A field, practice, or body of knowledge might reasonably be called pseudoscientific when (1) it is presented as consistent with the accepted norms of scientific research; but (2) it demonstrably fails to meet these norms, most importantly, in misuse of scientific method.

Subjects may be considered pseudoscientific for various reasons; Popper considered astrology to be pseudoscientific simply because astrologers keep their claims so vague that they could never be refuted, whereas Thagard considers astrology pseudoscientific because its practitioners make little effort to develop the theory, show no concern for attempts to critically evaluate the theory in relation to others, and are selective in considering evidence. More generally, Thagard stated that pseudoscience tends to focus on resemblances rather than cause-effect relations.

Science is also distinguishable from revelation, theology, or spirituality in that it claims to offer insight into the physical world obtained by “scientific” means. Systems of thought that derive from divine or inspired knowledge are not considered pseudoscience if they do not claim either to be scientific or to overturn well-established science.

Some statements and commonly held beliefs in popular science may not meet the criteria of science. “Pop” science may blur the divide between science and pseudoscience among the general public, and may also involve science fiction.[18] Indeed, pop science is disseminated to, and can also easily emanate from, persons not accountable to scientific methodology and expert peer review.

The following have been proposed to be indicators of poor scientific reasoning.

Use of vague, exaggerated or untestable claims
Assertion of scientific claims that are vague rather than precise, and that lack specific measurements
Failure to make use of operational definitions. (i.e. a scientific description of the operational means in which a range of numeric measurements can be obtained).[20]
Failure to make reasonable use of the principle of parsimony, i.e. failing to seek an explanation that requires the fewest possible additional assumptions when multiple viable explanations are possible (see: Occam’s Razor)
Use of obscurantist language, and misuse of apparently technical jargon in an effort to give claims the superficial trappings of science.
Lack of boundary conditions: Most well-supported scientific theories possess boundary conditions (well articulated limitations) under which the predicted phenomena do and do not apply.

Over-reliance on confirmation rather than refutation
Assertion of scientific claims that cannot be falsified in the event they are incorrect, inaccurate, or irrelevant (see also: falsifiability)
Assertion of claims that a theory predicts something that it has not been shown to predict
Assertion that claims which have not been proven false must be true, and vice versa (see: Argument from ignorance)
Over-reliance on testimonials and anecdotes. Testimonial and anecdotal evidence can be useful for discovery (i.e. hypothesis generation) but should not be used in the context of justification (i.e. hypothesis testing).
Selective use of experimental evidence: presentation of data that seems to support its own claims while suppressing or refusing to consider data that conflict with its claims.
Reversed burden of proof. In science, the burden of proof rests on the individual making a claim, not on the critic. “Pseudoscientific” arguments may neglect this principle and demand that skeptics demonstrate beyond a reasonable doubt that a claim (e.g. an assertion regarding the efficacy of a novel therapeutic technique) is false. It is essentially impossible to prove a universal negative, so this tactic incorrectly places the burden of proof on the skeptic rather than the claimant.
Appeals to holism: Proponents of pseudoscientific claims, especially in organic medicine, alternative medicine, naturopathy and mental health, often resort to the “mantra of holism” to explain negative findings.

Lack of openness to testing by other experts
Evasion of peer review before publicizing results (called “science by press conference”). Some proponents of theories that contradict accepted scientific theories avoid subjecting their work to the often ego-bruising process of peer review, sometimes on the grounds that peer review is inherently biased against claims that contradict established paradigms, and sometimes on the grounds that assertions cannot be evaluated adequately using standard scientific methods. By remaining insulated from the peer review process, these proponents forego the opportunity of corrective feedback from informed colleagues.
The science community expects authors to share data necessary to evaluate a paper. Failure to provide adequate information for other researchers to reproduce the claimed results is a lack of openness.
Assertion of claims of secrecy or proprietary knowledge in response to requests for review of data or methodology.

Lack of progress
Failure to progress towards additional evidence of its claims. Terrence Hines has identified astrology as a subject that has changed very little in the past two millennia.
Lack of self correction: scientific research programmes make mistakes, but they tend to eliminate these errors over time. By contrast, theories may be accused of being pseudoscientific because they have remained unaltered despite contradictory evidence.

Personalization of issues
Tight social groups and granfalloons. Authoritarian personality, suppression of dissent, and groupthink can enhance the adoption of beliefs that have no rational basis. In attempting to confirm their (confirmation bias), the group tends to identify their critics as enemies.
Assertion of claims of a conspiracy on the part of the scientific community to suppress the results.
Attacking the motives or character of anyone who questions the claims (see Ad hominem fallacy).

(Source: Wikipedia) 

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