"I am a very optimistic person by nature. I tend to look on the brighter side of life, and am not too depressed by gloomy thoughts of the world’s destruction. But if I did not know what I do know, I would have little hope that humanity would survive, little hope that in time humanity would awaken to the real problems that beset it, and begin to change. I am very doubtful that on our own we would do that."