How Can We Differentiate Between Science and Pseudoscience?

From the Lecture Series: Your Deceptive Mind — A Scientific Guide to Critical Thinking Skills

By Steven Novella, M.D., Yale School of Medicine

In the Age of Information, differentiating between real science and pseudoscience seems to be simultaneously easier and harder. How can we separate the two and acknowledge a grey area in between?

(Image: Bimbim/Shutterstock)

Is anthropogenic global warming a legitimate science or a pseudoscience, as some claim? What about cryptozoology, the study of unusual creatures unknown to current science, such as Bigfoot, the Lochness Monster, or the Chupacabra, or how about string theory that is held by prominent cosmologists of today or ESP, psi research? Are these legitimate sciences, are they on the fringe of science or are they pseudosciences?

What is Pseudoscience?

The term pseudoscience refers to beliefs and practices that claim to be scientific but lack the true method and essence of science. They have the patina of legitimate science, but something has gone terribly wrong.

Pseudoscience goes beyond just making a few errors or a few sloppy practices. The methods are so flawed that the entire endeavor is suspect. The practice doesn’t even warrant the label of legitimate science. But in reality, there is not a clean division between pristine science on one end and rank pseudoscience on the other. There is rather, a continuum or spectrum between these two extremes.

This is a transcript from the video series Your Deceptive Mind: A Scientific Guide to Critical Thinking Skills. Watch it now, on The Great Courses Plus.

The Grey Zone

Many legitimate sciences may incorporate one or more features normally associated with pseudoscience. A well-trained, respected, successful scientist may still make errors in judgment, poor methodology, may over-interpret their results. For example, they may commit all or many of the errors in cognitive thinking that I have discussed in this course. And some pseudoscientists may occasionally get something right. They may in fact use some legitimate or valid scientific methods, in order to promote their ideas and beliefs. In the middle, between these two extremes of science and pseudoscience, there is a fuzzy grey zone, the borderlands between legitimate science and what Carl Sagan has called the “cheap imitation.”

Philosophers call the difficulty in drawing a sharp line between the two ends of the spectrum the “demarcation problem.” However, this doesn’t mean that there aren’t sciences that are mostly legitimate and other practices that are hopelessly pseudoscientific. Remember, that is the false continuum legible fallacy, the denial of two extremes of a continuum simply because there is no sharp demarcation line in between the two of them. This fuzziness in the middle does not mean that these two extremes do not exist and that we cannot meaningfully speak about them. The key is to know how to recognize the features of pseudoscience and the features of legitimate science.

Learn more about several specific examples of pseudoscience

Recognizing Pseudosciences

Examining extreme cases of pseudoscience is like a doctor studying an advanced form of a disease. The features will be much more obvious and extreme. They will therefore help a doctor to recognize the more subtle signs and milder forms of the pathology. It is for this reason that I think it’s very instructive to examine those with belief systems which, while they purport to be scientific, are on the fringe of science, like cold fusion, crypto zoology, belief in UFOs for example. Some people may denigrate spending any time on such beliefs because they’re on the fringe and they are unusual. But I maintain that they are excellent learning examples. By studying the fringes of science, we will learn a great deal about legitimate science and how to do the best science possible.

In the same way, we can study these extreme pseudosciences and develop a picture of what extreme pseudoscientific pathological features have in common. We also will then see the patterns, the commonality among them. What are the types of cognitive flaws that those practicing pseudoscience tend to make? It is an excellent opportunity for studying the features of what are even called sometimes, “pathological science.”

Learn more about how to think about thinking itself

How Pseudoscientists Use Science

In essence, pseudoscientists use the processes of science, these superficial processes or similarities of science to science, in order to rationalize, scientifically rationalize a conclusion that they wish to be true, rather than using the methods of science to determine if their belief is true or not. What they have failed to do is make a concerted effort, therefore, to prove their own theories wrong. That should always be the first step of any scientist. When you come up with a new idea, a new hypothesis, the first thing you should do is everything possible, in order to disprove your own theory. Find every way possible to conduct an experiment or an observation that can falsify the theory. When the theory or the hypothesis has survived every attempt you can think of to prove it wrong, only then is it reasonable to give it provisional assent, to think, all right, now this is a theory that may be true. Then it’s a good idea to check with your colleagues, publish your results in peer reviewed journals and see what other scientists believe, other experts. Can they think of any ways that maybe you missed that could be an alternate to the theory that you have or that could potentially prove it wrong?

Lloyd Pye

The Galileo Process is a common red flag for pseudoscience. In this case, far reaching claims that overturn entire segments of well-established science are extrapolated from very little research or small bits of evidence.

 bigfoot yeti sasquatch vector illustration
(Image: IreneJedi/Shutterstock)

One example of this “alternative science” is a book written by a researcher called Lloyd Pye called, Everything You Know is Wrong, Book One: Human Origins. This results from this chain reaction of pseudoscientific claims. Pye believes, for example, that there were ancient civilizations unknown to modern archeology that aliens were somehow involved in human history and even evolution and that this can tie into observations of Big Foot and other humanoid creatures, again, unknown to science. In each case, when he has a specific explanation or a specific claim that conflicts with archeology, or paleontology, or biology, or even modern physics. He simply dismisses the modern findings of science and replaces them with yet another pseudoscientific belief system in this, what I called chain reaction, until by the end of it all, you have replaced all of science with an alternative version of reality or everything that scientists claim must therefore be wrong.

