April 2002
by Steven Novella, MD

Aristotle advanced a philosophy of vice and virtue which he termed the philosophy of the mean. He proposed that virtue is best viewed as a mean of moderation between two extreme vices. The virtue of frugality is a mean between the vices of excess and stinginess, for example. I have come to view healthy skepticism in the same way, as a delicate balance between the vice of gullibility at one extreme and dedicated denial at the other.

Skeptics often find themselves confronted with paranormal, pseudoscientific, or otherwise extraordinary claims, and careful examination often leads the skeptic to the conclusion that such claims are not likely to be true. This constitutes the preponderance of our experience as skeptics, and so we tend to view our position as being in opposition to that of the “true believers.” Occasionally, however, we are confronted with those who deny established scientific or historical facts. Such denial creates an interesting role-reversal where the skeptic is forced to defend a belief from systematic attack.

So-called deniers, such as those who deny that the Jewish holocaust of World War II ever occurred, believe themselves to be skeptics. On the other hand, true believers, such as UFO enthusiasts, will often portray those skeptical of their beliefs as being closed-minded deniers. A coherent and functional skeptical philosophy must accommodate both ends of this spectrum. In other words, it must not only provide a consistent guide to differentiate skepticism from gullibility at one end, it must also distinguish open-minded skepticism from closed-minded denial at the other end of this spectrum.

Looked at another way, the “philosophy of the mean” approach to skepticism means that skeptics are not always in the position of advocating a greater requirement of evidence and scientific rigor before accepting a belief. Rather, a good scientific skeptic should advocate an appropriate amount of evidence of sufficient quality before accepting a scientific claim as probably true. What is “appropriate” and “sufficient” is a judgment call, covers a fairly broad spectrum, and depends on such variables as the complexity of the subject matter and the plausibility of the specific claims. As standards become looser, one errs more towards acceptance a false claim rather than rejecting a true claim. Extremely loose standards eventually become abject gullibility. However, higher requirements for evidence err more towards rejecting what’s true rather than accepting what’s false. Higher requirements are not always more skeptical, as eventually requirements can become unreasonable to meet, even impossible, and this is the realm of denial.

At this point it is important to note that so far I have been referring to claims which operate within the paradigm of science. Beliefs can also reject the methods and philosophy of science itself, or apply them so poorly as to operate essentially outside the realm of legitimate science. Here there is no spectrum of gray, but rather an absolute form of anti-science.

The Demarcation Problem

Philosophers of science often speak of the demarcation problem, referring to the difficulty of distinguishing consistently between science and pseudoscience. I am proposing that there are two subsets to this demarcation problem, between appropriately skeptical science and true belief or gullibility at one end, and absolute denial at the other. Both extremes represent pseudoscience, in the former case the process of science is distorted to affirm a desired conclusion, and in the latter it is distorted in order to deny an undesired conclusion. At both ends healthy scientific skepticism blends imperceptibly into pseudoscience, with no sharp demarcation, hence the problem.

At both extremes, gullibility and denial, the core of pseudoscience is the same – namely that pseudoscientists begin with a desired conclusion, and then go through the superficial motions of science to arrive at their predetermined conclusion. Whereas with healthy science inquiry precedes belief or condemnation. For deniers, their dedication to the denial of the offensive belief supercedes fair-minded skepticism. While attempting to portray themselves as skeptics, they are forced to employ a series of pseudoscientific tactics and logical fallacies to maintain their denial.

With a fuzzy border between skepticism and denial, how do we tell the difference? Adding to the difficulty, individuals or groups may combine legitimate skeptical arguments with denial strategies. What is necessary is to identify specific strategies that represent denial and distinguish them from the strategies of good skepticism.
There are many examples of deniers we can use for this purpose. The two most prominent deniers faced by skeptics are those who deny the reality of the Jewish holocaust, and those who deny that evolution is an established scientific fact. Both holocaust deniers and evolution deniers have their own literature, filled with sophisticated arguments to support their denials.

