At a Washington press conference last year, a reporter asked General John M Shalikashvili, chairman of the US Joint Chiefs of Staff, to "assure us that our country is effectively protected" from "invasion, abduction and other mischief from some kind of alien being".
"Am I the alien being you're talking about?" the general replied. But he can't joke these millennial anxieties away. The historian and UFO-ologist David M Jacobs, in his latest book, The Threat: the secret alien agenda (Simon & Schuster, £16.99), warns that it may already be too late to stop an alien breeding programme aimed at taking over the planet. Handsome, Levi-wearing aliens, he tells us, have been assigned as "personal-project hybrids" to have regular sex with various earth-women. The aliens tell lies and have several projects apiece, but they are so seductive, romantic and cute that most of the women fall in love with them. "After intercourse," Jacobs reports, "some hybrids linger for a short time before putting on their clothes and going to another task."
Most apocalyptic scenarios and conspiracy theories are about threats and mischief of some kind. Because the final years of a century or millennium suggest to many people more a death than a date, images of sickness and danger tend to dominate in fin-de-siecle fantasies. As we get closer to the start of the new century, however, images of rebirth begin to appear alongside those of destruction or decay. In the film Contact, for instance, Jodie Foster plays a scientist who meets a spiritually advanced species of extraterrestrial radiance; in real life, the Harvard professor John Mack believes that aliens are benevolent, and that "the abduction phenomenon is . . . about the preservation of life on earth". In this New Age version of the apocalypse, aliens are actually gods - divine or at least advanced beings who are trying to communicate with us, and who have inspiring messages of immortality. We may have to master Sanskrit or astrology to decode their veiled prophecies, but these beings are on our side, and if we can solve their mysteries we can learn the secrets of the universe.
Specialists in solving these cosmic codes insist that truth cannot be apprehended through fact and reason alone. As Michael Baigent, in Ancient Traces, writes: "Reality encompasses more than that which we can see, touch, smell, taste, measure, weigh and generally record. There is the part of our reality which is after, or beyond the physical, the so-called metaphysical or supernatural; that part which encompasses things we call divine." He is, not surprisingly, studying for an MA in mysticism and religious experience at Kent. Similarly, Graham Hancock warns that "poised on the edge of a millennium, at the end of a century of unparalleled wickedness and bloodshed in which greed has flourished, humanity faces a stark choice between matter and spirit - the darkness and the light".
Yet gnostic or not, these books seem addressed to obsessive lobbyists with lots of leisure time: chariot-spotters of the gods. Whether pedants or jet-setters, academics or autodidacts, the authors revel in factoids and the trappings of science - terminology, citation, diagrams, photographs and experiment swaddling the hypotheses, anecdotes, uplifting quotations, wild suppositions and rhetorical questions. They are all looking for a unified field theory of everything, striving to fit random bits of information into a coherent world view.
Baigent argues, along with religious creationists, that the fossil record doesn't support Darwin's theory of evolution, because there is no evidence of transitional forms. He believes instead that an advanced human civilisation existed millions of years before the cavemen, probably on the lost continent of Atlantis, and that when it was destroyed the refugees spread all over the world, "high initiates who carried the secrets of Atlantean technology, religion and science". They coded their wisdom into huge buildings, instructed initiates in alchemy and left sacred scriptures about reincarnation. Indeed, he notes triumphantly that "a staggering 38 million Americans believe that they have lived before".
Thus, while he easily discounts Darwinian theory, classical archaeology and medical science, Baigent places great store in anecdotes like the story of a Mrs Culp who in 1891 found a gold chain of exquisite workmanship (now, alas, lost) in a lump of coal which could have been 260 million years old; or in the claim that in 1922 a geologist found a fossilised human footprint over 200 million years old wearing shoes. (Unfortunately, only a photograph of the shoe-print remains.) He believes in sea-serpents, prefers the mystical theology of one Bolus of Mendes to Aristotle, and assumes that because evolutionists argue about the causal agents of organic change, he can cite them in support of his logic.
Percy Seymour, an astrophysicist who has written books on astrology and the paranormal, argues that the actual birth of Christ was 15 September 7BC, when a conjunction of Saturn and Jupiter would have created a sign for the Magi and led them to Bethlehem. In his view, astrology can be scientifically explained by magnetic fields which influence birth. In particular, the planet Jupiter influences political leadership, and indeed it was rising when Tony Blair was born, although not nearly so prominent for John Major.
Erich Von Daniken, whose previous books about the gods have sold 56 million copies worldwide, thanks his wife Elisabeth "who has much patience and understanding for my work, although it means that I am so seldom at home". He lives in Switzerland but travels 100,000 kilometres a year. In Arrival of the Gods, he travels to Peru to inspect the mysterious "scrape lines" and figures of Nazca, mammoth images he calls "man's most mysterious picture book". In his view, the images and designs were created by a Peruvian cargo cult as signals to extraterrestrials who had landed there millions of years ago. He cites Francis Crick in support of his theory that "an alien civilisation might have shot micro-organisms into the universe millions of years ago with the help of spaceships, thus sowing the whole cosmos into life". Generally, however, Von Daniken marvels at the otiose scientists and theologians who will go on ignoring the obvious until "the ETs land in St Peter's Square in Rome and celebrate a service in honour of all creation" - an event to which I, for one, would pay serious attention. Meanwhile, he is planning a theme park of the gods in Interlaken in the Berne mountains and invites readers to send for "a free detailed prospectus".
Finally, Graham Hancock, who has sold a mere four million copies of his books, takes a spectacular voyage around the world with his photographer wife and a full TV crew. In Heaven's Mirror, he pulls all of these ideas together with a theory that the mysterious monuments and megaliths of the world - Stonehenge, the pyramids of Giza, Chichen Itza, La Venta, Angkor Wat, Nan Douwas and Easter Island - were actually a "network", all constructed by the busy "navigators and architects" of a single lost civilisation, and reflecting a religious view "disseminated all around the world, that carried down from remote antiquity the distinctive doctrine of sky-ground dualism". Rightly understood, Hancock argues, all these monuments are designed to imitate various constellations.
Michael Shermer, in Why People Believe Weird Things, points out the fallacies in pseudo-scientific reasoning, all of which occur in chariot-spotting. Among other things, just because the establishment thinks you are crazy doesn't prove that you are Galileo. Heresy is not necessarily divinest truth. But Shermer concludes that people continue to have trouble "distinguishing science from pseudo-science, history from pseudo-history, and sense from nonsense". In part, believing these weird things is comforting and consoling. In part, they offer "canons of morality and meaning".
But in the 1990s, I fear, there are also darker pleasures to be obtained from believing weird things. The chariot-spotters agree that, in Hancock's words, we are collectively suffering from an "almost total amnesia" of our prehistory, and need to recover memories by piecing together the scattered fragments of a great cosmic puzzle. As Baigent reminds us, "many dysfunctions of the personality - and even of the body - can be traced back to strong, deeply buried hurts, confusions, betrayals, frustrations, and similar inharmonious events, which until brought into the light of consciousness, lie buried like land-mines". When pseudo-scientific belief systems come up against "scattered" fragments and "buried" hurts, it will not be long before they start looking for the agents who scattered and buried them. Beyond every chariot- spotter, a conspiracy-theorist is lurking. And they can't blame Bill Clinton for everything.
Elaine Showalter, professor of English at Princeton University, is the author of "Hystories: hysterical epidemics in modern culture" (Picador, £6.99)