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

by Carl Sagan

The existence of any false accusation of childhood sexual abuse—especially those created under the ministrations of an authority figure—has, it seems to me, relevance to the alien abduction issue. If some people can with great passion and conviction be led to falsely remember being abused by their own parents, might not others, with comparable passion and conviction, be led to falsely remember being abused by aliens?

Now, what’s the difference between an invisible, incorporeal, floating dragon who spits heatless fire and no dragon at all? If there’s no way to disprove my contention, no conceivable experiment that would count against it, what does it mean to say that my dragon exists? Your inability to invalidate my hypothesis is

not at all the same thing as proving it true. Claims that cannot be tested, assertions immune to disproof are veridically worthless, whatever value they may have in inspiring us or in exciting our sense of wonder. What I’m asking you to do comes down to believing, in the absence of evidence, on my say-so.

Magic requires tacit cooperation of the audience with the magician—an abandonment of skepticism, or what is sometimes described as the willing suspension of disbelief. It immediately follows that to penetrate the magic, to expose the trick, we must cease collaborating.

You must systematically check out all the alternatives, and see which ones can be eliminated. You don’t declare that aliens have been found when your only evidence is an enigmatic nonrepeating signal.

No anecdotal claim—no matter how sincere, no matter how deeply felt, no matter how exemplary the lives of the attesting citizens—carries much weight on so important a question.

And if the alien abduction accounts are mainly about brain physiology, hallucinations, distorted memories of childhood, and hoaxing, don’t we have before us a matter of supreme importance—touching on our limitations, the ease with which we can be misled and manipulated, the fashioning of our beliefs, and perhaps even the origins of our religions?

Tools for skeptical thinking. What skeptical thinking boils down to is the means to construct, and to understand, a reasoned argument and—especially important—to recognize a fallacious or fraudulent argument. The question is not whether we like the conclusion that emerges out of a train of reasoning, but whether the conclusion follows

from the premise or starting point and whether that premise is true. Among the tools: • Wherever possible there must be independent confirmation of the “facts.” • Encourage substantive debate on the evidence by knowledgeable proponents of all points of view. • Arguments from authority carry little weight—“authorities” have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts. • Spin more than one hypothesis. If there’s something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among “multiple working hypotheses,” has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.* • Try not to get overly attached to a hypothesis just because it’s yours. It’s only a way station in the pursuit of knowledge. Ask yourself why you like the idea. Compare it fairly with the alternatives. See if you can find reasons for rejecting it. If you don’t, others will. • Quantify. If whatever it is you’re explaining has some measure, some numerical quantity attached to it, you’ll be much better able to discriminate among competing hypotheses. What is vague and qualitative is open to many explanations. Of course there are truths...

Argumentation cannot suffice for the discovery of new work, since the subtlety of Nature is greater many times than the subtlety of argument. Control experiments are essential. If, for example, a new medicine is alleged to cure a disease 20 percent of the time, we must make sure that a control population, taking a dummy sugar pill which as far as the subjects know might be the new drug, does not also experience spontaneous remission of the disease 20 percent of the time. Variables must be separated. Suppose you’re seasick, and given both an acupressure bracelet and 50 milligrams of meclizine. You find the unpleasantness vanishes. What did it—the bracelet or the pill? You can tell only if you take the one without the other, next time you’re seasick. Now imagine that you’re not so dedicated to science as to be willing to be seasick. Then you won’t separate the variables. You’ll take both remedies again. You’ve achieved the desired practical result; further knowledge, you might say, is not worth the discomfort of attaining it. Often the experiment must be done “double-blind,” so that those hoping for a certain finding are not in the potentially compromising position of evaluating t...

each independently ascertained. Then you can determine what correlation exists. Or in conducting a police lineup or photo identification, the officer in charge should not know who the prime suspect is, so as n...

