在《純粹理性批判》B 版的論證（B274-9）中，康德提出一個有說服力 的策略，嚴肅地正面回擊懷疑論者對於外在世界真實性的質疑。他直接攻擊 懷疑論者的核心假設。首先，康德以懷疑論者都應該能夠接受的自我知識的 構想為起點，然後逐步地揭露它的矛盾性。這使得懷疑論者陷入兩難困境。 或者他們必須承認，在他們的假設之下，自我知識是不可能的；或者他們必 須放棄那個假設，換句話說，他們不僅必須承認自我知識的直接明證性，同 時也必須接受作為它的可能性條件的外部事物存在的直接明證性。 本文主張：（1）「駁斥」是有說服力的；（2）「駁斥」與「先驗觀念論」 的核心主張是相容的。 論文分為三大部分。首先，釐清「駁斥」在先驗哲學中的系統性地位， 並藉此闡明「現實性設準」的經驗認知意義；其次，批判地分析「駁斥」的 論證結構與理由證成；第三，藉由釐清關鍵術語的歧義，來闡明「駁斥」與 先驗觀念論的相容性；最後，總結「駁斥」的策略。

In the demonstration of the second edition of the Critique of Pure Reason (B274-9), Kant brings up a persuasive strategy for seriously refuting skeptics’ position concerning the reality of outer world. He attacks directly the core presupposition of skeptics. First of all, Kant takes as a starting point the conception of self-knowledge that should be accepted by all skeptics. Kant then uncovers step by step the sceptics’ contradiction and he hence puts them in a dilemma. Under the sceptics’ assumption, either they must acknowledge the impossibility of self-knowledge or they must give up that assumption. In other words, not only must skeptics acknowledge the direct veridicality of self-knowledge, but also accept the direct veridicality of the existence of outer things as the condition of the possibility of self-knowledge. This paper argues that (1) the ‘refutation’ is persuasive, and (2) the ‘refutation’ and the core theses of ‘transcendental idealism’ are compatible. This essay contains three parts. The first part is to clarify the systematic status of the ‘refutation’ in transcendental philosophy and, by this clarification, to expound the empirically cognitive significance of the ‘postulate of actuality’; the second part is to critically analyze the structure of demonstration and justification of the ‘refutation’; the third part is to expound the compatibility of ‘refutation’ with ‘transcendental idealism’ by clarifying the ambiguity of key terms. The paper ends with a conclusion summarizing the strategy of the ‘refutation’.