I will focus on two other forms of denial as well, the first being HIV denial. There is now a camp of individuals who deny that the human immunodeficiency virus (HIV) is the cause of the acquired immunodeficiency syndrome (AIDS), despite a wealth of scientific evidence establishing the connection. The second is what I will term psychiatry denial, those who deny that the medical specialty of psychiatry has any scientific legitimacy. Among psychiatry skeptics there is a spectrum of beliefs from harsh but fair skepticism to vehement denial. When I refer to psychiatry denial heretofore in this article I will be referring to the hard-core deniers, which includes those who go so far as to deny the very concept of mental illness. I will refer briefly to other examples of denial, such as the persistent denial by the tobacco industry of the link between smoking and lung cancer.

I will also use UFO skepticism as an example of legitimate skepticism which is often unfairly characterized by true-believers as denial.

Characteristics and Tactics of the Deniers

Argument from Final Consequences

At the heart of all denial is a motivation to deny the specific claim or science, a motivation that has nothing to do with the truth. Often deniers give away their a priori bias against a claim by stating outright the logical fallacy known as the argument from final consequences. In other words, they state that the denied claim is not true because if it were adverse consequences would result.

For the classic denials this motivation, or hidden agenda, is obvious. Identifying underlying motivation is important to understanding the phenomenon of denial and the psychology of deniers. It is also a useful “red flag” to identify individuals who may not be the fair-minded skeptics they portray themselves to be. Although it is important to make clear that identifying a secondary motivation is not a substitute for substantive analysis. It is possible for someone to be correct for the wrong reasons. Also, it is easy to fall into the trap of searching for a secondary motive in order to dismiss skepticism out-of-hand as denial. In fact, UFO believers will often dismiss skeptics with the argument that they are afraid of the truth of UFO’s, or that they have a misguided desire to protect the status quo. Such arguments are specious to the point of being silly, but more importantly UFO skeptics do not cite the implications of the reality of UFO’s as a reason for their skepticism.

Regarding holocaust denial, the website of the Institute for Historical Review (IHR) reveals their motive: “Around the world awareness is growing that the ’Holocaust’ campaign is a major weapon in the Jewish-Zionist arsenal, that it is used to justify otherwise unjustifiable Israeli policies, and serves as a powerful tool for blackmailing enormous sums of money from Americans and Europeans.” (IHR 2001)

Many prominent evolution deniers also openly admit their underlying agenda. Although they will claim that the scientific evidence has led them to their conclusion that evolution is wrong, evolution denial remains mostly isolated to religious belief systems which maintain as an important tenet of their faith a divine creation. In addition is the conviction that belief in evolution will lead to the moral decay of our society. Evolutionists preach that man is just an animal, say the deniers, and therefore belief in evolution encourages a hedonistic immorality.

The HIV denial literature reflects a basic distrust of authority and the institutions of medicine. Perhaps it is just the fascination of uncovering a conspiracy, or the psychological secondary gain of being involved in a righteous crusade. The AIDSrealitycheck website, for example, proudly displays the header, “This website is not brought to you by any pharmaceutical company.” At least in some cases there is a more direct secondary gain to HIV denial. Dr. Mohammed Al-Bayati, founder of Toxi-Health International, proclaims that “HIV Does Not Cause AIDS.” (Al-Bayati, 1999) Rather, he claims, it is caused by toxins, which his clinic is uniquely qualified to diagnose and treat.

Many psychiatry deniers express a clear political agenda to their denial. Thomas Szasz (a prominent denier) for example, believes that psychiatry is being used as an instrument of political oppression, to silence those who are critical of the powers-that-be by labeling them as crazy. He writes, “If we recognize that ‘mental illness’ is a metaphor for disapproved thoughts, feelings, and behaviors, we are compelled to recognize as well that the primary function of Psychiatry is to control thought, mood, and behavior.” (Szasz 1998)

At the same time they warn that psychiatric explanations for behavior may be used as an excuse for criminal behavior, even to the point of allowing criminals to go free based upon an insanity defense. Whether or not this is true, they have chosen as the intellectual instrument of their political agenda the argument that there is no such thing as mental illness. Some have even taken this argument to the extreme of denying the biological basis of mood and cognition. Their mantra is “thoughts cannot be disease.”

