(Note: This essay was originally posted November 15, 2003.)

When I awoke this morning, there was an elm tree growing outside my window. It wasn't much, not old growth or a giant, but I liked it there. It provided a much-needed buffer from my neighbors, and it was a welcome place to rest my eyes when they became tired of asphalt black and cement grey. When the sun blazed brightly, its leafy branches would break up the light into a green and gold dapple, and when it rained, its leaves would drip with rainwater. In this urban place, I appreciated having its living green outside my window. I would look out at it often as I sat at my computer to write.

Now it's gone. In a single afternoon, in a roar of dust and heat and chainsaw smoke, my tree was reduced to a stack of cut logs and a scattering of fallen leaves. Outside my window now, there is nothing but the rundown black-shingled roof of the house next door. When I came home and discovered the devastation, there was a lone squirrel scampering in confusion across the ground, among the remains of the tree.

What is done cannot be undone. In a few hours, the patient growth of decades was destroyed. Life that survived the changing of the seasons, the drought of summers, the frost of winters and the storm winds of autumn did not survive the bite of oiled metal teeth. My tree cannot be restored, and if another were planted, it would be many years before it grew tall enough that it could be seen from my window.

As the night comes and the sky fades to blue and black, are the stacked branches of my tree making a last effort to photosynthesize? Are the leaves on the cut logs still drinking the fading light, still interweaving the sugar chains they manufacture with their last reserves of minerals drawn up hours ago from the now-disembodied roots? Is my tree even aware of its death, in some dim vegetable way, or will its individual parts continue to patiently perform the tasks they were grown for until decay claims them at last?

To living beings as short-lived and fragile as humans, a full-grown tree seems to be the epitome of strength and stability: its roots delving deep into the earth, its massive trunk towering high overhead, rising to a spreading green canopy of leaves or needles that endure sun, rain and wind. They hardly seem alive, so different is their kind of life from ours: slow, weathered, endlessly patient, watching the years pass around them like falling snow settling, more akin to the earth and the mountains than to flesh and blood creatures like ourselves.

But they are alive, and like all living things, they must inevitably die. It is one of science's most profound insights that all life on Earth is related by deep and fundamental bonds of kinship at the molecular level - from the humble blue-green cyanobacteria to the whales whose songs echo in the ocean deeps; from the smallest flower to the mightiest redwood; from the tiniest free-floating plankton to the human beings whose six-billion-strong civilization makes the planet glow at nighttime. We are all members of the same family, and we share a common bond: we are all mortal, and we must all, eventually, face death.

Life is fragile. All life is a struggle for existence, besieged by predators above and parasites below, and all living things are at the mercy of vast and uncaring natural forces that could wipe them out at any time. Entire forests burn in enormous wildfires; toxic algae blooms suffocate thousands of fish; drought, war and plague sweep human civilizations; and the introduction of a drop of chlorine or hydrogen peroxide is a holocaust on the microscopic level.

Life is fleeting. Insects such as mayflies are born, live out their lives and die in hours. We humans, who are long-lived for mammals, can expect, at best, a few decades of existence. Even the most ancient and wizened bristlecone pine tree is at most a few millennia old. Compared to the age of our planet - a tiny bit of rock and metal ash whirling around its home sun - the lifespan of the longest-lived creature dwindles into nothingness. Like dew that burns off in the morning, like bubbles in the foam on the surface of a river, we arise, die, and fade away.

Life is limited. Compared to the range of environments and temperatures that exist in the universe, from the near absolute zero cold of the interstellar void to the multimillion-degree nuclear furnaces at the hearts of stars, living things can exist only in an extremely rare and narrow set of conditions. Even our own planet, the most hospitable place in the universe we know of, allows us to survive only on its surface: we are a thin skim of life on the cool, blue-green-white exterior of our Earth, while its interior rages with tectonic fires, inaccessible. Even the extremophile archaebacteria that thrive in the crushing pressure, boiling hot temperatures and lightless environment of the "dark biosphere" of the ocean bottom can barely penetrate any distance at all into our planet's crust.

Life ends. We are all like travelers passing through a dark and unfamiliar wood at twilight, each of us carrying a lone torch to hold back the gathering night. Looking ahead, one can see - but only for a little way - the lights of those who have gone before us, like a river of distant twinkling stars, before those far-away lights fade and ultimately disappear into a veil of shadows that no eye can see through. What lies ahead, beyond that mysterious dusk? Might there be a welcoming village, where the golden lights of inn windows gleam through the dark, where a warm dinner, a blazing hearth and a soft bed await weary travelers? We cannot say. Though whispered rumors course through the ranks of we who walk toward the veil, no one has ever come back from beyond it to tell the story. Though many travelers announce their certainty of something they cannot possibly know, the shadow ahead remains vast and mysterious, and we must all inevitably proceed toward it.

There is not a human being alive who has not, in some way, been touched by the shadow of death. Some of us it touches only lightly, leaving wounds that heal and fade with time; some of us it cuts to the quick, a sharper blade than was ever forged of metal, leaving scars that last for a lifetime and the pain of a grief that never fully subsides. We know that it is not fair. Not fair that death does not respect power, wealth, or accomplishment; not fair that we cannot stay it through good works and compassion; not fair that it so often seems to take the best of us early, as if in mockery; not fair that it does not provide for those who survive us, not fair that it does not always come when we expect it, not fair that it does not wait to let us finish our life's work, and not fair that it does not take the evil and spare the good. Above all, it is not fair that anyone should have to bear such a burden as the burden of grief. When someone we love passes on, we mourn, and through our tears we cry for justice to a universe that seems vast and impersonal, deaf to our pleas. But still we wonder, and we hope. The human mind rebels at accepting the idea that tragedy can truly be senseless, that life can ever truly end. Could there not be something more? Could there not be another place, where all tears will be wiped away and everything set right at last?

