Die Stijl, ("The Style") included a group of Dutch artists in Amsterdam in 1917 (such as painters Piet Mondrian, Theo van Doesburg, the architects Gerrit Rietveld, Pieter Oud, and the poet A. Kok). Its members, working in an abstract style, were seeking laws of equilibrium and harmony applicable both to art and to life. De Stijl's most outstanding painter was Mondrian, whose art was rooted in the mystical ideas of Theosophy. Although influenced by his contact with Analytical Cubism in Paris before 1914, Mondrian thought that it had fallen short of its goal by not having developed toward pure abstraction, or, as he put it, "the expression of pure plastics" (which he later called Neoplasticism). In his search for an art of clarity and order that would also express his religious and philosophical beliefs, Mondrian eliminated all representational components, reducing painting to its elements: straight lines, plane surfaces, rectangles, and the primary colours (red, yellow, and blue) combined with neutrals (black, gray, and white). Van Doesburg, who shared Mondrian's austere principles, launched the group's periodical, De Stijl (1917-32), which set forth the theories of its members.