Also counted among the psychiatry deniers are Scientologists. Part of the belief system of scientology is that mental illness is caused by engrams, which are the hidden memories of traumatic events. The goal of scientologists is to become “clear” of all engrams. Their philosophy stands in stark contrast to scientific psychiatry, and therefore they must deny it.

The lesson for skeptics is to be conscious of our own motives. It is easy to fall into the pattern of vehemently defending a position simply because we have adopted it as our own, such as the stance that we are probably not being visited by aliens. Once we have become “certain” of this conclusion it becomes easy to adopt more and more denial strategies, and lose sight of the fact that all conclusions in science are tentative and require an ongoing openness to change.

Selective use of Evidence

For any complex scientific idea or historical event there will be a large amount of relevant evidence to consider in any scientific assessment. With sufficient complexity, almost any desired conclusion can be supported if only a selective subset of the data is considered. Selective use of evidence allows for the presentation of pseudoscholarly articles and books which can seem very compelling.

Holocaust deniers, for example, have argued that the remains of certain alleged gas chambers have less cyanide residue than would a delousing chamber. This fact may seem compelling by itself, until one learns that lice require 100 times the amount of cyanide to kill than do humans.

Evolution deniers are also notorious for this tactic. They will typically focus on gaps in the fossil record, for example, while ignoring the many compelling connections established between species and higher taxonomic groups. They have also argued that the small brain size of supposed fossils of early hominids does not indicate that they are transitional from apes to humans, because some modern humans have similar brain sizes. They leave out the information, however, that it is not just brain size, but brain size relative to body size that counts. Modern humans with small brains have small bodies, and the ratio of brain to body size is the same as for larger-brained humans. Early hominids, however, had brain to body size ratio’s that are somewhere between that of modern apes and that of humans.

Those who deny the reality of mental illness have a vast medical literature to draw from, from which they select out those studies which show that a given medication is not effective for a certain mental illness, or those studies which show inconsistencies in our model of the pathogenesis of a psychiatric disease. In general, they do not fairly assess the entirety of psychiatric research, but focus single-mindedly on what we currently do not know and current inconsistencies in our understanding.

The HIV deniers behave similarly to the psychiatry deniers. For example, one pro-HIV denial article states that semen samples from HIV positive individuals often contain the same concentration of HIV as does saliva, and yet HIV is allegedly transmitted by semen and not by saliva. (Farber, 1992) This is only partly correct, however. The article leaves out the important fact that intercourse creates small abrasions that allow for the virus to get into the blood stream, whereas the virus cannot penetrate the oral mucosa. In fact, if someone had a cut in their mouth then they could acquire HIV through saliva. Also, the rate of transmission of HIV is much higher in individuals who have other sexually transmitted diseases because they often have open sores which allow easier access to the virus.

Do UFO skeptics take a similar approach to the evidence for the extraterrestrial hypothesis of UFO’s? I do not think so. The skeptical literature, in fact, includes a very thorough treatment of UFO claims. In fact, UFO skeptics often challenge believers to present their best case, or their most compelling evidence. Deniers, on the other hand, with often focus on weaknesses in the evidence without proper treatment or acknowledgment of the best evidence put forth by proponents.

Argument by Definition

If one wants to argue that object X does not belong to set A, one can always narrow the definition of set A in such a way as to specifically exclude object X. Evolution deniers, for example, attempt to argue that evolution is not just wrong, it is not even a science. However, they have arbitrarily formed their definition of science specifically to exclude evolution. They have narrowly defined science as the process of performing repeated experiments in a laboratory in order to test specific hypotheses. The Creation Science website, for example, pays lip service to “scientific principles” and describes for us the scientific method as: “1) State the question, 2) form a hypothesis, 3) do experiments, 4) interpret data and draw conclusions, 5) revise theory go back to step 2). (Creation Science, 1995) If something cannot be studied experimentally in a lab, by this narrow definition, then it isn’t science. It is only they, however, who have such a limited conception of science. Evolution deniers in this way have actually extended their denial to all historical sciences. We cannot know anything scientifically about the past, they argue, because no one was there to see it and because we can’t reproduce the past in a laboratory.

