With this new column, we are delighted to welcome back to our pages on a regular basis our esteemed colleague the philosopher and evolutionary biologist Massimo Pigliucci. His first SI column, “Thinking about Science,” ran for twelve years from 2002 to 2015. This new column will explore skepticism from the viewpoint of the philosophy of science. —The Editors

The term pseudoscience has been the object of a renewed interest by philosophers of science in recent years. This is not just because the so-called demarcation problem—the question of what distinguishes science from pseudoscience—is inherently interesting to philosophers and epistemologists. It is also because pseudoscience matters, as in the case of the increasingly clear negative personal and societal effects of, for instance, vaccine and climate change denialism.

But is denialism the same thing as pseudoscience? What do people who reject the notion of evolution, say, have in common with people who push homeopathic “remedies”? My colleague Sven Ove Hansson of the Royal Institute of Technology in Stockholm has written an insightful paper about this (Hansson 2017). [Hansson also wrote “The Hidden Connection between Academic Relativists and Science Denial” in the September/October 2021 Skeptical Inquirer.—Eds.] Hansson begins by distinguishing two kinds of bad epistemic practices that fall under the broader umbrella of pseudoscience: science denialism and pseudotheory promotion. The former includes denial of evolution, climate change, vaccine efficacy, etc. The latter has to do with homeopathy, astrology, ancient astronaut theories, and so on.

Hansson suggested in a previous paper that a statement should be considered pseudoscientific if it satisfies three criteria: 1) it refers to an issue that falls within the domain of science, broadly construed; 2) it is so unreliable that it cannot be trusted; and 3) its proponents actively attempt to create the impression that the statement is highly reliable in its own domain.

Let’s take one example each of denialism and pseudotheory promotion to see how they fit the three criteria. Evolution denialism concerns the domain of biological history and variation, clearly within the purview of the science of biology. It is unreliable because it hinges on a seriously flawed interpretation of the evidence, as when creationists argue that the Grand Canyon was formed in the span of a single worldwide flood. And yet creationists insist that not only are they doing sound science, but such “science” ought to be taught in public schools.

Consider now astrology as an instance of pseudotheory promotion. It is easy to see how it too satisfies Hansson’s three criteria. Astrologers are interested in a domain that properly belongs to science—in this case psychology, not astronomy as it is often claimed, because astrology has to do with the causes of human behavior, not with celestial mechanics or physics. Claims by astrologers have repeatedly been shown to be highly unreliable, for instance in a famous paper published by Shawn Carlson (1985) in Nature. [See News and Comment, “Double-Blind Test of Astrology Avoids Bias, Still Refutes the Astrological Hypothesis,” in the Spring 1986 Skeptical Inquirer, pp. 194–196, for a summary of that paper.] And astrologers certainly do present themselves as making reliable statements in their chosen domain.

Notice that the two categories of pseudoscience identified by Hansson are not mutually exclusive and should in fact be considered as endpoints along a continuum. Sometimes the very same set of claims is both an example of denialism and one of pseudotheory promotion. Creationists both deny the scientific theory of evolution and promote their own pseudotheories as if they were scientifically sound.

Philosophers of science have recognized for some time now that there are two conceptually distinct, yet intertwined, aspects of both science and pseudoscience. Let’s call them the epistemic and the sociological aspects. Science is a social activity, not in the naive social constructionist sense but in the obviously undeniable one that it is a human endeavor, characterized by accepted practices (peer review, granting agencies, publications, etc.) and power structures (mentor-student, senior-junior colleagues, administrator-researcher, etc.). But science is also, obviously, an epistemic activity, meaning that it aims at reliably discovering things about the world.

Hansson uses the same dual approach to better characterize pseudoscience. Let’s begin with the epistemic aspect, where we find four kinds of recurrent epistemic vices, so to speak, in the practice of pseudoscience. The first one is cherry-picking. For instance, deniers of the general theory of relativity (oh yeah, that’s a thing!) have published a list of alleged counterexamples to the theory in Conservapedia, the conservative “equivalent” of Wikipedia. While many of these anomalies are actually perfectly explicable by contemporary physicists, the list entirely ignores the overwhelming positive evidence for the theory, which has steadily and impressively accumulated over the past century.

