Professor, Theatre Department Taipei National University of the Arts, Taiwan Abstract ”Horizontal Theory” is the turning point of Wang Kuo-Wei's aesthetic thinking from ”tired in philosophy” and thus ”being transforid to literal arts”. After the ace in ”filing song-tze”, Won Kuo-Wei wrote down his critical work ”Comment on the tze of the human world”, the universal criterion for his criticism-Horizontal Theory is not only as the universal criterion for his criticism but also been taken as the metaphisical idea for the modern Chinese literature and art criticism. Thus the ”Horizontal Theory” is the most orignial tribution of Wang Kuo-Wei to Chinese modern aesthetics and criticism. In writing this essay, the first aspect is to catch the origin point of Wang Kuo-Wei's aesthetic thinking, then the succeeding analysis is on the metaphisical foundations of his horizontal theory, while the main parts of this study is on the first understanding of Wang Kuo-Wei to Aristotle's Poetics. That is the real origin of Wang's confined definition of ”singing theatre” (Shi Chu), and this is also the foundation of his Chinese theatre study. 1. The Wang's foundation of ”old science” and his re-orientation to ”new science”. His study of Kant's philosophy and aesthetics. 2. ”Tired in philosophy” and thus being ”transferred to literature (poetry composition and critism)”. 3. Wang Kuo-Wei's Horizontal Theory was originated from Buddist phynominalogical idea of horizontal as the metaphisical foundation of the aesthetic world of liberal arts. 4. The foundation of singing theatre as science of theatre arts and it's origin of critical theory. The begining of Wang's study on science of theatre arts started from the composition of ”tze for human world” and its criticism; while we can point out that his science of Chinese theatre art has his roots on Aristotle's Poetics as following: 1. To judge the real drama and the real ”singing theatre” according to dialectic discour between narrative mode and mimesis. 2. Wang's definition of ”drama in wholly signitication” is to represent a story with speech, movement and singing medium, this is a definition according to the theatre elements as in the first chapter of Poetics. 3. The difference and interchangeability between tragedy and comedy according to Horace's Poetic art. 4. The citation of Katharsis theory as the telos of tragedy and as the telos of Ethics. 5. To explain the sublime value in ”Red Chambre Story” as ”Tragedy in Tragedy”, and gave two examples in Yuan Tza-Ghu: Guan Han-Ching's great tragedy ”The indesignable of Dao-Oe” and Ghi Ghun-Shiang's ”Orphrin of Chao's family”. 6. The initiative ability to found a science of singing theatre as reveal in Shon and Yuan History of singing theatre (1914). 7. Comment the composition of Yuan Tza-Ghu (Northern style) and Song-Yuan Nan Xi (Southern style) with the saying of ”having Horizontal of Images” (Yi-Gheng), this is also the extension of his horizontal theory.