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{{Short description|Argument that uses faulty reasoning}}
{{Redirect|Logical error|logical errors in data storage|Data integrity#Logical integrity}}
{{Rhetoric}}

A '''fallacy''' is the use of [[Validity (logic)|invalid]] or otherwise faulty [[reason]]ing in the construction of an [[argument]]<ref name="GenslerAZ">{{Cite book |last=Gensler |first=Harry J. |title=The A to Z of Logic |date=2010 |publisher=Rowman & Littlefield |isbn=978-0810875968 |page=74}}</ref><ref>{{Cite book |last=Woods |first=John |title=The Death of Argument |date=2004 |isbn=978-9048167005 |series=Applied Logic Series |volume=32 |pages=3–23 |chapter=Who Cares About the Fallacies? |doi=10.1007/978-1-4020-2712-3_1 |author-link=John Woods (logician)}}</ref> that may appear to be well-reasoned if unnoticed. The term was introduced in the Western intellectual tradition by the [[Aristotle|Aristotelian]] ''[[Sophistical Refutations|De Sophisticis Elenchis]]''.<ref name="Downden" /> 

Fallacies may be committed intentionally to [[Psychological manipulation|manipulate]] or [[Persuasion|persuade]] by [[deception]], unintentionally because of human limitations such as [[carelessness]], [[Biases in judgment and decision making|cognitive or social biases]] and [[ignorance]], or potentially due to the limitations of language and understanding of language. These delineations include not only the ignorance of the right [[Psychology of reasoning|reasoning standard]] but also the ignorance of relevant properties of the [[Context (language use)|context]]. For instance, the [[soundness]] of [[legal argument]]s depends on the context in which they are made.<ref>{{Cite book |title=Argument types and fallacies in legal argumentation |date=2015 |publisher=Springer International Publishing |isbn=978-3-319-16147-1 |editor-last=Bustamente |editor-first=Thomas |location=Heidelberg |page=x |editor-last2=Dahlman |editor-first2=Christian}}</ref>

Fallacies are commonly divided into "formal" and "informal". A [[formal fallacy]] is a flaw in the structure of a [[deductive reasoning|deductive]] [[logical argument|argument]] that renders the argument invalid, while an [[informal fallacy]] originates in an error in reasoning other than an improper [[logical form]].<ref name="garns">{{Cite web |last=Garns |first=Rudy |date=1997 |title=Informal Fallacies |url=http://www.nku.edu/~garns/165/ppt3_2.html |url-status=dead |archive-url=https://web.archive.org/web/20170201173411/http://www.nku.edu/~garns/165/ppt3_2.html |archive-date=2017-02-01 |access-date=2013-09-10 |publisher=Northern Kentucky University}}</ref> Arguments containing informal fallacies may be formally [[Validity (logic)|valid]], but still fallacious.<ref name="Downden">{{Cite web |last=Dowden |first=Bradley |title=Fallacy |url=http://www.iep.utm.edu/fallacy |access-date=17 February 2016 |website=Internet Encyclopedia of Philosophy}}</ref>

A special case is a [[mathematical fallacy]], an intentionally invalid [[mathematical proof]] with a concealed, or subtle, error. Mathematical fallacies are typically crafted and exhibited for educational purposes, usually taking the form of false proofs of obvious [[contradiction]]s.<ref>{{Cite web |title=Mathematical Fallacies |url=https://brilliant.org/wiki/mathematical-fallacies/ |access-date=4 February 2023 |website=brilliant.org}}</ref>

== Overview ==
Fallacies are types of erroneous reasoning that render arguments [[Soundness|logically unsound]].<ref>{{Cite web |title=Definition of fallacy |url=https://www.dictionary.com/browse/fallacy |access-date=2023-02-18 |website=www.dictionary.com |language=en}}</ref> According to The New Handbook of Cognitive Therapy Techniques, they include "unsubstantiated assertions that are often delivered with a conviction that makes them sound as though they are proven facts".<ref name="The new handbook of cognitive...">{{Cite book |last=McMullin |first=Rian E. |title=The new handbook of cognitive therapy techniques |date=2000 |publisher=W.W. Norton |isbn=978-0393703139 |edition=Rev. |location=New York |oclc=41580357}}</ref> Informal fallacies, in particular, are frequently found in mass media such as television and newspapers.<ref name="McMurty1990">{{Cite journal |last=McMurtry |first=John |date=December 1990 |title=The mass media: An analysis of their system of fallacy |journal=Interchange |volume=21 |issue=4 |pages=49–66 |doi=10.1007/BF01810092 |s2cid=144780081}}</ref> Understanding fallacies may allow one to recognize them in either one's own or others' writing. Avoiding fallacies may help improve one's ability to produce sound arguments.<ref>{{Cite web |date=14 March 2017 |title=The Importance of Logical Fallacies |url=https://thelogicofscience.com/2017/03/14/the-importance-of-logical-fallacies/ |access-date=4 February 2023 |website=thelogicofscience.com}}</ref>

It can be difficult to evaluate whether an argument is fallacious, as arguments exist along a continuum of soundness and an argument that has several stages or parts might have some sound sections and some fallacious ones.<ref name="DeLancey_Handout">{{Cite web |last=DeLancey |first=Craig|title=Evaluating Arguments – Distinguishing between reasonable and fallacious tactics |url=https://writingcenter.ua.edu/wp-content/uploads/2012/02/evaluatingarguments.pdf |url-status=dead |archive-url=https://web.archive.org/web/20130903171329/http://writingcenter.ua.edu/wp-content/uploads/2012/02/evaluatingarguments.pdf |archive-date=2013-09-03 |access-date=7 March 2018 |website=oswego.edu |publisher=self-published}}</ref> Moreover, whether a specific argument is fallacious often depends on the content rather than the form of the argument. An example is a [[Validity (statistics)|probabilistically valid]] instance of the formally invalid argument form of [[denying the antecedent]] or [[affirming the consequent]]. <ref>{{Cite journal |last1=Godden |first1=David |last2=Zenker |first2=Frank |date=2015-03-05 |title=Denying Antecedents and Affirming Consequents: The State of the Art |url=http://ojs.uwindsor.ca/ojs/leddy/index.php/informal_logic/article/view/4173 |journal=Informal Logic |volume=35 |issue=1 |pages=88 |doi=10.22329/il.v35i1.4173 |issn=0824-2577 |doi-access=free}}</ref>  Thus, "fallacious arguments usually have the deceptive appearance of being good arguments, <ref name="Damer 2009">{{Citation |last=Damer |first=T. Edward |title=[[Attacking Faulty Reasoning]]: A Practical Guide to Fallacy-free Arguments |page=52 |year=2009 |edition=6th |place=Belmont, California |publisher=Wadsworth |isbn=978-0-495-09506-4 |author-link=T. Edward Damer}}</ref> because for most fallacious instances of an argument form, a similar but non-fallacious instance can be found". Evaluating an instance of an argument as fallacious is therefore often a matter of evaluating the context of the argument.   

