by Carl Sagan

It takes courage to be afraid.
—Montaigne, Essays, III, 6 (1588)

Apollo, an Olympian, was god of the Sun. He was also in charge of other matters, one of which was prophecy. That was one of his specialties. Now the Olympian gods could all see into the future a little, but Apollo was the only one who systematically offered this gift to humans. He established oracles, the most famous of which was at Delphi, where he sanctified the priestess. She was called the Pythia, after the python that was one of her incarnations. Kings and aristocrats — and occasionally ordinary people — would come to Delphi and beg to know what was to be.

Among the supplicants was Croesus, King of Lydia. We remember him in the phrase “rich as Croesus” which is still nearly current. Perhaps he has come to be synonymous with wealth because it was in his time and kingdom that coins were invented — minted by Croesus in the seventh century B.C. (Lydia was in Anatolia, contemporary Turkey.) Clay money was a much earlier Sumerian invention. His ambition could not be contained within the boundaries of his small nation. And so, according to Herodotus’s History, he got it into his head that it would be a good idea to invade and subdue Persia, then the superpower of Western Asia. Cyrus had united the Persians and the Medes and forged a mighty Persian Empire. Naturally, Croesus had some degree of trepidation.

In order to judge the wisdom of invasion, he dispatched emissaries to consult the Delphic Oracle. You can imagine them laden with opulent gifts — which, incidentally, were still on display in Delphi a century later, in Herodotus’s time. The question the emissaries put on Croesus’s behalf was, What will happen if Croesus makes war on Persia?”

Without hesitation, the Pythia answered, He will destroy a mighty empire.”

The gods are with us,” thought Croesus, or words to that effect. “Time to invade!”

Licking his chops and counting his satra­pies, he gathered his mercenary armies. Croesus invaded Persia — and was humiliatingly defeated. Not only was Lydian power destroyed, but he himself became, for the rest of his life, a pathetic functionary in the Persian court, offering little pieces of advice to often indifferent officials — a hanger-on ex-king. It’s a little bit like the Emperor Hirohito living out his days as a consultant on the Beltway in Washington, D.C.

Well, the injustice of it really got to him. After all, he had played by the rules. He had asked for advice from the Pythia, he had paid handsomely, and she had done him wrong. So he sent another emissary to the Oracle (with much more modest gifts this time, appropriate to his diminished circumstances) and asked, “How could you do this to me?” Here, from Herodotus’s History, is the answer:

The prophecy given by Apollo ran that if Croesus made war upon Persia, he would destroy a mighty empire. Now in the face of that, if he had been well-advised, he should have sent and inquired again, whether it was his own empire or that of Cyrus that was spoken of. But Croesus did not understand what was said, nor did he make question again. And so he has no one to blame but himself.

If the Delphic Oracle were only a scam to fleece gullible monarchs, then of course it would have needed excuses to explain away the inevitable mistakes. Disguised ambiguities were its stock in trade. Nevertheless, the lesson of the Pythia is germane: Even of oracles we must ask questions, intelligent questions — even when they seem to tell us exactly what we wish to hear. The policymakers must not blindly accept; they must understand. And they must not let their own ambitions stand in the way of understanding. The conversion of prophecy into policy must be made with care.

This advice is fully applicable to the modern oracles, the scientists and think tanks and universities, the industry-funded institutes, and the advisory committees of the National Academy of Sciences. The policymakers send, sometimes reluctantly, to ask of the oracle, and the answer comes back. These days the oracles often volunteer their prophecies even when no one asks. Their utterances are usually much more detailed than the questions — involving methyl bromide, say, or the circumpolar vortex, hydro- chlorofluorocarbons or the West Antarctic Ice Sheet. Estimates are sometimes phrased in terms of numerical probabilities. It seems almost impossible for the honest politician to elicit a simple yes or no. The policymakers must decide what, if anything, to do in response. The first thing to do is to understand. And because of the nature of the modern oracles and their prophecies, policymakers need — more than ever before — to understand science and technology. (In response to this need, the Republican Congress has foolishly abolished its own Office of Technology Assessment. And there are almost no scientists who are members of the U.S. Congress. Much the same is true of other countries.)

* * *

But there’s another story about Apollo and oracles, at least equally famous, at least equally relevant. This is the story of Cassandra, Princess of Troy. (It begins just before the Mycenaean Greeks invade Troy to start the Trojan War.) She was the smartest and the most beautiful of the daughters of King Priam. Apollo, constantly on the prowl for attractive humans (as were virtually all the Greek gods and goddesses), fell in love with her. Oddly — this almost never happens in Greek myth — she resisted his advances. So he tried to bribe her. But what could he give her? She was already a princess. She was rich and beautiful. She was happy. Still, Apollo had a thing or two to offer. He promised her the gift of prophecy. The offer was irresistible. She agreed. Quid pro quo. Apollo did whatever it is that gods do to create seers, oracles, and prophets out of mere mortals. But then, scandalously, Cassandra reneged. She refused the overtures of a god.

