There is a further advantage [to hydrogen bombs]: the supply of uranium in the planet is very limited, and it might be feared that it would be used up before the human race was exterminated, but now that the practically unlimited supply of hydrogen can be utilized, there is considerable reason to hope that homo sapiens may put an end to himself, to the great advantage of such less ferocious animals as may survive. But it is time to return to less cheerful topics.

Human Knowledge: Its Scope and Limits (1948), part I, "The World of Science", chapter 3, "The World of Physics", p. 41