Recognizing fallacies in everyday arguments may be difficult since arguments are often embedded in [[rhetoric]]al patterns that obscure the logical connections between statements. Informal fallacies may also exploit the [[emotion]]al, intellectual, or [[psychology|psychological]] weaknesses of the audience. Recognizing fallacies can develop reasoning skills to expose the weaker links between premises and conclusions to better discern between what appears to be true and what is true.

[[Argumentation theory]] provides a different approach to understanding and classifying fallacies. In the [[pragma-dialectics|pragma-dialectical theory]], for instance, an argument is regarded as an interactive protocol between individuals who attempt to resolve their disagreement on the merits of a case.<ref>{{Cite book |last=Frans van |first=Eemeren |url=http://worldcat.org/oclc/1048664485 |title=Argumentation Theory : a Pragma-Dialectical Perspective |date=2018 |publisher=Springer International Publishing |isbn=978-3-319-95380-9 |oclc=1048664485}}</ref> The protocol consists of [[Pragma-dialectics|normative rules of interaction]], and violations of these rules are considered fallacies because they frustrate the attempt at resolving the disagreement.

Fallacies are used in place of valid reasoning to communicate a point with the intention to persuade. Examples in the [[mass media]] today include but are not limited to [[propaganda]], [[advertisement]]s, [[politics]], newspaper editorials, and opinion-based news shows.<ref>{{Cite web |title=Fallacies in Propaganda |url=https://www.termpaperwarehouse.com/essay-on/Fallacies-In-Propaganda/5CEBA75592A5824A |access-date=4 February 2023 |website=www.termpaperwarehouse.com}}</ref>

== <span id="Material fallacy"></span>Systems of classification ==
Fallacies are generally classified strictly by either their structure or their content, such as by classifying them as [[Formal fallacy|formal fallacies]] or [[Informal fallacy|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.<ref name="Pirie2006">{{Cite book |last=Pirie |first=Madsen |url=https://books.google.com/books?id=Gh5UjNNc0v4C&pg=PA46 |title=How to Win Every Argument: The Use and Abuse of Logic |publisher=A&C Black |year=2006 |isbn=978-0-8264-9006-3 |page=46 |author-link=Madsen Pirie |access-date=10 September 2015}}</ref> Alternatively, fallacies may be classified by the process by which they occur, such as [[Material fallacy|material fallacies]] (content), [[Verbal fallacy|verbal fallacies]] (linguistic), and formal fallacies (error in inference). In turn, material fallacies may be placed into the more general category of informal fallacies. Verbal fallacies may be placed in either formal or informal classifications: Compare [[equivocation]], which is a word- or phrase-based [[ambiguity]], to the [[fallacy of composition]], which is premise- and inference-based ambiguity.<ref>{{Cite web |title=fallacy |url=https://www.britannica.com/topic/fallacy#toc280530 |access-date=13 June 2017 |website=|publisher=Encyclopedia Britannica}}</ref>

=== <span id="Verbal fallacy"></span>Greek logic ===
The Greek philosopher [[Aristotle]] (384–322 BC) was the first to systematize logical errors into a list to make it easier to refute an opponent's thesis and thus win an argument.<ref name="eem">{{Cite book |last1=van Eemeren |first1=Frans |title=Fallacies and judgements of reasonableness, Empirical Research Concerning the Pragma-Dialectical Discussion Rules |last2=Garssen |first2=Bart |last3=Meuffels |first3=Bert |date=2009 |publisher=Springer Science+Business Media B.V. |isbn=978-90-481-2613-2 |location=Dordrecht |language=en |chapter=1}}</ref>{{rp|2}} Aristotle's ''[[Sophistical Refutations]]'' ({{transliteration|el|De Sophisticis Elenchis}}) identifies thirteen fallacies. He divided them up into two major types: linguistic fallacies and non-linguistic fallacies, some of which depend on language and others that do not.<ref>{{Cite web |date=March 13, 2008 |title=Aristotle's original 13 fallacies |url=http://thenonsequitur.com/?page_id=621 |access-date=28 May 2013 |publisher=The Non Sequitur}}</ref><ref>{{Cite web |title=Aristotle's 13 fallacies |url=http://www.logiclaw.co.uk/fallacies/Straker3.html |url-status=dead |archive-url=https://web.archive.org/web/20180718072028/http://www.logiclaw.co.uk/fallacies/Straker3.html |archive-date=2018-07-18 |access-date=2017-12-12 |website=www.logiclaw.co.uk}}</ref> These fallacies are called verbal fallacies and material fallacies, respectively. A [[material fallacy]] is an error in what the arguer is talking about, while a [[verbal fallacy]] is an error in how the arguer is talking. Verbal fallacies are those in which a conclusion is obtained by improper or ambiguous use of words.<ref>{{Cite web |title=PHIL 495: Philosophical Writing (Spring 2008), Texas A&M University |url=http://aristotle.tamu.edu/~rasmith/Courses/PhilosophicalWriting/08a/fallacies.html |url-status=dead |archive-url=https://web.archive.org/web/20080905215503/http://aristotle.tamu.edu/~rasmith/Courses/PhilosophicalWriting/08a/fallacies.html |archive-date=2008-09-05 |access-date=2013-09-10}}</ref>
An example of a language dependent fallacy is given as a debate as to who in humanity are learners: the wise or the ignorant.{{r|eem|page1=3}} A language-independent fallacy is, for example:
# "[[Coriscus of Scepsis|Coriscus]] is different from [[Socrates]]."
# "Socrates is a man."
# "Therefore, Coriscus is different from a man."{{r|eem|page1=4}}

