But Duchamp stresses that since "the tubes of paint used by an artist are manufactured and readymade products we must conclude that all the paintings in the world are Readymades aided' and also works of assemblage." (Duchamp, 83) How can art be so unique, asks Duchamp, within any particular context, when all individuals are using the same modalities of plastic production. Similarly, according to Greenburg's analysis of Manet, "it was the stressing of the ineluctable flatness of the surface that remained, however, more fundamental than anything else to the processes by which pictorial art criticized and defined itself under Modernism. For flatness alone was unique and exclusive to pictorial art." (Greenburg, 195) The distinction between Greenburg and Duchamp, however, lies not so much in the latter's stress upon the physical standardization not the modes of artistic production, which has existed, depending on the artist's media, over all cultures and during all periods -- technical limits are endemic to all periods of art, and all artists must creatively deploy what lies at their disposal, from chalk to computer animation. Rather, Greenburg suggests that the self-critique of art is a unique characteristic...

But Duchamp suggests that the only difference is that modern art has suddenly recognized this aspect of self-parody, standardization, and limitation in art itself. Even in art that is not self-conscious, like an actual ready-made implement itself, there are still the philosophic elements of modern art. Consider the circularity of representation and repetition, and the celebration and creative use of limitations as a source of self-parody, in a mechanized work. Even if these philosophic elements are not manifestly recognized by the generator of the work, the artistic or mechanistic work still depends upon such limitations to generate interest in the eye of the beholder, Duchamp suggests -- by making a living human form static in a statue, or flat on a canvas and standardizing it, the form becomes more rather than less interesting.
Works Cited

Greenburg, Clement. "Modernist Painting." From Esthetics Contemporary. Edited by Richard Kostelanetz. New York: Prometheus Books, 2001.

Duchamp, Marcel. "Apropos of Readymades." From Esthetics Contemporary. Edited by Richard Kostelanetz. New York: Prometheus Books, 2001.