Once upon a time, in a land not far away, there was a horrible virus that instilled terror in every town and home. Although most people who became infected showed no symptoms or recovered within a week, in a small fraction of cases the illness progressed, causing loss of reflexes and muscle control, paralysis and, sometimes, death.

Children were especially vulnerable, so parents watched anxiously for any sign of infection, often keeping them away from swimming pools, movie theaters, bowling alleys, anywhere where there were crowds and the dreaded microbe might lurk. Travel and business were sometimes curtailed between places with outbreaks, and public health authorities imposed quarantines on healthy people who may have been exposed, in order to halt the spread of the disease. In the first half of the 1950s, with no cure and no vaccine, more than 200,000 Americans were disabled  by the poliovirus. The virus was second only to the atomic bomb as to what Americans feared most.

Then, on April 12, 1955, public health officials at the University of Michigan announced that a “safe, effective, and potent” vaccine had been found. This set off a national celebration that recalled the end of World War II. Church bells rang, car horns honked, people wept with relief. President Eisenhower invited the vaccine’s inventor, Jonas Salk, to the White House. In a Rose Garden ceremony, the former Supreme Allied Commander told the scientist in a trembling voice, “I should like to say to you that when I think of the countless thousands of American parents and grandparents who are hereafter to be spared the agonizing fears of the annual epidemic of poliomyelitis, when I think of all the agony that these people will be spared seeing their loved ones suffering in bed, I must say to you I have no words in which adequately to express the thanks of myself and all the people I know—all 164 million Americans, to say nothing of all the people in the world that will profit from your discovery.”

But, alas, not everyone joined the party and expressed such gratitude. One group in particular did not welcome the vaccine as a breakthrough. Chiropractors actively opposed the vaccination campaign that followed Salk’s triumph. Many practitioners dismissed the role of contagious pathogens and adhered to the founding principle of chiropractic that all disease originated in the spine. Just a few years after the introduction of the vaccine, as the number of polio cases was declining rapidly, an article in the Journal of the National Chiropractic Association asked, “Has the Test Tube Fight Against Polio Failed?” It recommended that, rather than take the vaccine, once stricken, “Chiropractic adjustments should be given of the entire spine during the first three days of polio.”

Opposition to the polio vaccine and to vaccination in general continued in the ranks such that even four decades later, long after polio had been eradicated from the United States, as many as one third of chiropractors still believed that there was no scientific proof that vaccination prevents any disease, including polio. That belief and resistance continues to this day, with some chiropractors campaigning against state vaccination mandates.

I was shocked when I first learned about chiropractors’ opposition to the polio vaccine. The vaccine is widely viewed as one of medicine’s greatest success stories: Why would anyone have opposed it? My shock turned into excitement, however, when I began to recognize the chiropractors’ pattern of arguments was uncannily similar to those I was familiar with from creationists who deny evolutionary science. And once I perceived those parallels, my excitement became an epiphany when I realized that the same general pattern of arguments—a denialist playbook—has been deployed to reject other scientific consensuses from the health effects of tobacco to the existence and causes of climate change. The same playbook is now being used to deny facts concerning the COVID-19 pandemic.

In brief, the six principal plays in the denialist playbook are:

  1. Doubt the Science
  2. Question Scientists’ Motives and Integrity
  3. Magnify Disagreements among Scientists and Cite Gadflies as Authorities
  4. Exaggerate Potential Harm
  5. Appeal to Personal Freedom
  6. Reject Whatever Would Repudiate A Key Philosophy

The purpose of the denialism playbook is to advance rhetorical arguments that give the appearance of legitimate debate when there is none. My purpose here is to penetrate that rhetorical fog, and to show that these are the predictable tactics of those clinging to an untenable position. If we hope to find any cure for (or vaccine against) science denialism, scientists, journalists and the public need to be able recognize, understand and anticipate these plays.

To illustrate how the playbook works—and sadly, it is very effective –I will break down the chiropractor and creationist versions, which have endured for many decades in spite of overwhelming evidence, and point out parallels to the coronavirus rhetoric.