=== <span id="Verbal fallacy"></span>Indian logic ===
[[Indian logic|Indian logicians]] took great pains to identify fallacies in arguments. An influential collection of texts on logic and reason, the ''[[Nyāya Sūtras]]'', attributed to [[Aksapada Gautama]], variously estimated to have been composed between the 6th century BCE and the 2nd century CE, lists in its theory of inference five such reasons used in an argument that was further developed by later logicians.<ref>{{Cite encyclopedia |title=Epistemology in Classical Indian Philosophy |encyclopedia=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |url=https://plato.stanford.edu/archives/spr2019/entries/epistemology-india/ |access-date=2021-05-07 |last=Phillips |first=Stephen |date=2019 |editor-last=Zalta |editor-first=Edward N. |edition=Spring 2019}}</ref><ref>{{Cite book |last=Mahamahopadhyaya Satisa Chandra Vidyabhushana |url=http://archive.org/details/NyayaSutrasOfGautama |title=The Nyaya Sutras Of Gautama (English)}}</ref><ref>{{Cite encyclopedia |title=Analytic Philosophy in Early Modern India |encyclopedia=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |url=https://plato.stanford.edu/archives/sum2019/entries/early-modern-india/ |access-date=2021-05-07 |last=Ganeri |first=Jonardon |date=2019 |editor-last=Zalta |editor-first=Edward N. |edition=Summer 2019}}</ref>

# ''Asiddha'': It is the unproved reason that results in this fallacy. [Paksadharmata]
# ''Savyabhichara'': This is the fallacy of irregular reason.
# ''Satpratipaksa'': Here the reason is contradicted by another reason. If both have equal force, then nothing follows. 'Sound is eternal, because it is audible', and 'Sound is non-eternal, because it is produced'. Here 'audible' is counterbalanced by 'produced' and both are of equal force.
# ''Badhita'': When another proof (as by perception) definitely contradicts and disproves the middle term (reason). 'Fire is cold because it is a substance'.
# ''Viruddha'': Instead of proving something it is proving the opposite. 'Sound is eternal because it is produced'.

=== Whately's grouping ===
English scholar and theologian [[Richard Whately]] (1787–1863) defines a fallacy broadly as, "any argument, or apparent argument, which professes to be decisive of the matter at hand, while in reality it is not".{{r|eem|page1=8}}

Whately divided fallacies into two groups: ''logical'' and ''material''. According to Whately, logical fallacies are arguments where the conclusion does not follow from the premises. Material fallacies are not logical errors because the conclusion follows from the premises. He then divided the logical group into two groups: purely logical and semi-logical. The semi-logical group included all of Aristotle's [[sophisms]] except ''[[ignoratio elenchi]]'', ''[[petitio principii]]'', and ''[[non causa pro causa]]'', which are in the material group.<ref name="Coffey1912">{{Cite book |last=Coffey |first=P. |url=https://archive.org/details/thescienceoflogi01coffuoft |title=The Science of Logic |publisher=Longmans, Green, and Co.|year=1912 |isbn=978-0371778951 |edition=1st |volume=1 |page=[https://archive.org/details/thescienceoflogi01coffuoft/page/302 302] |language=en-US |lccn=12018756 |oclc=797892247 |ol=7104938M |access-date=2016-02-22 |ol-access=free}}</ref>

=== Other systems of classification ===
Other famous methods of classifying fallacies are those of [[Francis Bacon (philosopher)|Francis Bacon]] and [[John Stuart Mill|J. S. Mill]]. Bacon (''[[Novum Organum]]'', Aph. 33, 38 sqq.) divided fallacies into four Idola (Idols, i.e. False Appearances), which summarize the various kinds of mistakes to which the human intellect is prone. J. S. Mill discussed the subject in book five of his Logic, and [[Jeremy Bentham]]'s ''Book of Fallacies'' (1824) contains valuable remarks.

== Formal fallacy ==
{{Main|Formal fallacy}}

A formal fallacy, deductive fallacy, [[logical fallacy]] or ''non sequitur'' ([[Latin]] for "it does not follow") is a flaw in the structure of a [[deductive reasoning|deductive]] [[logical argument|argument]] that renders the argument [[Validity (logic)|invalid]]. The flaw can be expressed in the standard system of logic.<ref name="GenslerAZ" /> Such an argument is always considered to be wrong.
The presence of the formal fallacy does not imply anything about the argument's [[premise]]s or its conclusion. Both may actually be true or may even be more probable as a result of the argument, but the deductive argument is still invalid because the conclusion does not follow from the premises in the manner described.

Even non-deductive arguments can be said to be fallacious: for example, an [[Inductive reasoning|inductive]] argument that incorrectly applies principles of probability or [[causality]]. But "since deductive arguments depend on formal properties and inductive arguments don't, formal fallacies apply only to deductive arguments".<ref name="garns" />

A [[logical form]] such as "''A'' and ''B''" is independent of any particular conjunction of meaningful propositions. Logical form alone can guarantee that, given true premises, a true conclusion must follow. However, formal logic makes no such guarantee if any premise is false; the conclusion can be either true or false. Any formal error or logical fallacy similarly invalidates the deductive guarantee. Both the argument and all its premises must be true for a conclusion to be true.

The term ''logical fallacy'' is in a sense self-contradictory because ''logic'' refers to valid reasoning, whereas a ''fallacy'' is the use of poor reasoning. Therefore, the term ''formal fallacy'' is preferred. In informal discourse, however, ''logical fallacy'' is used to mean an argument that is problematic for any reason.

The term ''non sequitur'' denotes a general formal fallacy, often meaning one that does not belong to any named subclass of formal fallacies, like [[affirming the consequent]].

