According to Greenberg, the avant-garde concept embedded in modernist painting originates from attempts to escape the literary effects that had persisted in painting throughout the seventeenth and eighteenth centuries in order to secure independence within the realm of art. By “literary effects,” he refers to the thematization of content that painting acquires through imitation and representation. Such effects generate factual illusion within artworks, functioning as channels of connection to the external world, thereby allowing art to convey notions of social ideology. However, these characteristics reduce art to nothing more than a medium of communication and transmission of ideas, devoid of intrinsic purpose and value. At the same time, they raised the need for painting to establish its identity as a distinct domain, separate from literature. Greenberg described the mission of the avant-garde as freeing art from the concepts that had contaminated it through society’s ideological struggles, and as directing artists to concern themselves only with, and feel responsible for, the values intrinsic to art itself—thus realizing art’s instinct for self-preservation.

His inquiry centers on the analysis of artistic media. Greenberg asserted that the unique and exclusive sphere of authority of each art corresponds to the unique nature of its medium. He further claimed that in order for an art form to regain its identity, the opacity of its medium must be emphasized. The reason why the medium matters is because it is intimately bound up with the purity of art. For Greenberg, the purity of art lies in willingly embracing the limitations of its particular medium. For instance, since painting takes the canvas as its medium, its two-dimensional flatness becomes its inherent limitation, and such limitation is precisely what endows painting with its distinctive essence and independent status. According to Greenberg, the opacity of the medium becomes the pure form of art that takes this limitation as its basis. Purity first emerged in music, which conveys nothing beyond sensation itself. This sensation, moreover, can only be apprehended through the sensory organs by which it enters consciousness, and through nothing else—making music an art of purely formal quality. What he discerned in the sensorial form of music is that structural form is indispensable to art, and indeed its pure element. The ultimate aim of this line of inquiry, therefore, is to emphasize the unique sensory experience of pure artistic form.

Greenberg distinguished between pure and impure forms according to the type of illusion they generate. In his view, impure form produces the illusion of three-dimensional spatial depth, while pure form produces only visual illusion. The former induces factual illusion, whereas the latter allows one to perceive reality through the cognition of visual structures. In this sense, the superiority of modernist painting lies in the way its medium-specific attribute—two-dimensional flatness—blocks spatial illusion and elevates sensitivity to the surface of the canvas itself. He argued that, as in the past and continuing into the present, the only consistency that truly holds value in art is aesthetic consistency, and that the aesthetic never reveals itself through method or means, but only through the result. By emphasizing such sensorial and immediate aesthetic experience, Greenberg concludes that the essence of art resides in pure form.

Summary

Greenberg maintained that art must be emphasized solely through the pure form unique to each medium. This was in order to highlight the specificity of each medium, to restore the purity of painting that had been contaminated by the purpose of conveying ideological notions, and ultimately to reaffirm the essential value of art.