The second broad category of quackery we will consider is 'Denialism / Pseudoskepticism'.
Denialists categorically dismiss certain claims that are generally accepted as being coherent with science or history. Denialists are prone to making 'type 2 errors'. They wrongly reject something that is true (they wrongly accept the null hypothesis). This differentiates denialism from pseudoscience in that pseudoscience is characterized more by 'type 1 errors'. Otherwise, denialists share many of the common features outlined on the Pseudoscience page. There is a great deal of overlap between pseudoscience and denialism, for the denialist often rationalizes his/her position with pseudoscience and the pseudoscientist often must defend his/her position by denying established science.
Denialists may argue against an established concept from different 'angles' (stasis points) and switch between them when confronted with immovable facts. One may argue that a concept doesn't exist (conjecture). If not succeeding, the denialist may switch to the stasis point of definition, conceding that maybe it exists in one form, but that we are really talking about something else. If definition cannot be denied, then the argument often shifts to quality (eg. "OK, it may exist and we agree on definition, but the subject really doesn't matter anyway"). Changes in stasis points can happen almost imperceptibly, unless the listener recognizes this rhetorical trick. The trick is not unique to denialism, but it certainly is prominent.
Within any robust scientific field, one can always find debates and conflicting data among scientists concerning various details of the science. Foundational theories such as germ theory, atomic theory, relativity theory, quantum theory and evolutionary theory are supported by nearly all of the scientists who study them. However, one should expect there to be arguments over the fringe details. Denialists classically portray these healthy disagreements as deep conflicts within the scientific community concerning the very foundations of the theories. Thus, denialists resemble conspiracy theorists in that they imply that many experts disagree with the particular theory but their opinions are being ignored or suppressed by higher authorities.
People initially form beliefs emotionally, rather than logically. Beliefs are then rationalized with logic or logical fallacies after the fact. Many beliefs are firmly embedded in belief systems and ideologies which are held by groups. The beliefs are further strengthened for the group member by the support of the group. Denialism is not limited to any particular ideological groups such as the 'right' and the 'left', religious and nonreligious, white-collar and blue-collar, and many others. .
Often, scientific or historical facts / consensus will conflict with the beliefs of an ideology, producing cognitive dissonance. Dissonance theory predicts that the members of a group, defined by the given ideology, will adopt the position of denialism and rationalize reasons for rejecting the facts. By identifying the ideological group to which someone belongs, one may be able to predict which facts or theories that person is likely to deny. Keep in mind, these are vague generalizations describing the generally recognized stances of groups. The individuals that self-identify with those groups may in fact differ in opinion with some of their group members on individual issues.
Denialism can be found in many fields of study.
History denialists may refer to themselves as 'Revisionists'. There are many examples. Holocaust denialists hold that there never was an organized, intentional, Nazi program to exterminate the European Jewish population. The idea of the holocaust conflicts with their deeply held and previous belief system/ world-view (see Cognitive Dissonance). When confronted with numerous lines of factual evidence in support of the Holocaust, denialists turn to pseudoskepticism. They seek and point out small anomalies or gaps in the historic record. They overweight anecdotal testimony of witnesses that deny the claims.
HIV denialists do not accept that HIV is the necessary causative factor in AIDS. Vaccine denialists do not accept that vaccinations decrease disease rates and improve survival. They attack the generally held beliefs under the veil of pseudoskepticism. When presented with generally accepted evidence, denialists and pseudoskeptics do not change their minds.
Denialism does not come from healthy skepticism. It does not come from the proper application of the scientific method. Denialism stems from preexisting, emotionally-charged beliefs against a given historical or scientific notion. Denialists gather or manufacture as many anomalies and factoids that seem to confirm their underlying, biased belief and use the language of science to present their case against the given theory or fact. It is confirmation bias at its finest.
Denialism can be extraordinarily dangerous. Particularly damaging areas of medical denialism are listed below. Click to read further.
