Bork shrugged. "Plain good sense. Why should there be a sky shell around the planet? Look, there's a legend here. You should know it, since for all I know it has some meaning for you. Long ago--or away, or whatever--there was a world called Thare and another called Erath. Two worlds, separate and distinct, on their own branching time paths. They must have been that way since the moment of creation. One was a world of rule and law. One plus one might not always equal two, but it had to equal something. There seems to be some similarity to your world in that, doesn't there? The other was--well, you'd call it chaos, though it had some laws, if they could be predicted. One plus one there depended--or maybe there was no such thing as unity. Mass-energy wasn't conserved. It was deserved. It was a world of anarchy, from your point of view. It must have been a terrible place to live, I guess." He hesitated somberly. "As terrible as this one is getting to be," he said at last. "Anyway, there were people who lived there. There were the two inhabited worlds in their own time lines, or probability orbits, or whatever. You know, I suppose, how worlds of probability would separate and diverge as time goes on? Of course. Well, these two worlds _coalesced_." He looked searchingly at Dave. "Do you see it? The two time lines came together. Two opposites fused into one. Don't ask me to explain it; it was long ago, and all I know for sure is that it happened. The two worlds met and fused, and out of the two came this world, in what the books call the _Dawnstruggle_. When it was over, our world was as it has been for thousands of centuries. In fact, one result was that in theory, neither original world could have a real past, and the fusion was something that had been--no period of change. It's pretty complicated." "It sounds worse than that," Dave grumbled. "But while that might explain the mystery of magic working here, it doesn't explain your sky." Bork scratched his head. "No, not too well," he admitted. "I've always had some doubts about whether or not all the worlds have a shell around them. I don't know. But our world does, and the shell is cracking. The Satheri don't like it; they want to stop it. We want it to happen. For the two lines that met and fused into one have an analogue. Doesn't the story of that fusion suggest something to you, Dave Hanson? Don't you see it, the male principle of rule and the female principle of whim; they join, and the egg is fertile! Two universes join, and the result is a nucleus world surrounded by a shell, like an egg. We're a universe egg. And when an egg hatches, you don't try to put it back together!" He didn't look like a fanatic, Dave told himself. Crazy or not, he took this business of the hatching egg seriously. But you could never be sure about anyone who joined a cult. "What is your egg going to hatch into?" he asked.