In addition to teaching us what to do when evaluating a claim to knowledge, any good baloney detection kit must also teach us what not to do. It helps us recognize the most common and perilous fallacies of logic and rhetoric. Many good examples can be found in religion and politics, because their practitioners are so often obliged to justify two contradictory propositions. Among these fallacies are: • ad hominem—Latin for “to the man,” attacking the arguer and not the argument (e.g., The Reverend Dr. Smith is a known Biblical fundamentalist, so her objections to evolution need not be taken seriously); • argument from authority (e.g., President Richard Nixon should be re-elected because he has a secret plan to end the war in Southeast Asia—but because it was secret, there was no way for the electorate to evaluate it on its merits; the argument amounted to trusting him because he was President: a mistake, as it turned out); • argument from adverse consequences (e.g., A God meting out punishment and reward must exist, because if He didn’t, society would be much more lawless and dangerous—perhaps even ungovernable.* Or: The defendant in a widely publicized murder trial must

be found guilty; otherwise, it will be an encouragement for other men to murder their wives); • appeal to ignorance—the claim that whatever has not been proved false must be true, and vice versa (e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist—and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we’re still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence. • special pleading, often to rescue a proposition in deep rhetorical trouble (e.g., How can a merciful God condemn future generations to torment because, against orders, one woman induced one man to eat an apple? Special plead: you don’t understand the subtle Doctrine of Free Will. Or: How can there be an equally godlike Father, Son, and Holy Ghost in the same Person? Special plead: You don’t understand the Divine Mystery of the Trinity. Or: How could God permit the followers of Judaism, Christianity, and Islam—each in their own way enjoined to heroic measures of loving kindness and compassion—to have perpetrated so much cruelty for so long? Special plead: You don’t understand Free Will again. And anyway, God moves in mysterious ways.) • begging the question, also called assuming the answer (e.g., We must institute the death penalty to discourage violent crime. But do...

non sequitur—Latin for “It doesn’t follow” (e.g., Our nation will prevail because God is great. But nearly every nation pretends this to be true; the German formulation was “Gott mit uns”). Often those falling into the non sequitur fallacy have simply failed to recognize alternative possibilities; • post hoc, ergo propter hoc—Latin for “It happened after, so it was caused by” (e.g., Jaime Cardinal Sin, Archbishop of Manila: “I know of … a 26-year-old who looks 60 because she takes [contraceptive] pills.” Or: Before women got the vote, there were no nuclear weapons); • meaningless question (e.g., What happens when an irresistible force meets an immovable object? But if there is such a thing as an irresistible force there can be no immovable objects, and vice versa); • excluded middle, or false dichotomy—considering only the two extremes in a continuum of intermediate possibilities (e.g., “Sure, take his side; my husband’s perfect; I’m always wrong.” Or: “Either you love your country or you hate it.” Or: “If you’re not part of the solution, you’re part of the problem”); • short-term vs. long-term—a subset of the excluded middle, but so important I’ve pulled it out for special atte...

the killing of a full-term infant. Or, conversely: If the state prohibits abortion even in the ninth month, it will soon be telling us what to do with our bodies around the time of conception); • confusion of correlation and causation (e.g., A survey shows that more college graduates are homosexual than those with lesser education; therefore education makes people gay. Or: Andean earthquakes are correlated with closest approaches of the planet Uranus; therefore—despite the absence of any such correlation for the nearer, more massive planet Jupiter—the latter causes the former*); • straw man—caricaturing a position to make it easier to attack (e.g., Scientists suppose that living things simply fell together by chance—a formulation that willfully ignores the central Darwinian insight, that Nature ratchets up by saving what works and discarding what doesn’t. Or—this is also a short-term/long-term fallacy—environmentalists care more for snail darters and spotted owls than they do for people); • suppressed evidence, or half-truths (e.g., An amazingly accurate and widely quoted “prophecy” of the assassination attempt on President Reagan is shown on television; but—an important detail—...

