The main thing wrong with painting is that it is a rectangular plane placed flat against the wall. A rectangle is a shape itself; it is obviously the whole shape; it determines and limits the arrangement of whatever is on or inside of it. In work before 1946 the edges of the rectangle are a boundary, the end of the picture. The composition must react to the edges and the rectangle must be unified, but the shape of the rectangle is not stressed; the parts are more important, and the relationships of color and form occur among them. In the paintings of Pollock, Rothko, Still and Newman, and more recently of Reinhardt and Noland, the rectangle is emphasized. The elements inside the rectangle are broad and simple and correspond closely to the rectangle. […] The simplicity required to emphasize the rectangle limits the arrangements possible within it. The sense of singleness also has a duration, but it is only beginning and has a better future outside of painting. Its occurrence in painting now looks like a beginning, in which new forms are often made from earlier schemes and materials.
from Donald Judd’s Specific Objects