The Search for Negative Evidence

Joe Nickell and James McGaha

Everyone loves a mystery. Solve one in science, and accolades are forthcoming. Not so, however, in the realm of the paranormal, where evidence, logic, and theories are often stood on their heads. Whereas forensic scientists, say, begin with the evidence and let it lead to the most likely solution to a mystery, “parascientists” typically begin with the desired answer and work backward to the evidence, employing confirmation bias: They look for that which seems to confirm their prior-held belief and seek to discredit whatever—or whoever—would argue against it.

For example, in the paranormal field of cryptozoology (a term coined by Ivan T. Sanderson to describe the study of “hidden” or unverified animals [Heuvelmans 1968, 508]), proponents of Bigfoot offer a large quantity of evidence. Unfortunately, it is of very poor quality: eyewitness reports, footprint casts, hair samples—just what is attributable to misperception or deception. It is all questionable evidence because, hoaxes aside, neither a live Bigfoot nor a carcass nor even a DNA specimen is available for scientific study.

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The same situation holds true for other claims. They include psychic phenomena; ghosts, poltergeists, and demons; flying saucers and aliens; cryptids, such as the Loch Ness monster; spontaneous human combustion; faith healing and weeping statues; the Devil’s Triangle; and so on and on. Mainstream science has not verified as genuinely paranormal any of these objects, entities, or occurrences.

Arguing from Mysteries

Parascientists usually take a different tack. For them, investigation is not a quest to explain a mystery (what they deride as “trying to explain it away”) but rather to collect mysteries about whatever paranormalities they believe in, by which they hope to convince others there must be “something to it.” In short, they are not detectives but mystery mongers.

For them, the mystery is essentially an end point rather than a beginning. If it is not readily explained, they do not blame a lack of evidence; instead they suppose thereby that something has been established: “We don’t know what caused oil to appear on the statue; therefore, it must be a sign from God.” But this is a type of logical fallacy known as argumentum ad ignorantiam, an argument from ignorance—that is, drawing a conclusion from a lack of knowledge. One cannot say “We don’t know” and then assert that therefore we do know.

And yet that very faulty reasoning is behind most paranormal claims: “We can’t explain what caused a; therefore, it’s likely b,” where a is a hairy-monster sighting or hovering light or an unexpected medical cure, and b is presumed to be, respectively, a Bigfoot, or flying saucer, or miracle. Actually it might instead be, again respectively, an upright-standing bear, Venus seen through layers of atmosphere, or the result of prior medical treatment.

Negative Evidence

As psychologist Ray Hyman (1996, 23) observed of one paranormal field: “The history of parapsychology is replete with ‘successful’ experiments that subsequently could not be replicated.” Pointing out that so-called remote viewing and other supposed forms of ESP were defined negatively—that is, as an effect remaining after other normal explanations had supposedly been eliminated—Hyman noted that a mere glitch in the experimental data could thus be counted as evidence for psychic phenomena. “What is needed, of course,” he said wisely, “is a positive theory of psychic functioning that enables us to tell when psi is present and when it is absent” (emphasis in original). He added, “As far as I can tell, every other discipline that claims to be a science deals with phenomena whose presence or absence can clearly be decided.”

This requirement—this need—for positive rather than negative evidence is ignored or dismissed by the mystery mongers. In the titles of their books and TV documentaries, they trot out such words as unsolved, unexplained, unknown—presenting not mysteries to be investigated and solved but supposedly eternal enigmas that prove (by arguing from ignorance) the existence of the paranormal.

Consider, for example, the claims of miraculous healings at Lourdes, the French healing shrine. Claims there are derived not positively but from those cases that are held to be “medically inexplicable”—a classic argument from ignorance. (In 2008, however, the International Medical Committee of Lourdes announced that the physicians’ panel would no longer be in the “miracle” business, thereafter only indicating whether a case is “remarkable.” They will not be inferring a miracle from “medically inexplicable” [Nickell 2013, 183–185].)

Elsewhere, in “miracle” and other paranormal claims, the appeal to negative evidence remains all too common. For example:

  • Grant Wilson, who partnered with Jason Hawes in TV’s Ghost Hunters, says their approach to ghost hunting was to “end up with only those things you can’t explain away” (Hawes and Wilson 2007, 6).
  • Larry Arnold (1995, 463), in his book Ablaze! The Mysterious Fires of Spontaneous Human Combustion, states unabashedly: “I am the first to admit that SHC [spontaneous human combustion] defies common sense and smacks of the unknowable. I don’t have all the answers to it; I may have none of the answers. And certainly, I don’t have all the pieces to this jigsaw of enigmas.” Nevertheless, he concludes, “What I can say with confidence is this: Spontaneous (as well as preternatural) human combustibility happens, though it has remained hidden.”
  • Crop circle advocates have suggested various “theories” to explain the supposedly inexplicable patterns in English grain fields (despite extensive evidence of hoaxing [Nickell 2004, 115–122]). Ken Rogers of the Unexplained Society opines, “The circles are indeed the result of a UFO landing to probe the crops. There is no other explanation . . .” (qtd. in Randles and Fuller 1990, 16).