=== Common examples ===
{{main|List of fallacies#Formal fallacies}}

==== Ecological fallacy ====
An [[ecological fallacy]] is committed when one draws an inference from data based on the premise that qualities observed for groups necessarily hold for individuals; for example, "if countries with more Protestants tend to have higher suicide rates, then Protestants must be more likely to commit suicide".<ref>{{Cite encyclopedia |year=2004 |title=Ecological Fallacy |encyclopedia=Encyclopedia of Social Science Research Methods |publisher=Sage |location=Thousand Oaks, CA |last=Freedman |first=David A. |editor-last=Lewis-Beck |editor-first=Michael S. |pages=293–295 |isbn=978-0761923633 |editor2-first=Alan |editor2-last=Bryman |editor3-first=Tim Futing |editor3-last=Liao}}</ref>

=== Fallacy fork ===
[[Maarten Boudry]]<ref name=Boudry/> and others<ref>{{Cite book |last1=Eemeren |first1=Frans H. van |title=Handbook of Argumentation Theory |last2=Garssen |first2=Bart |last3=Krabbe |first3=Erik C. W. |last4=Snoeck Henkemans |first4=A. Francisca |last5=Verheij |first5=Bart |last6=Wagemans |first6=Jean H. M. |date=2014 |publisher=Springer |isbn=978-9048194728 |edition=Revised |location=New York |doi=10.1007/978-90-481-9473-5 |oclc=871004444 |author-link=Frans H. van Eemeren}}</ref> have argued that formal, deductive fallacies rarely occur in real life and that arguments that would be fallacious in formally deductive terms are not necessarily so when context and prior probabilities are taken into account, thus making the argument defeasible and/or inductive. Boudry coined the term ''fallacy fork''.<ref name=Boudry/> For a given fallacy, one must either characterize it by means of a deductive [[argumentation scheme]], which rarely applies (the first prong of the fork), or one must relax definitions and add nuance to take the actual intent and context of the argument into account (the other prong of the fork).<ref name=Boudry/> To argue, for example, that one became nauseated after eating a mushroom because the mushroom was poisonous could be an example of the ''post hoc ergo propter hoc'' fallacy.<ref name="Boudry">{{Cite journal |last=Boudry |first=Maarten |author-link=Maarten Boudry |date=2017 |title=The Fallacy Fork: Why It's Time to Get Rid of Fallacy Theory |journal=[[Skeptical Inquirer]] |volume=41 |issue=5 |pages=46–51}}</ref>

== Informal fallacy ==
{{main|Informal fallacy}}
In contrast to a formal fallacy, an informal fallacy originates from a reasoning error other than a flaw in the logical form of the argument.<ref name="garns" /> A [[deductive argument]] containing an informal fallacy may be formally [[Validity (logic)|valid]],<ref name="Downden" /> but still remain rationally unpersuasive. Nevertheless, informal fallacies apply to both deductive and non-deductive arguments.

Though the form of the argument may be relevant, fallacies of this type are "types of mistakes in reasoning that arise from the mishandling of the ''content'' of the propositions constituting the argument".<ref>{{Cite book |last1=Copi |first1=Irving M. |title=Introduction to Logic |last2=Cohen |first2=Carl |publisher=Pearson Education, Inc. |year=2005 |isbn=978-0-13-189834-9 |edition=12th|page=125}}</ref>

=== Faulty generalization ===
A special subclass of the informal fallacies is the set of [[faulty generalization]]s, also known as inductive fallacies. Here, the most important issue concerns inductive strength or methodology (for example, [[statistical inference]]). In the absence of sufficient evidence, drawing conclusions based on induction is [[Warrant (rhetoric)|unwarranted]] and fallacious. With the backing of sufficient amounts of the right type of [[empirical evidence]], however, the conclusions may become warranted and convincing (at which point the arguments are no longer considered fallacious).<ref>{{Cite journal |last=Neyman |first=J. |date=1937-08-30 |title=Outline of a Theory of Statistical Estimation Based on the Classical Theory of Probability |journal=Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |language=en |volume=236 |issue=767 |pages=333–380 |bibcode=1937RSPTA.236..333N |doi=10.1098/rsta.1937.0005 |issn=0080-4614 |s2cid=19584450 |doi-access=free}}</ref>

==== Hasty generalization ====
[[Hasty generalization]] is described as making assumptions about a whole group or range of cases based on a [[Sample (statistics)|sample]] that is inadequate (usually because it is atypical or just too small).
Stereotypes about people ("frat boys are drunkards", "grad students are nerdy", "women don't enjoy sports", etc.) are common examples of the principle.

Hasty generalization often follows a pattern such as:

:X is true for A.
:X is true for B.
:Therefore, X is true for C, D, etc.

While never a valid logical deduction, if such an inference can be made on statistical grounds, it may nonetheless be convincing. This is because with enough empirical evidence, the generalization is no longer a hasty one.

=== Relevance fallacy ===
The [[fallacy of relevance|fallacies of relevance]] are a broad class of informal fallacies, generically represented by [[missing the point]]: presenting an argument that may be [[soundness|sound]] but fails to address the issue in question.

==== Argument from silence ====
An [[argument from silence]] is a faulty conclusion that is drawn based on the absence of evidence rather than on the presence of evidence.

=== Examples of informal fallacies ===
{{Main|List of fallacies#Informal fallacies}}

==== ''Post hoc'' (false cause) ====
The post hoc fallacy assumes that because B comes after A, A caused B. It gets its name from the Latin phrase "''post hoc, ergo propter hoc''", which translates as "after this, therefore because of this". 

Sometimes one event really does cause another one that comes later—for example, if one registers for a class and their name later appears on the roll, it's true that the first event caused the one that came later. But sometimes two events that seem related in time are not really related as cause and event. That is, [[Correlation does not imply causation|temporal correlation does not necessarily entail causation]]. For example, if one eats a sandwich and then gets food poisoning, that does not necessarily mean the sandwich caused the food poisoning. Something else eaten earlier might have caused the food poisoning.