Vaccine Denialism (click here)
Parents are repeatedly bamboozled by myths of the anti-vaccination movement. This is all very difficult to watch. We have read the studies. We understand the tremendous benefit of vaccines. We understand their safety. We understand the dangers of denying vaccines. We understand the confusion that the propaganda has caused. We understand that people only want what is best for their children. We need to help people make good decisions. (read more)
AIDS denialism has been linked to hundreds of thousands of deaths. South Africa is one of the nations that has been hit the hardest by AIDS. A 2008 Journal of Acquired Immunodeficiency Syndrome study revealed that, between the years 2000 and 2005, over 330,000 South African deaths were directly linked to the AIDS denialism of South Africa's government and President Thabo Mbeki. Mbeki apparently felt that AIDS was a conspiracy promoted by Western pharmaceutical companies to poison South Africa with ARVs. He resigned from office in 2008 (for different reasons). (read more)
The word "psuedoskepticism" was coined in a commentary by the late sociologist Marcello Truzzi. Just as pseudoscience may superficially resemble science, pseudoskepticism shares superficial qualities with actual skepticism. Skeptics and pseudoskeptics both express doubt. They ask a lot of questions. However, they differ in very key ways.
When faced with a claim, the skeptic asks for the evidence and weighs the evidence against the prior probability of the claim. The skeptic naturally uses a Bayesian approach. A claim can neither be proved or disproved with 100% certainty. The skeptic's primary interest lies in finding the best explanatory model to fit observations so that accurate predictions can be made. The skeptic is willing to change his/her mind in light of proper evidence and a better theory. The skeptic embraces Occam's Razor and the Extraordinary Claims Axiom.
A pseudoskeptic's primary interest seems to lie in discrediting claims that conflict with their previously held belief. Pseudoskeptics fancy themselves as skeptics. A pseudoskeptic asks hard questions but is rarely willing to accept hard answers. When faced with good, conflicting evidence, the pseudoskeptic is rarely willing to change his/her mind.
A psuedoscience promoter may claim that an idea is absolutely true without sufficient evidence and use fallacious arguments to support the claim. A pseudoskeptic may claim that something is absolutely false without sufficient evidence and use equally fallacious arguments to deny the claim.
In this sense, pseudoskepticism is often synonymous with 'Denialism'.
The above examples apply to those who categorically dismiss ideas that are generally accepted as "good ideas" (ideas that cohere with established knowledge). It must be pointed out that 'pseudoskepticism' may also apply to those who categorically dismiss ideas that are generally accepted as "bad ideas" (ideas that do not necessarily cohere with established knowledge).
A real skeptic may point out that, due to conflicting or lacking evidence, an idea may have such a low prior probability that its acceptance is not warranted. Skeptics cannot dismiss a claim categorically, but may take a position against the claim in favor of a theory with coherent evidence. This may entail making recommendations against the unlikely claim. This is a philosophical position based on a Bayesian weighing of the evidence. Those who identify themselves as 'skeptics', yet dismiss out of hand an unlikely claim without weighing evidence, are technically 'pseudoskeptics'.
Truzzi points out that the burden of proof for a claim falls on the claimant. This is a basic axiom of science and skepticism. That burden of proof holds for those making negative claims as well. A negative claim also requires evidence. To avoid being a pseudoskeptic, when faced with an extraordinary claim, the skeptic may ask for evidence. Without extraordinary evidence, the real skeptic may promote (even strongly) the null hypothesis. The null position has no burden of proof. The real skeptic may provisionally reject the claim in favor of a stronger, coherent idea. A blanket rejection is rarely, if ever, warranted.
John Byrne, M.D.
"Commentaries: On Pseudo-Skepticism - The Anomalist."
<http://www.anomalist.com/commentaries/pseudo.html>
"Holocaust denial - Wikipedia, the free encyclopedia." 2003.
<http://en.wikipedia.org/wiki/Holocaust_denial>
"Marcello Truzzi - Wikipedia, the free encyclopedia." 2005.
<http://en.wikipedia.org/wiki/Marcello_Truzzi>