"All advances are [fantasies in origin] until someone makes them into reality. Airplanes have existed in fantasy ever since the story of Daedalus; Arthur C. Clarke invented communication satellites as part of a fantasy; a thermos flask figures in several Celtic tales as one of the miraculous Treasures of Britain. And so on. The ability to fantasize is the most precious one we know. Because it solves problems, it has tremendous survival value. And--fortunately--it is built into us so that, unless mistaken adults inhibit us, we all have to do it. "Children, of course, do it all the time, but even the most adult of businessmen in the most boring meeting will say "Let's play with a few figures here" or "Let's play around with this idea for a bit"--and this is the right way to talk about it because it helps if your imagination is exercised with a lot of pleasure and in a great deal of hope. Then your "What ifs" go with a verve and you're...