 Denialism and Selective Acceptance. A Psychological Phenomenon. Which of these statements would you say you are comfortable with? Smoking causes cancer. I'm generalizing here to lung cancer. Matter can be converted to energy. HIV causes AIDS. Man and chimpanzees share a common ancestor. Now all of these statements were confirmed by scientific research. All were arrived at by experimental evidence and testing. The process involved in verifying these facts is the same. The people who did the work are trained the same way, with the same underlying philosophies of science. And yet some people accept that smoking causes cancer. Matter can transform to energy. Humans are related to chimps, but not that HIV causes AIDS. Others believe one, two, and three, but not four. But wait, many of you are saying the evidence for three or four isn't as strong as it is for one and two. How do you know? Have you subjected one and two to as much scrutiny as three or four? Have you read the scientific papers? Do you buy books on relativity or cancer research? Do you demand that scientists constantly defend the principles of nuclear energy? Do you insist that no one has ever actually observed a tumor forming in a lung? Of course not, because the first two are no longer political issues. There were deniers once for the dangers of smoking, and there probably still are some. There were in the 50s those who denied that nuclear power even existed. They denied the evidence of Hiroshima and Nagasaki. They said the US government was perpetrating a hoax to scare the Soviets. This test illustrates a well-documented phenomenon called selective acceptance. People apply a different scrutiny to non-favored viewpoints than to their own. There is an active community of HIV deniers. They apply a level of scrutiny to HIV that they do not apply to other diseases, like viral hepatitis or influenza. They accept that a vast global conspiracy of scientists, physicians and drug companies is perpetrating the greatest hoax of the millennium for the purposes of making money. Yet they accept that those same companies, doctors and scientists, are probably right about tuberculosis and malaria. Why HIV specifically? I'll deal with that in another video. Then there are those who deny the relatedness of humans and chimpanzees, despite the fact that we share over 95% of our genome with them, that we are remarkably similar in behavior and physiology. They accept that scientists are right about relativity, that they are really smart about cancer and HIV, but when it comes to evolution and common descent, those same scientists are suddenly blind, deluded or deceitful. The evolution deniers demand evidence to be presented to them, that the theory must pass common knowledge tests, that it must be intuitive, a standard that, if applied to things like cancer biology or general relativity, would certainly fail. They insist that non-scientific alternatives be taught, and yet none of them are clamoring for the HIV denialist viewpoint to be taught in schools. There are scientists in the HIV denialism and evolution denialism camps who make a living writing books on their controversial viewpoints. Because the non-science layperson can't tell the difference between two PhDs both espousing different viewpoints, the issue becomes muddled. To the scientists familiar with the evidence, there is no debate. HIV causes AIDS. Evolution is a well-supported theory. Where does that leave us? If selective acceptance makes all science suspect, any politically charged issue that collides with science fact will lead to confusion and distrust. My advice, and I know this will draw some fire, is that unless you are prepared to really examine the facts, to spend time learning the basics of a field, going to school, visiting labs, talking with scientists, reading scientific papers, doing lab research yourself, the best way to know which side is based in evidence and which is the result of selective acceptance is to look at the number of respected scientists on either side of the issue. For HIV causes AIDS, the number of scientists who oppose this viewpoint is maybe 50 out of a few million. For evolution, the number of scientists who oppose common descent is probably about the same. So challenge yourself. If you are going to deny HIV but accept cancer, ask yourself why you scrutinize one but not the other. And if you reject evolution but accept relativity, can you defend why the same scientists made a mistake on one but not the other?