(b Buffalo, NY, 24 Dec. 1913; d New York, 30 Aug. 1967). American painter. From the beginning of his career his painting was abstract, but it changed radically in style over the years. During the 1930s he worked in a crisp, boldly contoured geometrical style that owed something to both Cubism and to the Neo-Plasticism of Mondrian. In the 1940s he passed through a phase of all-over painting which has been likened to that of Mark Tobey, and in the late 1940s he was close to certain of the Abstract Expressionists, particularly Motherwell, with whom he jointly edited the book Modern Artists in America (1950), based on conversations with contemporary artists. During the 1950s he turned to monochromatic paintings. At first they were usually red or blue, but from the late 1950s he devoted himself to all-black paintings with geometrical designs of squares or oblongs barely perceptibly differentiated in value from the background colour—works that were influential on the development of Minimal art.