weasel words (e.g., The separation of powers of the U.S. Constitution specifies that the United States may not conduct a war without a declaration by Congress. On the other hand, Presidents are given control of foreign policy and the conduct of wars, which are potentially powerful tools for getting themselves re-elected. Presidents of either political party may therefore be tempted to arrange wars while waving the flag and calling the wars something else—“police actions,” “armed incursions,” “protective reaction strikes,” “pacification,” “safeguarding American interests,” and a wide variety of “operations,” such as “Operation Just Cause.” Euphemisms for war are one of a broad class of reinventions of language for political purposes. Talleyrand said, “An important art of politicians is to find new names for institutions which under old names have become odious to the public”). Knowing the existence of such logical and rhetorical fallacies rounds out our toolkit. Like all tools, the balo...

The question, as always, is how good is the evidence? The burden of proof surely rests on the shoulders of those who advance such claims.

Or am I being too harsh? How is the occasional charlatan in faith-healing different from the occasional fraud in science? Is it fair to be suspicious of an entire profession because of a few bad apples? There are at least two important differences, it seems to me. First, no one doubts that science actually works, whatever mistaken and fraudulent claim may from time to time be offered. But whether there are any “miraculous” cures from faith-healing, beyond the body’s own ability to cure itself, is very much at issue. Secondly, the exposé of fraud and error in science is made almost exclusively by science. The discipline polices itself—meaning that scientists are aware of the potential for charlatanry and mistakes. But the exposure of fraud and error in faith-healing is almost never done by other faith-healers. Indeed, it is striking how reluctant the churches and synagogues are in condemning demonstrable deception in their midst.

One of the saddest lessons of history is this: If we’ve been bamboozled long enough, we tend to reject any evidence of the bamboozle. We’re no longer interested in finding out the truth. The bamboozle has captured us. It’s simply too painful to acknowledge, even to ourselves, that we’ve been taken. Once you give a charlatan power over you, you almost never get it back. So the old bamboozles tend to persist as the new ones rise.

So how is shamanistic or theological or New Age doctrine different from quantum mechanics? The answer is that even if we cannot understand it, we can verify that quantum mechanics works. We can compare the quantitative predictions of quantum theory with the measured wavelengths of spectral lines of the chemical elements, the behavior of semiconductors and liquid helium, microprocessors, which kinds of molecules form from their constituent atoms, the existence and properties of white dwarf stars, what happens in masers and lasers, and which materials are susceptible to which kinds of magnetism. We don’t have to understand the theory to see what it predicts. We don’t have to be accomplished physicists to read what the experiments reveal. In every one of these instances—as in many others—the predictions of quantum mechanics are strikingly, and to high accuracy, confirmed.

Whether the shaman grasps why his cures work is another story. In quantum mechanics we have a purported understanding of Nature on the basis of which, step by step and quantitatively, we make predictions about what will happen if a certain experiment, never before attempted, is carried out. If the experiment bears out the prediction—especially if it does so numerically and precisely—we have confidence that we knew what we were doing. There are at best few examples with this character among shamans, priests, and New Age gurus.

Certain kinds of folk knowledge are valid and priceless. Others are at best metaphors and codifiers. Ethnomedicine, yes; astrophysics, no. It is certainly true that all beliefs and all myths are worthy of a respectful hearing. It is not true that all folk beliefs are equally valid—if we’re talking not about an internal mindset, but about understanding the external reality.

Science is different from many another human enterprise—not, of course, in its practitioners being influenced by the culture they grew up in, nor in sometimes being right and sometimes wrong (which are common to every human activity), but in its passion for framing testable hypotheses, in its search for definitive experiments that confirm or deny ideas, in the vigor of its substantive debate, and in its willingness to abandon ideas that have been found wanting. If we were not aware of our own limitations, though, if we were not seeking further data, if we

were unwilling to perform controlled experiments, if we did not respect the evidence, we would have very little leverage in our quest for the truth. Through opportunism and timidity we might then be buffeted by every ideological breeze, with nothing of lasting value to hang on to.

