Karl Popper, the eminent historian of science, once recounted the story of a man in the Stone Age asked to imagine the invention of the wheel in some distant future. “Describe what this invention will look like,” his friend asks. The man struggles to find words. “It’ll be round and solid, like a disk,” he says. “It will have spokes and a hub. Oh, and an axle to connect it to the other wheel, also a disk.” And then the man pauses to reconsider what he’s done. In anticipating the invention of the wheel, he has already invented it.
