The spear, the bow, the gun, and finally the guided missile had given him weapons of infinite range and all but infinite power. Without those weapons, often though he had used them against himself, Man would never have conquered his world. Into them he had put his heart and soul, and for ages they had served him well. But now, as long as they existed, he was living on borrowed time.
This passage appears at the end of Part One of 2001, as the narrator concludes his story of the evolution of man to his present state. Foremost, it is the first mention of one of the major themes of the book—the destructive potential of nuclear weapons. Inasmuch as the central story line does not explicitly mention nuclear weapons, this mention is one of the critical passages that alert us to the author's concern with weapons of mass destruction. This passage is also interesting in illustrating the unclear phenomenon in an evolutionary context. Nuclear weapons are conceived, not as an independent invention, or in relation to the study of physics that produced them, but rather as an advanced weapon that comes as part of a long chain of human tools and weapons developed over millennia. By placing nuclear weapons in this context, the author acknowledges that such weapons were not made in order to be destructive and, further, that man generally had good reasons for making weapons. The potential negative side effect of nuclear weapons, however, was too great to be ignored.