==== Slippery slope ====
For an argument to be a [[slippery slope]] type of argument, it must meet the requirements of that [[argumentation scheme]]. A slippery slope argument originates from a conversation or debate in which two actors take turns. It usually originates from one actor giving advice on a decision or act. Along the way, the actor must make additional choices on similar matters through which the actor enters the ‘grey area’ of the slippery slope. At this point, the actor potentially loses control over the direction of the arguments, thus leading to a ‘fatal’ outcome.<ref>{{Cite journal |last=Walton |first=Douglas |date=2015-09-02 |title=The Basic Slippery Slope Argument |url=https://informallogic.ca/index.php/informal_logic/article/view/4286 |journal=Informal Logic |language=en |volume=35 |issue=3 |pages=273–311 |doi=10.22329/il.v35i3.4286 |issn=2293-734X |doi-access=free}}</ref>

Such an argument is built up according to the following argumentation scheme: initial premise, sequential premise, indeterminacy premise, control premise, loss of control premise, catastrophic outcome premise, and conclusion. Slippery slope arguments may be defeated by asking critical questions or giving counterarguments.<ref>{{Cite book |last=Walton |first=Douglas |title=Slippery Slope Arguments. |publisher=Oxford University Press |year=1992 |isbn=978-0198239253 |location=Oxford |language=EN}}</ref>

There are several reasons for a slippery slope to be fallacious: for example, the argument is going too far into the future, it is a too complex argument whose structure is hard to identify, or the argument makes emotional appeals.<ref>{{Cite journal |last=Govier |first=Trudy |date=June 1982 |title=What's Wrong with Slippery Slope Arguments? |url=https://www.cambridge.org/core/product/identifier/S0045509100009796/type/journal_article |journal=Canadian Journal of Philosophy |language=en |volume=12 |issue=2 |pages=303–316 |doi=10.1080/00455091.1982.10715799 |issn=0045-5091 |s2cid=170107849}}</ref>

It may be that a slippery slope is not necessarily fallacious if context is taken into account and there is an effort to assess plausibility.<ref>{{Cite web |last=Dwyer |first=Christopher |date=September 13, 2019 |title=Critically Thinking About the Slippery Slope "Fallacy" |url=https://www.psychologytoday.com/us/blog/thoughts-thinking/201909/critically-thinking-about-the-slippery-slope-fallacy |website=Psychology Today}}</ref>

==== False analogy ====
Informally known as the "[[apples and oranges]]" fallacy, a [[false analogy]] uses unsound comparisons.<ref>{{Cite journal |last=Kornprobst |first=Markus |year=2007 |title=Comparing Apples and Oranges? Leading and Misleading Uses of Historical Analogies |journal=Millennium&nbsp;— Journal of International Studies |volume=36 |pages=29–49 |doi=10.1177/03058298070360010301 |s2cid=145785208}}</ref>

==== Straw man fallacy ====
The [[straw man]] fallacy refers to the refutation of a standpoint in an argument that was never proposed. The fallacy usually occurs in the presentation of an opponent's standpoint as more extreme, distorted, or simplistic than it actually is. Compared to criticizing the opponent's actual standpoint, this allows the arguer to offer a seeming refutation of what is, however, not the actual standpoint.<ref>{{Cite journal |last1=Lewiński |first1=Marcin |last2=Oswald |first2=Steve |date=2013-12-01 |title=When and how do we deal with straw men? A normative and cognitive pragmatic account |url=https://www.sciencedirect.com/science/article/pii/S0378216613001227 |journal=Journal of Pragmatics |series=Biases and constraints in communication: Argumentation, persuasion and manipulation |language=en |volume=59 |pages=164–177 |doi=10.1016/j.pragma.2013.05.001 |issn=0378-2166}}</ref> Such an argument involves two arguers, with one criticizing the other's perspective.<ref>{{Cite journal |last1=Aikin |first1=Scott F. |last2=Casey |first2=John P. |date=2016-10-01 |title=Straw Men, Iron Men, and Argumentative Virtue |url=https://www.academia.edu/107692810 |url-access=registration |journal=Topoi |language=en |volume=35 |issue=2 |pages=431–440 |doi=10.1007/s11245-015-9308-5 |issn=1572-8749 |s2cid=145321942}}</ref> The reason for the straw man argument to be fallacious originates from the problem of how to deal with natural discourse. The opponent's argument is not reflected by the arguments that are proposed by the speaker.<ref>{{Cite journal |last1=Talisse |first1=Robert |last2=Aikin |first2=Scott F. |date=2006-09-01 |title=Two Forms of the Straw Man |journal=Argumentation |language=en |volume=20 |issue=3 |pages=345–352 |url=https://www.academia.edu/48271903 |url-access=registration |doi=10.1007/s10503-006-9017-8 |issn=1572-8374 |s2cid=15523437}}</ref>

== Measurement fallacy ==
Some of the fallacies described above may be committed in the context of measurement.
Where [[mathematical fallacies]] are subtle mistakes in reasoning leading to invalid mathematical proofs, measurement fallacies are unwarranted inferential leaps involved in the extrapolation of raw data to a measurement-based value claim. The ancient Greek Sophist [[Protagoras]] was one of the first thinkers to propose that humans can generate reliable measurements through his "human-measure" principle and the practice of ''dissoi logoi'' (arguing multiple sides of an issue).<ref>{{Cite book |last=Schiappa |first=Edward |title=Protagoras and Logos: A Study in Greek Philosophy and Rhetoric |publisher=University of South Carolina Press |year=1991 |isbn=978-0872497580 |location=Columbia}}</ref><ref>{{Cite book |last=Protagoras |url=https://archive.org/details/oldersophistscom0000unse |title=The Older Sophists |publisher=Hackett Publishing Co. |year=1972 |isbn=978-0872205567 |location=Indianapolis, IN |url-access=registration}}</ref> This history helps explain why measurement fallacies are informed by [[informal logic]] and [[argumentation theory]].

