Carl Sagan was not only one of the greatest scientific minds in modern history, he was also an unrelenting humanist with profound insight on spirituality, psychology, and even literature. From The Meaning of Life: Reflections in Words and Pictures on Why We Are Here (public library) — the same wonderful 1991 anthology that gave us timeless meditations on existence from such luminaries as John Cage, Annie Dillard, Stephen Jay Gould, Arthur C. Clarke, and Charles Bukowski — comes a remarkable contribution from Sagan, an anchoring reminder that rings with exquisite timeliness:

In the past few decades, the United States and the Soviet Union have accomplished something that — unless we destroy ourselves first — will be remembered a thousand years from now: the first close-up exploration of dozens of other worlds. Together we have found much out there that is magnificent, instructive and of practical value. But we have found no trace, no hint of life. The Earth is an anomaly. In all the solar system, it is, so far as we know, the only inhabited planet.

We humans are one among millions of separate species who live in a world burgeoning, overflowing with life. And yet, most species that ever were are no more. After flourishing for one hundred fifty million years, the dinosaurs became extinct. Every last one. No species is guaranteed its tenure on this planet. And humans, the first beings to devise the means for their own destruction, have been here for only several million years.

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.