Denialism: what is it and how should scientists respond?

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. Few, if any, of the readers of this journal will believe any of these statements. Yet each can be found easily in the mass media. The consequences of policies based on views such as these can be fatal. Thabo Mbeki's denial that that HIV caused AIDS prevented thousands of HIV positive mothers in South Africa receiving anti-retrovirals so that they, unnecessarily, transmitted the disease to their children.1 His health minister, Manto Tshabalala-Msimang, famously rejected evidence of the efficacy of these drugs, instead advocating treatment with garlic, beetroot and African potato. It was ironic that their departure from office coincided with the award of the Nobel Prize to Luc Montagnier and Francoise Barre-Sinoussi for their discovery that HIV is indeed the case of AIDS. The rejection of scientific evidence is also apparent in the popularity of creationism, with an estimated 45% of Americans in 2004 believing that God created man in his present form within the past 10 000 years.2 While successive judgements of the US Supreme Court have rejected the teaching of creationism as science, many American schools are cautious about discussing evolution. In the United Kingdom, some faith-based schools teach evolution and creationism as equally valid ‘faith positions’. It remains unclear how they explain the emergence of antibiotic resistance. Elsewhere, the hand of powerful corporate interests can be seen. It took many decades for the conclusions of authoritative reports by the US Surgeon General3 and the British Royal College of Physicians4 on the harmful effects of smoking to be accepted, while even now, despite clear evidence of rapid reductions in myocardial infarctions …