Fallacy

"Logical error" redirects here. For logical errors in data storage, see Data integrity § Logical integrity.

A fallacy is the use of invalid or otherwise faulty reasoning, or "wrong moves" in the construction of an argument, not necessarily in the conclusion. A fallacious argument may be deceptive by appearing to be better than it really is. Some fallacies are committed intentionally to manipulate or persuade by deception, while others are committed accidentally due to carelessness or ignorance. The soundness of legal arguments depends on the context in which the arguments are made.

Fallacies are commonly divided into "formal" and "informal". A formal fallacy is a flaw in the structure of a deductive argument which renders the argument invalid, while an informal fallacy originates in an error in reasoning other than an improper logical form. Arguments containing informal fallacies may be formally valid, but still fallacious.

A special case is a mathematical fallacy, an intentionally invalid mathematical proof, often with the error subtle and somehow concealed. Mathematical fallacies are typically crafted and exhibited for educational purposes, usually taking the form of spurious proofs of obvious contradictions.

Overview

Fallacies are defects that weaken arguments. Fallacious arguments are very common and can be persuasive in common use. They may be even "unsubstantiated assertions that are often delivered with a conviction that makes them sound as though they are proven facts". Informal fallacies in particular are found frequently in mass media such as television and newspapers. It is important to understand what fallacies are so that one can recognize them in either one's own or others' writing. Avoiding fallacies will strengthen one's ability to produce strong arguments.

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.

"Fallacious arguments usually have the deceptive appearance of being good arguments." Recognizing fallacies in everyday arguments may be difficult since arguments are often embedded in rhetorical patterns that obscure the logical connections between statements. Informal fallacies may also exploit the emotional, intellectual, or 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 this approach, an argument is regarded as an interactive protocol between individuals that attempts to resolve their disagreements. The protocol is regulated by certain rules of interaction, so violations of these rules are fallacies.

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, advertisements, politics, newspaper editorials and opinion-based "news" shows.

Systems of classification

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 their 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. Yet, verbal fallacies may be placed in either formal or informal 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".

Even the definitions of the classes may not be unique. For example, Whately treats material fallacies as a complement to logical fallacies, which makes them synonymous to informal fallacies, while others consider them to be a subclass of informal fallacies, like mentioned above.

Greek logic

Greek philosopher Aristotle (384 – 322 BC) was the first to systematize logical errors into a list, as being able to refute an opponent's thesis is one way of winning an argument. Aristotle's "Sophistical Refutations" (De Sophisticis Elenchis) identifies thirteen fallacies. He divided them up into two major types, linguistic fallacies and non-linguistic fallacies, some which depend on language and others that do not. 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. An example of a language dependent fallacy is given as a debate as to who in humanity are learners: the wise or the ignorant. A language-independent fallacy is for example:

1. "Coriscus is different from Socrates."
2. "Socrates is a man."
3. "Therefore, Coriscus is different from a man."

Indian logic

Indian logicians took great pain in identifying fallacies in an argument. An influential collection of texts on logic and reason, the Nyāya Sūtras, attributed to Aksapada Gautama, variously estimated to have been composed between 6th-century BCE and 2nd-century CE, in its theory of inference lists five such reasons used in an argument which was further developed by later logicians.

1. Asiddha: It is the unproved reason that results in this fallacy. [Paksadharmata]
2. Savyabhichara: This is the fallacy of irregular reason.
3. 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.
4. Badhita: When another proof (as by perception) definitely contradicts and disproves the middle term (reason). 'Fire is cold because it is a substance'.
5. 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".

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 does follow 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.

Other systems of classification

Of other classifications of fallacies in general the most famous are those of Francis Bacon and 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. With these should be compared the Offendicula of Roger Bacon, contained in the Opus maius, pt. i. J. S. Mill discussed the subject in book v. of his Logic, and Jeremy Bentham's Book of Fallacies (1824) contains valuable remarks. See Rd. Whateley's Logic, bk. v.; A. de Morgan, Formal Logic (1847); A. Sidgwick, Fallacies (1883) and other textbooks.

Formal fallacy

Main article: 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 argument which renders the argument invalid. The flaw can neatly be expressed in standard system of logic. Such an argument is always considered to be wrong. The presence of the formal fallacy does not imply anything about the argument's premises 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.

By extension, an argument can contain a formal fallacy even if the argument is not a deductive one: for instance, an inductive argument that incorrectly applies principles of probability or causality can be said to commit a formal fallacy. "Since deductive arguments depend on formal properties and inductive arguments don't, formal fallacies apply only to deductive arguments."

