John Varley

I had to choose between a panic if the fathead got them to thinking, and a possible panic from the flash of the gun. But when a 20th gets to talking about his “rights” and what he is “owed,&rdauo; things can get out of hand.

The crew had to stun just about everybody. The only bright spot was the number we’d managed to shuffle through during the thinning phase. The rest would have to go through on our backs.

For one thing, paradoxes can occur. Say you build a time machine, go backwards in time and murder your father when he was ten years old. That means you were never born. And if you were never born, how did you build the time machine? Paradox! It's the possibility of wiping out your own existence that makes most people rule out time-travel. Still, why not? If you were careful, you could do it.