Editor’s note: This weekend was a big grant writing weekend for me. I’m resubmitting my R01, which means that between now and July 1 or so, my life is insanity, as I try to rewrite it into a form that has a fighting chance of being in the top 7%, which is about the level the NCI is funding at right now. This weekend, I buried myself in my Sanctum Sanctorum and tried like heck to try to pound the revision into a really good draft that I can distribute to my colleagues for feedback. Fortunately, I have some old posts that I can pull out, tart up (i.e., update a bit, as in correcting the parts that led me to groan as I reread them, thereby hopefully making them better). I think they’re quite good, if I do say so myself; so hopefully you will too.

There are some arguments made in blogs, articles, or books that strike me so hard that I remember them, even three and a half years later. Sometimes I even file them away for later use or response if the issue raised by them is interesting, relevant or compelling enough to me. Although this topic is a bit broader than many of the topics I write about for this blog, I think it also goes to the heart of science-based medicine and communicating scientific skepticism about medicine to the masses. A few years back, a Swedish blogger named Martin Rundkvist made a rather provocative observation about skepticism. Specifically, he argued that a “real skeptic always sides with scientific consensus.” Among his reasons was this one:

Science presupposes that all participants have a skeptical frame of mind and arrive at conclusions through rational deliberation. If a large group of knowledgeable people working in this way arrive at a consensus opinion, then there is really no good reason for anybody with less knowledge of the subject to question it. Informed consensus is how scientific truth is established. It’s always provisional and open to reevaluation, but as long as there’s informed consensus, then that’s our best knowledge. Humanity’s best knowledge.

Although at the time I saw where Martin was coming from, I found this viewpoint somewhat disturbing, leading me to echo Martin’s own words in response to his own rhetorical question asking whether accepting a scientific consensus is nothing more than “kowtowing to white-coated authority”: Well, yes and no.

For a skeptic and supporter of science-based medicine, in matters of science it is undoubtedly true that the scientific consensus is always the best place to start when evaluating unfamiliar issues. While it is certainly possible that a given scientific consensus regarding an issue can be wrong in almost any area, it nonetheless almost always represents the best current scientific understanding. It is also correct, as Martin argues, that legitimate authority matters. I emphasize the word “legitimate” because in pseudoscience arguments from authority are common, but rarely is the authority relevant to the point being argued. Often it’s not even legitimate, as in when anti-vaccine activists point to Andrew Wakefield’s work as justification for their claims that vaccines cause autism and other conditions. Like Martin, I’m more inclined to accept the pronouncements of someone who has actually dedicated his or her life to studying the issue systematically; i.e., an expert. If the topic is evolution, then that expert would be an evolutionary biologist. If the topic is the Holocaust, then a historian specializing in World War II and/or the Holocaust would represent an appropriate expert. For cancer, an appropriate expert would be an oncologist (or an surgical oncologist, such as myself). The list goes on.

Where I start to have a bit of a problem with Martin’s viewpoint is when I start to contemplate the nature of scientific consensus itself in many areas of science. Not all scientific consensuses are created equal because, in different fields the strength of scientific consensus can vary quite markedly depending upon the topic or even the subtopic within the topic. For example, the scientific consensus supporting the theory of evolution, particularly common descent, is exceedingly strong. It’s one of the strongest of all scientific consensuses, arguably the strongest. Similarly, the consensus that natural selection is a major driving force behind evolution is very nearly as strong. However, as the discussion devolves into more detailed areas, inevitably the consensus weakens. Eventually, subsidiary areas of a discipline are reached where the consensus is weak or where there is no consensus, such as what the function of “junk DNA” is, whether it is subject to natural selection, and if so how much. (Real evolutionary biologists could probably come up with a better example.) These sorts of questions are often at the cutting edge of scientific knowledge, and it is not always easy to recognize what they are. It is also these issues at the edge of our knowledge that are attacked as proxies for the much more strongly supported core theory. Creationists are notorious for this sort of tactic, often using new findings of molecular biology that appear peculiar or out of sync with specifics of evolution as wrecking balls to try to demolish the edifice of “Darwinism.” I can’t count the number of times I’ve seen supporters of “intelligent design” creationism point to either “junk DNA” or the findings of new genomic techniques as “evidence” that “Darwinism” is doomed. Never mind that some of the very strongest support for the theory of evolution, in particular common descent, comes from genetics and that new genomic techniques only keep confirming that.

