Sometime, perhaps 50,000 years ago or more, a relatively thin layer of neurons, emerging out of and covering the ancient sensory-motor and limbic-emotional brain centers, exploded - and along with it memory of the distant past and more revolutionary projections into the future. The capacity to create mental images not presented by the sensory or emotional systems grew like a supernova, including the use of symbols, language and metaphor; a word, for example, standing in place of a thing. So powerful and explosive was this new image-making capacity that it quickly swamped the other systems, filing what we call consciousness with dream-images that were so real that we forgot that we were dreaming. Like a giant snowball of dream-images, once set into motion this capacity grew by one dream image triggering another and another, creating a virtual reality machine unparalleled in the known universe.