Greenberg wrote several seminal essays that defined his views on art history in the 20th century. In 1940, Greenberg joined
Partisan Review as an editor. He became art critic for
The Nation in 1942. He was associate editor of
Commentary from 1945 until 1957. In December 1950, Greenberg joined the government funded
American Committee for Cultural Freedom. He believed modernism provided a critical commentary on experience. It was constantly changing to adapt to kitsch pseudo-culture, which was itself always developing. In the years after World War II, Greenberg pushed the position that the best avant-garde artists were emerging in America rather than Europe. Particularly, he championed Jackson Pollock as the greatest painter of his generation, commemorating the artist's
"all-over" gestural canvases. In the 1955 essay "American-Type Painting", Greenberg promoted the work of Abstract Expressionists, among them Pollock,
Willem de Kooning,
Hans Hofmann,
Barnett Newman, and
Clyfford Still, as the next stage in Modernist art, arguing that these painters were moving toward greater emphasis on the "
flatness" of the picture plane. Greenberg helped to articulate a concept of
medium specificity. It posited that there are inherent qualities specific to each artistic medium, and part of the modernist project involved creating artworks that are more and more committed to their particular medium. In the case of painting, the two-dimensional reality of the medium led to an increasing emphasis on flatness, in contrast with the illusion of depth commonly found in painting since the
Renaissance and the invention of pictorial perspective. In Greenberg's view, after World War II the United States had become the guardian of "advanced art". He praised similar movements abroad and, after the success of the
Painters Eleven exhibition in 1956 with the
American Abstract Artists at New York's Riverside Gallery, he traveled to
Toronto in 1957 to see the group's work. He was particularly impressed by the potential of painters
William Ronald and
Jack Bush, and later developed a close friendship with Bush. Greenberg saw Bush's post-Painters Eleven work as a clear manifestation of the shift from abstract expressionism to
color field painting and
lyrical abstraction, a shift he had called for in most of his critical writings of the period. Greenberg expressed mixed feelings about
pop art. On the one hand he maintained that pop art partook of a trend toward "openness and clarity as against the turgidities of second generation Abstract Expressionism." But Greenberg claimed that pop art did not "really challenge taste on more than a superficial level". During the 1960s, Greenberg remained an influential figure on a younger generation of critics, including
Michael Fried and
Rosalind E. Krauss. His antagonism to "
postmodernist" theories and socially engaged movements in art caused him to become a target for critics who labeled him, and the art he admired, "old-fashioned". In 1968, Greenberg delivered the inaugural
John Power Memorial Lecture at the
Power Institute of Fine Arts at the University of Sydney, Australia. In his book
The Painted Word,
Tom Wolfe criticized Greenberg along with
Harold Rosenberg and
Leo Steinberg, whom he dubbed the kings of "Cultureburg". Wolfe argued that these three critics were dominating the world of art with their theories and that, unlike the world of literature in which anyone can buy a book, the art world was controlled by an insular circle of rich collectors, museums and critics with outsized influence. == Post-painterly abstraction ==