The same is true of scientific consensuses in many other disciplines, including my own disciplines of medicine and surgery. However, scientific consensuses in medicine are almost never as strong as the theory of evolution. Germ theory of infectious disease probably comes close, but otherwise I’m hard-pressed to think of one. Usually, the strength of a consensus in medicine is proportional to the ratio of data supporting it that comes from randomized clinical trials to data from epidemiological studies, the latter of which are more prone to confounding factors. That does not, however, mean that there doesn’t exist strong consensus about many medical issues. For example, there is, for all intents and purposes, no doubt that HIV is the causative agent for AIDS, the claims of HIV/AIDS denialists notwithstanding. Similarly, there is in essence no doubt that smoking cigarettes vastly increases a person’s risk of lung cancer and heart disease, along with a host of other medical problems. Not even the tobacco companies try to argue against that anymore. When we come to subsidiary questions, however, the consensus is generally not as strong. For example, it has become increasingly appreciated that secondhand tobacco smoke increases the risk of heart disease and lung cancer in people chronically exposed to it. However, because the effect is considerably smaller than it is for people who actually smoke cigarettes, there is a lot more “noise” in the studies, giving more wiggle room for people who dislike the idea of the government banning smoking to claim that such bans are not scientifically supported, and it’s taken a long time for scientific and clinical studies to firm up the conclusion enough to the point that it is now a strong consensus.

Not surprisingly, given the difficulty doing controlled experiments and the nature of the material, which makes it more easily politicized or influenced by biases, a truly strong consensus is harder to come by in the humanities and social sciences. However, even so, it is not impossible. For example, one of my areas of interest is the Holocaust. There is overwhelming and incontrovertible evidence that the Nazi regime embarked on a systematic program to round up and exterminate the Jews in territories they controlled. Methods used included shooting, hanging, gas chambers, and a system of camps designed to literally work their inmates to death through a combination of grueling labor, insufficient food, and unsanitary and crowded conditions. However, this consensus becomes less clear when various issues surrounding the Holocaust are discussed. For example, there is the whole “intentionalism” versus “functionalism” debate. In a nutshell, this debate is over the question of whether the intent was there from the very beginning of the Nazi regime or even before the Nazis rose to power to exterminate the Jews or whether the Holocaust evolved “organically” or “functionally” from the persecution of Jews that began early in the Nazi regime and became increasingly radical and violent in the pre-war era, the radicalization of Nazis carrying out the program, and the question of what to do with the millions of Jews that suddenly fell under Nazi control after Hitler had invaded the Soviet Union. Holocaust deniers love to misrepresent and misuse this debate to claim that Hitler didn’t know about and didn’t order the Holocaust or to claim that there was never a plan to systematically exterminate European Jewry.

One thing that I’ve come to realize is that it’s not always obvious when skepticism devolves into denialism. In some cases it’s pretty easy, for example creationism, Holocaust denial, HIV/AIDS denialism, anti-vaccine activism and the germ theory denialism that often fuels it, and many sectarian belief systems that lead to the use of unscientific “alternative” medicine, such as homeopathy. Sometimes, appropriate skepticism about most scientific issues can exist side-by-side in a single person with credulity and pseudoskepticism about other scientific issues. For example, among skeptics who count themselves science-based, there is a disturbingly large contingent who do not accept the science behind anthropogenic global climate change, as Penn Jillette, for example, does not. Only recently does he appear to be grudgingly dragged towards accepting the scientific consensus in this area. His resistance to the idea appears to be due to his Libertarian beliefs.

One example that I used to use routinely before she shut down her blog was Sandy Szwarc at Junkfood Science. Most of her non-obesity-related posts were often actually not too bad. However, whenever she blogged about diet and obesity, there was usually a problem, sometimes a big problem like the one Steve Novella blogged about a couple of years ago. And it’s not the sort of thing that necessarily jumps right at you off of her blog, as it does from an obvious crank blog like Age of Autism. Certainly it didn’t for me. Rather, it’s the sort of thing you have to read her blog closely for a while (which I did) to start to realize. As I read her blog, more and more it bothered me that all of her “skepticism” was inevitably in the direction that being obese is not only not unhealthy but is actually at least as healthy as not being obese, that eating fatty foods is perfectly fine, and that virtually any study she looks at that says that eating fatty foods or too many calories predisposes to health problems is a pile of crap while any pile of crap study claiming otherwise is the latest and greatest. All of this led her to conclude that virtually every warning made by scientists and physicians about diet is fearmongering. Worse, she had a distressing tendency to use unscientific tactics, such as cherry picking data, attacking consensus, and alleging conspiracies. I also found it telling that, unlike most bloggers, myself included, Szwarc does not permit comments. If there’s one thing that skeptics usually encourage (as we do here on SBM), it’s spirited debate. That’s impossible in a blog that doesn’t permit comments.

In the end, I remain a bit uncomfortable with Martin’s blanket statement that “a real skeptic always sides with scientific consensus.” The reason is that what the scientific consensus actually says is not always that clear for many issues, even among those who work in the field. Indeed, there are comparatively few issues in science (evolution, for example) for which a strong consensus exists, and even fewer in the social sciences and history (the Holocaust, for example) for which an equally strong consensus exists. These are very strong consensuses, and to overturn them would require extraordinary evidence, evidence at least equal to the evidence supporting them. Consequently, when someone says that evolution is false or that the Holocaust didn’t happen (or the lessor form of Holocaust denial, that nowhere near 6 million Jews died), it’s fairly easy to recognize such person as a crank and denialist, and I usually do not hesitate to label them as such when appropriate.