=== Knowledge value measurement fallacy ===
The increasing availability and circulation of [[big data]] are driving a proliferation of new metrics for scholarly authority,<ref name="Meho">{{Cite journal |last=Meho |first=Lokman I. |year=2007 |title=The Rise and Rise of Citation Analysis |journal=[[Physics World]] |volume=January |pages=32–36 |arxiv=physics/0701012 |bibcode=2007physics...1012M |doi=10.1088/2058-7058/20/1/33 |s2cid=16532275}}</ref><ref>{{Cite news |last=Jensen |first=Michael |date=June 15, 2007 |title=The New Metrics of Scholarly Authority |work=[[The Chronicle of Higher Education]] |publisher=The Chron |editor-last=Riley |editor-first=Michael G. |url=http://chronicle.com/article/The-New-Metrics-of-Scholarly/5449 |access-date=28 October 2013 |issn=0009-5982 |oclc=1554535}}</ref> and there is lively discussion regarding the relative usefulness of such metrics for measuring the value of knowledge production in the context of an "information tsunami".<ref name="Baveye 2010 191–215">{{Cite journal |last=Baveye |first=Phillippe C. |year=2010 |title=Sticker Shock and Looming Tsunami: The High Cost of Academic Serials in Perspective |journal=[[Journal of Scholarly Publishing]] |volume=41 |issue=2 |pages=191–215 |doi=10.1353/scp.0.0074 |s2cid=145424660}}<!--|access-date=28 October 2013--></ref>

For example, [[anchoring]] fallacies can occur when unwarranted weight is given to data generated by metrics that the arguers themselves acknowledge are flawed. For example, the limitations of the [[journal impact factor]] (JIF) are well documented,<ref>{{Cite book |last=National Communication Journal |url=http://www.natcom.org/uploadedFiles/More_Scholarly_Resources/CCA%20Impact%20Factor%20Report%20Final.pdf |title=Impact Factors, Journal Quality, and Communication Journals: A Report for the Council of Communication Associations |publisher=National Communication Association |year=2013 |location=Washington, D.C. |access-date=2016-02-22 |archive-url=https://web.archive.org/web/20160404212454/http://www.natcom.org/uploadedFiles/More_Scholarly_Resources/CCA%20Impact%20Factor%20Report%20Final.pdf |archive-date=April 4, 2016 |url-status=dead}}</ref> and even JIF pioneer Eugene Garfield notes that, "while citation data create new tools for analyses of research performance, it should be stressed that they supplement rather than replace other quantitative and qualitative indicators".<ref>{{Cite journal |last=Garfield |first=Eugene |year=1993 |title=What Citations Tell us About Canadian Research |journal=Canadian Journal of Library and Information Science |volume=18 |issue=4 |page=34}}</ref> To the extent that arguers jettison the acknowledged limitations of JIF-generated data in evaluative judgments or leave behind Garfield's "supplement rather than replace" caveat, they commit anchoring fallacies.

A [[naturalistic fallacy]] can occur, for example, in the case of sheer quantity metrics based on the premise "more is better"<ref name="Baveye 2010 191–215" /> or, in the case of developmental assessment in the field of psychology, "higher is better".<ref>{{Cite journal |last=Stein |first=Zachary |date=October 2008 |title=Myth Busting and Metric Making: Refashioning the Discourse about Development |url=http://www.archive-ilr.com/archives-2008/2008-10/2008-10-article-stein.php |journal=Integral Leadership Review |volume=8 |issue=5 |archive-url=https://archive.today/20131030094158/http://www.archive-ilr.com/archives-2008/2008-10/2008-10-article-stein.php |archive-date=October 30, 2013 |access-date=October 28, 2013}}</ref>

A [[false analogy]] occurs when claims are supported by unsound comparisons between data points. For example, the [[Scopus]] and [[Web of Science]] bibliographic databases have difficulty distinguishing between citations of scholarly work that are arms-length endorsements, ceremonial citations, or negative citations (indicating the citing author withholds endorsement of the cited work).<ref name=Meho/> Hence, measurement-based value claims premised on the uniform quality of all citations may be questioned on false analogy grounds.

As another example, consider the [[Faculty Scholarly Productivity Index]] of Academic Analytics. This tool purports to measure overall faculty productivity, yet it does not capture data based on citations in books. This creates a possibility that low productivity measurements using the tool commit [[argument from silence]] fallacies, to the extent that such measurements are supported by the absence of book citation data.

[[Ecological fallacy|Ecological fallacies]] can be committed when one measures the scholarly productivity of a sub-group of individuals (e.g. "Puerto Rican" faculty) via reference to aggregate data about a larger and different group (e.g., "Hispanic" faculty).<ref>{{Cite journal |last=Allen |first=Henry L. |year=1997 |title=Faculty Workload and Productivity: Ethnic and Gender Disparities |url=http://www.nea.org/assets/img/PubAlmanac/ALM_97_04.pdf |url-status=dead |journal=NEA 1997 Almanac of Higher Education |page=39 |archive-url=https://web.archive.org/web/20150707001555/http://www.nea.org/assets/img/PubAlmanac/ALM_97_04.pdf |archive-date=July 7, 2015 |access-date=October 29, 2013}}</ref>

== Intentional fallacy ==
Sometimes a speaker or writer uses a fallacy intentionally. In any context, including academic debate, a conversation among friends, political discourse, advertising, or comedic purposes, the arguer may use fallacious reasoning to try to persuade the listener or reader, by means other than offering relevant evidence, that the conclusion is true.

