The first modern sighting of a UFO (Unidentified Flying Object) occurred two days before my sixteenth birthday, on June 24, 1947.

Kenneth Arnold, a businessman, was flying his private plane near Mount Rainier in Washington State when he saw nine shining discs moving against the background of the mountain. He estimated their speed as about 1,000 mph. He said that they swerved in and out of the peaks of the Cascade Mountains with "flipping, erratic movements." He later told a reporter that the objects moved as a saucer would "if you skipped it across the water." The next day the story appeared in newspapers all over the nation, calling the strange objects "flying saucers." Hundreds of people soon began reporting sightings of flying saucers, and a US Air Force investigation was initiated; on 4 July, ten days after the sighting, the US Air Force announced confidently that Arnold had been "hallucinating."

My own feeling about them was one of alarm and disquiet. This was because in my early teens I had experienced a profound sense of meaninglessness, which I labeled "nihilism;" it amounted to a feeling that all our human ideas and beliefs are illusions. This had started when I was 13, when a group of us in the art class at school began discussing the problem of where space ends, or whether it goes on forever. Suddenly, it dawned on me that no human being knows the answer to this question, and that moreover it is impossible to even imagine an answer. This realization produced a sinking feeling inside me, as if I had just heard a piece of terrifying bad news. As I went home on the bus, surrounded by people, I felt that I was the only person on earth who understood this frightening secret, and that if they all understood, they would be paralyzed with horror.

This explains why the item about flying saucers disturbed me so much. I had learned to live with my feeling that human beings are trapped in unreality, but it now seemed to me that I was the only human being who understood a terrible secret. By 1948 the many news items about flying saucers were a permanent reminder.

The US Air Force statement that Kenneth Arnold had been "hallucinating" seemed typical of official obstructionism. Arnold had been out searching for the wreckage of a lost plane at the time he made the sighting, and obviously had no reason to invent such a story.

It was obvious that the newspaper publicity was causing a certain amount of hysteria, and that many people thought they had seen flying saucers when they had only seen weather balloons or aircraft tail-lights. But was it conceivable that thousands of people—in fact, millions—could all be mistaken? For by 1966, a Gallup Poll revealed that five million Americans believed they had seen flying saucers. And some of these sightings were at close quarters.

Yet in spite of an increasing number of reports, the Air Force continued to insist that UFO sightings were hoaxes, mistakes, or downright lies. An official investigation, known as "Project Sign," began in September 1947, and later became known as "Project Blue Book." This also concluded that UFOs were an illusion. But one of its advisers was the astronomer J. Allen Hynek, who began as a skeptic but was soon convinced by the obvious truthfulness of witnesses that UFOs were a reality.

Hynek's studies finally convinced him that, no matter how many cranks, simpletons, and downright liars managed to obscure the facts, these facts unequivocally indicated the real existence of flying saucers, and even of "space men." It was Hynek who coined the phrase "close encounters of the third kind," meaning encounters with grounded saucers and "humanoids." He begins his chapter on such encounters (in The UFO Experience, A Scientific Enquiry, 1972): "We come now to the most bizarre and seemingly incredible aspect of the entire UFOs phenomenon. To be frank, I would gladly omit this part if I could without offense to scientific integrity..." He goes on to consider a number of cases that, although they sound preposterous, were too well-authenticated to be dismissed.

Another investigator whose name deserves to be taken seriously is Jacques Vallee, who was born in France in 1939. Working at the Paris Observatory in 1961, he was tracking a UFO when the director erased the tape data, leading Vallee to suspect a cover-up. He became a friend of the French researcher Aimé Michell, and soon had no doubt of the reality of UFOs. Baffled by the small-minded attitudes of fellow astronomers, Vallee annoyed them by remarking that it seemed to him that UFOs were the "first collective intelligence test to which mankind has been subjected."

In 1962 Vallee and his wife Janine moved to America. Although he remarked that the American idea of researching UFOs is to shoot at them, he seems to have found Americans more open-minded than the French. Vallee's book Challenge to Science: the UFO Enigma (1963) had the effect of causing many American scientists to be willing to reassess the UFO mystery in the 1960s.

