List of fallacies

From Wikipedia, the free encyclopedia

In reasoning to argue a claim, a fallacy is reasoning that is evaluated as logically incorrect and that undermines the logical validity of the argument and permits its recognition as unsound. Regardless of their soundness, all registers and manners of speech can demonstrate fallacies.

 

Because of their variety of structure and application, fallacies are challenging to classify so as to satisfy all practitioners. Fallacies can be classified strictly by either their structure or content, such as classifying them as formal fallacies or informal fallacies, respectively. The classification of informal fallacies may be subdivided into categories such as linguistic, relevance through omission, relevance through intrusion, and relevance through presumption. On the other hand, fallacies may be classified by the process by which they occur, such as material fallacies (content), verbal fallacies (linguistic), and again formal fallacies (error in inference). In turn, material fallacies may be placed into the more general category of informal fallacies, while formal fallacies may be clearly placed into the more precise category of logical (deductive) fallacies. Yet, verbal fallacies may be placed into either informal or deductive classifications; compare equivocation which is a word or phrase based ambiguity, e. g. "he is mad", which may refer to either him being angry or clinically insane, to the fallacy of composition which is premise and inference based ambiguity, e. g. "this must be a good basketball team because each of its members is an outstanding player".

Faulty inferences in deductive reasoning are common formal or logical fallacies. As the nature of inductive reasoning is based on probability, a fallacious inductive argument or one that is potentially misleading, is often classified as "weak".

The conscious or habitual use of fallacies as rhetorical devices are prevalent in the desire to persuade when the focus is more on communication and eliciting common agreement rather than the correctness of the reasoning. The effective use of a fallacy by an orator may be considered clever, but by the same token, the reasoning of that orator should be recognized as unsound, and thus the orator's claim, supported by an unsound argument, will be regarded as unfounded and dismissed.

Formal fallacies

A formal fallacy is an error in logic that can be seen in the argument's form. All formal fallacies are specific types of non sequiturs.

• Appeal to probability – a statement that takes something for granted because it would probably be the case (or might be the case).
• Argument from fallacy (also known as the fallacy fallacy) – assumption that if an argument for some conclusion is fallacious, then the conclusion is false.
• Base rate fallacy – making a probability judgment based on conditional probabilities, without taking into account the effect of prior probabilities.
• Conjunction fallacy – assumption that an outcome simultaneously satisfying multiple conditions is more probable than an outcome satisfying a single one of them.
• Masked-man fallacy (illicit substitution of identicals) – the substitution of identical designators in a true statement can lead to a false one.

Propositional fallacies

A propositional fallacy is an error in logic that concerns compound propositions. For a compound proposition to be true, the truth values of its constituent parts must satisfy the relevant logical connectives that occur in it (most commonly: , , , , ). The following fallacies involve inferences whose correctness is not guaranteed by the behavior of those logical connectives, and hence, which are not logically guaranteed to yield true conclusions.

Types of propositional fallacies:

• Affirming a disjunct – concluding that one disjunct of a logical disjunction must be false because the other disjunct is true; A or B; A, therefore not B.
• Affirming the consequent – the antecedent in an indicative conditional is claimed to be true because the consequent is true; if A, then B; B, therefore A.
• Denying the antecedent – the consequent in an indicative conditional is claimed to be false because the antecedent is false; if A, then B; not A, therefore not B.

Quantification fallacies

A quantification fallacy is an error in logic where the quantifiers of the premises are in contradiction to the quantifier of the conclusion. 

Types of quantification fallacies:

• Existential fallacy – an argument that has a universal premise and a particular conclusion.

Formal syllogistic fallacies

Syllogistic fallacies – logical fallacies that occur in syllogisms.

• Affirmative conclusion from a negative premise (illicit negative) – a categorical syllogism has a positive conclusion, but at least one negative premise.
• Fallacy of exclusive premises – a categorical syllogism that is invalid because both of its premises are negative.
• Fallacy of four terms (quaternio terminorum) – a categorical syllogism that has four terms.
• Illicit major – a categorical syllogism that is invalid because its major term is not distributed in the major premise but distributed in the conclusion.
• Illicit minor – a categorical syllogism that is invalid because its minor term is not distributed in the minor premise but distributed in the conclusion.
• Negative conclusion from affirmative premises (illicit affirmative) – a categorical syllogism has a negative conclusion but affirmative premises.
• Fallacy of the undistributed middle – the middle term in a categorical syllogism is not distributed.
• Modal fallacy – confusing possibility with necessity.

Informal fallacies

Informal fallacies – arguments that are fallacious for reasons other than structural (formal) flaws and usually require examination of the argument's content.