Examples of this include the speaker or writer:<ref name="Shewan">{{Cite book |last=Shewan |first=Edward |url=https://books.google.com/books?id=22s9JWeHJbAC&pg=PA92 |title=Applications of Grammar: Principles of Effective Communication |publisher=Christian Liberty Press |year=2003 |isbn=978-1-930367-28-9 |edition=2nd |chapter=Soundness of Argument |access-date=February 22, 2016 |chapter-url=https://books.google.com/books?id=22s9JWeHJbAC&pg=PA84}}</ref>

# Diverting the argument to unrelated issues with a [[Red herring#Logical fallacy|red herring]] (''[[Ignoratio elenchi]]'')
# Insulting someone's character ([[Ad hominem|''argumentum ad hominem'']])
# Assuming the conclusion of an argument, a kind of [[circular reasoning]], also called "[[begging the question]]" (''petitio principii'')
# Making jumps in logic ([[Non sequitur (logic)|''non sequitur'']])
# Identifying a false cause and effect (''[[post hoc ergo propter hoc]]'')
# Asserting that everyone agrees (''[[argumentum ad populum]]'', [[Bandwagon effect|bandwagoning]])
# Creating a [[false dilemma]] (either-or fallacy) in which the situation is oversimplified, also called ''false dichotomy''
# Selectively using facts ([[card stacking]])
# Making false or misleading comparisons ([[false equivalence]] or [[false analogy]])
# Generalizing quickly and sloppily ([[hasty generalization]]) (''[[secundum quid]]'')
# Using an argument's connections to other concepts or people to support or refute it, also called "guilt by association" ([[association fallacy]])
# Claiming that a lack of proof counts as proof ([[Argument from ignorance|appeal to ignorance]])

In humor, errors of reasoning are used for comical purposes. Groucho Marx used fallacies of [[amphiboly]], for instance, to make ironic statements; [[Gary Larson]] and [[Scott Adams]] employed fallacious reasoning in many of their cartoons. Wes Boyer and Samuel Stoddard have written a humorous essay teaching students how to be persuasive by means of a whole host of informal and formal fallacies.<ref name="How to Be Persuasive">{{Cite web |last1=Boyer |first1=Web |last2=Stoddard |first2=Samuel |title=How to Be Persuasive |url=http://www.rinkworks.com/persuasive/ |url-status=dead |archive-url=https://web.archive.org/web/20180727043805/http://www.rinkworks.com/persuasive/ |archive-date=July 27, 2018 |access-date=December 5, 2012 |website=Rink Works}}</ref>

When someone uses logical fallacies intentionally to mislead in academic, political, or other high-stakes contexts, the breach of trust calls into question [[Ethos|the authority and intellectual integrity of that person]].<ref>Habick, Timothy, and Linda Cook. (2018) AICPA Test Development Fairness Guidelines. Association of International Certified Public Accounts, Ewing, NJ.{{page needed |date=December 2016}}<!-- Where does one find this citation? --></ref>

== Assessment: pragmatic theory ==
{{See also|Argumentation scheme}}
According to the pragmatic theory,<ref>{{Cite book |last=Walton |first=Douglas N. |url=https://books.google.com/books?id=4uTWAAAAMAAJ |title=A Pragmatic Theory of Fallacy |publisher=[[University of Alabama Press]] |year=1995 |isbn=978-0817307981 |location=Tuscaloosa |pages=324 |author-link=Douglas N. Walton}}</ref> a fallacy can be either a heuristic error or a ploy used intentionally to unfairly win an argument. There are always two parties to an argument containing a fallacy: the perpetrator and the intended victim. 

The dialogue framework required to support the pragmatic theory of fallacy is built on the presumption that argumentative dialogue has both an adversarial component and a collaborative component. A dialogue has individual goals for each participant as well as shared goals that apply to all participants. A fallacy of the second kind is seen as more than simply a violation of the rule of reasonable dialogue. It is also a deceptive tactic of argumentation based on sleight-of-hand. Aristotle explicitly compared contentious reasoning to unfair fighting in athletic contests. But the roots of the pragmatic theory go back even further in history, to the Sophists. The pragmatic theory finds its roots in the Aristotelian conception of a fallacy as a sophistical refutation but also supports the view that many of the types of arguments traditionally labeled as fallacies are in fact reasonable techniques of argumentation that can be used, in many cases, to support legitimate goals of dialogue. Hence, under the pragmatic approach, each case needs to be analyzed individually to determine whether the argument is fallacious or reasonable.

== See also ==
{{columns-list|Lists
* {{annotated link|List of cognitive biases}}
* {{annotated link|List of fallacies}}
* {{annotated link|List of memory biases}}
* {{annotated link|List of paradoxes}}
* {{intitle|Fallacy}}
* {{intitle|Fallacious}}
* {{slink|Pragma-dialectics#Rules for critical discussion}}

'''Concepts'''
* {{annotated link|Aporia}}
* {{annotated link|Anti-pattern}}
* {{annotated link|Argument map}}
* {{annotated link|Argumentation theory}}
* {{annotated link|Association fallacy}}
* {{annotated link|Cognitive bias}}
* {{annotated link|Cognitive distortion}}
* {{annotated link|Critical thinking}}
* {{annotated link|Demagogue}}
* {{annotated link|Evidence}}
* {{annotated link|Fallacies of definition}}
* {{annotated link|False (logic)}}
* {{annotated link|False premise}}
* {{annotated link|False statement}}
* {{annotated link|Illusion}}
* {{annotated link|Inference objection}}
* {{annotated link|Inquiry}}
* {{annotated link|Jumping to conclusions}}
* {{annotated link|Lemma (logic)|Lemma}}
* {{annotated link|Lies, damned lies, and statistics}}
* {{annotated link|Mathematical fallacy}}
* {{annotated link|Paradox}}
* {{annotated link|Prosecutor's fallacy}}
* {{annotated link|Sophist}}
* {{annotated link|Soundness}}
* {{annotated link|Truth}}
* {{annotated link|Validity (logic)|Validity}}
* {{annotated link|Victim blaming}}

'''Works'''
* ''[[Attacking Faulty Reasoning]]''
* ''[[Straight and Crooked Thinking]]''
* [[Paul E. Meehl#"Why I Do Not Attend Case Conferences"|"Why I Do Not Attend Case Conferences"]]
}}

