The Demon-Haunted World: Science as a Candle in the Dark

by Carl Sagan

Sparse and poor popularizations of science abandon ecological niches that pseudoscience promptly fills. If it were widely understood that claims to knowledge require adequate evidence before they can be accepted, there would be no room for pseudoscience. But a kind of Gresham’s Law prevails in popular culture by which bad science drives out good.

In a typical passage Hippocrates wrote: “Men think epilepsy divine, merely because they do not understand it. But if they called everything divine which they do not understand, why, there would be no end of divine things.”

It is morally as bad not to care whether a thing is true or not, so long as it makes you feel good, as it is not to care how you got your money as long as you have got it.

For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring. Which attitude is better geared for our long-term survival? Which gives us more leverage on our future? And if our naïve self-confidence is a little undermined in the process, is that altogether such a loss? Is there not cause to welcome it as a maturing and character-building experience?

Pseudoscience is easier to contrive than science, because distracting confrontations with reality—where we cannot control the outcome of the comparison—are more readily avoided. The standards of argument, what passes for evidence, are much more relaxed. In part for these same reasons, it is much easier to present pseudoscience to the general public than science. But this isn’t enough to explain its popularity. Naturally people try various belief systems on for size, to see if they help. And if we’re desperate enough, we become all too willing to abandon what may be perceived as the heavy burden of skepticism. Pseudoscience speaks to powerful emotional needs that science often leaves unfulfilled. It caters to fantasies about personal powers we lack and long for (like those attributed to comic book superheroes today, and earlier, to the gods). In some of its manifestations, it offers satisfaction of spiritual hungers, cures for disease, promises that death is not the end. It reassures us of our cosmic centrality and importance. It vouchsafes that we are hooked up with, tied to, the Universe.* Sometimes it’s a kind of halfway house between old religion and new science, mistrusted by both.

In its oddly charismatic leader, its promise of community, and the offer of magical powers in exchange for money and fervent belief, it is typical of many pseudosciences marketed for sacerdotal export.

Some portion of the decision-making that influences the future of our civilization is plainly in the hands of charlatans.

Transcendental Meditation and Aum Shinrikyo seem to have attracted a large number of accomplished people, some with advanced degrees in physics or engineering. These are not doctrines for nitwits. Something else is going on.

But in parallel to the many scientists who seem reluctant to debate or even publicly discuss pseudoscience, many proponents of mainstream religions are reluctant to take on extreme conservatives and fundamentalists. If the trend continues, eventually the field is theirs; they can win the debate by default.

Pseudoscience differs from erroneous science. Science thrives on errors, cutting them away one by one. False conclusions are drawn all the time, but they are drawn tentatively. Hypotheses are framed so they are capable of being disproved. A succession of alternative hypotheses is confronted by experiment and observation. Science gropes and staggers toward improved understanding. Proprietary feelings are of course offended when a scientific hypothesis is disproved, but such disproofs are recognized as central to the scientific enterprise. Pseudoscience is just the opposite. Hypotheses are often framed precisely so they are invulnerable to any experiment that offers a prospect of disproof, so even in principle they cannot be invalidated. Practitioners are defensive and wary. Skeptical scrutiny is opposed. When the pseudoscientific hypothesis fails to catch fire with scientists, conspiracies to suppress it are deduced.

Perhaps the sharpest distinction between science and pseudoscience is that science has a far keener appreciation of human imperfections and fallibility than does pseudoscience (or “inerrant” revelation). If we resolutely refuse to acknowledge where we are liable to fall into error, then we can confidently expect that error—even serious error, profound mistakes—will be our companion forever.

If we teach only the findings and products of science—no matter how useful and even inspiring they may be—without communicating its critical method, how can the average person possibly distinguish science from pseudoscience? Both then are presented as unsupported assertion.

The method of science, as stodgy and grumpy as it may seem, is far more important than the findings of science.

Although it’s hard for me to see a more profound cosmic connection than the astonishing findings of modern nuclear astrophysics: Except for hydrogen, all the atoms that make each of us up—the iron in our blood, the calcium in our bones, the carbon in our brains—were manufactured in red giant stars thousands of light-years away in space and billions of years ago in time. We are, as I like to say, starstuff.

Two men came to a hole in the sky. One asked the other to lift him up … But so beautiful was it in heaven that the man who looked in over the edge forgot everything, forgot his companion whom he had promised to help up and simply ran off into all the splendor of heaven. from an Iglulik Inuit prose poem, early twentieth century, told by INUGPASUGJUK to KNUD RASMUSSEN, the Greenlandic arctic explorer

But there’s another reason: Science is more than a body of knowledge; it is a way of thinking.

We’ve arranged a global civilization in which most crucial elements—transportation, communications, and all other industries; agriculture, medicine, education, entertainment, protecting the environment; and even the key democratic institution of voting—profoundly depend on science and technology. We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.

