"Death in the individual is, of course, to some extent a confession of failure. It means inability, mostly due to ignorance, to adapt oneself to one's environment. Death of a race may be quite a different matter--an exhaustion of utility. However that may be, it is clear that the last of us to survive will represent the highest possible development of human potentiality. I speculate sometimes on the question of who the ultimate survivor will be. It may possibly be Professor YM6403 of the Outer Office. Some think so. I believe he thinks so himself. On the other hand, I may be the last survivor. However, there are still some thousands of us in existence, and for the present these disquisitions may appear to you idle." My clothes were damp and I was chilly, hungry, and tired. His jabber about professors and survivors had no interest for me. I ventured to point out to him that I was at present in urgent need of rest and refreshment. He rose on all fours again, and did so with extreme awkwardness. "True," he said. "I will attend to it. We are hospitable people, though it is seldom that a stranger visits us. I will proceed at once to conduct you to my house." "Your house? I fear that must be at some great distance, for there is no house in sight." For a moment he looked puzzled, and then light dawned again in his short-sighted eyes. "I see your mistake," he said. "You come from the old world, where the old type of house is still in existence. The history of the old world is the special study of my friend, the Professor. But of course there is general knowledge that every educated being may be supposed to possess, and I know the type of house you mean. I have seen pictures of it in the museum. Now in Thule, when many centuries ago aviation became the cheapest and most popular form of transit, it also became obviously impossible that we should have houses above ground. Aviation is a source of danger to such houses, and the houses themselves were dangerous to the aviator. Our buildings are all subterranean. We avoid danger of every kind. We dislike risk. You cannot see my house to which I am taking you, but as a matter of fact it is less than a quarter of a mile away." He went so slowly that I had to abate my usual pace, lest I should outstrip my guide. As he moved, he looked a little like a very small tired elephant. "Aviation," I said. "I suppose that with you that has been carried to a great point of perfection." "On the contrary," he said, "it is superseded. It is a back number. We no longer use it. But we have seen no reason to change our style of domicile, which possesses many advantages." "And what is it?" I asked, "that has superseded aviation?" "It is the power to dissipate and subsequently reconstruct identically at some different point the atoms of any organism or group of organisms." "I don't think I understand," I said. "It is natural that you should not. However, here we are at my house."