• Argument to moderation (false compromise, middle ground, fallacy of the mean, argumentum ad temperantiam) – assuming that the compromise between two positions is always correct.
• Continuum fallacy (fallacy of the beard, line-drawing fallacy, sorites fallacy, fallacy of the heap, bald man fallacy) – improperly rejecting a claim for being imprecise.
• Correlative-based fallacies
  • Suppressed correlative – a correlative is redefined so that one alternative is made impossible.
• Divine fallacy (argument from incredulity) – arguing that, because something is so incredible or amazing, it must be the result of superior, divine, alien or paranormal agency.
• Double counting – counting events or occurrences more than once in probabilistic reasoning, which leads to the sum of the probabilities of all cases exceeding unity.
• Equivocation – the misleading use of a term with more than one meaning (by glossing over which meaning is intended at a particular time).
  • Ambiguous middle term – a common ambiguity in syllogisms in which the middle term is equivocated.
  • Definitional retreat – changing the meaning of a word to deal with an objection raised against the original wording.
  • Motte-and-bailey fallacy – The arguer conflates two similar positions, one modest and easy to defend (the "motte") and one much more controversial (the "bailey"). The arguer advances the controversial position, but when challenged, they insist that they are only advancing the more modest position.
  • Fallacy of accent – a specific type of ambiguity that arises when the meaning of a sentence is changed by placing an unusual prosodic stress, or when, in a written passage, it's left unclear which word the emphasis was supposed to fall on.
  • (See also the if-by-whiskey fallacy, below.)
• Ecological fallacy – inferences about the nature of specific individuals are based solely upon aggregate statistics collected for the group to which those individuals belong.
• Etymological fallacy – reasoning that the original or historical meaning of a word or phrase is necessarily similar to its actual present-day usage.
• Fallacy of composition – assuming that something true of part of a whole must also be true of the whole.
• Fallacy of division – assuming that something true of a thing must also be true of all or some of its parts.
• False attribution – an advocate appeals to an irrelevant, unqualified, unidentified, biased or fabricated source in support of an argument.
  • Fallacy of quoting out of context (contextotomy, contextomy; quotation mining) – refers to the selective excerpting of words from their original context in a way that distorts the source's intended meaning.
• False authority (single authority) – using an expert of dubious credentials or using only one opinion to sell a product or idea. Related to the appeal to authority (not always fallacious).
• False dilemma (false dichotomy, fallacy of bifurcation, black-or-white fallacy) – two alternative statements are held to be the only possible options when in reality there are more.
• False equivalence – describing a situation of logical and apparent equivalence, when in fact there is none.
• Historian's fallacy – the assumption that decision makers of the past viewed events from the same perspective and had the same information as those subsequently analyzing the decision. (Not to be confused with presentism, which is a mode of historical analysis in which present-day ideas, such as moral standards, are projected into the past.)
• Historical fallacy – a set of considerations is thought to hold good only because a completed process is read into the content of the process which conditions this completed result.
• Homunculus fallacy – a "middle-man" is used for explanation; this sometimes leads to regressive middle-men. Explains without actually explaining the real nature of a function or a process. Instead, it explains the concept in terms of the concept itself, without first defining or explaining the original concept. Explaining thought as something produced by a little thinker, a sort of homunculus inside the head, merely explains it as another kind of thinking (as different but the same).
• Inflation of conflict – arguing that if experts of a field of knowledge disagree on a certain point, the experts must know nothing, and therefore no conclusion can be reached, or that the legitimacy of their entire field is put to question.
• If-by-whiskey – an argument that supports both sides of an issue by using terms that are selectively emotionally sensitive.
• Incomplete comparison – insufficient information is provided to make a complete comparison.
• Inconsistent comparison – different methods of comparison are used, leaving a false impression of the whole comparison.
• Intentionality fallacy – the insistence that the ultimate meaning of an expression must be consistent with the intention of the person from whom the communication originated (e.g. a work of fiction that is widely received as a blatant allegory must necessarily not be regarded as such if the author intended it not to be so.)
• Kettle logic – using multiple, jointly inconsistent arguments to defend a position.
• Ludic fallacy – the belief that the outcomes of non-regulated random occurrences can be encapsulated by a statistic; a failure to take into account unknown unknowns in determining the probability of events taking place.
• McNamara fallacy (quantitative fallacy) – making a decision based only on quantitative observations, discounting all other considerations.
• Mind projection fallacy – subjective judgments are "projected" to be inherent properties of an object, rather than being related to personal perceptions of that object.
• Moralistic fallacy – inferring factual conclusions from purely evaluative premises in violation of fact–value distinction. For instance, inferring is from ought is an instance of moralistic fallacy. Moralistic fallacy is the inverse of naturalistic fallacy defined below.
• Moving the goalposts (raising the bar) – argument in which evidence presented in response to a specific claim is dismissed and some other (often greater) evidence is demanded.
• Nirvana fallacy (perfect-solution fallacy) – solutions to problems are rejected because they are not perfect.
• Onus probandi – from the Latin onus probandi incumbit ei qui dicit, non ei qui negat the burden of proof is on the person who makes the claim, not on the person who denies (or questions the claim). It is a particular case of the argumentum ad ignorantiam fallacy, here the burden is shifted on the person defending against the assertion. Also known as "shifting the burden of proof".
• Proof by assertion – a proposition is repeatedly restated regardless of contradiction; sometimes confused with argument from repetition (argumentum ad infinitum, argumentum ad nauseam)
• Prosecutor's fallacy – a low probability of false matches does not mean a low probability of some false match being found.
• Proving too much – using a form of argument that, if it were valid, could be used to reach an additional, invalid conclusion.
• Psychologist's fallacy – an observer presupposes the objectivity of their own perspective when analyzing a behavioral event.
• Referential fallacy – assuming all words refer to existing things and that the meaning of words reside within the things they refer to, as opposed to words possibly referring to no real object or that the meaning of words often comes from how they are used.
• Reification (concretism, hypostatization, or the fallacy of misplaced concreteness) – a fallacy of ambiguity, when an abstraction (abstract belief or hypothetical construct) is treated as if it were a concrete, real event or physical entity. In other words, it is the error of treating as a "real thing" something that is not a real thing, but merely an idea.
• Retrospective determinism – the argument that because an event has occurred under some circumstance, the circumstance must have made its occurrence inevitable.
• Special pleading – a proponent of a position attempts to cite something as an exemption to a generally accepted rule or principle without justifying the exemption.

Improper premise

• Begging the question (petitio principii) – providing what is essentially the conclusion of the argument as a premise.
  • Loaded label – while not inherently fallacious, use of evocative terms to support a conclusion is a type of begging the question fallacy. When fallaciously used, the term's connotations are relied on to sway the argument towards a particular conclusion. For example, an organic foods advertisement that says "Organic foods are safe and healthy foods grown without any pesticides, herbicides, or other unhealthy additives." Use of the term "unhealthy additives" is used as support for the idea that the product is safe.
• Circular reasoning (circulus in demonstrando) – the reasoner begins with what he or she is trying to end up with; sometimes called assuming the conclusion.
• Fallacy of many questions (complex question, fallacy of presuppositions, loaded question, plurium interrogationum) – someone asks a question that presupposes something that has not been proven or accepted by all the people involved. This fallacy is often used rhetorically so that the question limits direct replies to those that serve the questioner's agenda.

Faulty generalizations

Faulty generalization – reach a conclusion from weak premises. Unlike fallacies of relevance, in fallacies of defective induction, the premises are related to the conclusions yet only weakly buttress the conclusions. A faulty generalization is thus produced.

• Accident – an exception to a generalization is ignored.
  • No true Scotsman – makes a generalization true by changing the generalization to exclude a counterexample.
• Cherry picking (suppressed evidence, incomplete evidence) – act of pointing at individual cases or data that seem to confirm a particular position, while ignoring a significant portion of related cases or data that may contradict that position.
  • Survivorship bias – a small number of successes of a given process are actively promoted while completely ignoring a large number of failures
• False analogy – an argument by analogy in which the analogy is poorly suited.
• Hasty generalization (fallacy of insufficient statistics, fallacy of insufficient sample, fallacy of the lonely fact, hasty induction, secundum quid, converse accident, jumping to conclusions) – basing a broad conclusion on a small sample or the making of a determination without all of the information required to do so.
• Inductive fallacy – A more general name to some fallacies, such as hasty generalization. It happens when a conclusion is made of premises that lightly support it.
• Misleading vividness – involves describing an occurrence in vivid detail, even if it is an exceptional occurrence, to convince someone that it is a problem; this also relies on the appeal to emotion fallacy.
• Overwhelming exception – an accurate generalization that comes with qualifications that eliminate so many cases that what remains is much less impressive than the initial statement might have led one to assume.
• Thought-terminating cliché – a commonly used phrase, sometimes passing as folk wisdom, used to quell cognitive dissonance, conceal lack of forethought, move on to other topics, etc. – but in any case, to end the debate with a cliché rather than a point.

Questionable cause

Questionable cause - Is a general type error with many variants. Its primary basis is the confusion of association with causation. Either by inappropriately deducing (or rejecting) causation or a broader failure to properly investigate the cause of an observed effect.