I worry that, especially as the Millennium edges nearer, pseudoscience and superstition will seem year by year more tempting, the siren song of unreason more sonorous and attractive. Where have we heard it before? Whenever our ethnic or national prejudices are aroused, in times of scarcity, during challenges to national self-esteem or nerve, when we agonize about our diminished cosmic place and purpose, or when fanaticism is bubbling up around us—then, habits of thought familiar from ages past reach for the controls.

Science is far from a perfect instrument of knowledge. It’s just the best we have. In this respect, as in many others, it’s like democracy. Science by itself cannot advocate courses of human action, but it can certainly illuminate the possible consequences of alternative courses of action. The scientific way of thinking is at once imaginative and disciplined. This is central to its success. Science invites us to let the facts in, even when they don’t conform to our preconceptions. It counsels us to carry alternative hypotheses in our heads and see which best fit the facts. It urges on us a delicate balance between no-holds-barred openness to new ideas, however heretical, and the most rigorous skeptical scrutiny of everything—new ideas and established wisdom. This kind of thinking is also an essential tool for a democracy in an age of change.

One of the reasons for its success is that science has built-in, error-correcting machinery at its very heart. Some may consider this an overbroad characterization, but to me every time we exercise self-criticism, every time we test our ideas against the outside world, we are doing science. When we are self-indulgent and uncritical, when we confuse hopes and facts, we slide into pseudoscience and superstition.

Moreover, scientists are usually careful to characterize the veridical status of their attempts to understand the world—ranging from conjectures and hypotheses, which are highly tentative, all the way up to laws of Nature which are repeatedly and systematically confirmed through many interrogations of how the world works. But even laws of Nature are not absolutely certain. There may be new circumstances never before examined—inside black holes, say, or within the electron, or close to the speed of light—where even our vaunted laws of Nature break down and, however valid they may be in ordinary circumstances, need correction.

But the history of science—by far the most successful claim to knowledge accessible to humans—teaches that the most we can hope for is successive improvement in our understanding, learning from our mistakes, an asymptotic approach to the Universe, but with the proviso that absolute certainty will always elude us.

One of the great commandments of science is, “Mistrust arguments from authority.”

“Spirit” comes from the Latin word “to breathe.” What we breathe is air, which is certainly matter, however thin. Despite

usage to the contrary, there is no necessary implication in the word “spiritual” that we are talking of anything other than matter (including the matter of which the brain is made), or anything outside the realm of science.

Is this worshiping at the altar of science? Is this replacing one faith by another, equally arbitrary? In my view, not at all. The directly observed success of science is the reason I advocate its use. If something else worked better, I would advocate the something else.

Again, the reason science works so well is partly that built-in error-correcting machinery. There are no forbidden questions in science, no matters too sensitive or delicate to be probed, no sacred truths. That openness to new ideas, combined with the most rigorous, skeptical scrutiny of all ideas, sifts the wheat from the chaff. It makes no difference how smart, august, or beloved you are. You must prove your case in the face of determined, expert criticism. Diversity and debate are valued. Opinions are encouraged to contend—substantively and in depth.

These efforts will continue as long as there are scientists. General Relativity is certainly an inadequate description of Nature at the quantum level, but even if that were not the case, even if General Relativity were everywhere and forever valid, what better way of convincing ourselves of its validity than a concerted effort to discover its failings and limitations? This is one of the reasons that the organized religions do not inspire me with confidence. Which leaders of the major faiths acknowledge that their beliefs might be incomplete or erroneous and establish institutes to uncover possible doctrinal deficiencies?

Wherever possible, scientists experiment. Which experiments suggest themselves often depends on which theories currently prevail. Scientists are intent on testing those theories to the breaking point. They do not trust what is intuitively obvious. That the Earth is flat was once obvious. That heavy bodies fall faster than light ones was once obvious. That bloodsucking leeches cure most diseases was once obvious. That some people are naturally and by divine decree slaves was once obvious. That there is such a place as the center of the Universe, and that the Earth sits in that exalted spot was once obvious. That there is an absolute standard of rest was once obvious. The truth may be puzzling or counterintuitive. It may contradict deeply held beliefs. Experiment is how we get a handle on it.

For me, there are four main reasons for a concerted effort to convey science—in radio, TV, movies, newspapers, books, computer programs, theme parks, and classrooms—to every citizen. In all uses of science, it is insufficient—indeed it is dangerous—to produce only a small, highly competent, well-rewarded priesthood of professionals.

The corollary, one that the United States sometimes fails to grasp, is that abandoning science is the road back into poverty and backwardness.

Science provides an essential early warning system.

In the long run, the greatest gift of science may be in teaching us, in ways no other human endeavor has been able, something about our cosmic context, about where, when, and who we are.

Science is a way to call the bluff of those who only pretend to knowledge.

Finding the occasional straw of truth awash in a great ocean of confusion and bamboozle requires vigilance, dedication, and courage. But if we don’t practice these tough habits of thought, we cannot hope to solve the truly serious problems that face us—and we risk becoming a nation of suckers, a world of suckers, up for grabs by the next charlatan who saunters along.