A second epistemic vice typical of pseudoscience is the neglect of contrary or refuting information. The above-mentioned general relativity denialists, for instance, keep holding on to pre-relativistic physics despite the fact that it has been abandoned by the physics community at large. For example, they bring up a proposal by Swiss physicist Georges-Louis Le Sage, who in the nineteenth century suggested that gravitation results from the collective pressure exercised on bodies by a large number of small invisible particles. As Hansson notes, this may have been plausible when Le Sage was alive, but it’s no longer so. The only reason deniers of general relativity keep bringing it up is because of the preconceived conclusion that they desperately wish to defend.

The third epistemic vice lies in the common fabrication of fake controversies by promoters of pseudoscience. Vaccine denialists often point to the occasional dissenting voice within the medical research community to project the image of a controversy that is not really there but which serves their purposes in terms of sowing doubt among the general public.

The last epistemic vice concerns the use of what Hansson calls “deviant” criteria of evaluation by proponents of pseudoscientific notions. Think of it as raising the bar in such a way as to make it impossible for the other side to meet your criteria of assent to a given theory. For instance, creationists often demand experimental evidence not just of speciation (i.e., the formation of new species) but of the origin of entire classes of living organisms. Speciation is achievable in the laboratory, though rarely. But the evolution of, say, mammals from a fish ancestor can be only indirectly inferred on the basis of the fossil record. To ask for direct proof of it is either disingenuous or extremely ignorant.

Let me now briefly touch on the sociological aspect of pseudoscience, which is just as revelatory as the epistemic one. Here Hansson’s detailed study comes up with a whopping ten relevant sociological marks of pseudoscience, but I’ll focus on a subset for purposes of illustration. Lack of expertise is one such mark. While the scientific community is made up of often highly specialized experts, expertise is exceedingly rare in pseudoscientific communities. Consider, for instance, those petitions listing a large number of “scientists” who oppose the notion of climate change or vaccines. Not surprisingly, such lists turn out to be made up of people who are considered to be scientists on the basis of having a bachelor of science degree or perhaps who are professional medical practitioners, say dentists, even though the issue under consideration pertains to atmospheric physics or immunology—areas in which dentists are, obviously, not experts.

Proponents of pseudoscience are also uncommonly prone to buy into conspiracy theories. As Hansson writes, climate change denialists think that the problem is a worldwide liberal conspiracy; creationists see immoral atheists at every corner and in every laboratory; and the general-relativity denialism of the 1920s and 1930s was naturally dominated by antisemitism.

Moreover, pseudoscientists have a tendency to appeal directly to the public, bypassing peer review and other forms of expert gatekeeping. They do so under the guise of defending democracy and freedom. Yet when they need, say, financial advice or to have their car fixed, they—reasonably enough—go to a proper expert, democracy and freedom be damned.

An additional recurrent sociological characteristic of pseudoscientific groups is that they are prone to launch vitriolic personal attacks on scientists. For instance, Albert Einstein was subjected to such levels of antisemitism that he considered it unsafe to visit Germany after he left the country. Contemporary scientists who have spoken publicly about climate change or vaccines have also found themselves in a similar predicament.

So upon careful consideration, the term pseudoscience refers to a continuum of activities that span from denialism to pseudotheory promotion. Pseudoscientific claims suffer from identifiable epistemic problems (cherry picking, neglect of refuting information, and so on), while pseudoscientific communities display several recognizable sociological markers (lack of expertise, proneness to conspiracy theories, etc.). Of course, individual scientists also can be found to engage in cherry picking or refusing to consider evidence that is damaging to their preferred theory. But what sets science apart is that as a community such vices are, by and large, kept in check. That is why neither science nor pseudoscience can be understood in terms of individual claims or individual agents. They can be understood only once we expand our analysis to the communal level.

References

Carlson, S. 1985. A double-blind test of astrology. Nature 318: 419–425.

Hansson, Sven Ove. 2017. Science denial as a form of pseudoscience. Studies in History and Philosophy of Science 63: 39–47.