Science has been an indispensable part of modern society for some time now. Indeed, science is a purveyor of our material betterment, and is being inevitably drawn into debates about the responsibilities of living in the world shaped by our scientific prowess. Inevitably, also, the cry of "Pseudoscience!" is heard ever more often, in accusation against perceived dishonest uses of science and its intellectual clout. We, the scientists, people with intimate knowledge of its workings, should pay attention to these developments.
There is no doubt that the methodology and spirit of science are abused and misused in the pursuit of goals unrelated to scientific truth. But these offenses are not all the same, so let us try to set up, however tentatively, a scale of dishonesty.
At the top of the scale are the efforts of industries to protect their economic interests from damaging scientific findings. Such efforts are highly dishonest, methodical, and well funded: an "institute" with a reputable-sounding name puts out press releases and white papers in scientific format and jargon, aiming to discredit or cast doubt on science that its sponsors find inconvenient. Tobacco industry has done this against the findings about health and smoking, and the fossil-fuel industry actively tries to discredit climate science. We could call such efforts actual pseudoscience, i.e. intentional deception cloaked as scientific work. They are difficult to counter, but greater public awareness can blunt their effects.
Next in rank is selective denialism, which is motivated by ideology rather than money. Main representatives are creationism and the flat-Earth movement; both are highly dishonest, given to misrepresenting and disregarding inconvenient evidence, and are characterized by a contrived, implacable "skepticism" toward a particular scientific topic, skepticism with which they obviously do not approach the rest of factual knowledge. Creationists will go so far as to "doubt" (without basis) the constant rate of radioactive decay, in order to subvert the timeline of the fossil record, and the flat-Earthers have constructed an entire fantastic alternative physics to accommodate their central proposition.
Next come spurious health and wellness claims which we could collectively call quackery. To the extent that quackery touches upon science, it is usually by vacuous "sciency" claims of cleansing and boosting something or another in your body. Quackery rarely damages the standing of good science, but it intentionally misappropriates the clout of science for unwarranted monetary gain.
In the fourth tier are beliefs we could call paranoid reasoning. For example, in the 1980s a tenacious belief developed that high-voltage power lines caused childhood leukemia. This belief was based on faulty analysis of the geographic distribution of leukemia cases, and on overblown fears of "radiation." Subsequent studies revealed no mechanism by which electromagnetic fields of power-line strength and frequency could cause cancers.
Similarly, contemporary anti-vaccine movement seems to be driven by exaggerated fears of minor risks posed by vaccines (as compared to risks of the actual diseases), fears supported by cherry-picked data. Like the selective denialism, this mindset practices an unassuageable skepticism in one narrow area, and even prides itself on scientific independent-mindedness for it. Hence the comical mantra "I did my own research!"
Paranoid reasoning is motivated by emotional rather than material gain. It is ostensibly well-intended, but its misuse of the scientific method in the justification of ill-founded fears can have tragic consequences.
And then there are inquiries that we should better describe as quixotic than pseudoscientific. Such are the occult and paranormal investigations, UFOs etc. The history of these efforts is rife with fraud and conspiracy mongering, they seldom have a plausible methodology, and they have turned up precious little of value over time. The deception in these activities seems to be mostly self-directed.
Some quixotic inquiries, however, may bring about future scientific benefits. The quest for "irreducible complexity" is an offshoot of creationism: its premise is that some biological systems require many parts working together; imperfection in any one of them would incapacitate the whole system. Consequently, such systems could not evolve by small iterative steps, and must be evidence of design by an intelligent entity.
To be fair, the molecular mechanism of DNA genetics fits that bill rather well. However, this mechanism could have plausibly evolved by "trellising" on a simpler RNA-based precursor, which could have in turn used an even simpler (hypothetically even mineral-based) replicator as a trellis. The irreducible complexity's proponents seek to prove that something is impossible without knowing the limits of what is possible, but they may yet stimulate better theoretical insights into the scope of the evolutionary process. After all, what are the laws of thermodynamics but a refutation of the quest for the perpetual motion machine!
In view of the above indignities, we scientists like to fall back on the "scientific method." There are different ways to define the scientific method, but we can broadly say that it requires empiricism (reliance on sensory evidence), and skepticism: every proposition is presumed false until confirmed by unambiguous evidence, and reasonable doubts are always due a consideration. But for all its proven strengths, scientific method is itself a heuristic, not an algorithm: it is justified because it works better than the alternatives (although notable criticisms were raised long ago), and its uniform application is limited by practical reasons:
[ An old, nerdy joke offers a wonderful illustration. Three scientists, traveling by train through Scottish countryside, spot a black sheep standing in a field:
"Look," cries the astronomer excitedly, "the sheep in Scotland are black!"
"No, my friend," cautions the experimental physicist, "we can only say that some sheep are black."
The mathematician gazes at the sheep, then proclaims: "In Scotland there exists at least one field, in which there exists at least one sheep, at least one side of which is black." ]
Looking at the scientific method from our mathematician's angle, we discover that the charge of pseudoscience could be leveled against surprisingly many things. Let's play the devil's advocate:
Are "soft" sciences – such as sociology or economics – pseudoscience? Their empirical evidence is rarely clear-cut, since fully controlled experiments are difficult, observations are sometimes limited to one-time events, and the studied systems are complex and only partially understood.
Is psychology? Almost all of psychology amounts to listening to people and observing their actions, little of it yielding anything "falsifiable" (e.g. per philosopher Karl Popper). Does this discipline therefore offer no meaningful knowledge, or is it fair to say that people are complicated and that psychology's conclusions are necessarily tentative?
Is brain science pseudoscience? It proposes, not unreasonably, to explain mental phenomena in terms of brain physiology, but as of today there is no substantive hypothesis that would spell out how EEG squiggles and MRI blotches might account for things like self-awareness, perception or will. Is this defensible science, or a quixotic quest oblivious of some fundamental difficulty?
In the "hard" sciences: is string theory pseudoscience? No currently feasible experiment can verify its predictions; all it has going for it is logical consistency and a promise of uniting gravity with other physical forces. Most physicists would call it an honest, unproven hypothesis.
Scientific method has unavoidable limitations, and we have to be prepared for the fact that dishonest actors will game these limitations to forward dishonest arguments. And the more complex the subject, the greater the opportunity to peddle falsehoods and quackery.
But let's also not be too quick with the accusation of pseudoscience. Scientific knowledge advances by reducing the scope of its limitations, by doing one more careful observation, by honestly addressing one more relevant objection – that is our best defense, and there is no single, canonical way of doing it. It goes very much against the scientific spirit to dismiss an inquiry merely because it is inexact, nascent or, worse, unfashionable.
Primary meaning of the prefix pseudo- (ψεύδω) is "to lie," to deceive intentionally. Deliberate self-serving lies, grift, and harmful self-deceptions are the real abuses of science, abuses committed for ulterior purposes. These are the things we should direct our indignation and our efforts against.