History of painting group's theories. Next to van Doesburg, the group's principal members were the painters Piet Mondrian, Vilmos Huszár, and Bart van der Leck, and the architects Gerrit Rietveld, Robert van 't Hoff, and J. J. P. Oud. The artistic philosophy that formed a basis for the group's work is known as "neoplasticism" — the new plastic art (or "Nieuwe Beelding" in Dutch). Proponents of De Stijl sought to express a new utopian ideal of spiritual harmony and order. They advocated pure abstraction and universality by a reduction to the essentials of form and colour; they simplified visual compositions to the vertical
Piet Mondrian his painting with his spiritual pursuits, and in 1913 he began to fuse his art and his theosophical studies into a theory that signaled his final break from representational painting. While Mondrian was visiting the Netherlands in 1914, World War I began, forcing him to remain in there for the duration of the conflict. During this period, he stayed at the Laren artists' colony, where he met Bart van der Leck and Theo van Doesburg, who were both undergoing their own personal journeys toward abstraction. Van der Leck's use of only primary colors in his art greatly influenced Mondrian. After