” and “product of the mind.” Unfortunately, however, Kant’s thoughts have undergone great changes or even huge reversals in his masterpiece “Principles of Moral Metaphysics” and “Practical Rational Criticism.” In the first book, we try to establish and deduce the law of morality from freedom, while the latter explicitly opposes any deduction of the moral law and meanwhile deduces the freedom from the moral law. In this context, the article first analyzes and evaluates these two different deductions and then explains the reasons and the significance of the change by comparison.