A more fair and complete definition of science is any discipline which empirically tests its ideas. Historical sciences test hypotheses by conducting field research or making observations of the current universe in order to infer the past. When astronomers view distant galaxies through a telescope, or paleontologists dig up fossils from the ground, they are looking for clues to the past in the remnants of the present. This is perfectly legitimate science which is capable of reaching conclusions with as much certitude as any laboratory discipline.

Psychiatry deniers use the similar strategy of preferring an arbitrarily narrow definition in order to exclude what is unwanted. In their case they have defined disease, illness, and even disorder in such a way as to exclude anything remotely psychiatric. Diseases, they argue, only include specific biological pathology in specific tissues. One denier writes, for example, “There is neither a blood test nor specific anatomic lesions for any major psychiatric disorder.” (Mosher 1998) Schizophrenia cannot be a disease, they argue, because you can’t show them the pathology. They selectively ignore, however, that patients with migraines, and many patients with mental retardation or epilepsy (to name three other brain diseases) also do not have demonstrable blood or anatomical pathology.

The brain is a unique and subtle organ. The manner in which neurons are connected, and the relative balance of neurotransmitters produces the normal cognitive and emotional function of the human mind. It therefore stands to reason that abnormalities of neuronal structure or neurotransmitter function can lead to abnormalities of cognition or emotional balance. Just looking at the brain under a microscope, however, will not show such abnormalities.

Moving Goalposts

Of all the characteristics of deniers this is often the most telling. The strategy is simple, always demand more evidence than can currently be provided, whatever that is. If that evidence is available at a later date, then just change the demand to even more evidence (for those readers who are not football fans – they move back the goalpost out of range of the kick). This pattern clearly demonstrates that no amount of evidence will ever satisfy a true denier. A skeptic, on the other hand, should make a reasonable demand for evidence, fitting the nature of the claim, and then stick to that criteria.

Closely related to the moving goalpost, is the goalpost which is set from the beginning out of possible range – by making an unreasonable demand for evidence. When it is argued, therefore, that a given claim lacks a specific type of evidence, it is helpful to ask the question of whether or not it is reasonable to expect that type of evidence.

Evolution deniers have the longest and richest history of “moving goalpost” syndrome, due to the extraordinary advance of evolutionary science in the past century. At the time Darwin first published Origin of the Species in 1864 the fossil record was very sparse. Early critics argued that if evolution were true there should be fossils of transitional species – species which demonstrate a morphology which appears to be part way between two known species, thereby establishing an evolutionary link.

Well, since that time thousands of such transitional fossils have been discovered. Each time the evolution deniers cry, well that’s not transitional enough or why aren’t there millions of transitional fossils. Show me a half-way whale, they challenged. Paleontologists dug up Ambulocetus in the 1980’s, a whale with short stubby legs, clearly demonstrating its terrestrial origins. That was no longer enough. Now they demand evidence that Ambulocetus in fact evolved into modern whales (an impossible standard) and mere transitional status is not enough. They decried the lack of connections between major groups, such as birds and other vertibrates. Then Archaeopteryx was discovered, a beautifully transitional species between birds and therapod dinosaurs. Yes, they countered, but its feathers are fully modern, therefore it is just another bird. Recently species of bird ancestors have been found with primitive feathers, and most recently a species with half-scales, half-feathers. Evolution deniers are sure to nudge the goalpost back further.