== References ==
{{Reflist|30em}}

== Further reading ==
* [[C. L. Hamblin]], ''Fallacies'', Methuen London, 1970. reprinted by Vale Press in 1998. {{ISBN|0916475247}}.
* {{Cite book |last1=Hans V. Hansen |title=Fallacies: classical and contemporary readings |last2=Robert C. Pinto |publisher=Penn State Press |year=1995 |isbn=978-0271014173}}
* {{Cite book |last1=Frans van Eemeren |title=Fallacies and Judgments of Reasonableness: Empirical Research Concerning the Pragma-Dialectical Discussion |last2=Bart Garssen |last3=Bert Meuffels |publisher=Springer |year=2009 |isbn=978-9048126132}}
* [[Douglas N. Walton]], ''Informal logic: A handbook for critical argumentation''. [[Cambridge University Press]], 1989. {{ISBN?}}
* {{Cite book |last=Douglas |first=Walton |title=Informal Fallacies |date=1987 |publisher=John Benjamins |location=Amsterdam}} {{ISBN?}}
* {{Cite book |last=Walton |first=Douglas |title=A Pragmatic Theory of Fallacy |date=1995 |publisher=University of Alabama Press |location=Tuscaloosa}} {{ISBN?}}
* {{Cite journal |last=Walton |first=Douglas |date=2010 |title=Why Fallacies Appear to Be Better Arguments than They Are |url=https://ojs.uwindsor.ca/ojs/leddy/index.php/informal_logic/article/download/2868/2407 |journal=Informal Logic |volume=30 |issue=2 |pages=159–184 |doi=10.22329/il.v30i2.2868 |doi-access=free}}
* {{Cite book |last=John Woods |title=The death of argument: fallacies in agent based reasoning |publisher=Springer |year=2004 |isbn=978-1402026638 |author-link=John Woods (logician)}}
* Woods, John (2013). ''Errors of Reasoning: Naturalizing the Logic of Inference''. London: College Publications. {{ISBN|978-1848901148}}
* Fearnside, W. Ward and William B. Holther, Fallacy: The Counterfeit of Argument, 1959. {{ISBN?}}
* [[Vincent F. Hendricks]], ''Thought 2 Talk: A Crash Course in Reflection and Expression'', New York: Automatic Press / VIP, 2005, {{ISBN|8799101378}}
* D. H. Fischer, ''Historians' Fallacies: Toward a Logic of Historical Thought'', Harper Torchbooks, 1970. {{ISBN?}}
* Warburton Nigel, ''Thinking from A to Z'', Routledge 1998. {{ISBN?}}
* [[Carl Sagan|Sagan, Carl]], "''[[The Demon-Haunted World|The Demon-Haunted World: Science As a Candle in the Dark]]''". [[Ballantine Books]], 1997 {{ISBN|0345409469}}, 480 pgs. 1996 hardback edition: [[Random House]], {{ISBN|039453512X}}, xv+457 pages plus addenda insert (some printings). Ch. 12.

=== Historical texts ===
* [[Aristotle]], [https://web.archive.org/web/20061004164921/http://etext.library.adelaide.edu.au/a/aristotle/sophistical/ On Sophistical Refutations], ''De Sophistici Elenchi''. library.adelaide.edu.au
* [[William of Ockham]], ''Summa of Logic'' (c. 1323) Part III.4.
* [[John Buridan]], ''Summulae de dialectica'' Book VII.
* [[Francis Bacon]], the doctrine of the idols in ''Novum Organum Scientiarum'', [http://fly.hiwaay.net/%7Epaul/bacon/organum/aphorisms1.html Aphorisms concerning The Interpretation of Nature and the Kingdom of Man, xxiii ff] {{Webarchive|url=https://web.archive.org/web/20200214120354/http://fly.hiwaay.net/~paul/bacon/organum/aphorisms1.html |date=2020-02-14 }}. fly.hiwaay.net
* [[Arthur Schopenhauer]], [https://www.gutenberg.org/files/10731/10731-8.txt The Art of Controversy]  | [http://coolhaus.de/art-of-controversy/ ''Die Kunst, Recht zu behalten – The Art Of Controversy'' (bilingual)], (also known as "Schopenhauers 38 stratagems"). gutenberg.org
* [[John Stuart Mill]], [http://www.la.utexas.edu/research/poltheory/mill/sol/ A System of Logic – Raciocinative and Inductive]. [https://www.laits.utexas.edu/poltheory/mill/sol/sol.b05.c07.html Book 5, Chapter 7, Fallacies of Confusion]. la.utexas.edu

== External links ==
{{Wiktionary|fallacy}}
{{Wikiquote}}
{{Wikiversity|Recognizing Fallacies}}
{{Portal|Philosophy|Psychology}}
* {{cite SEP |url-id=fallacies |title=Fallacies |last=Hansen |first=Hans}}
* {{cite SEP |url-id=logic-informal/#Fal |title=Informal logic}}
* {{cite IEP |url-id=fallacy}}
* {{PhilPapers|category|fallacies}}
* [https://www.scribd.com/doc/8009498/HUMBUG-eBook-by-Jef-Clark-and-Theo-Clark ''Humbug! The skeptic's field guide to spotting fallacies in thinking'']&nbsp;– textbook on fallacies. scribd.com
* [http://www.infidels.org/library/modern/mathew/logic.html List of fallacies with clear examples], infidels.org
* [https://web.archive.org/web/20150515000453/http://www.thefirstscience.org/syllogistic-machine Interactive Syllogistic Machine] A web based syllogistic machine for exploring fallacies, figures, and modes of syllogisms.
* [http://www.csun.edu/~dgw61315/fallacies.html Logical Fallacies and the Art of Debate], csun.edu
* [https://web.archive.org/web/20061006192956/http://onegoodmove.org/fallacy/welcome.htm Stephen Downes Guide to the Logical Fallacies], onegoodmove.org
* [https://web.archive.org/web/20120609064101/http://writingcenter.unc.edu/handouts/fallacies/ Explain fallacies, what they are and how to avoid them]
* [https://www.fallacyfiles.org/index.html Fallacy Files]
* {{cite EB1911 |wstitle=Fallacy |volume=10 |pages=153–154}}

{{Fallacies}}
{{Disinformation}}
{{Philosophical logic}}
{{Authority control}}
[[Category:Fallacies|*]]
[[Category:Barriers to critical thinking]]
[[Category:Information]]
[[Category:Philosophical logic]]
[[Category:Rhetoric]]