Maybe the oldest question in the world is "What's new?" It's certainly the oldest question in the various worlds of design. If it weren't for constant change, how could anyone prove he or she was designing in the first place? Priests, waiters, violinists—some people can go on doing pretty much what they did 30 years ago. But if an architect proposes the same building today that she would have produced in 1970, she isn't designing things, she's just making them, the way Colonial American cabinetmakers used to bang out identical highboys from the diagrams in old British copybooks.

Innovation is one of the engines of a market society, a point where economics converges with aesthetics. It was around the 1920s, for instance, that automakers hit upon the profitable notion of yearly style "advances" for new cars, the aesthetic equivalent of planned obsolescence. Change for its own sake also helped generate the annual couture collection, which led in turn to style crazes and recreational shopping, which led in turn to fashion victims, but that's another story.