"If you're certain you are ready," he replies, her petulance waking a mild teasing note in his own voice, "I shall try to explain. Think back through your life, and imagine all the choices that you made, that could have gone another way. The choices other people made. The random chances. All the way back from now... to the dawn of time." He gives her a moment to do that while he sips his coffee.

"Now imagine that one, just one of those chances going some other way. How different would the world have been? Now another. And another. Imagine that each of those histories, each of those possibilities, is a world unto itself. Each change brings you a step farther away from the world you know, yet each is true." Their food arrives, and he interrupts himself with a pleased, "ah," as the plates are set down.