So societies that teach contentment with our present station in life, in expectation of post-mortem reward, tend to inoculate themselves against revolution. Further, fear of death, which in some respects is adaptive in the evolutionary struggle for existence, is maladaptive in warfare. Those cultures that teach an

afterlife of bliss for heroes—or even for those who just did what those in authority told them—might gain a competitive advantage.

Those who cannot bear the burden of science are free to ignore its precepts. But we cannot have science in bits and pieces, applying it where we feel safe and ignoring it where we feel threatened—again, because we are not wise enough to do so. Except by sealing the brain off into separate airtight compartments, how is it possible to fly in airplanes, listen to the radio or take antibiotics while holding that the Earth is around 10,000 years old or that all Sagittarians are gregarious and affable?

Many pseudoscientific and New Age belief systems emerge out of dissatisfaction with conventional values and perspectives—and are therefore themselves a kind of skepticism.

[T]he skeptic might take a clue from cultural anthropology and develop a more sophisticated skepticism by understanding alternative belief systems from the perspective of the people who hold them and by situating these beliefs in their historical, social, and cultural contexts. As a result, the world of the paranormal may appear less as a silly turn toward irrationalism and more as an idiom through which segments of society express their conflicts, dilemmas, and identities

As I’ve tried to stress, at the heart of science is an essential balance between two seemingly contradictory attitudes—an openness to new ideas, no matter how bizarre or counterintuitive, and the most ruthlessly skeptical scrutiny of all ideas, old and new. This is how deep truths are winnowed from deep nonsense. The collective enterprise of creative thinking and skeptical thinking, working together, keeps the field on track.

At the same time, science requires the most vigorous and uncompromising skepticism, because the vast majority of ideas are simply wrong, and the only way to winnow the wheat from the chaff is by critical experiment and analysis.

Why should so many people find science hard to learn and hard to teach? I’ve tried to suggest some of the reasons—its precision, its counterintuitive and disquieting aspects, its prospects of misuse, its independence of authority, and so on.

The impediment to scientific thinking is not, I think, the difficulty of the subject. Complex intellectual feats have been

mainstays even of oppressed cultures. Shamans, magicians, and theologians are highly skilled in their intricate and arcane arts. No, the impediment is political and hierarchical. In those cultures lacking unfamiliar challenges, external or internal, where fundamental change is unneeded, novel ideas need not be encouraged. Indeed, heresies can be declared dangerous; thinking can be rigidified; and sanctions against impermissible ideas can be enforced—all without much harm. But under varied and changing environmental or biological or political circumstances, simply copying the old ways no longer works. Then, a premium awaits those who, instead of blandly following tradition, or trying to foist their preferences onto the physical or social Universe, are open to what the Universe teaches. Each society must decide where in the continuum between openness and rigidity safety lies.

Being freed from superstition isn’t enough for science to grow. One must also have the idea of interrogating Nature, of doing experiments.

thought fit only for slaves, as in the classical Græco-Roman world, the experimental method does not thrive. Science requires us to be freed of gross superstition and gross injustice both. Often, superstition and injustice are imposed by the same ecclesiastical and secular authorities, working hand in glove. It is no surprise that political revolutions, skepticism about religion, and the rise of science might go together. Liberation from superstition is a necessary but not a sufficient condition for science. At the same time, it is undeniable that central figures in the transition from medieval superstition to modern science were profoundly influenced by the idea of one Supreme God who created the Universe and established not only commandments that humans must live by, but laws that Nature itself must abide by.

What Ionia and ancient Greece provided is not so much inventions or technology or engineering, but the idea of systematic inquiry, the notion that laws of Nature, rather than capricious gods, govern the world. Water, air, earth, and fire all had their turn as candidate “explanations” of the nature and origin of the world. Each such explanation—identified with a different pre-Socratic philosopher—was deeply flawed in its details. But the mode of explanation, an alternative to divine intervention, was

productive and new. Likewise, in the history of ancient Greece, we can see nearly all significant events driven by the caprice of the gods in Homer, only a few events in Herodotus, and essentially none at all in Thucydides. In a few hundred years, history passed from god-driven to human-driven.

