It seems almost absurd to me that “sensible” people are able to deny evidence that AIDS is caused by HIV. Without trying to sound flippant, I would invite these people to voluntarily infect themselves with HIV and see how they fare. From the holocaust to smoking causing cancer, denialism appears to be rife – posing as scepticism. One might argue that we cannot deny freedom of expression. Indeed, revolutionaries such as Copernicus and Galileo held ideas that contradicted the scientific dogma of their time, and some doctrines that were once accepted by the scientific community have turned out to be false. However, it is important that we stick to the scientific method and provide valid proof for whatever theory or claim we may have, be it in line with or against the scientific consensus.

So what are the differences between scepticism and denial? Denialism in science is the rejection of accepted parts of the scientific consensus, perhaps as a means of avoiding the uncomfortable truth. In science, it is always important to keep a sceptical mind and challenge ideas; if they are still left standing after attempts at falsification then we can be reassured that they are scientific and therefore justified. Denialists do not evaluate the evidence and follow where it leads; instead they are motivated by some other ideology, which means that they already have a commitment to a belief before they have viewed the evidence. In a nutshell, sceptics are willing to change their minds, denialists are not.

Proponents of the denial movement portray themselves as underdogs who have dared to speak out against conspiracies and propaganda. Martin McKee (an epidemiologist at the London School of Hygiene and Tropical Medicine) has identified six commonly used tactics that denialists employ:

1.       Allege there’s a conspiracy;

2.       Use fake experts to support the claim;

3.       Selectively pick out supporting evidence;

4.       Demand an impossible level of proof;

5.       Misrepresent the scientific consensus then attack the fallacy;

6.       Claim that the scientific community are still divided in opinion.

Denial tends to be greatest in areas of science that necessitate a level of trust in the scientific method. For instance, the HIV virus is invisible to the naked eye and the consequences of infection are not immediately apparent; vaccines do not work for everyone and may be given for diseases we have never seen; and global warming is meant to be occurring, yet with the icy winds and snow-ridden airport runways it is difficult to see how contradicting weather patterns can co-exist. It may be true that denial is on the same spectrum as scepticism, with gullibility being on one end of the scale, denial on the other, and scepticism having a place somewhere in-between. The emotiveness and sense of gaining authority over nature makes denial so appealing. Moreover, anecdotal evidence laden with scientific jargon makes this pseudo-science appear scientific.

Suppose you are a smoker and you hear that smoking causes cancer. While conducting further enquiries you find several websites with cited research on the association between tobacco smoking and lung cancer. However, you also find a website claiming that the research is inconclusive and severely biased. As a sceptic, you would review the evidence and balance them to come to an informed conclusion. A denialist, though, biased because you have a vested interest in believing that smoking is harmless, you would dismiss the scientific evidence regardless of how conclusive it is.

Lack of faith, trust, or understanding of the core tenets of science can catalyse the transition from scepticism to denial, which may be fuelled by the fallacies disseminated by proficient denialists out there. In fact, the transition from scepticism to denial may be a pathological cognitive process, as per Seth Kalichman (a social psychologist at the University of Connecticut at Storrs), who submits that for denialists “[t]here is some fragility in their thinking that draws them to believe people who are easily exposed as frauds”. He even goes further to describe the leaders of denialist movements as displaying “all the features of paranoid personality disorder”.

Perhaps our sceptical minds are not solely to blame for denial; indeed corporate industries have a role, especially when it comes to tobacco smoking and climate change. The Waxman Hearings of 1994 are a particularly famous example of denialism in the corporate world. Before the U.S. Congress, seven CEOs of tobacco companies swore, under oath, that they did not believe nicotine to be addictive. The tactics used by the tobacco industry had been around for a long time in order to create doubt with regards to the health risks of tobacco smoking. These tactics were picked up by the coal and electricity companies, which led to the creation of the Information Council on the Environment (ICE). The role of the ICE was to “reposition climate change as theory (not fact)”.

It appears that when prominent scientists indulge in denialism the consequences can be dire. For instance, when Andrew Wakefield falsely reported that MMR vaccinations were linked to autism the immunisation rate in Britain dropped from 92% to 73%. In South Africa, AIDS denialism by the Mbeki government was supported by 5,000 doctors and scientists, including the American Peter Duesberg, who claims that HIV is merely a passenger virus in AIDS victims and that rather drug-use, malnutrition, and the side-effects of antiretroviral drugs lead to AIDS. This has, of course, been falsified and indeed HIV alone has been found to be inextricably linked with the likelihood of developing AIDS. The AIDS denialism movement in South Africa is reported to have resulted in the deaths of 330,000 to 340,000 people and a further 106,000 new infections.

With such a risk to public health, what is the solution to denialism? Censorship is not the answer. Today we may be in the privileged position of holding the popular opinion, but there may come a day when we are in the silenced minority. It seems that the only sensible way to tackle denialism is to try to address the arguments and be faithful to the scientific method of making valid inferences from accurate observations and experiments. It may well turn out that the denialists were right, but the truth will only be ascertained through scientific enquiry rather than unfounded speculation.