1. Doubt the Science

The first tactic of denialism is to raise objections to scientific evidence or interpretations. This may take the form of seemingly legitimate specific arguments against a scientific claim. For example, chiropractors sought other explanations besides vaccine efficacy to account for the decline of infectious diseases: “The Center for Disease Control statistics make it clear that the majority of diseases that are now routinely vaccinated against were disappearing before either the cause was discovered or the vaccine developed,” stated a 1995 letter to the editor of Dynamic Chiropractic magazine. In polio’s case, this argument does not hold up against the facts that: (a) the disease was surging in the 1950s; (b) the vaccine was proven effective in a massive double-blind, placebo-controlled trial; and (c) infections declined precipitously after the introduction of the vaccine.

Alternatively, some statements are blanket arguments against an entire scientific discipline. For example, Henry Morris, whose 1961 book The Genesis Flood is credited with reviving the creationism movement, alleged: “Since there is no real scientific evidence that evolution is occurring at present or ever occurred in the past, it is reasonable to conclude that evolution is not a fact of science, as many claim. In fact, it is not even science at all, but an arbitrary system built upon faith in universal naturalism.”

2. Question Scientists’ Motives and Integrity

As a growing body of consistent evidence can be hard to explain away, one fallback is to impugn the source. In the vaccination arena, this often takes the form of alleging financial conflicts of interest on the part of scientists, greed on the part of manufacturers, and complicity of government officials. “It appears that the scientific foundation on which these vaccines have been erected is fragile enough that only compulsory laws, expensive public relations efforts, outrageous propaganda, and expensive advertising must ensue for compliance to be maintained,” wrote one author in American Chiropractor. Salk, by the way, filed no patent.

In the evolution arena, scientists are often accused of being part of a conspiracy to undermine religion through educational systems. Kenneth Cumming, of the Institute for Creation Research, objected to a PBS series on evolution by drawing a parallel to the 9/11 attackers: “America is being attacked from within through its public schools by a militant religious movement of philosophical naturalists (i.e., atheists) under the guise of secular Darwinism. Both desire to alter the life and thinking of our nation.” One noteworthy counter to such assertions is the Clergy Letter Project, which has gained the support of more than 15,000 Christian clergy for the teaching of evolution.

3. Magnify Disagreements among Scientists and Cite Gadflies as Authorities

In all scientific arenas, there is honest disagreement about the interpretation of evidence. However, these differences are deliberately inflated by denialists to imply a lack of consensus on more fundamental points, while often propounding the contradictory views of a few unqualified outliers. An example of the latter is how some chiropractors have seized on the anti-vaccination stance of one critic, Viera Scheibner. Her claim that there is no evidence for vaccine efficacy or safety is cited repeatedly, while overlooking the fact that her training and expertise is in geology, not medicine.

In the evolution arena, differences of interpretation among scientists are relished by antievolution voices. For example, the initial discovery of a new fossil hominid usually elicits some different interpretations and expressions of uncertainty in the scientific community. Creationists often mischaracterize these normal dynamics of scientific discourse as “skepticism” over the significance of such finds so as to discount them. By overblowing legitimate disagreements and propounding “alternatives” to evolution, denialists often make appeals to “teach the controversy,” when no such controversy exists in the scientific community. Different interpretations of a fossil do not negate the discomfiting evidence for the antiquity of human ancestors.

Antievolution leaders in the U.S. also include a small number of scholars whose credentials are in other disciplines. For example, the abovementioned Henry Morris was an engineer, not a biologist. Phillip E. Johnson, whose book Darwin on Trial inspired many adherents to the intelligent design movement, was a law professor with no formal training in biology.

A lack of credentials or status within the scientific community is often seen not as a liability but as a virtue. Scientists Pascal Diethelm and Martin McKee note, “Denialists are usually not deterred by the extreme isolation of their theories, but rather see it as the indication of their intellectual courage against the dominant orthodoxy and the accompanying political correctness, often comparing themselves to Galileo.”

4. Exaggerate Potential Harm

When the evidence contradicts a position, another recourse is to try to incite fear. No vaccine or medicine is 100 percent safe, without any risk of side effects. Chiropractors have long emphasized the potential side effects of vaccines, for example in a statement in Dynamic Chiropractic offering a litant of possible effects: “death, encephalopathy, demyelinating diseases, brachial neuritis, Guillain-Barré syndrome, infections generated by vaccine agents, anaphylaxis, subacute sclerosing panencephalitis, seizure disorder, optic neuritis, arthritis,” and so on. However, they generally fail to acknowledge the serious consequences of infections that would be prevented by vaccination.

