Pseudoscience refers to any body of knowledge, methodology, or practice that is erroneously regarded as scientific. The standards determining such a distinction vary, but often include lack of empirical evidence, unfalsifiability, or failure to comply with scientific method or apply a heuristic such as Occam's Razor. A number of attempts have been made to apply philosophical rigor to the notion with mixed results. These include Karl Popper's criterion of falsifiability and the historiographical approach of Imre Lakatos in his Methodology of Scientific Research Programmes. Other historians and philosophers of science, chiefly Thomas Kuhn and Paul Feyerabend have argued, from a sociology of knowledge perspective, that a clear philosophical distinction between science and pseudoscience is neither possible nor desirable.

The term "pseudoscience" has negative connotations, implying generally that things so labeled are false and deceptive (though a strict interpretation of the term would not necessarily have it mean either). As such, those who are labelled as practicing or advocating a "pseudoscience" almost always reject this classification, and often the distinction itself.

Some critics of pseudoscience consider some or all forms of pseudoscience to be harmless entertainment. Others, such as Richard Dawkins and Carl Sagan, consider all forms of pseudoscience to be harmful, whether or not they result in immediate harm to their followers. These critics generally consider that advocacy of pseudoscience may occur for a number of reasons, ranging from simple naïveté about the nature of science and the scientific method, to deliberate deception for financial or political benefit.

Classifying pseudoscience

Pseudoscience fails to meet the criteria met by science generally (including the scientific method), and can be identified by a combination of these characteristics:

1. by asserting claims or theories unconnected to previous experimental results;
2. by asserting claims which cannot be verified or falsified (claims that violate falsifiability);
3. by asserting claims which contradict experimentally established results;
4. by failing to provide an experimental possibility of reproducible results;
5. by failing to submit results to peer review prior to publicizing them (called "science by press conference")
6. by claiming a theory predicts something that it does not;
7. by claiming a theory predicts something that it has not been shown to predict;
8. by violating Occam's Razor, the heuristic principle of choosing the explanation that requires the fewest additional assumptions when multiple viable explanations are possible (and the more egregious the violation, the more likely); or
9. by a lack of progress toward additional evidence of its claims.

Pseudoscience is distinguishable from revelation, theology, or spirituality in that it claims to offer insight into the physical world by "scientific" means. Systems of thought that rely upon "divine" or "inspired" knowledge are not considered pseudoscience if they do not claim either to be scientific or to overturn well-established science. There are also bodies of practical knowledge that are not claimed to be scientific. These are also not pseudoscience.

Pseudoscience is also distinguishable from misleading statements in some popular science, where commonly held beliefs are thought to meet the criteria of science, but often don't. The issue is muddled, however, because it is believed that "pop" science blurs the divide between science and pseudoscience among the general public.

The term "pseudoscience" is often used by adherents of fields considered pseudoscientific to criticize their mainstream equivalents. Hence, for instance, supporters of creationism often characterize evolution as a pseudoscience, as do supporters of Dianetics with respect to psychiatry. Such criticisms are, however, generally regarded as fringe viewpoints.

Pseudoscience contrasted with protoscience

Pseudoscience also differs from protoscience. Protoscience is a term sometimes used to describe a hypothesis that has not yet been tested adequately by the scientific method, but which is otherwise consistent with existing science or which, where inconsistent, offers reasonable account of the inconsistency.

Pseudoscience, in contrast, is characteristically wanting adequate tests or the possibility of them, occasionally untestable in principle, and its supporters are frequently strident in insisting that existing scientific results are wrong. Pseudoscience is often unresponsive to ordinary scientific procedures (for example, peer review, publication in standard journals). In some cases, no one applying scientific methods could disprove a pseudoscientific hypothesis (that is, untestable claims have been made) and failure to test and disprove these claims is often cited as evidence of the truth of the pseudoscience.

The boundaries between pseudoscience, protoscience, and "real" science are often unclear to non-specialist observers. They can even be obscure to experts. Many people have tried to offer objective criteria for the term, with mixed success. Often the term is used simply as a pejorative to express the speaker's low opinion of a given field, regardless of any objective measures.

If the claims of a given pseudoscience can be experimentally tested it may be real science, however odd, astonishing, or intuitively unacceptable. If they cannot be tested, it is likely pseudoscience. If the claims made are inconsistent with existing experimental results or established theory, it is often presumed to be pseudoscience. Conversely, if the claims of any given "science" cannot be experimentally tested it may not be a real science, however obvious or intuitively acceptable.

In such circumstances it may be difficult to distinguish which of two opposing "sciences" are valid; for example, both the proponents and opponents of the Kyoto Protocol on global warming have recruited the help of scientists to endorse contradictory positions, because of differing political goals. This enlistment of science in the service of politics is sometimes called "junk science".

Other examples of new scientific disciplines that some consider protoscience include

1. Search for Extraterrestrial Intelligence (SETI)
2. Communication with Extraterrestrial Intelligence (CETI)

However, these fields are not considered protoscientific by most scientists; they are genererally considered real science, albeit subjects that may offer only a low probability of revealing significant results.

