I think that psychology, medicine, and even philosophy should be evidence-based, which requires looking to scientific experts for reviews of current beliefs. But it is part of the nature of science that sometimes the experts are wrong. When is it legitimate to challenge scientific consensus?
Decisions about psychotherapy, other medical treatments, and even philosophical dilemmas should not be based on unsupported intuitions, but on experimental evidence. The best way to find out what evidence is available is to consult scientific experts who have reviewed relevant studies and objectively reported them. However, there are many cases in the history of science where the expert scientific consensus has been wrong. Examples include: Freudian psychoanalytic views of mental illness that were dominant in the 1950s, the pre-1990s medical view that stomach ulcers are caused by stress and excess acidity, and pre-Copernican astronomy that confidently placed the earth at the center of the universe.
Hence people may sometimes legitimately challenge the scientific consensus, and indeed without such challenges progress would be severely limited. For example, medicine now effectively treats ulcers with antibiotics that kill the bacterial infections that are usually the cause. My book How Scientists Explain Disease tells the story of how two obscure Australian doctors overturned what had been expert views about the causes and treatment of ulcers. It would be useful to have guidelines for when people should accept the scientific consensus and when it can legitimately be challenged. Here are some brief notes that will eventually turn into a full article with many more historical examples.
It is legitimate to trust scientific consensus when it is based (as it often is) on:
• Good evidence acquired by careful observations and experiments performed by researchers whose motivations are scientific rather than financial or ideological;
• Solid theories based on explanations of the evidence, taking into account opposing theories; AND
• Publications in high quality, peer-reviewed, scientific journals.
On the other hand, people should challenge scientific consensus when:
• The consensus is based on lore and tradition rather than published evidence and theory;
• The evidence on which the consensus is based was gathered by people whose motivations are financial or ideological; OR
• New evidence and theories have become available that undermine the consensus. (Note that it is a strength, not a weakness, of science that scientists change their minds as new evidence and theories become available.)
However, the following are NOT good reasons to challenge the scientific consensus:
• The challenges are based on reports on unreliable sources such as amateur blogs and websites;
• The challenges derive from theories based on poor evidence, such as astrology, naturopathy, homeopathy, etc.;
• The challenges are based on vague "clinical experience" or personal intuitions; OR
• The challenges are driven by financial or ideological motivations.