Holocaust deniers have also extensively used this strategy. Despite the copious amount of evidence documenting the deliberate Nazi policy of extermination for European Jews during World War II, no amount of such evidence is enough. They have moved the goalpost back to a position which is known to be out of range – they demand a document with Hitler’s signature ordering all European Jews to be killed. No such document is believed to exist. Documentation of the Wansee Conference, outlining the logistics of the death camps, is not enough. Reports of daily totals of Jews killed at various camps is not enough. Hitler’s speeches where he speaks of the “ausrotten” (pulling out by the roots) of the Jews from Europe is not enough. Nothing can be enough except the one piece of evidence they know not to exist.
Another common representation of the unreasonably far goalpost is the frequent demand by prominent holocaust deniers to be shown “one piece of evidence” which proves the holocaust happened. No one piece of evidence can establish such a complex historical event. Just as no one piece of evidence can establish that organic evolution happened on this planet. Not even the rather straight forward claim that HIV causes AIDS can be established by a single piece of evidence, it must be the result of a chain of evidence.
The HIV deniers have taken a similar stance. The correlation between the HIV virus and AIDS has been established beyond all reasonable doubt. Much is known about how HIV works, and drugs which specifically target retroviruses (the type of virus HIV is) have successfully prolonged survival and decreased opportunistic infections in HIV positive individuals. Yet this is not enough for the HIV deniers. They attack the pieces of the puzzle we don’t yet know, or which can only be inferred but have not yet been definitively proven. Why haven’t we seen the virus actually killing T-cells (the cells of the immune system targeted by HIV)?

Anti-HIV crusader, Dr. Peter Duesberg, has argued that HIV “fails to meet the postulates of Koch and Henle,” (Duesberg 1988) which were designed to establish criteria for demonstrating the link between an infectious agent and a disease. However, the Koch and Henle postulates were developed in 1840 and 1890 respectively, before viruses were even discovered. Biology has evolved far beyond Koch and Henle, whose postulates are no longer definitive.

They have also employed the “show me one piece of evidence” strategy. In fact, one HIV denier is offering a $10,000 prize (sound familiar) for anyone who can reference one article which demonstrates all the key elements necessary to establish HIV as the cause of AIDS. Typically, however, the research necessary to demonstrate such a connection would be spread out over many articles. The request is unfair and is made solely for its dramatic effect.

As stated before, the psychiatry deniers have also set their goalpost out of reasonable reach. They demand classic pathological changes in brain tissue directly correlating to specific psychiatry syndromes. However, our current models of brain function do not require such pathology in order to provide a mechanism for mental illness.

In the past decade we have developed new techniques for imaging the pattern and degree of connections in various parts of the brain, and we are beginning to see that many mental illnesses, like schizophrenia, do indeed show patterns of activity which differ from control subjects without schizophrenia. Deniers counter that the link is statistical only—not every schizophrenic has the same changes. They have moved the goalpost back, ignoring the fact that virtually all of medicine is statistically based, given the very complex and broad variability among its subject matter, the human species.

UFO believers have argued that skeptics also will never be satisfied by the evidence, and that we have set the impossible standard of the “smoking gun” as the only acceptable proof of aliens visiting the Earth. Some believers have specifically advocated logical inference, rather than direct evidence, as an acceptable scientific method of demonstrating the extraterrestrial hypothesis.

UFO skeptics have certainly been critical of the lack of any smoking gun evidence, legitimately so. But there is a risk here for slipping into denial by refusing to accept the inference of the existence of aliens without direct proof. Inference is a perfectly legitimate scientific method. Rather, I think that skeptics should directly address the inference argument. When this is done I believe it can be demonstrated that the evidence does not support the alien inference, but rather infers that the UFO phenomenon is due to a host of psychological and cultural factors.

UFO skeptics have also not retreated from better and better evidence, as evolution, holocaust, HIV, and psychiatry deniers have. If one looks at the claims of UFO believers from 30 years ago, for example, the quality and type of evidence is remarkably similar to what is present now. There has been a dramatic lack of improvement in the evidentiary basis of UFO claims. The goalpost remains fixed in place.

Confusing Internal Debate over Details with Negation of the Whole

As stated above, all the topics we are considering are complex phenomena or events. The deniers have no difficulty sifting through the copious amounts of published debate on their chosen topic and finding parts of the theory which have been altered or discarded, or which continue to be debated. They then deliberately confuse debate over such details as evidence that the entire theory is in jeopardy.