The difference between these subjects as science and pseudoscience may be seen by these examples: Scientists involved in SETI and CETI do not claim that they know for certain that intelligent extraterrestrials exist, although most consider the possibility likely (see Drake equation). They test their beliefs against available data.

Ultimately, whether something is pseudoscience or not has less to do with the ideas under study than the approach used to study or justify them. Acupuncture, for instance, while it involved a prescientific system, is not inherently pseudoscientific. This is because most of the claims can be tested scientifically so acupuncture can be viewed as a protoscience. Of course, a scientific investigation might fail to support the claims of acupuncture. In the presence of a number of tests that successfully falsify a particular claim, insisting that the claim is still scientifically supported becomes pseudoscience.

The problem of demarcation

After more than a century of active dialogue, the question of what marks the boundary of science remains fundamentally unsettled. As a consequence the issue of what constitutes pseudoscience continues to be controversial. Nonetheless, reasonable consensus exists on certain sub-issues. Criteria for demarcation have traditionally been coupled to one philosophy of science or another. Logical positivism, for example, espoused a theory of meaning which held that only statements about empirical observations are meaningful, effectively asserting that statements which are not derived in this manner (including all metaphysical statements) are meaningless. Later, Karl Popper attacked logical positivism and introduced his own criterion for demarcation, falsifiability. This in turn was criticised by Thomas Kuhn, who illustrated with historical examples that falsification did not play a largely causative role in changes between scientific theories, and also by Popper supporter Imre Lakatos, who proposed his own criteria that distinguished between progressive and degenerative research programs.

Many supporters of both science and pseudoscience have called into question whether there is a rigorous way to tell the difference, especially since, historically, many disciplines currently thought of as "science" exhibit trends which are often cited as those of pseudoscience, such as lack of reproducibility (due to the necessity of large, expensive, and specially created instruments), or the inability to create falsifying experiments. Because of the heterogeneous nature of the scientific enterprise itself, it is increasingly difficult to create a set of criteria which can apply to all disciplines at all times.

Fields often associated with pseudoscience

Examples of fields of endeavor that many consider — to varying extents — pseudoscientific include:

• Alchemy (pre- or proto-scientific rather than pseudoscientific)
• Astrology
• Chakra theory
• Chiropractic
• Clairvoyance
• Creation science and

  » Baraminology
  » Creation biology
  » Creationist cosmologies
  » Flood geology
  » Intelligent design

• Dianetics
• Expansion theory
• Eugenics
• Essentialism
• Electric universe
• Folk psychiatry
• Graphology
• Götaland theory
• Homeopathy
• Lunaception
• Megalithic yard and other pseudoscientific metrology
• Melanin Theory
• Metaphysics
• Modern geocentrism (see also Flat Earth Society)
• New Chronology
• Nonstandard cosmologies
• Orgonomy
• Palmistry
• Parapsychology
• Schemes for Perpetual motion
• Personology
• Phrenology
• Physiognomy
• Precognition
• Pseudoarchaeology

  » Pyramidology

• Gene Ray's Time Cube
• Telekinesis
• Telepathy
• Vedic science

Pseudoscientific science and medical practices are often quite popular. Medical pseudosciences even sometimes show notable therapeutic benefits, possibly due to the placebo effect or observer bias.

Many pseudosciences are associated with the New Age movement and there is a tendency to improperly associate all practices of the "New Age" with pseudoscience.

Certain "watchdog" groups, such as CSICOP, have released statements expressing concern about the apparent growing popularity of pseudoscience, especially when it applies to scientific fields that are intended to save people's lives. A number of self-proclaimed alternative medicine treatments have been designated pseudoscience by critics, largely because some of these methods inspire false hope in terminally ill patients, and end up costing large amounts of money without actually providing any real benefit, treatment, or cure for various ailments.

Pseudomathematics

Pseudomathematics is a form of mathematics-like activity undertaken by many non-mathematicians - and occasionally by mathematicians themselves. The efforts of pseudomathematicians divide into three categories:

attempting apparently simple classical problems long proved impossible by mainstream mathematics; trying metaphorically or (quite often) literally to square the circle
generating whole new theories of mathematics or logic from scratch
attempting hard problems in mathematics (the Goldbach conjecture comes to mind) using only high-school mathematical knowledge

Criticisms of the concept of pseudoscience

Members of the communities whose studies are considered pseudoscientific, consider the term pseudoscience" as inherently stigmating against those fields. Members of those communities often criticise the concept of pseudoscience and the process of mainstrem science. For example, they believe that using "peer review" to pass the quality of a scientific paper, is a conformist process that can be influenced by personality and social disputes, and they contend that the process tends to exclude originality from genuine science in a way that was not suffered by scientific pioneers. Scientists typically reject these arguments, and insist that peer review is essentially in ensuring some level of quality control.