 But what harm could arise from knowing a bit about evolution? Well, Hitler, of course! “Of the many factors that produced the Nazi Holocaust and World War II,” wrote one critic in the Journal of Creation, “one of the most important was Darwin’s notion that evolutionary progress occurs mainly as a result of the elimination of the weak in the struggle for survival.” It is an oft-repeated argument that has no bearing of course on the veracity of Darwin’s theory.

Vaccination foes have lobbed similar accusations, likening physicians who administer vaccines to Nazi doctors and alleging that vaccines violate the 1947 Nuremberg Code of medical ethics.

5. Appeal to Personal Freedom

If fear is not persuasive, there is another fallback position that resonates strongly with Americans: the freedom of choice. The American Chiropractic Association leaned on this cherished notion when it established its official vaccination policy:

“Since the scientific community acknowledges that the use of vaccines is not without risk, the American Chiropractic Association supports each individual’s right to freedom of choice in his/her own health care based on an informed awareness of the benefits and possible adverse effects of vaccination. The ACA is supportive of a conscience clause or waiver in compulsory vaccination laws… providing an elective course of action regarding vaccination.”

Likewise, the International Chiropractic Association “questions the wisdom of mass vaccination programs” and views compulsory programs as an infringement of “the individual’s right to freedom of choice.”

Similarly, the teaching of evolution in public schools is viewed as an assault upon the religious freedom of those who oppose it. Those holding this view advocate for disclaimers on textbooks (“just a theory”), the teaching of “alternative” views of the history of life (Genesis or intelligent design), or the freedom to opt out of the evolution curriculum of biology classes.

Notably, the U.S. Supreme Court has rejected challenges to compulsory vaccination partly on the grounds that individual belief cannot subordinate the safety of an entire community. And U.S. courts have repeatedly struck down attempts to subvert the teaching of evolution as religiously motivated and violations of the establishment clause of the First Amendment of the U.S. Constitution.

6. Reject Whatever Would Repudiate a Key Philosophy

Once the courts have spoken, and the scientific evidence grows to be overwhelming, one might think that denialists would be out of plays. But there is one last line of defense that reveals the nucleus of denial: It is not that some scientific claim is untrue; it is that it is unacceptable in light of some philosophical commitment. The science must be summarily rejected.

Chiropractic was founded in the early 20th century on the assertion that all disease has its origins in misalignments of the spine. “Chiropractors have found in every disease that is supposed to be contagious, a cause in the spine,” claimed Bartlett Joshua Palmer, the son of chiropractic founder Daniel David Palmer. Acceptance of germ theory and vaccination would repudiate the founding premise of the profession that all disease stems from vertebral misalignments. Therefore, that premise cannot be questioned.

With respect to evolution, Henry Morris made it plain: “When science and the Bible differ, science has obviously misinterpreted its data.”

Any credence granted to evolutionary science is a threat to a worldview based on interpretation of the Bible; David Cloud, a publisher of Bible study materials argues: “If the Bible does not mean what it says, there is no way to know what it does mean.

Historian of science and author Naomi Oreskes has coined a term for this stance: “implicatory denial”—the rejection of scientific findings because we don’t like their implications.

As these positions are reinforced by family or community, they harden into part of one’s identity. “In this way, cultural identity starts to override facts,” Norwegian climate psychologist Per Espen Stoknes has said. “And my identity trumps truth any day.”

Psychologists Elliot Aronson and Carol Tavris write in the Atlantic: “[W]hen people feel a strong connection to a political party, leader, ideology, or belief, they are more likely to let that allegiance do their thinking for them and distort or ignore the evidence that challenges those loyalties.”

The denialist playbook is now erupting around the coronavirus. Although COVID-19 is new, the reactions to public health measures, scientific claims, and expert advice are not. Attitudes and behaviors concerning the threat posed by the coronavirus (doubting the science), the efficacy of lockdowns and mask wearing (freedoms being eroded) and alternative treatments (gadflies over experts) are being driven as much or more by rhetoric than by evidence.

Polls indicate that despite the devastating health and economic impacts of the pandemic, with respect to a potential vaccine we are nowhere near as united as Americans were in 1955. But as epidemiologist Michael Osterholm noted in June, “Eventually there won't be any blue states or red states. There won't be any blue cities or red rural areas. It'll all be COVID colored.”

Now, sadly, there is no denying that.