本文從分析《中庸》形上系統之特質出發，在當代以知識探究為目的的觀解系統外，提供以形上學作為思考之背景與基礎的觀點；此一觀點在於強調文字體系內的形上學或本體論之理論建構之背後是具備存在性之基礎與根源的。其次，本文透過「天－人－地」三元的道德藍圖說明了《中庸》道德哲學的方法論，一方面從宇宙結構分析，「人」存在於「天」與「地」兩觀念之間建立文明，另一方面，則從知識結構，說明「人」為「知識性真理」與「存在性真理」的統合者，以及三元結構中「第三元」存在的必要性。最後，本文再從事物發展的規律，透過「權變」、「時中」，以及「處中」與「動態」觀念，指出「中道」為理想與現實兩端之統合原則。透過上述四個面向之論述，期能具體呈現「三元思維」實為掌握《中庸》道德哲學的方法性結構。

This paper begins with analyzing the aspects of the metaphysical system of Zhongyoung (The Doctrine of the Mean), offering an approach that takes metaphysics as its philosophical background and foundation. The point of such an approach lies in its emphasis on the existential foundation and source behind the theory construction of the metaphysics and ontology contained within the system of writing. Second, through the ternary diagram of morality, “heaven-man-earth,” we explain the methodology of morality philosophy in Zhongyong. On the one hand, in the light of the structure of the universe, we analyze how “man” establishes civilization between the concepts of “heaven” and “earth.” On the other hand, in view of the structure of knowledge, we explain how “man” is the integrator of the “epistemological truth” and the “existential truth” and why it’s essential for the “tertiary party” to exist in the ternary structure. Finally, considering the laws of the development of things, we point out that the “middle way” is the principle to integrate the ideal and the reality, through the concepts of “strategic flexibility,” “maintaining the mean,” “abiding in the mean,” and “dynamics.” Through the statements on the four aspects mentioned above, we wish to present concretely that “ternary thinking” is indeed the methodological structure for us to grasp the moral philosophy in Zhongyoung.