As an inadvertent side effect, the pattern-recognition machinery in our brains is so efficient in extracting a face from a clutter of other detail that we sometimes see faces where there are none. We assemble disconnected patches of light and dark and unconsciously try to see a face. The Man in the Moon is one result. Michelangelo Antonioni’s film Blowup describes another. There are many other examples.

This kind of hypothesis is falsifiable, a property that brings it well into the scientific arena.

But we humans have a talent for deceiving ourselves. Skepticism must be a component of the explorer’s toolkit, or we will lose our way. There are wonders enough out there without our inventing any.

I’ve remained fascinated long after my early enthusiasm for UFOs waned—as I understood more about that remorseless

taskmaster called the scientific method: Everything hinges on the matter of evidence. On so important a question, the evidence must be airtight. The more we want it to be true, the more careful we have to be. No witness’s say-so is good enough. People make mistakes. People play practical jokes. People stretch the truth for money or attention or fame. People occasionally misunderstand what they’re seeing. People sometimes even see things that aren’t there.

The tenets of skepticism do not require an advanced degree to master, as most successful used car buyers demonstrate. The whole idea of a democratic application of skepticism is that everyone should have the essential tools to effectively and constructively evaluate claims to knowledge. All science asks is to employ the same levels of skepticism we use in buying a used car

or in judging the quality of analgesics or beer from their television commercials. But the tools of skepticism are generally unavailable to the citizens of our society. They’re hardly ever mentioned in the schools, even in the presentation of science, its most ardent practitioner, although skepticism repeatedly sprouts spontaneously out of the disappointments of everyday life. Our politics, economics, advertising, and religions (New Age and Old) are awash in credulity. Those who have something to sell, those who wish to influence public opinion, those in power, a skeptic might suggest, have a vested interest in discouraging skepticism.

Gullibility about UFOs thrives on widespread mistrust of government, arising naturally enough from all those circumstances where—in the tension between public well-being and “national security”—the government lies.

Part of the reason that children are afraid of the dark may be that, in our entire evolutionary history up until just a moment ago, they never slept alone. Instead, they nestled safely, protected by an adult—usually Mom. In the enlightened West we stick them alone in a dark room, say goodnight, and have difficulty understanding why they’re sometimes upset. It makes good evolutionary sense for children to have fantasies of scary monsters. In a world stalked by lions and hyenas, such fantasies help prevent defenseless toddlers from wandering too far from their guardians. How can this safety machinery be effective for a vigorous, curious young animal unless it delivers industrial-strength terror? Those who are not afraid of monsters tend not to leave descendants.

So in an age when traditional religions have been under withering fire from science, is it not natural to wrap up the old gods and demons in scientific raiment and call them aliens?

In the early 1960s, I argued that the UFO stories were crafted chiefly to satisfy religious longings. At a time when science has complicated uncritical adherence to the old-time religions, an alternative is proffered to the God hypothesis: Dressed in scientific jargon, their immense powers “explained” by superficially scientific terminology, the gods and demons of old come down from heaven to haunt us, to offer prophetic visions, and to tantalize us with visions of a more hopeful future: a space-age mystery religion aborning.

Is it possible that people in all times and places occasionally experience vivid, realistic hallucinations, often with sexual content, about abduction by strange, telepathic, aerial creatures who ooze through walls—with the details filled in by the prevailing cultural idioms, sucked out of the Zeitgeist? Others, who have not personally had the experience, find it stirring and in a way familiar. They pass the story on. Soon it takes on a life of its own, inspires others trying to understand their own visions and hallucinations, and enters the realm of folklore, myth, and legend. The connection between the content of spontaneous temporal lobe hallucinations and the alien abduction paradigm is consistent with such a hypothesis. Perhaps when everyone knows that gods come down to Earth, we hallucinate gods; when all of us are familiar with demons, it’s incubi and succubi; when fairies are widely accepted, we see fairies; in an age of spiritualism, we encounter spirits; and when the old myths fade and we begin thinking that extraterrestrial beings are plausible, then that’s where our hypnogogic imagery tends.

Despite this apparent variety of extraterrestrials, the UFO abduction syndrome portrays, it seems to me, a banal Universe. The form of the supposed aliens is marked by a failure of the imagination and a preoccupation with human concerns. Not a single being presented in all these accounts is as astonishing as a cockatoo would be if you had never before beheld a bird. Any protozoology or bacteriology or mycology textbook is filled with wonders that far outshine the most exotic descriptions of the alien abductionists. The believers take the common elements in their stories as tokens of verisimilitude, rather than as evidence that they have contrived their stories out of a shared culture and biology.

Perhaps what we actually remember is a set of memory fragments stitched onto a fabric of our own devising. If we sew cleverly enough, we have made ourselves a memorable story easy to recall. Fragments by themselves, unencumbered by association, are harder to retrieve. The situation is rather like the method of science itself—where many isolated data points can be remembered, summarized, and explained in the framework of a theory. We then much more easily recall the theory and not the data.

Most of these tragic and incontestable cases of childhood sexual abuse, however, have been continuously remembered into adulthood. There is no hidden memory to be retrieved.