Defining science fiction has always been a tricky proposition. It has been suggested that "you know it when you see it," but that hardly seems a sufficient rule. Still less helpful is the notion that the science fiction moniker applies to any fiction dealing imaginatively with concepts borrowed from science. The fact of the matter remains that select staples of the literary cannon have displayed an interest in science from Shakespeare’s work through the likes of Thomas Pynchon. This does little to change the fact that when we speak of science fiction we hardly ever mean The Tempest (1610), and we usually don’t mean Gravity’s Rainbow (1973) either.