The world’s most public astronomer lost his two-year battle with blood disease on December 20, 1996. He was sixty-two. That day, Cornell’s chairman of astronomy, Yervant Terzian, issued a statement: “Carl was a candle in the dark. He was, quite simply, the best science educator in the world this century.” This was no hasty eulogy. By the common measures of “best”—number of persons taught, medals and honors, extraordinary production of bestselling books and film, worldwide media stardom–Terzian’s assessment of Carl Sagan was sober truth. Moreover, he was a working scientist who made fundamental contributions to planetary science, exobiology, and space exploration. His last work was the book Billions and Billions: he never finished the acknowledgements. Sagan wrote the final chapter, as its title indicates, “In the Valley of the Shadow.” The book needed only a postscript and a short epilogue from his wife and collaborator, Ann Druyan.

These essays are his signature mix of glad and evil tidings; they reveal the motives of his public (as opposed to scientific) life.

Celebrity and cultural influence such as Sagan commanded energize detractors. Sometimes, the derogations testify anyway to the high quality of the target, and diagnose the critics better than the object. And, what is not criticized in the productions of celebrity can be symptomatic of malady in the culture. So it is for responses to Carl Sagan. Billions and Billions and its predecessor, The Demon-Haunted World, have had and will yet have fulsome praise and bitter attack. These essays are his signature mix of glad and evil tidings; they reveal the motives of his public (as opposed to scientific) life.

Like his other works of popular science and hortation, Billions and Billions is wonderfully accessible. It had to be: many chapters were first published in the sovereign Sunday supplement, Parade (of which Sagan was a contributing editor, along with others such as Dr. Joyce Brothers, Larry L. King, and Norman Mailer). Other pieces, revised from elsewhere, are slightly more uphill, but serve like purposes. On this most public of Sagan’s activities, an unexpected critic, geneticist Richard Lewontin, wrote disdainfully but with a hint of justice, that Sagan “has become the most widely known, widely read, and widely seen popularizer of science since the invention of the video tube. His only rival in the haute vulgarization of science is Stephen Jay Gould, whose vulgarizations are often very haute indeed, and whose intellectual concerns are quite different.” But Lewontin approves of Gould’s “intellectual concerns,” not of Sagan’s; and thereby hangs a tale. First, however: what were Sagan’s intellectual concerns? In a nutshell: to teach the uniqueness of science for getting at truths about the physical world and the place of Homo sapiens and the other species in it; and, to insist upon the sharp double edge (his metaphor) of the sword of science, one good (knowledge), the other evil (technology gone wrong). If enough people cherish the knowledge and act on it, he believed, the perils of humanity and of Earth can be faced, and reduced or eliminated. Salvation is choosing the good edge and blunting the evil one.

Of our perils he was the most vociferous —and (scientifically) best qualified–prophet. In Billions and Billions, famous good cheer just perceptibly frayed, he almost identified with Cassandra: doomed to foretell the future and to be disbelieved. But of course he wasn’t disbelieved. Converts enormously outnumbered foes. He calculated environmental perils, often cleverly and accurately, and made the calculus transparent for the innumerate. Sometimes, though, he exaggerated for political effect (as in the cautionary marketing of nuclear winter) or neglected to calculate at all (as when propagating such enviro-scares as the falling sperm count).

He was both scientist and teacher, but also a political performer. He exulted in celebrity. Page 2 of Billions and Billions sports a photo of him with Johnny Carson, all smiles and old friends on the ultimate talk show. He was 100 percent sure of his message’s truth (which is not so unusual: how many public intellectuals are not 100 percent sure?). He delivered it to the great as well as on television. He conveyed it to a thousand religious and parliamentary luminaries at conferences in Oxford and Moscow. Our world is in grave danger of environmental and moral collapse, he said, threatened by climatic upheavals, excessive ultraviolet radiation, militarism, nuclear weapons, industrialization, and not least by our ancient lust for zero-sum games of hunting and killing (he made the game theory accessible). The heritage of our evolution: “Pleistocene emotions but without Pleistocene social safeguards.” The threat, he urged, can be met if religion, with its power of moral suasion, and science, with its grip on the real world, join forces to save the planet and to free minds of nonsense. Sagan thought that he knew the haunting demons, and who, if they really wanted to, could exorcise them.

Such pleas have been effective. Convince yourself, if necessary, by following religion in the media. Throughout the West, the old injunctions to be fruitful and multiply, to smite the faith’s enemies hip and thigh, to have dominion over Earth and its creatures, are rejected. Replacing them is our new, noninvasive stewardship (about which Sagan has much to say in the book). We are mere sextons of Nature’s (or God’s) dwelling-place—not its rulers. Sagan’s well-crafted science lessons swim in homilies. His secular humanism, despised by fundamentalists, is transmuted from many a pulpit to a kind of Gaia worship.

