"In theory there is nothing the matter with cubism; only, in practice, there are very few painters who can express themselves completely in abstract form. There are plenty of artists who can so express themselves, and they become musicians, architects, designers of furniture, etc., etc.; but precisely what makes a man turn painter is, as a rule, a desire to express himself through what he sees outside him and not through what goes on inside his head. Picasso and perhaps Braque expressed themselves completely in cubism; Metzinger, Gleizes, Gris, Leger, Hayden and Marcoussis have all expressed something worth expressing; nevertheless, the best cubist pictures are, for the most part, sensibly poorer than they need be, while the bulk are mere frauds."
Click here to read Clive Bell's thoughts on Marcel Proust.