But Vallee was one of the first to note one of the main characteristics of the phenomenon: what might be called the deliberate unbelievability of many cases. It is almost as if the force that lies behind the phenomenon wants to convince us of its absurdity. And most of what Hynek called "close encounters of the third kind" fall into this category.

Perhaps the most famous case was that of Barney and Betty Hill. In September 1961 they were returning through New Hampshire from a holiday in Canada when they saw a flying saucer apparently in the process of landing. Two hours later they found themselves thirty-five miles from this spot, with no recollection of what had happened in the meantime. Eventually they consulted an expert in amnesia, Dr. Benjamin Simon, who placed them under hypnosis; the Hills then described—independently of each other—what had happened. They had been taken aboard the saucer by a number of uniformed men who looked more or less human (Barney said they reminded him of red-haired, round-faced Irishmen), subjected to a number of medical tests or experiments—skin and nail shavings were taken, and Betty Hill had a needle inserted into her navel—then they were hypnotized and told to forget everything that had happened. Hynek himself was later present when Barney Hill was placed under hypnosis, and was allowed to question him. He ended by being convinced of the genuineness of the experience.

But the Air Force remained adamantly skeptical. By the mid-1960s the belief that it was involved in a cover-up became so persistent that in 1965 the Air Force itself ordered that a new scientific panel should be set up; Edward U. Condon, a well-known physicist, was appointed head of this panel, and it was sponsored by the University of Colorado. But when the panel issued its report in 1969 it was obvious that the scientists of the University of Colorado had reached the same conclusion as the Air Force investigators—one newspaper headline summarized the findings of the 965-page report in the headline: "Flying Saucers Do Not Exist—Official."

One basic problem was that the whole field of investigation had become a happy hunting-ground for cranks. In a book called Flying Saucers Have Landed, a Polish-American named George Adamski claimed that in 1952 he and a number of other saucer enthusiasts drove into the California desert—their route dictated by Adamski's "hunches"—and saw a huge cigar-shaped object in the sky. With a camera, Adamski wandered off alone, and saw a flying saucer land half a mile away. He hurried to the spot, and found a flying saucer, and a small man with shoulder-length blond hair, who identified himself in sign language as an inhabitant of the planet Venus. Then he flew off in his spacecraft. His friends had witnessed the encounter from a nearby hill, and later signed notarized statements to that effect.

In a second book Inside the Space Ships, Adamski told how he had been taken for a trip in a saucer—called a "scout ship"—with his Venusian acquaintance, plus a man from Mars and a man from Saturn. On this occasion they flew into space and went on board the mother ship. On another occasion Adamski was taken to the moon, where he saw rich vegetation, including trees, and four-legged furry animals. He was also shown live pictures of Venus on a television screen, and saw that it had cities, mountains, rivers, and lakes. Adamski died in 1965, four years before the moon landings, but three years after the space probe Mariner II had swept past Venus and revealed that it has an atmosphere of sulfuric acid gas, and that the surface is too hot to support life. But such small setbacks left Adamski unmoved—he was always able to claim that a mere space probe was less reliable than real Venusians—and he spent the final years of his life happily lecturing to audiences of UFO enthusiasts all over the world.

Understandably, then, the increasing flood of books by "ufologists" has aroused most serious investigators to fury or derision.

In 1975 the UFO story entered a new phase with the investigations of a New York artist named Budd Hopkins.

One day in November 1975, Hopkins visited a liquor store run by a man named George O'Barski, who told him how in January on his way home through North Hudson Park, New Jersey, he had seen an object like a "giant pancake," thirty feet long, and from which emerged about eleven small figures, who proceeded to dig with shovels and fill little bags with earth; they then clambered back in the UFO, which took off.

His son advised him to say nothing in case he was taken for a madman, which is why he stayed quiet until that November, when he told Hopkins. Hopkins told some other ufologists, and they began an investigation. Hopkins described these in an article in the Village Voice, which caused other witnesses to come forward, and Hopkins became aware of an odd aspect of many such cases—that those who experienced them often experienced amnesia about the event, and were aware simply of "missing time"—that minutes or hours might be missing from their lives (as in the case of the Hills).