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 statement 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 which is problematic for any reason.

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

Common examples

Main article: 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."

Fallacy fork

Maarten Boudry and others 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. 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). 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 unless one were actually arguing inductively and probabilistically that it is likely that the mushroom caused the illness since some mushrooms are poisonous, it is possible to misidentify a mushroom as edible, one doesn't usually feel nauseated, etc.

Informal fallacy

See also: Informal fallacy

In contrast to a formal fallacy, an informal fallacy originates in a reasoning error other than a flaw in the logical form of the argument. A deductive argument containing an informal fallacy may be formally valid, 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 the "types of mistakes in reasoning that arise from the mishandling of the content of the propositions constituting the argument".

Faulty generalization

A special subclass of the informal fallacies is the set of faulty generalizations, 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 unwarranted and fallacious. With the backing of empirical evidence, however, the conclusions may become warranted and convincing (at which point the arguments are no longer considered fallacious).

Hasty generalization

Hasty generalization is described as making assumptions about a whole group or range of cases based on a 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 fallacies of relevance are a broad class of informal fallacies, generically represented by missing the point: presenting an argument, which may be sound, but fails to address the issue in question.

Argument from silence

An argument from silence is a faulty conclusion that is made based on the absence of evidence rather than on the presence of evidence.

Examples of informal fallacies

Main article: List of fallacies § Informal fallacies

Post hoc (false cause)

This fallacy gets its name from the Latin phrase "post hoc, ergo propter hoc", which translates as "after this, therefore because of this". Definition: Assuming that because B comes after A, A caused B. 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, temporal correlation does not necessarily entail causation. For example, if I ate a sandwich and then I got food poisoning, that does not necessarily mean the sandwich gave me food poisoning. It is possible that I could have eaten something else earlier that caused the food poisoning.

Slippery slope

Definition: The arguer claims that a sort of chain reaction, usually ending in some dire consequence, will take place, but in fact there is not enough evidence for that assumption. The arguer asserts that if we take even one step onto the "slippery slope", we will end up sliding all the way to the bottom; they assume we cannot stop halfway down the hill. This mainly occurs when an arguer presents a chain of events without properly linking them, instead at most implying the connection.

False analogy

This error in reasoning occurs when claims are supported by unsound comparisons, Hence the false analogy's informal nickname: the "apples and oranges" fallacy.

Straw man fallacy

A straw man (sometimes written as strawman) is a form of argument and an informal fallacy of having the impression of refuting an argument, whereas the proper idea of the argument under discussion was not addressed or properly refuted. One who engages in this fallacy is said to be "attacking a straw man".

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). 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, 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".

For example, anchoring fallacies can occur when unwarranted weight is given to data generated by metrics that the arguers themselves acknowledge is flawed. For example, limitations of the journal impact factor (JIF) are well documented, and even JIF pioneer Eugene Garfield notes, "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." To the extent that arguers jettison acknowledged limitations of JIF-generated data in evaluative judgments, or leave behind Garfield's "supplement rather than replace" caveat, they court commission of anchoring fallacies.

A naturalistic fallacy can occur for example in the case of sheer quantity metrics based on the premise "more is better" or, in the case of developmental assessment in the field of psychology, "higher is better".

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). 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 fallacies can be committed when one measures 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).

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 for 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:

1. Diverting the argument to unrelated issues with a red herring (Ignoratio elenchi)
2. Insulting someone's character (argumentum ad hominem)
3. Assuming the conclusion of an argument, a kind of circular reasoning, also called "begging the question" (petitio principii)
4. Making jumps in logic (non sequitur)
5. Identifying a false cause and effect (post hoc ergo propter hoc)
6. Asserting that everyone agrees (argumentum ad populum, bandwagoning)
7. Creating a false dilemma (either-or fallacy) in which the situation is oversimplified, also called false dichotomy
8. Selectively using facts (card stacking)
9. Making false or misleading comparisons (false equivalence and false analogy)
10. Generalizing quickly and sloppily (hasty generalization)
11. Using an argument's connections to other concepts or people to support or refute it, also called "guilt by association" (association fallacy)
12. Claiming that a lack of proof counts as proof (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.

When someone uses logical fallacies intentionally to mislead in academic, political, or other high-stakes contexts, the breach of trust calls into question the authority and intellectual integrity of that person.

