Clement Greenberg, from "Modern Painting" 1960

"Modernism includes more than art and literature. By now it covers almost the whole of what is truly alive in our culture. It happens, however, to be very much of a historical novelty. Western civilization is not the first civilization to turn around and question its own foundations, but it is the one that has gone furthest in doing so. I identify Modernism with the intensification, almost the exacerbation, of this self-critical tendency that began with the philosopher Kant. Because he was the first to criticize the means itself of criticism, I conceive of Kant as, the first real Modernist.
The essence of Modernism lies, as I see it, in the use of characteristic methods of a discipline to criticize the discipline itself, not in order to subvert it but in order to entrench it more firmly in its area of competence. Kant used logic to establish the limits of logic, and while he withdrew much from its old jurisdiction, logic was left all the more secure in what there remained to it.

The self-criticism of Modernism grows out of, but is not the same thing as, the criticism of the Enlightenment. The Enlightenment criticized from the outside, the way criticism in its accepted sense does; Modernism criticizes from the inside, through the procedures themselves of that which is being criticized. It seems natural that this new kind of criticism should have appeared first in philosophy, which is critical by definition, but as the 19th century wore on, it entered many other fields. A more rational justification had begun to be demanded of every formal activity, and Kantian self-criticism, which had arisen in philosophy in answer to this demand in the first place, was called on eventually to meet and interpret it in areas that lay far from philosophy.

We know what has happened to an activity like religion, which could not avail itself of Kantian, immanent, criticism in order to justify itself. At first glance the arts might seem to have been in a situation like religion’s. Having been denied by the Enlightenment all tasks they could take seriously, they looked as though they were going to be assimilated to entertainment pure and simple, and entertainment itself looked as though it were going to be assimilated, like religion, to therapy. The arts could save themselves from this leveling down only by demonstrating that the kind of experience they provided was valuable in its own right and not to be obtained from any other kind of activity.

Each art, it turned out, had to perform this demonstration on its own account. What had to be exhibited was not only that which was unique and irreducible in art in general, but also that which was unique and irreducible in each particular art. Each art had to determine, through its own operations and works, the effects exclusive to itself. By doing so it would, to be sure, narrow its area of competence, but at the same time it would make its possession of that area all the more certain.

It quickly emerged that the unique and proper idea of competence of each art coincided with all that was unique in the nature of its medium. The task of self-criticism became to eliminate from the specific effects of each art any and every effect that might conceivably be borrowed from or by the medium of any other art. Thus would each art be rendered “pure,” and in its “purity” find the guarantee of its standards of quality as well as of its independence. “Purity” meant self-definition, and the enterprise of self-criticism in the arts became one of self-definition with a vengeance.

Realistic, naturalistic art had dissembled the medium, using art to conceal art; Modernism used art to call attention to art. The limitations that constitute the medium of painting–the flat surface, the shape of the support, the properties of the pigment–were treated by the old masters as negative factors that could be acknowledged only by implicitly or indirectly. Under Modernism these same limitations came to be regarded as positive factors, and were acknowledged openly. Manet’s became the first Modernist pictures by virtue of the frankness with which they declared the flat surfaces on which they were painted. The Impressionists, in Manet’s wake, abjured underpainting and glazes, to leave the eye under no doubt as to the fact that the colors they used were made of paint that came from tubes or pots. Cézanne sacrificed versimilitude, or correctness, in order to fit his drawing and design more explicitly into the rectangular shape of the canvas.

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. The enclosing shape of the picture was a limiting condition, or norm, that was shared with the art of the theater; color was a norm and a means shared not only with the theater, but also with sculpture. Because flatness was the only condition painting shared with no other art, Modernist painting oriented itself to flatness as it did to nothing else."

"Scientific method alone asks, or might ask, that a situation be resolved in exactly the same terms as that in which it is presented. But this kind of consistency promises nothing in the way of aesthetic quality, and the fact that the best art of the last seventy or eighty years approaches closer and closer to such consistency does not show the contrary. From the point of view of art in itself, its convergence with science happens to be a mere accident, and neither art nor science really gives or assures the other of anything more than it ever did. What their convergence does show, however, is the profound degree to which Modernist art belongs to the same specific cultural tendency as modern science, and this is of the highest significence as a historical fact."

"But I want to repeat that Modernist art does not offer theoretical demonstrations. It can be said, rather, that it happens to convert theoretical possibilities into empirical ones, in doing which it tests many theories about art for their relevance to the actual practice and actual experience of art. In this respect alone can Modernism be considered subversive. Certain factors we used to think essential to the making and experiencing of art are shown not to be so by the fact that Modernist painting has been able to dispense with them and yet continue to offer the experience of art in all its essentials. The further fact that this demonstration has left most of our old value judgments intact only makes it the more conclusive. Modernism may have had something to do with the revival of the reputations of Uccello, Piero della Francesca, El Greco, Georges de la Tour, and even Vermeer; and Modernism certainly confirmed, if it did not start, the revival of Giotto’s reputation; but it has not lowered thereby the standing of Leonardo, Raphael, Titian, Rubens, Rembrandt, or Watteau. What Modernism has shown is that, though the past did appreciate these masts justly, it often gave wrong or irrelevant reasons for doing so."