They mistake the decorations on the wall to be more than dried paint. Dried paint: the arbitrary colours superfluous to the purpose of the very structure in question. For its purpose is served by merely existing, and its decoration is purely subject to the whims of an ever-changing set of taste buds. This latter phenomenon can live or die, and the universe itself may not even notice its presence or absence. It is only us, the dramatic monkeys that live on the surface of things, that believe these decorations to be of greater worth and value than their definitive allotment provided for by sincerest nature.