Pseudoscientific theories are theories put forth as scientific when they are not scientific. A theory is scientific if empirical predictions can be deduced from it which might turn out to be false. This quality of scientific theories was called falsifiability by Karl Popper. A pseudoscientific theory claims to be scientific, i.e., be falsifiable, but either the theory is not really falsifiable or it has been falsified but its adherents refuse to accept that the theory has been refuted.
Pseudoscientists claim to base their theories on empirical evidence, and they may even use some scientific methods, though often their understanding of a controlled experiment is unquestionably incompetent. Many pseudoscientists relish being able to point out the consistency of their theories with known facts or with predicted consequences, but they do not recognize that such consistency is not proof of anything. It is a necessary condition but not a sufficient condition that a good scientific theory be consistent with the facts. A theory which is contradicted by empirical facts is obviously not a very good scientific theory, but it does not follow from that fact that a theory which is consistent with the facts is therefore a good theory. For example, "the truth of the hypothesis that plague is due to evil spirits is not established by the correctness of the deduction that you can avoid the disease by keeping out of the reach of the evil spirits." [note 1]
Several characteristics of pseudoscientists and pseudoscience seem to stand out:
1. The tendency to propose theories which are put forth as scientific, but which cannot be empirically tested in any meaningful way; that is, the theory is consistent with every conceivable empirical event and no deduced prediction from it could ever falsify it. Or, the theory is couched in terms of non-empirical entities. [e.g., L. Ron Hubbard's engram theory.]2. The dogmatic refusal to give up an idea in the face of overwhelming evidence that the idea is false, and the use of ad hoc hypotheses to try to explain away contrary evidence; [e.g., parapsychology].
3. Selective use of data: the tendency to attend only to confirming instances and to ignore disconfirming instances, i.e., to count the hits and ignore the misses; [e.g., biorhythms, dowsing, parapsychology].
4. The use of personal anecdotes as evidence; [e.g., biorhythms, dianetics, graphology, parapsychology].
5. The lack of concern over the absence of evidence in support of one's theory; [e.g., dianetics, Velikovsky].
6. The use of myths or ancient mysteries to support theories which are then used to explain the myths or mysteries; [e.g., creationism, Velikovsky, von Daniken, Julian Jaynes theory of the origins of consciousness].
7. Gullibility, especially about paranormal, supernatural or extraterrestrial claims [e.g., creationism, parapsychology]. [note 2]
See related entries for examples of pseudoscience: ad hoc hypotheses, psychic detectives, biorhythms, creationism, dianetics, dowsing, facilitated communication, graphology, and parapsychology, selective thinking, Velikovsky, von Daniken.
further reading
Russell Turpin's "Characterization of Quack Theories"
Friedlander, Michael W. At the Fringes of Science, (Boulder, Colorado: Westview Press, 1995).
Gardner, Martin. Fads and Fallacies in the Name of Science (New York: Dover Publications, Inc., 1957).
Gould, Stephen Jay. Ever Since Darwin, (New York: W.W. Norton & Company, 1979).
Radner and Radner, Daisie and Michael. Science and Unreason (Belmont, California: Wadsworth Publishing Co., 1982).
Sagan, Carl. Broca's Brain: Reflections on the Romance of Science (New York: Random House, 1979).