[Editorial note: This is taken from the book The Demon-Haunted World: Science as a Candle in the Dark.]

by Carl Sagan

My parents died years ago. I was very close to them. I still miss them terribly. I know I always will. I long to believe that their essence, their personalities, what I loved so much about them, are — really and truly — still in existence somewhere. I wouldn't ask very much, just five or ten minutes a year, say, to tell them about their grandchildren, to catch them up on the latest news, to remind them that I love them. There's a part of me — no matter how childish it sounds — that wonders how they are. "Is everything all right?" I want to ask. The last words I found myself saying to my father, at the moment of his death, were "Take care."

Sometimes I dream that I'm talking to my parents, and suddenly — still immersed in the dreamwork — I'm seized by the overpowering realization that they didn't really die, that it's all been some kind of horrible mistake. Why, here they are, alive and well, my father making wry jokes, my mother earnestly advising me to wear a muffler because the weather is chilly. When I wake up I go through an abbreviated process of mourning all over again. Plainly, there's something within me that's ready to believe in life after death. And it's not the least bit interested in whether there's any sober evidence for it.

So I don't guffaw at the woman who visits her husband's grave and chats him up every now and then, maybe on the anniversary of his death. It's not hard to understand. And if I have difficulties with the ontological status of who she's talking to, that's all right. That's not what this is about. This is about humans being human. More than a third of American adults believe that on some level they've made contact with the dead. The number seems to have jumped by 15 percent between 1977 and 1988. A quarter of Americans believe in reincarnation.

But that doesn't mean I'd be willing to accept the pretensions of a "medium," who claims to channel the spirits of the dear departed, when I'm aware the practice is rife with fraud. I know how much I want to believe that my parents have just abandoned the husks of their bodies, like insects or snakes molting, and gone somewhere else. I understand that those very feelings might make me easy prey even for an unclever con, or for normal people unfamiliar with their unconscious minds, or for those suffering from a dissociative psychiatric disorder. Reluctantly, I rouse some reserves of skepticism.

How is it, I ask myself, that channelers never give us verifiable information otherwise unavailable? Why does Alexander the Great never tell us about the exact location of his tomb, Fermat about his Last Theorem, John Wilkes Booth about the Lincoln assassination conspiracy, Hermann Goring about the Reichstag fire? Why don't Sophocles, Democritus, and Aristarchus dictate their lost books? Don't they wish future generations to have access to their masterpieces?

If some good evidence for life after death were announced, I'd be eager to examine it; but it would have to be real scientific data, not mere anecdote. As with the face on Mars and alien abductions, better the hard truth, I say, than the comforting fantasy. And in the final tolling it often turns out that the facts are more comforting than the fantasy.

The fundamental premise of "channeling," spiritualism, and other forms of necromancy is that when we die we don't. Not exactly. Some thinking, feeling, and remembering part of us continues. That whatever-it-is — a soul or spirit, neither matter nor energy, but something else — can, we are told, re-enter the bodies of human and other beings in the future, and so death loses much of its sting. What's more, we have an opportunity, if the spiritualist or channeling contentions are true, to make contact with loved ones who have died.

J.Z. Knight of the State of Washington claims to be in touch with a 35,000-year-old somebody called "Ramtha." He speaks English very well, using Knight's tongue, lips and vocal chords, producing what sounds to me to be an accent from the Indian Raj. Since most people know how to talk, and many — from children to professional actors — have a repertoire of voices at their command, the simplest hypothesis is that Ms. Knight makes "Ramtha" speak all by herself, and that she has no contact with disembodied entities from the Pleistocene Ice Age. If there's evidence to the contrary, I'd love to hear it. It would be considerably more impressive if Ramtha could speak by himself, without the assistance of Ms. Knight's mouth. Failing that, how might we test the claim? (The actress Shirley MacLaine attests that Ramtha was her brother in Atlantis, but that's another story.)

Suppose Ramtha were available for questioning. Could we verify whether he is who he says he is? How does he know that he lived 35,000 years ago, even approximately? What calendar does he employ? Who is keeping track of the intervening millennia? Thirty-five thousand plus or minus what? What were things like 35,000 years ago? Either Ramtha really is 35,000 years old, in which case we discover something about that period, or he's a phony and he'll (or rather she'll) slip up.

Where did Ramtha live? (I know he speaks English with an Indian accent, but where 35,000 years ago did they do that?) What was the climate? What did Ramtha eat? (Archaeologists know something about what people ate back then.) What were the indigenous languages, and social structure? Who else did Ramtha live with — wife, wives, children, grandchildren? What was the life cycle, the infant mortality rate, the life expectancy? Did they have birth control? What clothes did they wear? How were the clothes manufactured? What were the most dangerous predators? Hunting and fishing implements and strategies? Weapons? Endemic sexism? Xenophobia and ethnocentrism? And if Ramtha came from the "high civilization" of Atlantis, where are the linguistic, technological, historical and other details? What was their writing like? Tell us. Instead, all we are offered are banal homilies.

Here, to take another example, is a set of information channeled not from an ancient dead person, but from unknown non-human entities who make crop circles, as recorded by the journalist Jim Schnabel:

We are so anxious at this sinful nation spreading lies about us. We do not come in machines, we do not land on your earth in machines ... We come like the wind. We are Life Force. Life Force from the ground ... Come here ... We are but a breath away ... a breath away ... we are not a million miles away ... a Life Force that is larger than the energies in your body. But we meet at a higher level of life ... We need no name. We are parallel to your world, alongside your world ... The walls are broken. Two men will rise from the past ... the great bear ... the world will be at peace.

People pay attention to these puerile marvels mainly because they promise something like old-time religion, but especially life after death, even life eternal.

A very different prospect for something like eternal life was once proposed by the versatile British scientist J.B.S. Haldane, who was, among many other things, one of the founders of population genetics. Haldane imagined a far future when the stars have darkened and space is mainly filled with a cold, thin gas. Nevertheless, if we wait long enough statistical fluctuations in the density of this gas will occur. Over immense periods of time the fluctuations will be sufficient to reconstitute a Universe something like our own. If the Universe is infinitely old, there will be an infinite number of such reconstitutions, Haldane pointed out.

So in an infinitely old universe with an infinite number of appearances of galaxies, stars, planets, and life, an identical Earth must reappear on which you and all your loved ones will be reunited. I'll be able to see my parents again and introduce them to the grandchildren they never knew. And all this will happen not once, but an infinite number of times.

Somehow, though, this does not quite offer the consolations of religion. If none of us is to have any recollection of what happened this time around, the time the reader and I are sharing, the satisfactions of bodily resurrection, in my ears at least, ring hollow.

But in this reflection I have underestimated what infinity means. In Haldane's picture, there will be universes, indeed an infinite number of them, in which our brains will have full recollection of many previous rounds. Satisfaction is at hand — tempered, though, by the thought of all those other universes which will also come into existence (again, not once but an infinite number of times) with tragedies and horrors vastly outstripping anything I've experienced this turn.

The Consolation of Haldane depends, though, on what kind of universe we live in, and maybe on such arcana as whether there's enough matter to eventually reverse the expansion of the universe, and the character of vacuum fluctuations. Those with a deep longing for life after death might, it seems, devote themselves to cosmology, quantum gravity, elementary particle physics, and transfinite arithmetic.