I am also asking the reader to suppose that the concept of space has nothing to do with perception. Geometrical space is a pure abstraction… The visual third dimension is a misapplication of Descartes’s notion of three axes for a coordinate system. The doctrine that we could not perceive the world around us unless we already had the concept of space is nonsense. It is quite the other way around: We could not conceive of empty space unless we could see the ground under our feet and the sky above. Space is a myth, a ghost, a fiction for geometers. All that sounds very strange, no doubt, but I urge the reader to entertain the hypothesis.