My friend Peter Schmidt used to talk about ‘not doing the things that nobody had ever thought of not doing', which is an inverse process – where you leave out an assumption that everybody has always made and see what happens (e. g. music has to be made of intentionally produced sounds was the assumption that Cage left out). In that version of this process, you discover a value in the absence of something – in fact you discover that the absence of something is the revelation of something else (Buñuel, the film-maker, said, "Every object conceals another"