• Cum hoc ergo propter hoc (Latin for "with this, therefore because of this"; correlation implies causation; faulty cause/effect, coincidental correlation, correlation without causation) – a faulty assumption that, because there is a correlation between two variables, one caused the other.
  • Post hoc ergo propter hoc (Latin for "after this, therefore because of this"; temporal sequence implies causation) – X happened, then Y happened; therefore X caused Y.
  • Wrong direction (reverse causation) – cause and effect are reversed. The cause is said to be the effect and vice versa. The consequence of the phenomenon is claimed to be its root cause.
  • Ignoring a common cause
• Fallacy of the single cause (causal oversimplification) – it is assumed that there is one, simple cause of an outcome when in reality it may have been caused by a number of only jointly sufficient causes.
• Furtive fallacy – outcomes are asserted to have been caused by the malfeasance of decision makers.
• Gambler's fallacy – the incorrect belief that separate, independent events can affect the likelihood of another random event. If a fair coin lands on heads 10 times in a row, the belief that it is "due to the number of times it had previously landed on tails" is incorrect.
  • Inverse gambler's fallacy
• Magical thinking – fallacious attribution of causal relationships between actions and events. In anthropology, it refers primarily to cultural beliefs that ritual, prayer, sacrifice, and taboos will produce specific supernatural consequences. In psychology, it refers to an irrational belief that thoughts by themselves can affect the world or that thinking something corresponds with doing it.
• Regression fallacy – ascribes cause where none exists. The flaw is failing to account for natural fluctuations. It is frequently a special kind of post hoc fallacy.

Relevance fallacies

• Appeal to the stone (argumentum ad lapidem) – dismissing a claim as absurd without demonstrating proof for its absurdity.
• Argument from ignorance (appeal to ignorance, argumentum ad ignorantiam) – assuming that a claim is true because it has not been or cannot be proven false, or vice versa.
• Argument from incredulity (appeal to common sense) – "I cannot imagine how this could be true; therefore, it must be false."
• Argument from repetition (argumentum ad nauseam, argumentum ad infinitum) – repeating an argument until nobody cares to discuss it any more; sometimes confused with proof by assertion
• Argument from silence (argumentum ex silentio) – assuming that a claim is true based on the absence of textual or spoken evidence from an authoritative source, or vice versa.
• Ignoratio elenchi (irrelevant conclusion, missing the point) – an argument that may in itself be valid, but does not address the issue in question.

Red herring fallacies

A red herring fallacy, one of the main subtypes of fallacies of relevance, is an error in logic where a proposition is, or is intended to be, misleading in order to make irrelevant or false inferences. In the general case any logical inference based on fake arguments, intended to replace the lack of real arguments or to replace implicitly the subject of the discussion.

Red herring – a speaker attempts to distract an audience by deviating from the topic at hand by introducing a separate argument the speaker believes is easier to speak to. Argument given in response to another argument, which is irrelevant and draws attention away from the subject of argument.

• Ad hominem – attacking the arguer instead of the argument.
  • Circumstantial ad hominem - stating that the arguers personal situation or perceived benefit from advancing a conclusion means that their conclusion is wrong.
  • Poisoning the well – a subtype of ad hominem presenting adverse information about a target person with the intention of discrediting everything that the target person says.
  • Abusive fallacy – verbally abusing the opponent rather than arguing about the originally proposed argument.
  • Appeal to motive – dismissing an idea by questioning the motives of its proposer.
  • Kafka-trapping – a sophistical and unfalsifiable form of argument that attempts to overcome an opponent by inducing a sense of guilt and using the opponent's denial of guilt as further evidence of guilt.
  • Tone policing – focusing on emotion behind (or resulting from) a message rather than the message itself as a discrediting tactic.
  • Traitorous critic fallacy (ergo decedo, 'thus leave') – a critic's perceived affiliation is portrayed as the underlying reason for the criticism and the critic is asked to stay away from the issue altogether. Easily confused with the association fallacy ("guilt by association"), below.
• Appeal to authority (argument from authority, argumentum ad verecundiam) – an assertion is deemed true because of the position or authority of the person asserting it. The term is also used more broadly to describe arguments that are not always fallacious; see entry in the Conditional or questionable fallacies section.
  • Appeal to accomplishment – an assertion is deemed true or false based on the accomplishments of the proposer. This may often also have elements of appeal to emotion (see below).
  • Courtier's reply – a criticism is dismissed by claiming that the critic lacks sufficient knowledge, credentials, or training to credibly comment on the subject matter.
• Appeal to consequences (argumentum ad consequentiam) – the conclusion is supported by a premise that asserts positive or negative consequences from some course of action in an attempt to distract from the initial discussion.
• Appeal to emotion – an argument is made due to the manipulation of emotions, rather than the use of valid reasoning.
  • Appeal to fear – an argument is made by increasing fear and prejudice towards the opposing side
  • Appeal to flattery – an argument is made due to the use of flattery to gather support.
  • Appeal to pity (argumentum ad misericordiam) – an argument attempts to induce pity to sway opponents.
  • Appeal to ridicule – an argument is made by incorrectly presenting the opponent's argument in a way that makes it appear ridiculous.
  • Appeal to spite – an argument is made through exploiting people's bitterness or spite towards an opposing party.
  • Judgmental language – insulting or pejorative language to influence the audience's judgment.
  • Pooh-pooh – dismissing an argument perceived unworthy of serious consideration.
  • Wishful thinking – a decision is made according to what might be pleasing to imagine, rather than according to evidence or reason.
• Appeal to nature – judgment is based solely on whether the subject of judgment is 'natural' or 'unnatural'. (Sometimes also called the "naturalistic fallacy", but is not to be confused with the other fallacies by that name.)
• Appeal to novelty (argumentum novitatis, argumentum ad antiquitatis) – a proposal is claimed to be superior or better solely because it is new or modern.
• Appeal to poverty (argumentum ad Lazarum) – supporting a conclusion because the arguer is poor (or refuting because the arguer is wealthy). (Opposite of appeal to wealth.)
• Appeal to tradition (argumentum ad antiquitatem) – a conclusion supported solely because it has long been held to be true.
• Appeal to wealth (argumentum ad crumenam) – supporting a conclusion because the arguer is wealthy (or refuting because the arguer is poor). (Sometimes taken together with the appeal to poverty as a general appeal to the arguer's financial situation.)
• Argumentum ad baculum (appeal to the stick, appeal to force, appeal to threat) – an argument made through coercion or threats of force to support position.
• Argumentum ad populum (appeal to widespread belief, bandwagon argument, appeal to the majority, appeal to the people) – a proposition is claimed to be true or good solely because a majority or many people believe it to be so.
• Association fallacy (guilt by association and honor by association) – arguing that because two things share (or are implied to share) some property, they are the same.
• Ipse dixit (bare assertion fallacy) – a claim that is presented as true without support, as self-evidently true, or as dogmatically true. This fallacy relies on the implied expertise of the speaker or on an unstated truism.
• Bulverism (psychogenetic fallacy) – inferring why an argument is being used, associating it to some psychological reason, then assuming it is invalid as a result. The assumption that if the origin of an idea comes from a biased mind, then the idea itself must also be a falsehood.
• Chronological snobbery – a thesis is deemed incorrect because it was commonly held when something else, known to be false, was also commonly held.
• Fallacy of relative privation (also known as "appeal to worse problems" or "not as bad as") – dismissing an argument or complaint due to the existence of more important problems in the world, regardless of whether those problems bear relevance to the initial argument. First World problems are a subset of this fallacy.
• Genetic fallacy – a conclusion is suggested based solely on something or someone's origin rather than its current meaning or context.
• Moralistic fallacy – inferring factual conclusions from evaluative premises, in violation of fact–value distinction; e.g. making statements about what is, on the basis of claims about what ought to be. This is the inverse of the naturalistic fallacy.
• Naturalistic fallacy – inferring evaluative conclusions from purely factual premises in violation of fact–value distinction. Naturalistic fallacy in the stricter sense defined in the section "Conditional or questionable fallacies" (below) is a variety of this broader sense. Naturalistic fallacy (sometimes confused with appeal to nature) is the inverse of moralistic fallacy.
  • Is–ought fallacy – statements about what is, on the basis of claims about what ought to be.
• Naturalistic fallacy fallacy (anti-naturalistic fallacy) – inferring an impossibility to infer any instance of ought from is from the general invalidity of is-ought fallacy, mentioned above. For instance, is ${\displaystyle P\lor \neg P}$ does imply ought ${\displaystyle P\lor \neg P}$ for any proposition ${\displaystyle P}$, although the naturalistic fallacy fallacy would falsely declare such an inference invalid. Naturalistic fallacy fallacy is a type of argument from fallacy.
• Straw man fallacy – an argument based on misrepresentation of an opponent's position.
• Texas sharpshooter fallacy – improperly asserting a cause to explain a cluster of data.
• Tu quoque ('you too' – appeal to hypocrisy, whataboutism) – the argument states that a certain position is false or wrong or should be disregarded because its proponent fails to act consistently in accordance with that position.
• Two wrongs make a right – occurs when it is assumed that if one wrong is committed, another wrong will rectify it.
• Vacuous truth – a claim that is technically true but meaningless, in the form of claiming that no A in B has C, when there is no A in B. For example, claiming that no mobile phones in the room are on when there are no mobile phones in the room at all.

