 The more I learn about science denialism, the more I see a common thread running through all of them, like a common playbook. Regardless of the evidence to the contrary, they seem to be able to hold whatever contrarian position they like and justify it with a series of logical fallacies. But there are some scientific theories that you just think, well, there's just no way that could be denied. Who'd have a reason to doubt that theory? I would always have included the theory of gravitation, atomic theory, cell theory, and of course the germ theory of disease. But thanks to the internet, I've now found an active community of germ theory denialists. That's right, they either fully or partially deny the germ theory of disease. In fact, many of you may know one or more of these people. At this point, I hope you're asking how anyone could possibly deny that germs cause disease. Wouldn't any thinking person see that colds are contagious, that diarrhea is something you can get from contaminated food, that skin infections form around unsterilized cuts? What possible alternative explanation could they have to explain these phenomenon? To answer that, I have to take you back to two scientists, Louis Pasteur and Antoine Beichan, at or around 1870. The problem concerns certain diseases of silkworms, an important agricultural asset for the French silk industry. The harvest were failing, and it was a matter of national commerce that an explanation could be found. Louis Pasteur, as many of you might remember, performed many of the tests that formed the bases for the germ theory of disease we use today. His argument, based on his experiments with sealed flasks and breweries, was that an infectious agent was likely responsible. His course of action would be to quarantine and contain the spread. Beichan was an insect biologist and had a competing theory. His theory, which I will call the pleomorphic theory of disease, was that diseases are caused by environment. He said that bacteria actually form from the diseased cells, and their appearance tells us the underlying disorder. There's more to it, including an abiotic origin of microbes, but the key point is that he takes Pasteur's theory in reverse. The microbe does not cause the disease. The disease causes the microbe. His suggestion might have been not to quarantine the sick animals, but to feed them better, or move all of them to a brighter area with cleaner air. This was not a stupid idea in 1870. It strikes us as silly because we have the benefit of so much additional information. Antoine Beichan was wrong, of course, as has been demonstrated by thousands of experiments since then. His theory has been falsified and buried. Pasteur's has been predictive and explanatory in a way that we find useful, and Antoine Beichan's theory is not supported by the genomic data being produced on bacterial DNA, nor by serotype testing, phylogenetics, or electron microscopy of pure cultures. Now, there was a useful insight to be gained from his theory about the complexity of interaction between a disease agent and the host. It's true that environment, nutrition, and immune status plays a big role in the development of most diseases. I don't know any modern biologists who dispute that. To qualify as a germ theory denialist, you need to deny that infectious agents are responsible for diseases we currently attribute to transmissible pathogens. What kind of crazy internet troll believes this far out idea? This is the part that may surprise you. How about Bill Maher, the host of Politically Incorrect with Bill Maher, and the writer, producer, and star of Religious? Now, he has made a statement that he is not a germ theory denialist, but the fact that he had to deny it says a lot. He's strongly anti-vaccine, anti-medicine, but in an interview he brought up the signature move of germ theory denialism. He pulled out the deathbed recanting of Pasteur. The only place this text ever existed was the germ theory denialism website that created it out of whole cloth. It has no basis in fact, and represents a marker for someone who has spent time learning from anti-germ theory websites. This is a classic denialism move, attacking the discoverer's credibility, worthy of a creationist or AIDS denialist, and forever tarnishes Maher in my eyes. It goes beyond a disagreement with him. He's taken sides against science, medicine, and critical thinking. What he's advocating is dangerous to the innocent and naive. It's a misuse of his celebrity to promote pseudoscience. Who else can we put on our list? How about a large number of chiropractors? Many, but certainly not all, who practice as straights are taught that all disease from tooth decay to ebola are the result of improper alignment of the spine and atlas. You should also ask any naturopath or osteopathic physician where they stand on the germ theory of disease. Depending on the country they may have been taught that germs don't exist. We'll also find that a lot of AIDS denialists are in fact germ theory denialists, either wholly or in only in part. Some will use the pleomorphic theory, others won't, or will use something equally as invalid. In fact, anywhere you find quackery about nutrition or detoxification treating viral or bacterial conditions, look for their references to either Antoine Beicham or the deathbed recanting of Pasteur. You will have spotted the rare germ theory denialist in his natural habitat. This particular strain of pseudoscience has mutated though. It's realized that it can't survive with open denialism and antiquated beliefs. Instead, the approach now is to simply shift the focus from their failure to make a scientific case for their beliefs to the perceived flaws in Pasteur's theory. Not modern microbiology mind you, but actually the experiments and theory of Louis Pasteur. They advocate a softer form of germ theory denialism, still based on Beicham's teachings that sickness causes pathogens, not pathogens causing sickness. You'll see the thinking in these comments from a denialist on the Huffington Post. A healthy, strong body well nourished and properly exercised will easily be able to fight off just about any germ that invades its bodies without the need for magical elixirs. I hope the illusion to creationism, repackaged as ID, and the parallels of demonizing Pasteur and Darwin are not lost on you. This new germ theory denialism tends to refer to itself as natural hygienists, in that they assert that health and hygiene are sufficient to prevent disease. This is an offshoot of naturopathic medicine, strongly associated with raw food movement and the raw milk movement especially. They contend that most of the modern diseases we deal with are a result of meat consumption and processing of our diet, including pasteurizing our milk. They thrive on the internet and in a very small subculture of vocal activists. I'll deal with raw foodism and raw milk in a separate video. I just wanted to demonstrate how these very old ideas adapt to stay alive as quackery on the internet and among alt-med fringe groups. How much of a threat do these people pose? Not much so far. Like any small fringe group, they lack much political power. But we must always be watchful of pseudoscience advocacy and address the fundamental fallacies of their claims. The last thing we need in the modern age is another form of contentious fundamentalism, especially one that devalues such an important principle of modern medicine. Good health to you and may all your germs be benevolent. Thanks for watching.