When the training is unchanged for immense periods of time, traditions are passed on intact to the next generation. But when what needs to be learned changes quickly, especially in the course of a single generation, it becomes much harder to know what to teach and how to teach it. Then, students complain about relevance; respect for their elders diminishes. Teachers despair at how educational standards have deteriorated, and how lackadaisical students have become. In a world in transition, students and teachers both need to teach themselves one essential skill—learning how to learn.

These are typical questions in “scientific literacy.” The results are appalling. But what do they measure? The memorization of authoritative pronouncements. What they should be asking is

how we know—that antibiotics discriminate between microbes, that electrons are “smaller” than atoms, that the Sun is a star which the Earth orbits once a year. Such questions are a much truer measure of public understanding of science, and the results of such tests would doubtless be more disheartening still.

There’s only one, I think: Don’t talk to the general audience as you would to your scientific colleagues. There are terms that convey your meaning instantly and accurately to fellow experts. You may parse these phrases every day in your professional work. But they do no more than mystify an audience of nonspecialists. Use the simplest possible language. Above all, remember how it was before you yourself grasped whatever it is you’re explaining. Remember the misunderstandings that you almost fell into, and note them explicitly. Keep firmly in mind that there was a time when you didn’t understand any of this either. Recapitulate the first steps that led you from ignorance to knowledge.

But, where possible, popularizers should try to chronicle some of the mistakes, false starts, dead ends, and apparently hopeless confusion along the way. At least every now and then, we should provide the evidence and let the reader draw his or her own conclusion. This converts obedient assimilation of new knowledge into personal discovery. When you make the finding yourself—even if you’re the last person on Earth to see the light—you never forget it.

Dorothy Rich, an innovative teacher from Yonkers, New York, believes that far more important than specific academic subjects is the honing of key skills which she lists as: “confidence, perseverance, caring, teamwork, common sense and problem-solving.” To which I’d add skeptical thinking and an aptitude for wonder.

We must not believe the many, who say that only free people ought to be educated, but we should rather believe the philosophers who say that only the educated are free. EPICTETUS, Roman philosopher and former slave, Discourses

Other shortcomings are evident in television science fiction programming. Star Trek, for example, despite its charm and strong international and interspecies perspective, often ignores the most elementary scientific facts. The idea that Mr. Spock could be a cross between a human being and a life-form independently evolved on the planet Vulcan is genetically far less probable than a successful cross of a man and an artichoke. The idea does, however, provide a precedent in popular culture for the extraterrestrial/human hybrids that later became so central a component of the alien abduction story. There must be dozens of alien species on the various Star Trek TV series and movies. Almost all we spend any time with are minor variants of humans. This is driven by economic necessity, costing only an actor and a latex mask, but it flies in the face of the stochastic nature of the evolutionary process. If there are aliens, almost all of them I think will look devastatingly less human than Klingons and Romulans (and be at wildly different levels of technology). Star Trek doesn’t come to grips with evolution.

I can’t even recall seeing an accurate and comprehensible description on television of how television works.

Ubi dubium ibi libertas: Where there is doubt, there is freedom. LATIN PROVERB

Jefferson made the same point even more strongly: “If a nation expects to be both ignorant and free in a state of civilization, it expects what never was and never will be.” In a letter to Madison, he continued the thought: “A society that will trade a little liberty for a little order will lose both, and deserve neither.”

New ideas, invention, and creativity in general, always spearhead a kind of freedom—a breaking out from hobbling constraints. Freedom is a prerequisite for continuing the delicate experiment of science—which is one reason the Soviet Union could not remain a totalitarian state and be technologically competitive. At the same time, science—or rather its delicate mix of openness and skepticism, and its encouragement of diversity and debate—is a prerequisite for continuing the delicate experiment of freedom in an industrial and highly technological society.