The fate of the Earth

[T]he mere risk of extinction has a significance that is categorically different from, and immeasurably greater than, that of any other risk, and as we make our decisions we have to take that significance into account. Up to now, every risk has been contained within the frame of life; extinction would shatter that frame. It represents not the defeat of some purpose but an abyss in which all human purposes would be drowned for all time. We have no right to place the possibility of this limitless, eternal defeat on the same footing as risks that we run in the ordinary conduct of our affairs in our particular transient moment of human history. To employ a mathematical analogy, we can say that although the risk of extinction may be fractional, the stake is, humanly speaking, infinite, and a fraction of infinity is still infinity. In other words, once we learn that a holocaust might lead to extinction we have no right to gamble, because if we lose, the game will be over, and neither we nor anyone else will ever get another chance. Therefore, although, scientifically speaking, there is all the difference in the world between the mere possibility that a holocaust will bring about extinction and the certainty of it, morally they are the same, and we have no choice but to address the issue of nuclear weapons as though we knew for a certainty that their use would put an end to our species.

Regarded objectively, as an espisode in the development of life on earth, a nuclear holocaust that brought about the extinction of manking and other species by mutilating the ecosphere would constitute an evolutionary setback of possibly limited extent—the first to result from a deliberate action taken by the creature extinguished but perhaps no greater than any of several evolutionary setbacks, such as the extinction of the dinosaurs, of which the geological record offers evidence. […] However, regarded subjectively, from within human life, where we are all actually situated, and as something that would happen to us, human extinction assumes awesome, inapprehensible proportions. It is of the essence of the human condition that we are bornm live for a while, and then die. Through mishaps of all kindsm we may also suffer untimely death, and in extinction by nuclear arms the number of untimely deaths would reach the limit for any one catastrophe: everyone in the world would die. But although the untimely death of everyone in the world would in itself constitute an unimaginably huge loss, it would bring with it a separate, distinct loss that would be in a sense even huger—the cancellation of all future generations of human beings. According to the Bible, when Adam and Eve ate the fruit of the tree of knowledge God punished them by withdrawing from them the privilege of immortality and dooming them and their kind to die. Now our species has eaten more deeply of the fruit of the tree of knowledge, and has brought itself face to face with a second death—the death of mankind. In doing so, we have caused a basic change in the circumstances in which life was given to us, which is to say that we have altered the human condition. The distinctiveness of this second death from the deaths of all the people on earth can be illustrated by picturing two different global catastrophes. In the first, le ut suppose that most of th people on earth were killed in a nuclear holocaust but that a few million survived and the earth happened to remain habitable by human beings. In this catastrophe, billions of people would perish, but the species would survive, and perhaps one day would even repopulate the earth in its former numbers. But now let us suppose that a substance was released into the environment which had the effect of sterilizing all the people in the world but otherwise leaving them unharmed. Then, as the existing population died off, the world would empty of eople, until no one was left. Not one life would have been shortened by a single day, but the species would die. In extinction by nuclear arms, the death of the species and the death of all the people in the wold would happen together, but it is important to make a clear distinction between the two losses; otherwise, the mind, overwhelmed by the thought of the deaths of the billions of living people, might stagger back without realizing that behind this already ungraspable loss there lies the separate loss of the future generations.