“For two hundred and fifty years the kzinti had not attacked human space. They had nothing to attack with. For two hundred and fifty years men had not attacked the kzinti worlds; and no kzin could understand it. Men confused them terribly.”

“Long ago, Louis Wu had stood at the void edge of Mount Lookitthat. The Long Fall River, on that world, ends in the tallest waterfall in known space. Louis's eyes had followed it down as far as they could penetrate the void mist. The featureless white of the void itself had grasped at his mind, and Louis Wu, half hypnotized, had sworn to live forever. How else could he see all there was to see?Now he reaffirmed that decision.”

“There had been a popular joke on Freedom, started by a man named Calder. Looking down from space, he had said, the dominant life forms on Earth were obviously the cereals and other grasses. They occupied all the most desirable and fertile land; and they had tamed insects and animals to care for them. In particular, they had domesticated the bipeds to nurture and cultivate them and to save and plant their seed. Now, watching the farmers, Alex could easily imagine that they were worshiping and genuflecting before their masters.”

“The dinosaurs became extinct because they didn't have a space program. And if we become extinct because we don't have a space program, it'll serve us right!”

“It's very difficult for a black man to get out of South-Central Los Angeles, and get out civilized....The only men I know who have escaped, all began reading Robert Heinlein at age ten.”

“In the world of words the imagination is one of the forces of nature.”

“There were timelines branching and branching, a mega-universe of universes, millions more every minute. Billions? Trillions? The universe split every time someone made a decision. Split, so that every decision ever made could go both ways. Every choice made by every man, woman, and child was reversed in the universe next door.”