This article deals with Clement Greenberg’s theory of art whose influence once was overwhelming on the practice and theory of art in the second half of the 20th century. It has been a custom to identify Greenberg’s theory of art with Modernism and to regard it as the representative explanation of modem art. Greenberg’s Modernist theory of art is, indeed, the most powerful theorization of modernism in art. On the modem basis of the autonomy of art, Greenberg’s Modernism mark out a specific area for art and explained that the dynamics of that area came from the ‘self-criticism’ seeking the pure and irreducible nature of art. Truly successful in showing the seemingly inevitable developments of modem art, his Modernism has long been regarded as the logic of modem art as such and the sole relevant history of modem art. After Minimalsim, however, Modernism waned because of its inability to explain the new currents of art, and at the same time, doubts arose around the identification of Modernist art which Greenberg had always defended and modern art. Another history was implied and this implication I, in this article, would like to make explicit. I believe the significant problematic of Clement Greenberg is the role of his theory in the process when the prewar European modern art flowed in and settled down in the postwar America. So it is necessary to go back to the origin and developments of modern art and in it locate Greenberg’s theory. To locate the beginning of modern art in the history of western art is basically related to an epoch’s consciousness of modernity of its contemporary art. Modernity presupposes, above all, a particular consciousness that an epoch and its art is ‘modern’. For a long time, however, modernity had sought its base not on the present but on the past, the classical Antiquity or the idealized Middle-Ages. In the early 19th-century, at last, the modernity focusing on the present emerged, and this is the so-called aesthetic modernity. The aesthetic modernity was characterized by its prominent negativity. Negative in its nature, first of all, because of the paradoxical situation that the ‘modern’ art and artists true to the very present was not welcomed by the contemporary public too much accustomed to the art of the great past, that is, classicism. So the first moment of modern art appeared in Romanticism’s anti-classicism. The lack of understanding of the contemporary public led naturally to the negative attitude of modern art to the society. On this, an entirely new tradition which broke all kinds of past began, and this is the modernism which seeks to build an autonomous field of a critical culture and high art to the Bourgeois civilization and society. As a ciritical tradion of art, modernism, in the course of time, couldn’t escape the fate of institutionalization in the capitalist society. Losing its challenge and defiance, modernism replaced the old tradition of the classical and settled down as the tradition of the new. From this, attempts made to break the institutionalized autonomy of art and go beyond to seek to revolutionize art and life at the same time. This is the Avant-Garde, In sum, modern art begun in Romanticism in its negation of the past, and afterwards it developed dialectically through the interaction between modernism which sought the art for art’s sake in its negation of the society and Avant-Garde which sought the anti-art in its negation of any kinds of institutionalized tradition including modern one. The European development of modern art wholly had stopped with the historical event of the Second World War, and it found the new shelter during and after the War across the Atlantic Ocean. And there he was, Clement Greenberg, the young American critic who worried so much about the fate of Western culture. In front of the totalitarian communism and consumerist capitalism, he called for the “Avant-Garde” culture to spare art in that total crisis of culture. With no hope for the “authentic”, ciritical art to find in any existing political-economic system of world, he found urgent to keep and protect art itself and leaned on the art’s autonomy. So Greenberg advanced the concept of “Avant-Garde” on the doctrine of the Art for Art’s Sake seeking art’s purity with the style of abstraction. Considered above, the Art for Art’s Sake doctrine is the very base of European modernism before the War. So it is clear that what Greenberg has got in the postwar America with the name of “Avant-Garde” was not the European anti-artistic Avant-Garde, but the very artistic modernism. In the postwar posterity of America, Greenberg discarded the former cultural pessimism and changed his position to cultural optimism. He found out the cultural potentials in the postwar American society and mass public. According to this situational change, the society and its public was now not regarded hostile to modern art any more, and as the result, his “Avant-Garde” lost the counterpart to oppose. Left was the formal investigation to realize art’s autonomy against the society. In this way, the direction of art’s criticism became introverted. This Greenberg theorized as the famous “self-criticism”, and it is the beginning of his own theory, Greenbergian Modernism. Modernism in art, according to the theory, practices self-criticism keeping pace with the spirit of the modern age, materialism or positivism. And with this self-criticism to seek the irreducible nature of art, for example, to seek the flatness or two-dimensionality in the case of painting, and at the same time to resist tangibility or three-dimensionality which belongs to the art of sculpture, Modernist art, Greenberg claims, continues the history of “high” art of anti-sculptural tradition since the Venetian Renaissance. Now it can be clearly said that this Modernism is not the same thing as the prewar European modernism which Greenberg got in in the name of “Avant-Garde” about 20 years ago. Not because of the following reasons. 1) The European modernism as the artistic negativism was not keeping pace with the material spirit of the modern era, but the negation of that spirit. 2) In this regard, the European modernism was not concerned with the criticism of the “self”, but the art’s critical manifestation to the Bourgeois civilization. 3) So the autonomy of art which the European modernism took as its base was grounded not inside of art, but outside of art related to the society. But the final and fundamental deviation of Greenberg’s Modernism from the European modernism is the alleged continuity of the tradition of the tradition from the great past which Greenberg wanted so much to secure for his theory of art.