HIV deniers, for example, will point to literature which questions whether or not HIV is the sole cause of AIDS. There is legitimate debate over whether or not HIV requires a cofactor or another agent to be infectious, or perhaps which just renders it more infectious, or causes AIDS to progress more rapidly. They then present such debate as questioning that HIV has any role in the cause of AIDS.

Evolution deniers will also often quote evolutionary biologists out of context to make it seem as if they are denying evolution. For example, Stephen J. Gould, an evolutionary biologist and avid public defender of evolution, is also one of the architects of the theory of punctuated equilibrium. This theory of evolution states that species remain largely stable during the majority of their life on Earth (equilibrium), and then undergo relatively rapid speciation events (punctuation). The classic model of evolution, referred to as strict Darwinism, is that species are constantly undergoing slow change. Gould, therefore, will often make statements to the effect that Darwinism does not fit the evidence, in the context, of course, that it better fits punctuated equilibrium. Creationist literature, however, will then deliberately misrepresent such internal debate about tempo and pace of evolution as doubt that evolution occurred at all.

Holocaust deniers have also had an easy time pursuing this strategy, mainly because there are several prominent myths concerning the Jewish Holocaust. For example, it continues to be widely believed that the remains of some holocaust victims were used by the Nazis to manufacture products such as soap. This is not true, and is not a belief which is advocated by holocaust historians. Holocaust deniers, however, enjoy publicly dispelling such myths and then arguing that the holocaust itself is a myth and did not happen.

There is also a certain amount of legitimate historical debate concerning the exact number of European Jews who were killed in the holocaust. The 6 million figure is acknowledged to be an estimate – a representative figure. When legitimate historians disagree with this figure, arguing that perhaps it was only five or four million, their statements are then misconstrued by deniers to suggest that perhaps the real number is zero.

Psychiatry deniers also have a complex and only imperfectly understood realm in which to work. They like to point out that no one has been able to demonstrate one cause for schizophrenia which is consistent among all, or even most, people with this diagnosis. Several biological markers for schizophrenia have been discovered, such as differences in brain activity as measured by positron emission tomography (PET) scanning. However, only about 40% of patients with schizophrenia display such abnormal patterns. The same is true for various other biochemical markers. The deniers quote scientists who state that these tests are not reliable for diagnosis, and only correlate to a small subgroup of all schizophrenics, as if they are calling into question the existence of schizophrenia.

These same scientists, however, are not arguing that schizophrenia (let alone all mental illness) does not exist. The emerging consensus is quite different, that schizophrenia is in fact a group of diseases rather than just one disease. There may be several distinct neurological disorders each of which result in the same clinical picture (the same signs and symptoms) of schizophrenia. Therefore, the various tests are only picking up a subset of patients with schizophrenia who have that one particular cause.

Correlation is not Causation

Insufficiently skeptical believers will often commit the logical error of assuming that a correlation between variables equals a specific causal relationship between them (post hoc ergo propter hoc logical fallacy). The problem with this logic is not that correlation does not sometimes result from causation, but it is the simplistic assumption of causation without independent evidence, or a thorough analysis of all possible patterns of causation. It is equally invalid to simplistically dismiss correlation.

The best manner in which to logically approach an apparent correlation is as follows: if A is observed to correlate with B, then it must be considered that A causes B, B causes A, or another variable, C, causes both A and B. It must also be considered that A and B do not correlate and the observation is either in error or is simply a statistical anomaly. Plausibility and independent evidence can then be used to infer which causal relationship between A and B is most likely.

Deniers, however, often commit the fallacy of simplistically dismissing the correlation prior to a thorough analysis on the basis that “correlation does not equal causation.” The most notorious violators of this logical fallacy in this fashion is the tobacco industry, who continues to assure the public that their products are safe, and that the correlation between smoking and cancer does not in and of itself prove a causation. Perhaps, they argue, a mysterious factor X causes both smoking and cancer. It is true that the epidemiological evidence shows a correlation only.

