Piet Mondrian (1872-1944) developed the theory of Neoplasticism from the formal basis of De Stijl. In the journal, Le Néo-Plasticisme: principe général de l'équivalence plastique (first published in 1920), Mondrian articulated the basic principles of Neoplasticism, which he saw as the requirements for "new design" (Nieuwe Beelding) in painting, sculpture and architecture. These rules included an emphasis on the colours blue, yellow, and red, and white, grey and black, the primacy of vertical and horizontal lines and right angles, as well as equal and balanced composition. Mondrian’s painterly oeuvre is the most obvious, rigorous and consistent artistic realisation of the theoretical principles of Neoplasticism. Mondrian’s achievements were inspired by the work of the De Stijl painter, Bart Anthony van der Leck. His artistic ideas were also influenced by his encounters with former priest and philosopher M.H.J. Schoenmaker, and his mathematical & mystical beliefs about the order of the world. In contrast with strict Neoplasticism, Theo van Doesburg developed his theory of Elementarism, which focused on the diagonal as a central design element.