Hopkins proceeded to investigate the case, and wrote a book about it called Missing Time (1981), which quickly brought him a huge correspondence, including many cases of "abduction." In one such case, described in Intruders,a woman named Kathie Davis told him how, at the age of 19, she had found herself pregnant, and assumed her boyfriend was responsible. The pregnancy then vanished, although there no signs of a miscarriage. Hopkins hypnotized her, and she recalled how she had first been abducted when she was nineteen, and "floated" by two small gray figures to a place where she was medically examined. During another abduction, she was allowed to see the child she had "lost," a pretty blonde girl.

Hopkins now concluded, from this and other cases, that female abductees were being artificially impregnated and the baby being removed prior to birth for the purpose of breeding experiments whose aim was to populate the earth with hybrids. (A Roper poll in 1991 seemed to indicate that hundreds of thousands of Americans believed they had been abducted.)

I had learned of the phenomenon of alien abduction in the autumn of 1994, at a "FortFest" in Washington DC, organized by Phyllis Benjamin. I attended a lecture by David Jacobs, a professor at Temple University in Philadelphia, called "Abduction and the Paranormal." My wife Joy and I had had lunch with Jacobs, and I had asked him: "What do you think this UFO thing is all about?" He then told me that he was at present writing a book on the subject, which he hoped would provide the explanation I was seeking.

This finally came out in 1998, and I hastened to buy it. The title was The Threat, and it expressed the conviction that the aim of the abductions was to slowly replace the human race with a race of hybrids—a combination of humans and aliens.

This was also the conclusion arrived at by Professor John Mack, a psychologist at Harvard, when in 1989 Budd Hopkins persuaded him to meet a number of people who had reason to believe they were abductees. Mack, whose first reaction was that such people must be crazy, was soon convinced that most of them were as normal as he was. The result was his book Abduction: Human Encounters with Aliens (1994). It almost cost him his job at Harvard, but fortunately sanity prevailed.

But it was not quite as alarming as it might have been. To begin with, John Mack had already raised the same speculation at the end of Abducted. There he says (p.399):

"My own impression, gained from what abductees have told me, is that consciousness expansion and personal transformation is a basic aspect of the abduction phenomenon. I have come to this conclusion from noting in case after case the extent to which the information communicated by alien beings to experiencers is fundamentally about the need for a change in human consciousness and our relationship to the earth and one another. Even the helplessness and loss or surrender of control which are, at least initially, forced upon the abductees by the aliens—one of the most traumatic aspects of the experiences—seem to be in some way 'designed' to bring about a kind of ego death from which spiritual growth and the expansion of consciousness may follow."

He goes on to admit:

"But my focus upon growth and transformation might reflect a bias of mine. The people who choose to come to see me may know of my interest in such aspects of human psychology, and may be aware that I consider my work with abductees to be a co-creative process. In some cases the commitment to environmental sustainability and human transformation antedated contact with me."

In other words, the fact that David Jacobs and John Mack can both be aware of the "threatening" implications of the "hybridization" program, but take opposing views of it, obviously offers us a choice. I must admit that I am inclined to accept Mack's stance.

In fact, the reason will become clear to any reader of Mack's second book Passport to the Cosmos (1999). He emphasizes that for many native peoples, like the Dagara of West Africa, the supernatural is a part of their everyday lives; and he quotes an American Sequoyah Indian, saying that his people are spirit, and live in a world of spirit and meaning, while whites live in a world of science and facts. The implication is that such a person as Credo Mutwa, spiritual leader of the sangomas of South Africa (to whom Mack devotes a chapter), naturally inhabits a realm between physical and spiritual and is not troubled by the dichotomy.

Mack will not have had a chance to test his own theories since he wrote these words. In September 2004 he was killed in a car accident in Totteridge, north London, when emerging from a tube station.

But it is worth noting that his views at the time of his death were coming closer to those of Jacques Vallee and John Keel, already cited in this article. I must admit that I have come to find it increasingly probable that the answer to the UFO mystery must be sought in the realm of the paranormal.