But what about consensuses that are strong but not as bullet-proof, usually because, although there is a consensus, there are fairly wide error bars around the predictions or uncertainty regarding the importance of various factors? The prototypical example of this is anthropogenic global warming, for which there is a strong consensus among climate scientists but still a fair amount of uncertainty about the outcome. Another example, of course, is the scientific consensus about the link between obesity and adverse health outcomes. How do we differentiate legitimate skepticism about the consensus from denialism?

This is where I tend to agree with Mark Hoofnagle. It’s more about tactics and how evidence is used to support an argument. Scientific skepticism looks at the totality of evidence and evaluates each piece of it for its quality. Cranks are very selective about the data they choose to present, often vastly overselling its quality and vastly exaggerating flaws in current theory, in turn vastly overestimating their own knowledge of a subject and underestimating that of experts. In medicine in particular, denialists frequently emphasize anecdotes over epidemiology, clinical trials, and science. They also tend to leap to confuse correlation with causation. A great example that I just saw a week or two ago comes from our “friends” at the anti-vaccine group the International Council on Vaccination, a group that Mark Crislip and I had such fun deconstructing. There, Sherri Tenpenny posted an article entitled Vaccines and Blue Foot Syndrome (crossposted on her own blog). In the post, after citing anecdotes about “vaccine injury,” Tenpenny then segues into a story of a child who dropped a large frozen turkey on his foot, which became painful and blue within hours. The parents are then confronted with doctors who tell her that this is “Blue Foot Syndrome” and that they have shown by epidemiology that it is not linked to being struck by a frozen turkey. It’s an analogy obviously designed to mock scientists who quite correctly refer to the studies that have failed to find a link between vaccines and autism that ignores the fact that correlation does not necessarily equal causation and that the correlations reported by parents are not nearly as obvious as a blue foot after having a frozen turkey land on it. Anti-vaccine activists think they are, though.

In addition, because the mainstream rejects their ideas, there is often a strong sense of being underappreciated—persecuted, even—among cranks, leading them to view their failure to persuade the mainstream of the correctness of their views as being due to conspiracies or money. Global warming denialists, for example, tend to see the currently existing scientific consensus as being politically motivated by the desire of “liberals” to tell them how to live. Evolution deniers view evolution as the result of atheistic scientists wanting to deny God. People like Sandy Szwarc view the consensus that obesity leads to health problems as being due more to moralizing and bigotry against the obese, which, whether it is true or not, is an easy claim to make because there has been and is a lot of bigotry against the obese. Antivaccinationists view the rejection of their belief that mercury in vaccines or even vaccines themselves cause autism by mainstream medicine as evidence that we’re all in the pocket of big pharma. Practitioners of “complementary and alternative medicine” view the rejection of their beliefs in homeopathy, “energy healing,” and vitalism similarly: Science-based doctors must be in the pocket of big pharma! Or they’re close-minded! Or they’re threatened by the “success” of alternative medicine!

What a lot of this distinction boils down to is that crankery, denialism, pseudoskepticism, or whatever you want to call it tends, either intentionally through ideology or unintentionally through an ignorance of the scientific method, to conflate and/or confuse emotiona, nonscientific, and/or ideological arguments with scientific arguments. This is not to say that scientists and skeptics and supporters of SBM are free from their own biases, whether ideological or simply a desired result that they hope to find. Far from it. However, skepticism means applying the scientific method to claims, whatever its faults, scientific method is the best method thus far devised to minimize these biases. As scientists, the reason we use the scientific method is not because we consider ourselves superior to the cranks, but rather because we recognize that we are human too and thus just as prone to falling into the same traps as they. As Richard Feynman once famously said, “The first principle is that you must not fool yourself—and you are the easiest person to fool. So you have to be very careful about that. After you’ve not fooled yourself, it’s easy not to fool other scientists. You just have to be honest in a conventional way after that.” The scientific method is, above all, a methodology by which scientists try to avoid fooling themselves. Skeptics cross the line dividing skepticism and denialism and quacks the line between science and quackery when they forget that.

Moreover, skeptics and supporters of SBM know that science is a work in progress. What is considered correct today may well be modified tomorrow. This change, however, is not brought about by cranks cherry-picking data but by rather skeptical scientists probing for weak spots in our current understanding, making hypotheses, and then testing whether current theory or the new hypotheses make the better prediction. Thus, being skeptical of the consensus is not the mark of the crank. It’s how and why that skepticism exists that distinguishes crankery from genuine scientific skepticism.

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