Cubism is not a manner but an aesthetic, and even a state of mind; it is therefore inevitably connected with every manifestation of contemporary thought. It is possible to invent a technique or a manner independently, but one cannot invent the whole complexity of a state of mind.
"'Chez les cubistes' (in 'Bulletin de la Vie Artistique')". "Juan Gris: His Life and Work". Book by Daniel-Henry Kahnweiler, 1946.