The problem is, it is completely unethical to force a randomized cohort of patients to smoke in order to see if their risk of cancer is increased. We must rely upon correlation to infer a cause. Multiple correlations are used to increase the reliability of this inference: the longer people smoke the greater their risk of cancer, if they inhale or smoke unfiltered cigarettes their risk is increased, and if they quit their risk returns eventually to that of the non-smoking population. The hypothesis of a cause between smoking and cancer has been tested by looking for other correlations that should logically exist if smoking causes cancer, and such correlations exist. Therefore we can confidently infer that smoking causes cancer, even if it has not been directly proven.

HIV deniers use the same strategy. The presence of HIV in the blood strongly correlates with the acquired immune deficiency syndrome (AIDS), but deniers charge that this correlation does not prove causation. OK, so let’s look for other correlations that should exist. If the titer of HIV is reduced with drugs specifically designed to inhibit the replication of retroviruses, patients have fewer opportunistic infections and survive longer. HIV has been seen to infect lymphocytes, the cells in the immune system which are deficient in AIDS.

At present the psychiatry literature is filled with studies that show that specific clinical syndromes statistically correlate with differences in the pattern of brain function as seen on PET or functional MRI scanning. This wealth of evidence is dismissed at a stroke by psychiatry deniers with the simple statement that such correlations do not prove causation. Again, true, but the analysis cannot stop there. The parts of the brain which appear to be different are the ones we would predict based upon what we know of brain function. Legitimate questions about the role of medications in causing the observed changes have been addressed with more recent research, which shows that the correlation holds up even in unmedicated patients. No other plausible alternative explanation has been put forward to explain the observed correlations.

This strategy is also a favorite of evolution deniers. Most of the evidence for evolution ultimately rests on intelligent inference of the cause of observed correlations. Species morphologically correlate with each other in a pattern consistent with branching descent, genetic patterns correlate very well with what we would expect from morphological patterns, fossils correlate with an evolutionary temporal sequence, etc. Every correlation we expect to find is consistent with what we would predict from evolutionary theory. And all of this evidence can be denied if one rejects inference from correlation as a legitimate scientific method, and evolution deniers do.

Emerging Skepticism

A universal element in the denial literature is the claim that scientists or historians are increasingly coming over to the denier’s point of view. The rhetorical strategy is clear. Since deniers are typically denying an established belief they must contend with the fact that they appear to be cranks on the fringe. They are aware that the public must be asking themselves why the establishment still believes something which these people (the deniers) are saying is so obviously wrong. They have various strategies for dealing with this.

The first such strategy is to argue that scientists or historians working in the relevant field are just grossly misinformed. They are the victims of a conspiracy of silence and misinformation. Alternatively, they may be the agents of silence and misinformation – part of a grand conspiracy. These arguments, however, simply beg the question of why so many well trained and presumably intelligent scientists can be so ignorant and easily duped within their own field of specialty, when a group of amateurs can so easily see the truth.

A more subtle and more effective strategy is to suggest that scientists in the relevant field of study are increasingly being won over to the denier’s point of view. The undesirable belief is teetering on the brink of widespread dismissal by the scientific community, pushed there by the weight of new evidence. Evolution deniers have been using this strategy for years, and are fond of misquoting evolutionary biologists to suggest that any day now evolution will be exposed as the fraud they claim it to be. Creationist book, Evolution: A Theory in Crisis (Denton 1985), represents one such attempt. In reality evolutionary theory is a vibrant and growing scientific idea that enjoys continued almost universal support among scientists.

The HIV denial literature is also replete with similar claims of emerging skepticism. For example, Celia Farber wrote in a pro-HIV denial article, “More and more scientists are beginning to question the hypothesis that HIV single-handedly creates the chaos in the immune system that leads to AIDS.” (Farber, 1992) The article was published in 1992, and ten years later there remains a solid scientific consensus that HIV causes AIDS.

