“Another principle that I believe can be justified by scientific evidence so far is that nobody is going to emigrate from this planet not ever....It will be far cheaper, and entail no risk to human life, to explore space with robots. The technology is already well along....the real thrill will be in learning in detail what is out there...It is an especially dangerous delusion if we see emigration into space as a solution to be taken when we have used up this planet....Earth, by the twenty-second century, can be turned, if we so wish, into a permanent paradise for human beings...”

“We can learn from history, but we can also deceive ourselves when we selectively take evidence from the past to justify what we have already made up our minds to do.”

“A new consciousness is developing which sees the earth as a single organism and recognizes that an organism at war with itself is doomed. We are one planet. One of the great revelations of the age of space exploration is the image of the earth finite and lonely, somehow vulnerable, bearing the entire human species through the oceans of space and time.”

“We can either have a twenty-first-century conversation about morality and the human well-being - a conversation in which we avail ourselves of all scientific insights and philosophical arguments that have accumulated in the last two thousand years of human discourse - or we can confine ourselves to a first-century conversation as it is preserved in the Bible.”

“The question today, then, is whether the world's populations are not close to having done with soft sciences and technologies, which still take into account the preservation of the planet and its inhabitants; whether they are not now in danger of being swept away by the terrorist excesses of a Laputian ratio, a universal philanoia attacking a human species which has become 'undesirable' in its entirety, the scandal of an Earth which is, so far as we know, the only biosphere in the solar system.”

“It may be argued that the past is a country from which we have all emigrated, that its loss is part of our common humanity.”