Apollo was incensed. But he couldn’t withdraw the gift of prophecy, because, after all, he was a god. (Whatever else you might say about them, gods keep their promises.) Instead, he condemned her to a cruel and ingenious fate: that no one would believe her prophecies. (What I’m recounting here is largely from Aeschylus’s play Agamemnon.) Cassandra prophesies to her own people the fall of Troy. Nobody pays attention. She predicts the death of the leading Greek invader, Agamemnon. Nobody pays attention. She even foresees her own early death, and still no one pays attention. They didn’t want to hear. They made fun of her. They called her — Greeks and Trojans alike — “the lady of many sorrows.” Today perhaps they would dismiss her as a “prophet of doom and gloom.”

There’s a nice moment when she can’t understand how it is that these prophecies of impending catastrophe — some of which, if believed, could be prevented — were being ignored. She says to the Greeks, “How is it you don’t understand me? Your tongue I know only too well.” But the problem wasn’t her pronunciation of Greek. The answer (I’m paraphrasing) was, “You see, it’s like this. Even the Delphic Oracle sometimes makes mistakes. Sometimes its prophecies are ambiguous. We can’t be sure. And if we can’t be sure about Delphi, we certainly can’t be sure about you.” That’s the closest she gets to a substantive response.

The story was the same with the Trojans: “I prophesied to my countrymen,” she says, “all their disasters.” But they ignored her clairvoyances and were destroyed. Soon, so was she.

The resistance to dire prophecy that Cassandra experienced can be recognized today. If we’re faced with an ominous prediction involving powerful forces that may not be readily influenced, we have a natural tendency to reject or ignore the prophecy. Mitigating or circumventing the danger might take time, effort, money, courage. It might require us to alter the priorities of our lives. And not every prediction of disaster, even among those made by scientists, is fulfilled: Most animal life in the oceans did not perish due to insecticides; despite Ethiopia and the Sahel, worldwide famine has not been a hallmark of the 1980s; food production in South Asia was not drastically affected by the 1991 Kuwaiti oil well fires; supersonic transports do not threaten the ozone layer — although all these predictions had been made by serious scientists. So when faced with a new and uncomfortable prediction, we might be tempted to say: “Improbable.” “Doom and Gloom.” “We’ve never experienced anything remotely like it.” “Trying to frighten everyone.” “Bad for public morale.”

What’s more, if the factors precipitating the anticipated catastrophe are long-standing, then the prediction itself is an indirect or unspoken rebuke. Why have we, ordinary citizens, permitted this peril to develop? Shouldn’t we have informed ourselves about it earlier? Don’t we ourselves bear complicity, since we didn’t take steps to insure that government leaders eliminated the threat? And since these are uncomfortable ruminations — that our own inattention and inaction may have put us and our loved ones in danger — there is a natural, if maladap­tive, tendency to reject the whole business. It will need much better evidence, we say, before we can take it seriously. There is a temptation to minimize, dismiss, forget. Psychiatrists are fully aware of this temptation. They call it “denial.” As the lyrics of an old rock song go: “Denial ain’t just a river in Egypt.”

* * *

The stories of Croesus and Cassandra represent the two extremes of policy response to predictions of deadly peril — Croesus himself representing one pole of credulous, uncritical acceptance (usually of the assurance that all is well), propelled by greed or other character flaws; and the Greek and Trojan response to Cassandra representing the pole of stolid, immobile rejection of the possibility of danger. The job of the policymaker is to steer a prudent course between these two shoals.

Suppose a group of scientists claims that a major environmental catastrophe is looming. Suppose further that what is required to prevent or mitigate the catastrophe is expensive: expensive in fiscal and intellectual resources, but also in challenging our way of thinking — that is, politically expensive. At what point do the policymakers have to take the scientific prophets seriously? There are ways to assess the validity of the modern prophecies — because in the methods of science, there is an error-correcting procedure, a set of rules that have repeatedly worked well, sometimes called the scientific method. There are a number of tenets (I’ve outlined some of them in my book The Demon-Haunted World): Arguments from authority carry little weight (“Because I said so” isn’t good enough); quantitative prediction is an extremely good way to sift useful ideas from nonsense; the methods of analysis must yield other results fully consistent with what else we know about the Universe; vigorous debate is a healthy sign; the same conclusions have to be drawn independently by competent competing scientific groups for an idea to be taken seriously; and so on. There are ways for policymakers to decide, to find a safe middle path between precipitate action and impassivity. It takes some emotional discipline, though, and most of all an aware and scientifically literate citizenry — able to judge for themselves how dire the dangers are.

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