Sadly, the universe is not obliged to be as we wish, and even our fondest fantasies may, in the end, turn out to be nothing but that. We cannot assume something is true just because we want it to be, no matter how badly we want it to be. While there may be something more beyond death, we cannot count on it, and so we should not depend on it.

So what is the solution? Can we trust in technology to save us, perhaps? Will science at last conquer death and free humankind from its fate - perhaps through cloning, or cryonic suspension?

While in the remote future it is a very real possibility that we will unlock the key to personal immortality, for the time being such rosy scenarios are more science fiction than science fact. We have not yet begun to understand the functioning of the brain on a cellular level, and until we develop the ability to transfer memories from one brain to another - if we ever do - cloning of one's mere genes will remain nothing more than a very expensive and risky way to have a child. (Even if we could transfer memories, it would be an open question whether this process would preserve the continuity of selfhood needed for true immortality.) Likewise, the technology to put humans in suspended animation and later revive them simply does not exist. The most advanced freezing technology in existence today still causes massive cellular damage, irreversible in all except the most fantastic scenarios of what future technology will be capable of. In essence, this is little more than a materialist version of Pascal's Wager.

But if science cannot deliver us from death, then what chance do we have? Is life nothing more than a countdown to nonexistence, with every precious second ticking away like sand falling inexorably through an hourglass, never to be regained? Is there nothing for us to do but sink into despair over the finitude of life, living out our days in fear and gloom as we wait for the end? Can there be hope in the face of our own mortality?

No one human being can answer that question on another's behalf, but as far as this atheist is concerned - the answer is yes. Yes, there is hope, and no, we need not despair. Why? Because, come whatever may, here and now we are alive, with the potential to achieve amazing things and the chance to make a difference - and is that not enough? What more can we ask for? Yes, life ends; however, that is not a reason to despair, but a reason to celebrate life and all it has to offer. It is the implicit assumption of many theists that life must be endless to be worth anything at all, but there is no reason to believe this. Surely, what matters most is not whether your life will end at some point in the future - for an eternity of empty, pointless existence would be no better than a finite span of such existence - but whether you made the most of the time you did have, whether you lived with happiness and purpose. If that is the case, it does not matter what comes afterward.

If we cannot slip the bonds of mortality, if we must live out our lives in the period of time allotted to each of us - then let us make it worthwhile. Let our lives have meant something: let us have done some good, have changed things for the better, have reached out and made contact with our fellow human beings. Let us have made this world a bit brighter by having passed through it. Let us not stake our lives on the hope that there is something more, but let us live them now, with purpose and meaning, full of happiness and appreciation for the mere chance to exist, so we may rest assured that even if there is no afterlife, this life at least will not have been wasted. Let us establish reason and treat others with humanity and fairness; for if there is no final justice in this world independent of us, if there is no reciprocity written into the laws of the cosmos, then it is up to us to do so.

Granted, we should not be too hasty to dismiss all possibility of an afterlife. We should not be in a rush to tell the grieving that their hopes are without foundation, for the simple fact of the matter is that no one knows what happens after death. Regardless of the arguments for or against personal immortality, the truth is that many people in great pain derive comfort from this belief, and that is something even atheists should respect. As part of living a worthy life of the kind described above, we should always remain humble, bearing in mind that our knowledge will never be perfect, and we should respect the beliefs of those who respect ours, so long as those beliefs do not direct their holders to cause harm. Perhaps there is a blissful afterlife and perhaps there is not, but it does no harm merely to hope. The harm comes when simple, humble hope transforms into arrogant, dogmatic faith, and believers begin to regard their promised afterlife reward as so certain and so important that they value it more highly than this life - which is, after all, the only one anyone can know with certainty that we have. The sword of our ignorance cuts both ways. It is a fine line that atheists must tread - between not exacerbating the grief of those who have felt the pain of loss (which is everyone), and taking a forthright stand against afterlife beliefs of the sort that brought the Twin Towers crashing down and that sets off explosives-laden vests in crowded marketplaces. The solution, as in most matters, lies in moderation and counseling humility. Afterlife beliefs might be right, but they might also be wrong, and no one rational should throw away a certainty for a mere possibility.

Life ends; we cannot escape that fact. But nevertheless, there is hope - a brilliant golden fire kindled on the horizon ahead, a daybreak in the dark woods. Rather than letting ourselves be paralyzed by fear of the inevitable, rather than staking all our hopes on another life whose existence we can never know about, there is a third way. Let us find happiness and purpose in this existence; let us rejoice that life, however fleeting, is ours for any time at all, and offers so many chances to do good despite all the darkness we find in it. We may not know where our journey will take us, but let us go forward unafraid, with heads held high. Life is a wonderful and strange paradox - as delicate as a spiderweb glittering in the rain, as ephemeral as morning mist that burns off in the sun, as infinitesimal as a lone candle in the dark of twilight, and yet more precious than all the diamonds and gold of the world and all the stars that light the night sky. Life is valuable because it is unique, and precious because it is so fragile. So therefore, let us appreciate life - others' as well as our own - and yes, let us mourn the departed as they deserve, but not to the extent that it brings our own lives to a halt. If there is a blissful afterlife, we have nothing to worry about, and if there is not, then death is essentially a peaceful, dreamless sleep, free of suffering, free of concern. In either case, what matters most is the living. Life is fleeting, but it is not pointless; in fact, atheism teaches us, just the opposite is the truth.