HIV does not cause AIDS. The world was created in 4004 BCE. Smoking does not cause cancer. And if climate change is happening, it is nothing to do with man-made CO2 emissions.
****
All of these examples have one feature in common. There is an overwhelming consensus on the evidence among scientists yet there are also vocal commentators who reject this consensus, convincing many of the public, and often the media too, that the consensus is not based on ‘sound science’ or denying that there is a consensus by exhibiting individual dissenting voices as the ultimate authorities on the topic in question
****
All are seen as part of a larger phenomenon of denialism.
****
The Hoofnagle brothers, a lawyer and a physiologist from the United States, who have done much to develop the concept of denialism, have defined it as the employment of rhetorical arguments to give the appearance of legitimate debate where there is none,5 an approach that has the ultimate goal of rejecting a proposition on which a scientific consensus exists.
****
Denialism is a process that employs some or all of five characteristic elements in a concerted way. The first is the identification of conspiracies. When the overwhelming body of scientific opinion believes that something is true, it is argued that this is not because those scientists have independently studied the evidence and reached the same conclusion. It is because they have engaged in a complex and secretive conspiracy. The peer review process is seen as a tool by which the conspirators suppress dissent, rather than as a means of weeding out papers and grant applications unsupported by evidence or lacking logical thought.
****
The second is the use of fake experts. These are individuals who purport to be experts in a particular area but whose views are entirely inconsistent with established knowledge.
****
The use of fake experts is often complemented by denigration of established experts and researchers, with accusations and innuendo that seek to discredit their work and cast doubt on their motivations.
****
The third characteristic is selectivity, drawing on isolated papers that challenge the dominant consensus or highlighting the flaws in the weakest papers among those that support it as a means of discrediting the entire field.
****
The third characteristic is selectivity, drawing on isolated papers that challenge the dominant consensus or highlighting the flaws in the weakest papers among those that support it as a means of discrediting the entire field.
****
The fourth is the creation of impossible expectations of what research can deliver. For example, those denying the reality of climate change point to the absence of accurate temperature records from before the invention of the thermometer.
****
The fifth is the use of misrepresentation and logical fallacies.
Logical fallacies include the use of red herrings, or deliberate attempts to change the argument and straw men, where the opposing argument is misrepresented to make it easier to refute.
****
Other fallacies used by denialists are false analogy, exemplified by the argument against evolution that, as the universe and a watch are both extremely complex, the universe must have been created by the equivalent of a watchmaker and the excluded middle fallacy (either passive smoking causes a wide range of specified diseases or causes none at all, so doubt about an association with one disease, such as breast cancer, is regarded as sufficient to reject an association with any disease).