Conditional or questionable fallacies

• Appeal to authority (argument from authority, argumentum ad verecundiam) – a form of defeasible argument in which a claimed authority's support is used as evidence for an argument's conclusion. The argument may actually be cogent when all sides of a discussion agree on the reliability of the authority in the given context. See the Red herring fallacies section, above, for the fallacious variant.
• Broken window fallacy – an argument that disregards lost opportunity costs (typically non-obvious, difficult to determine or otherwise hidden) associated with destroying property of others, or other ways of externalizing costs onto others. For example, an argument that states breaking a window generates income for a window fitter, but disregards the fact that the money spent on the new window cannot now be spent on new shoes.
• Definist fallacy – involves the confusion between two notions by defining one in terms of the other.
• The ends justify the means – an assertion that may or may not be defensible depending on the ends and means in question. The various approaches to this sort of question are the subject of the normative ethical theories of consequentialism.
• Naturalistic fallacy – attempts to prove a claim about ethics by appealing to a definition of the term "good" in terms of either one or more claims about natural properties. The naturalistic fallacy also has a more general version, covered in the "Red herring fallacies" section, above.
• Slippery slope (thin edge of the wedge, camel's nose) – asserting that a relatively small first step inevitably leads to a chain of related events culminating in some significant impact/event that should not happen, thus the first step should not happen. It is, in its essence, an appeal to probability fallacy.

Scientific misconduct

From Wikipedia, the free encyclopedia

Scientific misconduct is the violation of the standard codes of scholarly conduct and ethical behavior in the publication of professional scientific research. A Lancet review on Handling of Scientific Misconduct in Scandinavian countries provides the following sample definitions: (reproduced in The COPE report 1999.)

• Danish definition: "Intention or gross negligence leading to fabrication of the scientific message or a false credit or emphasis given to a scientist"
• Swedish definition: "Intention[al] distortion of the research process by fabrication of data, text, hypothesis, or methods from another researcher's manuscript form or publication; or distortion of the research process in other ways."

The consequences of scientific misconduct can be damaging for perpetrators and journal audience and for any individual who exposes it. In addition there are public health implications attached to the promotion of medical or other interventions based on false or fabricated research findings.

Three percent of the 3,475 research institutions that report to the US Department of Health and Human Services' Office of Research Integrity, indicate some form of scientific misconduct. However the ORI will only investigate allegations of impropriety where research was funded by federal grants. They routinely monitor such research publication for red flags and their investigation is subject to a statute of limitations. Other private organizations like the Committee of Medical Journal Editors (COJE) can only police their own members.

The validity of the methods and results of scientific papers are often scrutinized in journal clubs. In this venue, members can decide amongst themselves with the help of peers if a scientific paper's ethical standards are met.

Motivation to commit scientific misconduct

According to David Goodstein of Caltech, there are motivators for scientists to commit misconduct, which are briefly summarised here.

Career pressure

Science is still a very strongly career-driven discipline. Scientists depend on a good reputation to receive ongoing support and funding, and a good reputation relies largely on the publication of high-profile scientific papers. Hence, there is a strong imperative to "publish or perish". Clearly, this may motivate desperate (or fame-hungry) scientists to fabricate results.

Ease of fabrication

In many scientific fields, results are often difficult to reproduce accurately, being obscured by noise, artifacts, and other extraneous data. That means that even if a scientist does falsify data, they can expect to get away with it – or at least claim innocence if their results conflict with others in the same field. There are no "scientific police" who are trained to fight scientific crimes; all investigations are made by experts in science but amateurs in dealing with criminals. It is relatively easy to cheat although difficult to know exactly how many scientists fabricate data.

Forms of scientific misconduct

The U.S. National Science Foundation defines three types of research misconduct: fabrication, falsification, and plagiarism.

• Fabrication is making up results and recording or reporting them. This is sometimes referred to as "drylabbing". A more minor form of fabrication is where references are included to give arguments the appearance of widespread acceptance, but are actually fake, or do not support the argument.
• Falsification is manipulating research materials, equipment, or processes or changing or omitting data or results such that the research is not accurately represented in the research record.
• Plagiarism is the appropriation of another person's ideas, processes, results, or words without giving appropriate credit. One form is the appropriation of the ideas and results of others, and publishing as to make it appear the author had performed all the work under which the data was obtained. A subset is citation plagiarism – willful or negligent failure to appropriately credit other or prior discoverers, so as to give an improper impression of priority. This is also known as, "citation amnesia", the "disregard syndrome" and "bibliographic negligence". Arguably, this is the most common type of scientific misconduct. Sometimes it is difficult to guess whether authors intentionally ignored a highly relevant cite or lacked knowledge of the prior work. Discovery credit can also be inadvertently reassigned from the original discoverer to a better-known researcher. This is a special case of the Matthew effect.
  • Plagiarism-fabrication – the act of taking an unrelated figure from an unrelated publication and reproducing it exactly in a new publication, claiming that it represents new data.
  • Self-plagiarism – or multiple publication of the same content with different titles or in different journals is sometimes also considered misconduct; scientific journals explicitly ask authors not to do this. It is referred to as "salami" (i.e. many identical slices) in the jargon of medical journal editors. According to some editors this includes publishing the same article in a different language.

Other types of research misconduct are also recognized:

• Ghostwriting – the phenomenon where someone other than the named author(s) makes a major contribution. Typically, this is done to mask contributions from authors with a conflict of interest.
• Conversely, research misconduct is not limited to not listing authorship, but also includes the act of conferring authorship on those that have not made substantial contributions to the research. This is done by senior researchers who muscle their way onto the papers of inexperienced junior researchers as well as others that stack authorship in an effort to guarantee publication. This is much harder to prove due to a lack of consistency in defining "authorship" or "substantial contribution".

