"You mention an ideal, sir," O'Hara said. "What is it?" "It was that this was one world, or should have been one world, not irrevocably halved by the Atomic Curtain. It was that if Providence had wished them separate worlds, It would have made them so." "Then it was a mistaken ideal," O'Hara said, "for if Providence had intended this to be one world, it would be now." His father smiled. "That's enough, my young philosopher. To bed with you!" And so we went to bed, but not to sleep, for O'Hara was excited by the conversation. He lay flat upon the counterpane, his cheekbones pressed against the butts of his palms and his dark eyes restless, seeming lighted by the intense curiosity of his young mind, talking on and on for hours, long after I was drowsy. "It's always been like that," he told me. "Down through the countless centuries of time--when a people have made a bad decision and have lost everything by it, they have described their motive as obedience to an ideal. Remember your American history?" "How could I remember it?" I asked. "Nobody teaches that." "They used to teach it. And they still have the books at Oxford. Great reading, too--the Revolution, the Civil War, the three World Wars. You'd be astonished how often that theme recurs in them--obedience to an ideal. Yes, I suppose it's true, those of us who left the Western Hemisphere before the Atomic Curtain blamed it on an ideal. And I'd bet it's equally true that those who stayed, knowing that they would forever be isolated from the world that you and I know, invoked the same apology--an ideal guided them. Eternal peace, freedom from want and from fear--" A clock was striking somewhere in the house. It was one o'clock. I shivered without knowing why. "And did they find it, I wonder?" O'Hara's voice resumed. "What has happened to the Americans in these two hundred and seventy years since they launched the Atomic Curtain? And what would have happened to the rest of us--to Europe and Asia and Africa--if they had not launched it? For they were a wonderful people, wonderful improvisers, wonderfully inventive. Oh, I don't mean the little things that we have here, electric lights, the radio--but the big things, the sublime things that changed history--or seemed about to change it. The atomic bomb of Los Alamos, the hydrogen bomb of Bikini and the tests at Yucca Flats, those alone were leading the world into new, strange paths, glorious paths for the scientific mind, and all the world was following them swiftly. All of us were to have the blessings along with the horrors of atomic fission, until--" "I know that much," I said. "Until the Third World War." O'Hara smiled queerly. "So you do read some?" "I read a great deal," I retorted. "Contemporary things, the important things, not long-forgotten books of useless American history." "But you remember, don't you, why the Third World War stopped?" "Oh, yes. It was thorium."