Unidentified Flying Objects

Perhaps nowhere is negative evidence sought and promoted more avidly than by UFOlogists, whose very subject of study begins with the word unidentified. Prominent among such collectors was Charles Fort (1874–1932). Sometimes considered the “first” UFOlogist (Clark 1998, I: 420), Fort was an armchair purveyor of strange mysteries. Having come into an inheritance that allowed him to indulge his hobby, he spent his last twenty-six years scouring old periodicals for reports of unusual occurrences—including anomalous aerial phenomena—that he taunted “orthodox” scientists to explain (Fort 1941). Not only was his evidence anecdotal and his approach non-investigative, but his “documentation was not always completely accurate” (Gross 2001, 204).

Nevertheless, Fort is the darling of many UFOlogists and other collectors of phenomena that supposedly “defy natural explanation,” what they term “Fortean phenomena” or “Forteana,” named after him (Guiley 2001, 212–213; Gross 2001, 203–205; Clark 1998, 420–425).

One of history’s top UFOlogists was astronomer J. Allen Hynek (1910–1986), once a consultant and self-claimed “debunker” on the U.S. Air Force’s UFO-investigating Project Blue Book. Hynek (1977, 7–9, 17) became impressed that, at first, 23 percent of UFOs he studied remained “unknowns” and—going on to found the Center for UFO Studies (CUFOS)—he embraced the negative evidence:

The transformation from skeptic to—no, not believer because that has certain “theological” connotations—a scientist who felt he was on the track of an interesting phenomenon was gradual, but by the late ’60’s it was complete. Today I would not spend one additional moment on the subject of UFOs if I didn’t seriously feel that the UFO phenomenon is real and that efforts to investigate and understand it, and eventually to solve it, could have a profound effect—perhaps even be the springboard to a revolution in man’s view of himself and his place in the universe.

Hynek nevertheless grew cautious about the extraterrestrial hypothesis, noting that it “runs up against a very big difficulty, namely, that we are seeing too many UFOs. The earth is only a spot of dust in the Universe. Why should it be honored with so many visits?” Instead, he said, “I am more inclined to think in terms of something metaterrestrial, a sort of parallel reality,” positing “that UFOs are related to certain psychic phenomena” (qtd. in Story 2001, 252). Thus he tried to “explain” one unknown by invoking another!

Today, UFOlogists such as Peter B. Davenport, director of the National UFO Reporting Center (NUFORC), believe that the great number of unidentifieds indicate at least something momentous is behind them. Given “impressive quantities of principally eyewitness data,” says Davenport, while most eyewitness descriptions are of poor quality, “many of the high-quality sighting reports involve certain objective aspects, which, to an open-minded bystander, are quite impressive.” He adds, “Strong evidence suggests that we are dealing with a phenomenon that is being caused by palpable solid objects whose characteristics are not of human design, and whose behavior is suggestive of intelligent control” (qtd. in Story 2001, 150). He is, of course, hinting at extraterrestrials—albeit coyly—while the “objects” remain unidentified.

Another who cites the unexplained nature of UFOs is Richard Hall, a UFO advocate associated with such groups as MUFON and CUFOS. He emphasizes, “Among the hundreds of so-called ‘UFO reports’ each year, a sizeable fraction of those clearly observed by reputable witnesses remain unexplained—and difficult to explain in conventional terms.” He believes that “Collectively, these cases constitute a genuine scientific mystery, badly in need of well-supported, systematic investigation.” Again he says, “The circumstantial—and sometimes physical—evidence indicates that something real is going on for which no satisfactory explanation currently exists.”

Hall believes that mistaken observations of terrestrial objects as well as “hoaxes/imagination” are to be rejected as explanations because both are “inapplicable to the hard-core unexplained cases.” He prefers instead the possibility of “so-called ‘nuts and bolts’ visitors from elsewhere” (qtd. in Story 2001, 239).

Even vacillating UFOlogist/folklorist Thomas E. Bullard (2010, 311) suggests—at least tentatively:

Investigators of current and historical UFO reports have sifted out cases with sufficient credible evidence to qualify as defensible. These cases suggest that the character of UFO narratives depends in some part on the character of UFO events, and those events owe their character to a source independent of UFO mythology. . . . Even allowing for human fallibility and self-deception, a genuine mystery seems to be left over.

Bullard is clearly relying on the process-of-elimination method that is the basis of negative evidence.

Then there is Stanton T. Friedman, who promotes the notion of extraterrestrial visitation with bluster, smoke screens, and ballyhoo. He rationalizes, “I learned early on that absence of evidence is not the same as evidence for absence.” True enough, but then he is still left with absence of evidence. Friedman, a onetime self-described “itinerant nuclear physicist” was fooled by the amateurishly forged “MJ-12 documents” that purported to prove the U.S. government had retrieved a crashed saucer and its humanoid occupants—proof, Friedman believes, that positive evidence has been covered up by a high-level conspiracy (Friedman 1996, 8, 13, 209–219; Nickell with Fischer 1992, 81–105).