What have his detractors to urge against him? Among strong religionists the complaints are the obvious. Sagan is a materialist. His overtures to religion are hypocritical. David N. Menton, of Computers for Christ in San Jose, cites Sagan’s “crass materialism” and “scientism” as a competing faith to theism, so Sagan’s scientific assertions can have no special claim to truth. Among anti-evolutionists, he is simply wrong. What he takes for evidence of organic evolution is, really, evidence against it; he has, according to Dr. Larry Vardiman of the Institute for Creation Research, “rejected out of hand the evidences he has clearly seen for design of the universe” and is willfully “blinded to the evidence that God exists.” For the cultists at The Velikovskian, his is the hubris of official science, “glaringly unscientific and unscholarly.”

These judgments get a boost from an unexpected quarter: academics adopting, as regards natural science, some form of social constructionism, the argument that “scientific knowledge” is made by social forces, which play a decisive role in its content. In a blast against Sagan and other authors such as E. O. Wilson, Richard Dawkins, and Lewis Thomas, Richard Lewontin, writing in The New York Review of Books, contrasts them unfavorably with Gould, who is “primarily concerned … with what the nature of organisms, living and dead, can reveal about the social construction of scientific knowledge.” (I trust this was a surprise to Gould.) Resentful of the suggestion that he, Lewontin, is of the “academic left,” something “recently invented but undefined,” he charges Sagan and the others with promoting a flood of unsupported science claims and confusing truth with freedom. “It is not the truth that makes you free,” he asserts. “It is your possession of the power to discover the truth. Our dilemma is that we do not know how to provide that power.” Explaining science to the public is thus hopeless: the masses should be taught how to get power.

Well, what of these criticisms? Was Sagan just a media darling, a philosophical naïve ignorant of postpositivism? Was he a hypocrite about religion, hoping to eject God from culture? Did he conspire against the threat of genius—like that of Velikovsky? Was Cosmos just smoke and mirrors? No. Lewontin does not need to depend, as he claims to, on Sagan for “truths” (scare quotes are obligatory) about astronomy. He can acquire truths with his own eyes, on the TV screen, as hard data arrive from, yes, billions of miles away in space. The planets are where astronomy says they are. Whatever social forces acted upon Ptolemy, Copernicus, Kepler, Galileo; whatever Newton’s alchemical hang-ups, science kept the wheat and discarded the chaff. It had little to do with struggles for political power and everything to do with the way good science works.

Is Sagan hypocritical about religion? No. He stated his beliefs and doubts. To be sure those depend upon a naturalistic metaphysics; but he did not hide it. Moreover he supported his beliefs with evidence. Evidence, to some reasonable standard thereof, is what the Institute for Creation Research and The Velikovskian have never provided. Sagan’s overtures to the world’s religions were a recognition of their power over minds and of their proper moral mission. They were a plea for help.

There is a little problem with Billions and Billions, though. Not that the science is wrong. Most (but not quite all) of it is as well-confirmed as anything we know. Not that it is superficial (some of it is, but what the layman gets from it is sound). Not that he is a materialist disguised as a man of the cloth. He was always forthcoming about his philosophy and able to defend it. The problem is that to succeed in contemporary public debates that have partly to do with science but mostly with something else (on, say, national defense, the environment, abortion), one must immerse facts in a sauce of homily. The facts must not be too many, and they must be packaged entertainingly. Inevitably, then, facts conveyed are facts selected; and the temptation of convenient ones is irresistible. (Lewontin’s argument that modern medicine has done nothing about the treatment of cancer is a fine example.) Sagan, like everybody else in the policy game, selected, and interpreted what he had selected.

Whatever social forces acted upon Ptolemy, Copernicus, Kepler, Galileo; whatever Newton’s alchemical hang-ups, science kept the wheat and discarded the chaff.

One instance. Proud of his adventures in U.S.-Soviet moral equivalence and scornful, in the academic way, of the “conservative” notion of Soviet evil, he prepared in 1988 an article on the Soviet Union and America for simultaneous publication in Parade and Ogonyok (reprinted in Billions and Billions). The article lists the crimes against humanity of both sides. The game was to show equal guilt, that at base we and the Soviets are the same, that we should therefore forget old villainies and march toward a future of disarmed cooperation. Three things matter: (1) Sagan’s listed crimes include over- or understatements, rhetoric representing inexactly the underlying facts (which exist); (2) overstatements of Western misdeeds are as frequent as understatements of Soviet ones; and (3) the version published in the Soviet Union was, despite the esteem in which Soviet leaders were supposed to hold Sagan, radically censored by them. Facts of the censorship are given in the book, along with a copy of a “gracious” apology, long after the odious fact, by Dr. Georgi Arbatov. Sagan’s argument for moral equivalence is demolished by the Soviet censorship. Even so, there is no evidence that Sagan recognized this fact at the time or later. In general, his peers among political and cultural mandarins also fail to recognize such errors. The argument for moral equivalence, ignoring among other things the difference between a free press and implacable censorship, is an example of self-refutation unremarked. It is the dog that did not bark in the night.