We are rare and precious because we are alive, because we can think. We are privileged to influence and perhaps control our future. We have an obligation to fight for life on Earth — not just for ourselves but for all those, humans and others, who came before us and to whom we are beholden, and for all those who, if we are wise enough, will come after. There is no cause more urgent than to survive to eliminate on a global basis the growing threats of nuclear war, environmental catastrophe, economic collapse and mass starvation. These problems were created by humans and can only be solved by humans. No social convention, no political system, no economic hypothesis, no religious dogma is more important.

The hard truth seems to be this: We live in a vast and awesome universe in which, daily, suns are made and worlds destroyed, where humanity clings to an obscure clod of rock. The significance of our lives and our fragile realm derives from our own wisdom and courage. We are the custodians of life’s meaning. We would prefer it to be otherwise, of course, but there is no compelling evidence for a cosmic Parent who will care for us and save us from ourselves. It is up to us.

—Carl Sagan