The problem with all such grandiose extrapolation from the data is that it lacks positive evidence. No actual flying saucer or extraterrestrial pilot has ever been captured—notwithstanding hoaxes, folktales, and conspiracy claims. There are only eyewitness reports, photos, ground traces, and the like—all of something unidentified.

But don’t all those unidentifieds count for something? Well, quantity is not quality. As extensive evidence shows, cases once touted as unexplained were only that; they were not unexplainable, and, as a matter of fact, many of them have since succumbed to investigation. Not one proved to be anything other than a natural or manmade phenomenon—not such classic cases, for example, as Roswell, Rendlesham Forest, Flatwoods, Kecksburg, Exeter, Phoenix, and Stephenville (Nickell and McGaha 2012; McGaha and Nickell 2011, 2015). Some cases may never be explained because of original eyewitness error, falsified evidence, lack of essential information, or other flaws. For similar reasons some murders remain unsolved, yet we do not consider those cases evidence of a homicide gremlin.

Nothing said so far means we should not continue to investigate unexplained phenomena, including UFOs. After all, onetime skepticism of fiery stones falling from the skies ultimately gave way to proof of meteorites. Science has nothing to fear from the examination of UFO reports, which, to date, have not been useless after all: We have learned much about illusions and misperceptions and fantasy, about personality traits, about rare phenomena such as ball lightning, about the propensity of immature persons to perpetrate hoaxes (skeptics included!), and much more. But investigation must go beyond just collecting negative evidence. It must represent a real attempt to solve—that is, to explain—a mystery.



  • Arnold, Larry E. 1995. Ablaze! The Mysterious Fires of Spontaneous Human Combustion. New York: M. Evans and Co.
  • Bullard, Thomas E. 2010. The Myth and Mystery of UFOs. Lawrence: The University Press of Kansas.
  • Clark, Jerome. 1998. The UFO Encyclopedia, 2nd ed. (in two volumes). Detroit, MI: Omnigraphics.
  • Fort, Charles. 1941. The Complete Books of Charles Fort. Reprinted New York: Dover, 1974.
Friedman, Stanton T. 1996. Top Secret/Magic. New York: Marlowe & Co.
  • Gross, Loren E. 2001. In Story 2001, 203–205.
  • Guiley, Rosemary Ellen. 2001. Encyclopedia of the Strange, Mystical, & Unexplained. New York: Grammercy Books.
  • Hawes, Jason, and Grant Wilson. 2007. Ghost Hunting. New York: Pocket Books.
  • Heuvelmans, Bernard. 1968. In the Wake of the Sea Serpents; trans. Richard Garnett. New York: Hill and Wang.
  • Hyman, Ray. 1996. Evaluation of the military’s twenty-year program on psychic spying. Skeptical Inquirer 20(2)(March/April): 21–26.
  • Hynek, J. Allen. 1977. The UFO Report. Reprinted New York: Barnes & Noble, 1997.
  • McGaha, James, and Joe Nickell. 2011. Exeter incident solved! Skeptical Inquirer 34(6)(November/December): 16–19.
  • ———. 2015. Alien lights? At Phoenix, Stephenville, elsewhere: A postmortem. Skeptical Inquirer 39(2)(March/April): 50–53.
Nickell, Joe. 2004. The Mystery Chronicles. Lexington: University Press of Kentucky.
  • ———. 2013. The Science of Miracles. Amherst, New York: Prometheus Books.
  • Nickell, Joe, with John F. Fischer. 1992. Mysterious Realms: Probing Paranormal, Historical, and Forensic Enigmas. Lexington: University Press of Kentucky.
  • Nickell, Joe, and James McGaha. 2012. The Roswellian syndrome. Skeptical Inquirer 36(3)(May/June): 30–36.
  • Randles, Jenny, and Paul Fuller. 1990. Crop Circles: A Mystery Solved. London: Robert Hale.
Story, Ronald. 2001. The Encyclopedia of Extraterrestrial Encounters. New York: New American Library.

Joe Nickell and James McGaha

Joe Nickell, Ph.D., is Senior Research Fellow of the Committee for Skeptical Inquiry (CSI) and “Investigative Files” Columnist for Skeptical Inquirer. A former stage magician, private investigator, and teacher, he is author of numerous books, including Inquest on the Shroud of Turin (1998), Pen, Ink and Evidence (2003), Unsolved History (2005) and Adventures in Paranormal Investigation (2007). He has appeared in many television documentaries and has been profiled in The New Yorker and on NBC’s Today Show. His personal website is at

Astronomer James McGaha is director of the Grasslands Observatory, Tucson, Arizona. He is a pilot and retired U.S. Air Force major, a longtime evaluator of UFO reports and claims, and a scientific consultant to the Committee for Skeptical Inquiry.