Photo manipulation

Compared to other forms of scientific misconduct, image fraud (manipulation of images to distort their meaning) is of particular interest since it can frequently be detected by external parties. In 2006, the Journal of Cell Biology gained publicity for instituting tests to detect photo manipulation in papers that were being considered for publication. This was in response to the increased usage of programs such as Adobe Photoshop by scientists, which facilitate photo manipulation. Since then more publishers, including the Nature Publishing Group, have instituted similar tests and require authors to minimize and specify the extent of photo manipulation when a manuscript is submitted for publication. However, there is little evidence to indicate that such tests are applied rigorously. One Nature paper published in 2009 has subsequently been reported to contain around 20 separate instances of image fraud.

Although the type of manipulation that is allowed can depend greatly on the type of experiment that is presented and also differ from one journal to another, in general the following manipulations are not allowed:

• splicing together different images to represent a single experiment
• changing brightness and contrast of only a part of the image
• any change that conceals information, even when it is considered to be aspecific, which includes:
  • changing brightness and contrast to leave only the most intense signal
  • using clone tools to hide information
• showing only a very small part of the photograph so that additional information is not visible

Responsibility of authors and of coauthors

All authors of a scientific publication are expected to have made reasonable attempts to check findings submitted to academic journals for publication. 

Simultaneous submission of scientific findings to more than one journal or duplicate publication of findings is usually regarded as misconduct, under what is known as the Ingelfinger rule, named after the editor of the New England Journal of Medicine 1967-1977, Franz Ingelfinger.

Guest authorship (where there is stated authorship in the absence of involvement, also known as gift authorship) and ghost authorship (where the real author is not listed as an author) are commonly regarded as forms of research misconduct. In some cases coauthors of faked research have been accused of inappropriate behavior or research misconduct for failing to verify reports authored by others or by a commercial sponsor. Examples include the case of Gerald Schatten who co-authored with Hwang Woo-Suk, the case of Professor Geoffrey Chamberlain named as guest author of papers fabricated by Malcolm Pearce, (Chamberlain was exonerated from collusion in Pearce's deception) – and the coauthors with Jan Hendrik Schön at Bell Laboratories. More recent cases include that of Charles Nemeroff, then the editor-in-chief of Neuropsychopharmacology, and a well-documented case involving the drug Actonel.

Authors are expected to keep all study data for later examination even after publication. The failure to keep data may be regarded as misconduct. Some scientific journals require that authors provide information to allow readers to determine whether the authors might have commercial or non-commercial conflicts of interest. Authors are also commonly required to provide information about ethical aspects of research, particularly where research involves human or animal participants or use of biological material. Provision of incorrect information to journals may be regarded as misconduct. Financial pressures on universities have encouraged this type of misconduct. The majority of recent cases of alleged misconduct involving undisclosed conflicts of interest or failure of the authors to have seen scientific data involve collaborative research between scientists and biotechnology companies (Nemeroff, Blumsohn).

Responsibilities of research institutions

In general, defining whether an individual is guilty of misconduct requires a detailed investigation by the individual's employing academic institution. Such investigations require detailed and rigorous processes and can be extremely costly. Furthermore, the more senior the individual under suspicion, the more likely it is that conflicts of interest will compromise the investigation. In many countries (with the notable exception of the United States) acquisition of funds on the basis of fraudulent data is not a legal offence and there is consequently no regulator to oversee investigations into alleged research misconduct. Universities therefore have few incentives to investigate allegations in a robust manner, or act on the findings of such investigations if they vindicate the allegation.

Well publicised cases illustrate the potential role that senior academics in research institutions play in concealing scientific misconduct. A King's College (London) internal investigation showed research findings from one of their researchers to be 'at best unreliable, and in many cases spurious' but the college took no action, such as retracting relevant published research or preventing further episodes from occurring. It was only 10 years later, when an entirely separate form of misconduct by the same individual was being investigated by the General Medical Council, that the internal report came to light.

In a more recent case an internal investigation at the National Centre for Cell Science (NCCS), Pune determined that there was evidence of misconduct by Dr. Gopal Kundu, but an external committee was then organised which dismissed the allegation, and the NCCS issued a memorandum exonerating the authors of all charges of misconduct. Undeterred by the NCCS exoneration, the relevant journal (Journal of Biological Chemistry) withdrew the paper based on its own analysis.

Responsibilities of uninvolved scientific colleagues

Some academics believe that scientific colleagues who suspect scientific misconduct should consider taking informal action themselves, or reporting their concerns. This question is of great importance since much research suggests that it is very difficult for people to act or come forward when they see unacceptable behavior, unless they have help from their organizations. A "User-friendly Guide," and the existence of a confidential organizational ombudsman may help people who are uncertain about what to do, or afraid of bad consequences for their speaking up.

Responsibility of journals

Journals are responsible for safeguarding the research record and hence have a critical role in dealing with suspected misconduct. This is recognised by the Committee on Publication Ethics (COPE) which has issued clear guidelines on the form (e.g. retraction) that concerns over the research record should take.

• The COPE guidelines state that journal editors should consider retracting a publication if they have clear evidence that the findings are unreliable, either as a result of misconduct (e.g. data fabrication) or honest error (e.g. miscalculation or experimental error). Retraction is also appropriate in cases of redundant publication, plagiarism and unethical research.
• Journal editors should consider issuing an expression of concern if they receive inconclusive evidence of research or publication misconduct by the authors, there is evidence that the findings are unreliable but the authors' institution will not investigate the case, they believe that an investigation into alleged misconduct related to the publication either has not been, or would not be, fair and impartial or conclusive, or an investigation is underway but a judgement will not be available for a considerable time.
• Journal editors should consider issuing a correction if a small portion of an otherwise reliable publication proves to be misleading (especially because of honest error), or the author / contributor list is incorrect (i.e. a deserving author has been omitted or somebody who does not meet authorship criteria has been included).

Evidence emerged in 2012 that journals learning of cases where there is strong evidence of possible misconduct, with issues potentially affecting a large portion of the findings, frequently fail to issue an expression of concern or correspond with the host institution so that an investigation can be undertaken. In one case the Journal of Clinical Oncology issued a Correction despite strong evidence that the original paper was invalid. In another case, Nature allowed a Corrigendum to be published despite clear evidence of image fraud. Subsequent Retraction of the paper required the actions of an independent whistleblower.

The cases of Joachim Boldt and Yoshitaka Fujii in anaesthesiology focussed attention on the role that journals play in perpetuating scientific fraud as well as how they can deal with it. In the Boldt case, the Editors-in-Chief of 18 specialist journals (generally anaesthesia and intensive care) made a joint statement regarding 88 published clinical trials conducted without Ethics Committee approval. In the Fujii case, involving nearly 200 papers, the journal Anesthesia & Analgesia, which published 24 of Fujii's papers, has accepted that its handling of the issue was inadequate. Following publication of a Letter to the Editor from Kranke and colleagues in April 2000, along with a non-specific response from Dr. Fujii, there was no follow-up on the allegation of data manipulation and no request for an institutional review of Dr. Fujii's research. Anesthesia & Analgesia went on to publish 11 additional manuscripts by Dr. Fujii following the 2000 allegations of research fraud, with Editor Steven Shafer stating in March 2012 that subsequent submissions to the Journal by Dr. Fujii should not have been published without first vetting the allegations of fraud. In April 2012 Shafer led a group of editors to write a joint statement, in the form of an ultimatum made available to the public, to a large number of academic institutions where Fujii had been employed, offering these institutions the chance to attest to the integrity of the bulk of the allegedly fraudulent papers.

