建立一個批判的思考，「懷疑」（Doubt）是非常重要的基本態度。本文 以西方思想發展軌跡，提出三種懷疑的層次：一、一般的懷疑（General Doubt）： 對事物、對現象的懷疑，如蘇格拉底的懷疑；二、方法論的懷疑（Methodological Doubt）：把懷疑的方向拉回主體，如笛卡兒、胡塞爾；三、徹底的懷疑（Radical Doubt）：從基礎、根源起便開始懷疑。批判思考既以「懷疑」為基本態度，那其 基本方法呢？就是「辯證」。在辯證的介紹上，筆者簡述了黑格爾的辯證方法—— 「矛盾」與「統一」、馬克思的辯證方法；以及批判理論學者所用的辯證方法—— 否定辯證法，並藉之來建立自己的方法。在建立「批判」方法的嘗試上，筆者分 成理論的（或說思考的）層次以及實際的（或可稱為實踐的）層次加以陳述。在 理論的層次上，我著重在於「事實之理解與陳述」——「事實的分析」——「事 實的批判及否定」的整個過程，同時在批判時，也點出了何謂「正常」的關係， 藉由否定現存事實之扭曲面來形成新的理論；在實踐的層次，我則著眼於「批判 否定」和「文化傳統」之間的辯證關係－即必須得先了解群眾賴以存在的文化脈 絡，而採取適當的行動策略。最後，就實踐危機發生之可能性作一個反省。實踐 危機的發生可能來自兩個面向：一是實踐者對於理論所揭露之目標的依循能力、 可能性以及意願；一是方法的問題——方法和理論的基本要求是否相符合。藉由 對危機之反省而避免實踐上的異化所導致的失敗。

Doubt is a highly important and basic attitude for the cultivation of critical thinking. Tracking the development of Western philosophy, this paper presents the three different levels of doubt: first, General Doubt-doubt about things and phenomena, like Socrates' doubt; second, Methodological Doubt-doubt about subject, like that of Descartes and Husserl; third, Radical Doubt-doubt about hypostasis and first cause. While doubt is the basic attitude of critical thinking, dialectic is the fundamental method. In the introduction of dialectic, the writer sketches Hegel's dialectic "opposites" and "unity", Marx's dialectic, and the dialectic exercised by the scholars of critical theory-negative dialectic, in order to construct his own method. In the attempt to construct "critical" methods, the writer makes his statement on both the theoretical (or thinking) level and the practical (or pragmatic) level. On the practical level, we lay stress on the whole process-"the understanding and account of facts, "the analysis of facts," and "the critique and denial of facts." In the time, we also point out what a "normal" relation is, denying the twisted side of extant facts to constitute new theories. On the practical level, I stress the dialectic relation between "critical denial" and "cultural tradition," that is, we have to understand first the cultural context that the public count on for their being and then proceed with feasible strategies. Finally, reflecting on the possibility that crises of practice may occur, we can see that the occurrence of practical crises may come from two sides. One is about how much ability, possibility and willingness the practicer has to follow the goal revealed by the theory, the other is about methods--whether the basic requirements for methods and for theories meet each other. Through the reflection on crises, we try to avoid failures caused by alienation on the practical level.