https://en.wikipedia.org/wiki/Crank_(person)
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According to these authors, virtually universal characteristics of cranks include:
Cranks overestimate their own knowledge and ability, and underestimate that of acknowledged experts.
Cranks insist that their alleged discoveries are urgently important.
Cranks rarely, if ever, acknowledge any error, no matter how trivial.
Cranks love to talk about their own beliefs, often in inappropriate social situations, but they tend to be bad listeners, being uninterested in anyone else's experience or opinions.
Some cranks lack academic achievement, in which case they typically assert that academic training in the subject of their crank belief is not only unnecessary for discovering the truth, but actively harmful because they believe it poisons the minds by teaching falsehoods. Others greatly exaggerate their personal achievements, and may insist that some achievement (real or alleged) in some entirely unrelated area of human endeavor implies that their cranky opinion should be taken seriously.
Some cranks claim vast knowledge of any relevant literature, while others claim that familiarity with previous work is entirely unnecessary; regardless, cranks inevitably reveal that whether or not they believe themselves to be knowledgeable concerning relevant matters of fact, mainstream opinion, or previous work, they are not in fact well-informed concerning the topic of their belief.
In addition, many cranks:
seriously misunderstand the mainstream opinion to which they believe that they are objecting,
stress that they have been working out their ideas for many decades, and claim that this fact alone entails that their belief cannot be dismissed as resting upon some simple error,
compare themselves with Galileo or Copernicus , implying that the mere unpopularity of some belief is in itself evidence of plausibility,
claim that their ideas are being suppressed, typically by secret intelligence organizations, mainstream science, powerful business interests, or other groups which, they allege, are terrified by the possibility of their revolutionary insights becoming widely known,
appear to regard themselves as persons of unique historical importance.
Cranks who contradict some mainstream opinion in some highly technical field, such as mathematics or physics, frequently:
exhibit a marked lack of technical ability,
misunderstand or fail to use standard notation and terminology,
ignore fine distinctions which are essential to correctly understand mainstream belief.
That is, cranks tend to ignore any previous insights which have been proven by experience to facilitate discussion and analysis of the topic of their cranky claims; indeed, they often assert that these innovations obscure rather than clarify the situation.[3]
In addition, cranky scientific theories do not in fact qualify as theories as this term is commonly understood within science. For example, crank theories in physics typically fail to result in testable predictions, which makes them unfalsifiable and hence unscientific. Or the crank may present their ideas in such a confused, not even wrong manner that it is impossible to determine what they are actually claiming.
Perhaps surprisingly, many cranks may appear quite normal when they are not passionately expounding their cranky belief, and they may even be successful in careers unrelated to their cranky beliefs.
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