As part of this strategy deniers tend to rally around a figure head, a scientist insider who spearheads the denial movement. HIV deniers have virologist Dr. Peter Duesberg as their champion. The psychiatry deniers are lead by psychiatrist Thomas Szasz, who has been crusading against perceived abuses of psychiatry for the last thirty years. Szasz, now over 80, continues to write and lecture about the evils of modern psychiatry. However, his portrayal of psychiatry is about 30 years out of date. Many of his legitimate complaints have been dealt with through institutional and legal changes in the past few decades, such as the right of every patient to refuse treatment. His criticisms, however, go far beyond patient rights to denying the concept of mental illness. Szasz also established the basic political view of the psychiatry deniers that mental illness is being used as a political tool to silence dissidents.

Holocaust deniers also have their leader in the guise of academic historian David Irving. Irving recently lost a court case against Deborah Lipstadt, whom he was suing for what he claimed was slander for characterizing him as a denier. Lipstadt won the suit, meeting the burden of proof (in a British court) that Irving is indeed a denier.

Evolution deniers have had a series of champions for their cause, going back to William Jennings Bryan and the Scopes trial. Today, they have turned to a small group of academics, including Michael Behe and Philip Johnson, who are trying to gain acceptance for what they call Intelligent Design theory (ID). ID is nothing more than the same denial arguments that have been put forward for the past 150 years, but they have been somewhat successful in putting an academic face on evolution denial.

Debating the Deniers

Over the years I have had many opportunities to engage in debate with various deniers, mostly evolution deniers and psychiatry deniers. I have found the experience very enlightening, for I was placed in the position of defending the legitimacy of a scientific discipline from accusations of pseudoscience. The most sophisticated of my opponents utilized many of the arguments and tactics of skeptics, including accusations of logical fallacies, having belief which exceeds the evidence, and being a motivated true-believer. At times I even found myself using arguments that were strangely reminiscent of true believers I have debated on other topics. I have had to defend the legitimacy of logical inference, for example, even when direct evidence is lacking, or explain why direct evidence is currently lacking and difficult to obtain. “Evolution is too slow for fossils to capture one species in the act of evolving into another,” I have explained to evolution deniers. “How convenient,” they have responded. “There’s always an excuse.”

Experience with deniers has at times brought me face-to-face with what is potentially the ugly side of skepticism – smugness, arrogance, and sarcastic belittlement. It has enabled me to see more clearly why skeptics can sometimes evoke such anger and hatred in those who are the target of our skepticism. I hope it has also enabled me to better avoid those comments which are likely to evoke feelings of anger. What is most important, I have found, is to scrupulously avoid any ad hominen commentary, and to remain rigorously focused on arguments of logic and evidence alone.

Conclusion

In the final analysis there is no single or simple way to distinguish genuine skepticism from dedicated denial, just as there is no simple way to distinguish science from pseudoscience. A detailed and thorough analysis of the evidence and arguments on both sides of an issue is required to separate the deniers from the skeptics. The characteristics outlined above, however, should be helpful in making this determination.

They are also a useful guide to help skeptics avoid slipping from skepticism to denial. We must as skeptics remain dedicated to the methods of skeptical inquiry, and remain vigilant against adopting the current conclusions of skeptics as a belief unto themselves, to be defended at all costs. If the Earth is indeed being visited by aliens, or one day is, then evidence will likely surface that should convince an open-minded skeptic of this reality.

By helping us to avoid the tactics and demeanor of denial, understanding the deniers has the potential to make us better skeptics.

References

Institute for Historical Review, www.ihr.org, 11/2001
Mohammed A. Al-Bayati, Toxi-Health International, www.toxi-health.com, 4/2002
Thomas Szasz, Cybercenter for Liberty and Responsibility, www.szasz.com/manifesto.html, 1998
Celia Farber, Fatal Distraction, Spin June 1992
Creation Science Website, www.emporium.turnpike.net, September, 1995
Loren Mosher, MD, letter to the APA dated December 4, 1998.
Peter Duesberg, HIV is not the cause of AIDS, Science, Vol. 241, pp 514-517, July 29, 1988.
Michael Denton, Evolution: A Theory in Crisis, Adler & Adler, Bethesda Maryland, 1985

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