Consequences for science

The consequences of scientific fraud vary based on the severity of the fraud, the level of notice it receives, and how long it goes undetected. For cases of fabricated evidence, the consequences can be wide-ranging, with others working to confirm (or refute) the false finding, or with research agendas being distorted to address the fraudulent evidence. The Piltdown Man fraud is a case in point: The significance of the bona-fide fossils that were being found was muted for decades because they disagreed with Piltdown Man and the preconceived notions that those faked fossils supported. In addition, the prominent paleontologist Arthur Smith Woodward spent time at Piltdown each year until he died, trying to find more Piltdown Man remains. The misdirection of resources kept others from taking the real fossils more seriously and delayed the reaching of a correct understanding of human evolution. (The Taung Child, which should have been the death knell for the view that the human brain evolved first, was instead treated very critically because of its disagreement with the Piltdown Man evidence.) 

In the case of Prof Don Poldermans, the misconduct occurred in reports of trials of treatment to prevent death and myocardial infarction in patients undergoing operations. The trial reports were relied upon to issue guidelines that applied for many years across North America and Europe.

In the case of Dr Alfred Steinschneider, two decades and tens of millions of research dollars were lost trying to find the elusive link between infant sleep apnea, which Steinschneider said he had observed and recorded in his laboratory, and sudden infant death syndrome (SIDS), of which he stated it was a precursor. The cover was blown in 1994, 22 years after Steinschneider's 1972 Pediatrics paper claiming such an association, when Waneta Hoyt, the mother of the patients in the paper, was arrested, indicted and convicted on five counts of second-degree murder for the smothering deaths of her five children. While that in itself was bad enough, the paper, presumably written as an attempt to save infants' lives, ironically was ultimately used as a defense by parents suspected in multiple deaths of their own children in cases of Münchausen syndrome by proxy. The 1972 Pediatrics paper was cited in 404 papers in the interim and is still listed on Pubmed without comment.

Consequences for those who expose misconduct

The potentially severe consequences for individuals who are found to have engaged in misconduct also reflect on the institutions that host or employ them and also on the participants in any peer review process that has allowed the publication of questionable research. This means that a range of actors in any case may have a motivation to suppress any evidence or suggestion of misconduct. Persons who expose such cases, commonly called whistleblowers, can find themselves open to retaliation by a number of different means. These negative consequences for exposers of misconduct have driven the development of whistle blowers charters – designed to protect those who raise concerns. A whistleblower is almost always alone in their fight – their career becomes completely dependent on the decision about alleged misconduct. If the accusations prove false, their career is completely destroyed, but even in case of positive decision the career of the whistleblower can be under question: their reputation of "troublemaker" will prevent many employers from hiring them. There is no international body where a whistleblower could give their concerns. If a university fails to investigate suspected fraud or provides a fake investigation to save their reputation the whistleblower has no right of appeal.

Exposure of fraudulent data

With the advancement of the internet, there are now several tools available to aid in the detection of plagiarism and multiple publication within biomedical literature. One tool developed in 2006 by researchers in Dr. Harold Garner's laboratory at the University of Texas Southwestern Medical Center at Dallas is Déjà vu, an open-access database containing several thousand instances of duplicate publication. All of the entries in the database were discovered through the use of text data mining algorithm eTBLAST, also created in Dr. Garner's laboratory. The creation of Déjà vu and the subsequent classification of several hundred articles contained therein have ignited much discussion in the scientific community concerning issues such as ethical behavior, journal standards, and intellectual copyright. Studies on this database have been published in journals such as Nature and Science, among others.

Other tools which may be used to detect fraudulent data include error analysis. Measurements generally have a small amount of error, and repeated measurements of the same item will generally result in slight differences in readings. These differences can be analyzed, and follow certain known mathematical and statistical properties. Should a set of data appear to be too faithful to the hypothesis, i.e., the amount of error that would normally be in such measurements does not appear, a conclusion can be drawn that the data may have been forged. Error analysis alone is typically not sufficient to prove that data have been falsified or fabricated, but it may provide the supporting evidence necessary to confirm suspicions of misconduct.

Data sharing

Kirby Lee and Lisa Bero suggest, "Although reviewing raw data can be difficult, time-consuming and expensive, having such a policy would hold authors more accountable for the accuracy of their data and potentially reduce scientific fraud or misconduct."

Notable individual cases

Andrew Wakefield, who claimed links between the MMR vaccine, autism and inflammatory bowel disease. He was found guilty of dishonesty in his research and banned from medicine by the UK General Medical Council following an investigation by Brian Deer of the London Sunday Times.

Perpetual motion

From Wikipedia, the free encyclopedia

Robert Fludd's 1618 "water screw" perpetual motion machine from a 1660 wood engraving. This device is widely credited as the first recorded attempt to describe such a device in order to produce useful work, that of driving millstones. Although the machine would not work, the idea was that water from the top tank turns a water wheel (bottom-left), which drives a complicated series of gears and shafts that ultimately rotate the Archimedes' screw (bottom-center to top-right) to pump water to refill the tank. The rotary motion of the water wheel also drives two grinding wheels (bottom-right) and is shown as providing sufficient excess water to lubricate them.

 

Perpetual motion is motion of bodies that continues indefinitely. A perpetual motion machine is a hypothetical machine that can do work indefinitely without an energy source. This kind of machine is impossible, as it would violate the first or second law of thermodynamics.

These laws of thermodynamics apply regardless of the size of the system. For example, the motions and rotations of celestial bodies such as planets may appear perpetual, but are actually subject to many processes that slowly dissipate their kinetic energy, such as solar wind, interstellar medium resistance, gravitational radiation and thermal radiation, so they will not keep moving forever.

Thus, machines that extract energy from finite sources will not operate indefinitely, because they are driven by the energy stored in the source, which will eventually be exhausted. A common example is devices powered by ocean currents, whose energy is ultimately derived from the Sun, which itself will eventually burn out. Machines powered by more obscure sources have been proposed, but are subject to the same inescapable laws, and will eventually wind down.

In 2017, new states of matter, time crystals, were discovered in which on a microscopic scale the component atoms are in continual repetitive motion, thus satisfying the literal definition of "perpetual motion". However, these do not constitute perpetual motion machines in the traditional sense or violate thermodynamic laws because they are in their quantum ground state, so no energy can be extracted from them; they have "motion without energy".

History

The history of perpetual motion machines dates back to the Middle Ages. For millennia, it was not clear whether perpetual motion devices were possible or not, but the development of modern theories of thermodynamics has shown that they are impossible. Despite this, many attempts have been made to construct such machines, continuing into modern times. Modern designers and proponents often use other terms, such as "over unity", to describe their inventions.

Basic principles

Oh ye seekers after perpetual motion, how many vain chimeras have you pursued? Go and take your place with the alchemists.

— Leonardo da Vinci, 1494

There is a scientific consensus that perpetual motion in an isolated system violates either the first law of thermodynamics, the second law of thermodynamics, or both. The first law of thermodynamics is a version of the law of conservation of energy. The second law can be phrased in several different ways, the most intuitive of which is that heat flows spontaneously from hotter to colder places; relevant here is that the law observes that in every macroscopic process, there is friction or something close to it; another statement is that no heat engine (an engine which produces work while moving heat from a high temperature to a low temperature) can be more efficient than a Carnot heat engine.

