A French artist, theoretician, philosopher, a self-proclaimed founder of Cubism and an influence on the School of Paris. With Jean Metzinger, he wrote the first major treatise on Cubism in 1912. He was a founding member of the Section d'Or group of artists. He was also a member of Der Sturm, and his many theoretical writings were originally most appreciated in Germany, where especially at the Bauhaus his ideas were given thoughtful consideration. He spent four crucial years in New York and played an important role in making America aware of modern art. He exhibited regularly at the Galerie de l’Effort Moderne in Paris. He was also a founder, organiser and director of Abstraction-Création. From the mid-1920s to the late 1930s much of his energy went into writing.