The renowned philosopher Karl Popper coined the term "demarcation problem" to describe the quest to distinguish science from pseudoscience. He also proposed a solution. As Popper argued in a 1953 lecture, "The criterion of the scientific status of a theory is its falsifiability." In other words, if a theory articulates which empirical conditions would invalidate it, then the theory is scientific; if it doesn't, it's pseudoscience.He then goes on to describe the theories of the noted crank Immanuel Velikovsky, whose work Gordin has studied extensively. Velikovsky's most famous book, Worlds in Collision, describes how a chunk of the planet Jupiter was ejected, went into a highly elliptical orbit, and in several close passes with the Earth caused a variety of catastrophes that were recorded in historical documents (e.g. the biblical flood story and the parting of the Red Sea). After zooming about the solar system for several centuries, near contacts with the other planets (notably Mars) caused it to settle down into an almost perfectly circular orbit -- and became the planet Venus.
That seems clear enough. Unfortunately, it doesn't work. Epistemologists present several challenges to Popper's argument. First, how would you know when a theory has been falsified? Suppose you are testing a particular claim using a mass spectrometer, and you get a disagreeing result. The theory might be falsified, or your mass spectrometer could be on the fritz. Scientists do not actually troll the literature with a falsifiability detector, knocking out erroneous claims right and left. Rather, they consider their instruments, other possible explanations, alternative data sets, and so on. Rendering a theory false is a lot more complicated than Popper imagined—and thus determining what is, in principle, falsifiable is fairly muddled.
About Velikovsky, Gordin says:
(Velikovsky) courted his fellow Princeton resident Albert Einstein for legitimacy and sought to bolster the scenario from Worlds in Collision with claims that discoveries from the emergent Space Age confirmed his theories about Venus and other planets. He tried to establish himself through testimonials from scientific authorities and validated predictions as a legitimate scientist, not a crank... There is an important lesson in this. All so-called pseudoscientists believe they are simply scientists, albeit ones with heterodox views marginalized by the mainstream... But to be a scientist, you need to behave like one, and one thing scientists do constantly is, well, demarcate. Velikovsky and his peers knew there was an edge to legitimate science, and they policed it very carefully, just like "establishment" scientists did and continue to do.And of Velikovsky's detractors, especially the late astronomer Carl Sagan, Gordin says:
Carl Sagan and other anti-Velikovskians believed that greater scientific literacy could "cure" the ill of pseudoscience. Don't get me wrong—scientific literacy is a wonderful thing, and I am committed to expanding it. But it won't eradicate the fringe, and it won't prevent the proliferation of doctrines the scientific community decries as pseudoscience.Finally, he concludes that demarcation is critical, even if it is (in his opinion) a moving target:
Demarcation may be an activity without rules, a historically fluctuating marker of the worries of the scientific community, but it is also absolutely vital. Not everything can or should be taught in science courses in school. Not every research proposal can or should receive funds. When individuals spread falsehood and misinformation, they must be exposed.Gordin's analysis is an interesting one, and although he speaks of the scientific process and the men and women who engage in it with obvious respect, I can't help but feel that he has things the wrong way around. Pseudoscience, such as Velikovsky's ideas and a hundred other wild theories (astrology, homeopathy, psychic phenomena, and so on) fail not simply because they are heterodox -- they fail on the grounds of lacking evidence and a plausible mechanism. They are not pseudoscience because the scientific community says they are; the scientific community considers them pseudoscience because they fail to meet the criteria of (1) making predictions that can be verified in controlled studies (what Gordin and Popper call "falsifiability") and (2) positing a mechanism by which they could operate that is consistent with already-verified science.
We can sensibly build science policy only upon the consensus of the scientific community. This is not a bright line, but it is the only line we have.
So even the realms of science that make claims that aren't falsifiable (the first standard) can still be considered from the standpoint of the second. Gordin says, "the more 'historical' sciences, like geology and astronomy, pose theories that are more explanatory narratives than up-or-down (and therefore falsifiable) protocol statements of empirical bullet points," which he believes places them outside Popper's criterion of falsifiability. We can't, for example, falsify claims by geologists that the continents were once a single land mass that subsequently fragmented, because no one was there to see it. However, the Pangaea theory still lies in the realm of science, not pseudoscience, on the basis of (1) having a plausible mechanism that is in agreement with processes we do see operating in the here and now, and (2) being consistent with the evidence left behind in the rocks, minerals, and fossils we have at hand.
So, my sense is that demarcation isn't as complicated as Gordin makes it. That's not to say that scientists practice it perfectly; one of my heroes, the Nobel Prize winning geneticist Barbara McClintock, was ostracized by the scientific community for years because of her claims that genetic material moved around in the genome, a phenomenon she called transposition and her detractors ridiculed as "jumping genes." Transposition has now been observed in every eukaryote studied, and is considered one of the main processes regulating gene switching during development. The scientists who refused to consider McClintock's groundbreaking work for over two decades did so because they weren't applying the rules correctly, not because the rules themselves are "muddled." McClintock's evidence did support transposition, and once geneticists began to look for a mechanism by which it could occur, it was found in short order.
Just because it may be difficult at time to separate the wheat from the chaff in science doesn't mean that we should give it up as a bad job, nor that we should wait for the scientific community to come to consensus on a topic before labeling it as pseudoscience. Any sufficiently literate person has the tools to analyze the claims of (for example) homeopathy, and to come to the correct conclusion that it is unscientific nonsense. The methods of critical thinking are not so fluid, nor so esoteric, that anyone can't learn to apply them. While "eradicating the fringe" might be, as Gordin claims, an impossibility, educating yourself in the scientific method is a pretty good way to avoid falling prey to its claims.