In other words:

• In any isolated system, one cannot create new energy (law of conservation of energy). As a result, the thermal efficiency—the produced work power divided by the input heating power—cannot be greater than one.
• The output work power of heat engines is always smaller than the input heating power. The rest of the heat energy supplied is wasted as heat to the ambient surroundings. The thermal efficiency therefore has a maximum, given by the Carnot efficiency, which is always less than one.
• The efficiency of real heat engines is even lower than the Carnot efficiency due to irreversibility arising from the speed of processes, including friction.

Statements 2 and 3 apply to heat engines. Other types of engines which convert e.g. mechanical into electromagnetic energy, cannot operate with 100% efficiency, because it is impossible to design any system that is free of energy dissipation. 

Machines which comply with both laws of thermodynamics by accessing energy from unconventional sources are sometimes referred to as perpetual motion machines, although they do not meet the standard criteria for the name. By way of example, clocks and other low-power machines, such as Cox's timepiece, have been designed to run on the differences in barometric pressure or temperature between night and day. These machines have a source of energy, albeit one which is not readily apparent so that they only seem to violate the laws of thermodynamics.

Even machines which extract energy from long-lived sources - such as ocean currents - will run down when their energy sources inevitably do. They are not perpetual motion machines because they are consuming energy from an external source and are not isolated systems.

Classification

One classification of perpetual motion machines refers to the particular law of thermodynamics the machines purport to violate:

• A perpetual motion machine of the first kind produces work without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy.
• A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However, it does violate the more subtle second law of thermodynamics. The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.
• A perpetual motion machine of the third kind is usually (but not always) defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever (due to its mass inertia). (Third in this case refers solely to the position in the above classification scheme, not the third law of thermodynamics.) It is impossible to make such a machine, as dissipation can never be completely eliminated in a mechanical system, no matter how close a system gets to this ideal (see examples in the Low Friction section).

Impossibility

October 1920 issue of Popular Science magazine, on perpetual motion. Although scientists have established them to be impossible under the laws of physics, perpetual motion continues to capture the imagination of inventors. The device shown is a "mass leverage" device, where the spherical weights on the right have more leverage than those on the left, supposedly creating a perpetual rotation. However, there are a greater number of weights on the left, balancing the device.

 

"Epistemic impossibility" describes things which absolutely cannot occur within our current formulation of the physical laws. This interpretation of the word "impossible" is what is intended in discussions of the impossibility of perpetual motion in a closed system.

The conservation laws are particularly robust from a mathematical perspective. Noether's theorem, which was proven mathematically in 1915, states that any conservation law can be derived from a corresponding continuous symmetry of the action of a physical system. For example, if the true laws of physics remain invariant over time then the conservation of energy follows. On the other hand, if the conservation laws are invalid, then the foundations of physics would need to change.

Scientific investigations as to whether the laws of physics are invariant over time use telescopes to examine the universe in the distant past to discover, to the limits of our measurements, whether ancient stars were identical to stars today. Combining different measurements such as spectroscopy, direct measurement of the speed of light in the past and similar measurements demonstrates that physics has remained substantially the same, if not identical, for all of observable time spanning billions of years.

The principles of thermodynamics are so well established, both theoretically and experimentally, that proposals for perpetual motion machines are universally met with disbelief on the part of physicists. Any proposed perpetual motion design offers a potentially instructive challenge to physicists: one is certain that it cannot work, so one must explain how it fails to work. The difficulty (and the value) of such an exercise depends on the subtlety of the proposal; the best ones tend to arise from physicists' own thought experiments and often shed light upon certain aspects of physics. So, for example, the thought experiment of a Brownian ratchet as a perpetual motion machine was first discussed by Gabriel Lippmann in 1900 but it was not until 1912 that Marian Smoluchowski gave an adequate explanation for why it cannot work. However, during that twelve-year period scientists did not believe that the machine was possible. They were merely unaware of the exact mechanism by which it would inevitably fail.

The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

— Sir Arthur Stanley Eddington, The Nature of the Physical World (1927)

In the mid 19th-century Henry Dircks investigated the history of perpetual motion experiments, writing a vitriolic attack on those who continued to attempt what he believed to be impossible:

There is something lamentable, degrading, and almost insane in pursuing the visionary schemes of past ages with dogged determination, in paths of learning which have been investigated by superior minds, and with which such adventurous persons are totally unacquainted. The history of Perpetual Motion is a history of the fool-hardiness of either half-learned, or totally ignorant persons.

— Henry Dircks, Perpetuum Mobile: Or, A History of the Search for Self-motive (1861)

Techniques

“	One day man will connect his apparatus to the very wheelwork of the universe [...] and the very forces that motivate the planets in their orbits and cause them to rotate will rotate his own machinery.	”
— Nikola Tesla

Some common ideas recur repeatedly in perpetual motion machine designs. Many ideas that continue to appear today were stated as early as 1670 by John Wilkins, Bishop of Chester and an official of the Royal Society. He outlined three potential sources of power for a perpetual motion machine, "Chymical [sic] Extractions", "Magnetical Virtues" and "the Natural Affection of Gravity".

The seemingly mysterious ability of magnets to influence motion at a distance without any apparent energy source has long appealed to inventors. One of the earliest examples of a magnetic motor was proposed by Wilkins and has been widely copied since: it consists of a ramp with a magnet at the top, which pulled a metal ball up the ramp. Near the magnet was a small hole that was supposed to allow the ball to drop under the ramp and return to the bottom, where a flap allowed it to return to the top again. The device simply could not work. Faced with this problem, more modern versions typically use a series of ramps and magnets, positioned so the ball is to be handed off from one magnet to another as it moves. The problem remains the same. 

Perpetuum Mobile of Villard de Honnecourt (about 1230).

 

The "Overbalanced Wheel".

Gravity also acts at a distance, without an apparent energy source, but to get energy out of a gravitational field (for instance, by dropping a heavy object, producing kinetic energy as it falls) one has to put energy in (for instance, by lifting the object up), and some energy is always dissipated in the process. A typical application of gravity in a perpetual motion machine is Bhaskara's wheel in the 12th century, whose key idea is itself a recurring theme, often called the overbalanced wheel: moving weights are attached to a wheel in such a way that they fall to a position further from the wheel's center for one half of the wheel's rotation, and closer to the center for the other half. Since weights further from the center apply a greater torque, it was thought that the wheel would rotate for ever. However, since the side with weights further from the center has fewer weights than the other side, at that moment, the torque is balanced and perpetual movement is not achieved. The moving weights may be hammers on pivoted arms, or rolling balls, or mercury in tubes; the principle is the same. 

Perpetual motion wheels from a drawing of Leonardo da Vinci.

 

Another theoretical machine involves a frictionless environment for motion. This involves the use of diamagnetic or electromagnetic levitation to float an object. This is done in a vacuum to eliminate air friction and friction from an axle. The levitated object is then free to rotate around its center of gravity without interference. However, this machine has no practical purpose because the rotated object cannot do any work as work requires the levitated object to cause motion in other objects, bringing friction into the problem. Furthermore, a perfect vacuum is an unattainable goal since both the container and the object itself would slowly vaporize, thereby degrading the vacuum.