Learn more about the nature of perception

Neal Adams

Another example is the comic book artist turned pseudoscientist, in my opinion, Neal Adams, who is a proponent of the hollow or growing earth idea. This is the notion that the planet earth was much, much smaller in the historical past and has been slowly getting larger over time, by the generation of new matter. He believes this is true because the continents of the earth fit together like puzzle pieces. We know that they do fit together to some extent because of plate tectonics, but he thinks they fit together all the way around because at one point in time they were all connected on a small earth, which later expanded with the oceans filling in the cracks that emerged in between. However, there are major scientific problems with this theory. Where is this new matter coming from? How is gravity increasing on the earth? If all of the planets of the solar system were increasing, as he believes, how could their orbits be stable? Each time one of these reasonable scientific objections is raised to this theory, he simply waves his hand and wipes away an entire other discipline of science. Well, “Perhaps it’s magnetism,” he says, “That holds the planets in the orbits and not gravity.” So now all of gravitation and magnetism has to be rethought just to fix this problem with the growing earth theory. He also adds spontaneous creation of matter from nothing. This is something that simply is unknown to physics.

There is the generation of virtual pairs of particles, but then they immediately annihilate each other. But the creation of new stable matter from nothing would violate the conservation of matter and energy, a very well-established law of physics. It would also, his growing earth hypothesis, would violate much of what we know about from modern geology and plate tectonics and volcanism, for example. Again, he would overturn virtually all of modern science that touches on his theories, in order to protect or defend his one idea that he does not want to surrender.

Learn more about the vital role that memories play in critical thinking

D. D. Palmer

You’ll often find pseudoscientists making the hasty generalization logical fallacy basing far reaching principles on a single piece of, perhaps, unreliable evidence

A chiropractor performing a precise vertebral adjustment of the lumbar spine on a patient.
Vertebral Subluxation (Image: By Aleksander Chaibi/Public domain)

An excellent example of this is D. D. Palmer, the father of chiropractic. He based the principles of subluxation theory on a single case of an alleged curing of a person of deafness with neck manipulation. He then extrapolated from this all of chiropractic theory, at least the classic theory of subluxation, the notion that a blockage in the flow of some essence or life force that he called innate or innate intelligence through the spinal cord and through the nerves are what keep the organs and the parts of the body healthy. Blockage of that flow, therefore, causes illness, disease, and symptoms. He believed that he freed up the flow of this life energy in this patient, enabling them to hear, curing their deafness. At the time though, he was not aware, apparently, that the nerves that subsume hearing in at no point pass through the neck. So there isn’t really any plausibility to the notion that manipulating the neck can relieve the underlying neurological pathways that we need to hear.


An iris chart used in iridology
An iris chart used in iridology (Image: By Fabiform/Public domain)

Another example is the founder of Iridology. Iridology is the notion that the iris of the eyes reflect health and disease of the whole body. This is based upon a general approach called the homunculus approach to diagnosis, the belief that the entire is represented in one small part or piece of the body, in this case the iris of the eye. The founder of Iridology made a single observation of an owl who had broken its wing and he observed that a gold fleck in the owl’s eye went away when the wing was healed. From this single observation, he elaborated the entire principle of homunculus based notion that all diseases and ailments can be diagnosed and even predicted by simply looking at the random colors of the flecks in a patient’s eye. Or principles may not be based on just a simple or a single observation, but on a philosophical idea, a philosophy that itself has not been empirically tested or developed as a scientific theory or discipline.

Life Energy

The notion of life energy is a pre-scientific idea, but it forms the basis of many so-called “alternative therapies” like therapeutic touch or Reiki, acupuncture, straight chiropractic, and even homeopathy to some degree. Prior to us having a thorough understanding of all of the physiology, anatomy, biochemistry, all the processes that go to make up a living organism, it was hypothesized that there must be some energy, a life energy that makes some things alive and other things not alive. In the final analysis, it was really a placeholder, an argument from ignorance, if you will. Whatever we currently didn’t understand, that’s what life energy did.

Eventually, we were able, however, to explain all the processes of life, at least to a reasonable degree of detail and there simply was nothing left for life energy to do. It was a philosophy, a philosophical idea of how the body works, never supported or tested by science. Now, it’s an obsolete philosophical idea, but it still forms the core principle of many healing modalities.

Learn more about logical fallacies

Hulda Clarke

Another aspect of pseudoscience is that simple answers are often offered to very complex or multi-factorial problems. One example of that is Hulda Clarke. She believed that liver flukes are the cause of all human diseases therefore, all diseases can be cured by treating this liver fluke. Therefore, she has the cure for all disease, or at least she had before she died.

Common Questions About the Difference Between Science and Pseudoscience

Q: Do pseudoscience and science share anything in common?

Both pseudoscience and science purport to exalt evidence, yet only science reliably, repeatedly, and rigorously tests hypotheses to discover evidence which either supports or denies the hypothesis. Pseudoscience looks only for evidence that supports the hypothesis.

Q: How do you draw the line between science and pseudoscience?

Although sometimes the line between science and pseudoscience can be hazy, what it ultimately comes down to is that pseudoscientific claims can be shaped to meet just about any outcome. In other words, they cannot be proven true or false, as opposed to a scientific claim.

Q: How do you avoid pseudoscience?

In order to avoid articles based on pseudoscience, you should stay away from anything with exaggerated claims or claims that the article or product contains “secret medical knowledge.” Additionally, any reference to esoteric theories is probably pseudoscience.

Q: What are examples of pseudoscience?

Examples of pseudoscience include phrenology, homeopathy, full moon lunacy, astrology, and intelligent design.

This article was updated on 9/27/2019

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