To extract work from heat, thus producing a perpetual motion machine of the second kind, the most common approach (dating back at least to Maxwell's demon) is unidirectionality. Only molecules moving fast enough and in the right direction are allowed through the demon's trap door. In a Brownian ratchet, forces tending to turn the ratchet one way are able to do so while forces in the other direction are not. A diode in a heat bath allows through currents in one direction and not the other. These schemes typically fail in two ways: either maintaining the unidirectionality costs energy (requiring Maxwell's demon to perform more thermodynamic work to gauge the speed of the molecules than the amount of energy gained by the difference of temperature caused) or the unidirectionality is an illusion and occasional big violations make up for the frequent small non-violations (the Brownian ratchet will be subject to internal Brownian forces and therefore will sometimes turn the wrong way). 

The "Float Belt". The yellow blocks indicate floaters. It was thought that the floaters would rise through the liquid and turn the belt. However, pushing the floaters into the water at the bottom takes as much energy as the floating generates, and some energy is dissipated.

 

Buoyancy is another frequently misunderstood phenomenon. Some proposed perpetual-motion machines miss the fact that to push a volume of air down in a fluid takes the same work as to raise a corresponding volume of fluid up against gravity. These types of machines may involve two chambers with pistons, and a mechanism to squeeze the air out of the top chamber into the bottom one, which then becomes buoyant and floats to the top. The squeezing mechanism in these designs would not be able to do enough work to move the air down, or would leave no excess work available to be extracted.

Patents

Proposals for such inoperable machines have become so common that the United States Patent and Trademark Office (USPTO) has made an official policy of refusing to grant patents for perpetual motion machines without a working model. The USPTO Manual of Patent Examining Practice states:

With the exception of cases involving perpetual motion, a model is not ordinarily required by the Office to demonstrate the operability of a device. If operability of a device is questioned, the applicant must establish it to the satisfaction of the examiner, but he or she may choose his or her own way of so doing.

And, further, that:

A rejection [of a patent application] on the ground of lack of utility includes the more specific grounds of inoperativeness, involving perpetual motion. A rejection under 35 U.S.C. 101 for lack of utility should not be based on grounds that the invention is frivolous, fraudulent or against public policy.

The filing of a patent application is a clerical task, and the USPTO will not refuse filings for perpetual motion machines; the application will be filed and then most probably rejected by the patent examiner, after he has done a formal examination. Even if a patent is granted, it does not mean that the invention actually works, it just means that the examiner believes that it works, or was unable to figure out why it would not work.

The USPTO maintains a collection of Perpetual Motion Gimmicks. 

The United Kingdom Patent Office has a specific practice on perpetual motion; Section 4.05 of the UKPO Manual of Patent Practice states:

Processes or articles alleged to operate in a manner which is clearly contrary to well-established physical laws, such as perpetual motion machines, are regarded as not having industrial application.

Examples of decisions by the UK Patent Office to refuse patent applications for perpetual motion machines include:

• Decision BL O/044/06, John Frederick Willmott's application no. 0502841
• Decision BL O/150/06, Ezra Shimshi's application no. 0417271

The European Patent Classification (ECLA) has classes including patent applications on perpetual motion systems: ECLA classes "F03B17/04: Alleged perpetua mobilia ..." and "F03B17/00B: [... machines or engines] (with closed loop circulation or similar : ... Installations wherein the liquid circulates in a closed loop; Alleged perpetua mobilia of this or similar kind ...".

Apparent perpetual motion machines

As "perpetual motion" can exist only in isolated systems, and true isolated systems do not exist, there are not any real "perpetual motion" devices. However, there are concepts and technical drafts that propose "perpetual motion", but on closer analysis it is revealed that they actually "consume" some sort of natural resource or latent energy, such as the phase changes of water or other fluids or small natural temperature gradients, or simply cannot sustain indefinite operation. In general, extracting work from these devices is impossible.

Resource consuming

The "Capillary Bowl"

Some examples of such devices include:

• The drinking bird toy functions using small ambient temperature gradients and evaporation. It runs until all water is evaporated.
• A capillary action-based water pump functions using small ambient temperature gradients and vapour pressure differences. With the "Capillary Bowl", it was thought that the capillary action would keep the water flowing in the tube, but since the cohesion force that draws the liquid up the tube in the first place holds the droplet from releasing into the bowl, the flow is not perpetual.
• A Crookes radiometer consists of a partial vacuum glass container with a lightweight propeller moved by (light-induced) temperature gradients.
• Any device picking up minimal amounts of energy from the natural electromagnetic radiation around it, such as a solar powered motor.
• Any device powered by changes in air pressure, such as some clocks (Cox's timepiece, Beverly Clock). The motion leeches energy from moving air which in turn gained its energy from being acted on.
• The Atmos clock uses changes in the vapor pressure of ethyl chloride with temperature to wind the clock spring.
• A device powered by radioactive decay from an isotope with a relatively long half-life; such a device could plausibly operate for hundreds or thousands of years.
• The Oxford Electric Bell and Karpen Pile driven by dry pile batteries.

Low friction

• In flywheel energy storage, "modern flywheels can have a zero-load rundown time measurable in years".
• Once spun up, objects in the vacuum of space—stars, black holes, planets, moons, spin-stabilized satellites, etc.—dissipate energy very slowly, allowing them to spin for long periods. Tides on Earth are dissipating the gravitational energy of the Moon/Earth system at an average rate of about 3.75 terawatts.
• In certain quantum-mechanical systems (such as superfluidity and superconductivity), very low friction movement is possible. However, the motion stops when the system reaches an equilibrium state (e.g. all the liquid helium arrives at the same level.) Similarly, seemingly entropy-reversing effects like superfluids climbing the walls of containers operate by ordinary capillary action.

Thought experiments

In some cases a thought (or gedanken) experiment appears to suggest that perpetual motion may be possible through accepted and understood physical processes. However, in all cases, a flaw has been found when all of the relevant physics is considered. Examples include:

• Maxwell's demon: This was originally proposed to show that the Second Law of Thermodynamics applied in the statistical sense only, by postulating a "demon" that could select energetic molecules and extract their energy. Subsequent analysis (and experiment) have shown there is no way to physically implement such a system that does not result in an overall increase in entropy.
• Brownian ratchet: In this thought experiment, one imagines a paddle wheel connected to a ratchet. Brownian motion would cause surrounding gas molecules to strike the paddles, but the ratchet would only allow it to turn in one direction. A more thorough analysis showed that when a physical ratchet was considered at this molecular scale, Brownian motion would also affect the ratchet and cause it to randomly fail resulting in no net gain. Thus, the device would not violate the Laws of thermodynamics.
• Vacuum energy and zero-point energy: In order to explain effects such as virtual particles and the Casimir effect, many formulations of quantum physics include a background energy which pervades empty space, known as vacuum or zero-point energy. The ability to harness zero-point energy for useful work is considered pseudoscience by the scientific community at large. Inventors have proposed various methods for extracting useful work from zero-point energy, but none have been found to be viable, no claims for extraction of zero-point energy have ever been validated by the scientific community, and there is no evidence that zero-point energy can be used in violation of conservation of energy.