Assessment: pragmatic theory

See also: Argumentation scheme

According to the pragmatic theory, 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, but also collective (shared) goals that apply to all participants. A fallacy of the second kind is seen as more than simply violation of a 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 contest. 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 on the pragmatic approach, each case needs to be analyzed individually, to determine by the textual evidence whether the argument is fallacious or reasonable.

See also

Lists

• List of cognitive biases – Systematic patterns of deviation from norm or rationality in judgment
• List of fallacies – Types of reasoning that are logically incorrect
• List of memory biases – Wikipedia list article
• List of paradoxes – Wikipedia list article
• All pages with titles containing Fallacy
• All pages with titles containing Fallacious
• Pragma-dialectics § Rules for critical discussion

Concepts

• Aporia – State of puzzlement or expression of doubt, in philosophy and rhetoric
• Anti-pattern – Common response to a recurring problem that is usually ineffective or counterproductive
• Argument map – Visual representation of the structure of an argument
• Argumentation theory – Study of how conclusions are reached through logical reasoning; one of four rhetorical modes
• Association fallacy
• Cognitive bias – Systematic pattern of deviation from norm or rationality in judgment
• Cognitive distortion – Exaggerated or irrational thought pattern
• Critical thinking – Analysis of facts to form a judgment
• Demagogue – Politician or orator who panders to fears and emotions of the public
• Evidence – Material supporting an assertion
• Fallacies of definition
• False premise – Incorrect proposition that forms the basis of an argument
• False statement
• Illusion – Distortion of the perception of reality
• Inference objection – Objection to an argument based on the relationship between premise and contention
• Inquiry – any process that has the aim of augmenting knowledge, resolving doubt, or solving a problem
• Jumping to conclusions
• Lemma
• Lies, damned lies, and statistics
• Mathematical fallacy – Certain type of mistaken proof
• Paradox – Statement that apparently contradicts itself
• Prosecutor's fallacy – Fallacy of statistical reasoning
• Sophist – Specific kind of teacher in both Ancient Greece and in the Roman Empire
• Soundness – Logical term meaning that an argument is valid and its premises are true
• Truth – Property of being in accord with fact or reality
• Validity – Argument whose conclusion must be true if its premises are
• Victim blaming – Social phenomenon

Works

• Attacking Faulty Reasoning
• Straight and Crooked Thinking
• "Why I Do Not Attend Case Conferences"

Further reading

• C. L. Hamblin, Fallacies, Methuen London, 1970. reprinted by Vale Press in 1998 as ISBN 0-916475-24-7.
• Hans V. Hansen; Robert C. Pinto (1995). Fallacies: classical and contemporary readings. Penn State Press. ISBN 978-0-271-01417-3.
• Frans van Eemeren; Bart Garssen; Bert Meuffels (2009). Fallacies and Judgments of Reasonableness: Empirical Research Concerning the Pragma-Dialectical Discussion. Springer. ISBN 978-90-481-2613-2.
• Douglas N. Walton, Informal logic: A handbook for critical argumentation. Cambridge University Press, 1989.
• Douglas, Walton (1987). Informal Fallacies. Amsterdam: John Benjamins.
• Walton, Douglas (1995). A Pragmatic Theory of Fallacy. Tuscaloosa: University of Alabama Press.
• Walton, Douglas (2010). "Why Fallacies Appear to Be Better Arguments than They Are". Informal Logic. 30 (2): 159–184. doi:10.22329/il.v30i2.2868.
• John Woods (2004). The death of argument: fallacies in agent based reasoning. Springer. ISBN 978-1-4020-2663-8.
• Fearnside, W. Ward and William B. Holther, Fallacy: The Counterfeit of Argument, 1959.
• Vincent F. Hendricks, Thought 2 Talk: A Crash Course in Reflection and Expression, New York: Automatic Press / VIP, 2005, ISBN 87-991013-7-8
• D. H. Fischer, Historians' Fallacies: Toward a Logic of Historical Thought, Harper Torchbooks, 1970.
• Warburton Nigel, Thinking from A to Z, Routledge 1998.
• Sagan, Carl, "The Demon-Haunted World: Science As a Candle in the Dark". Ballantine Books, March 1997 ISBN 0-345-40946-9, 480 pgs. 1996 hardback edition: Random House, ISBN 0-394-53512-X, xv+457 pages plus addenda insert (some printings). Ch.12.

Historical texts

• Aristotle, On Sophistical Refutations, De Sophistici Elenchi. library.adelaide.edu.au
• William of Ockham, Summa of Logic (ca. 1323) Part III.4.
• John Buridan, Summulae de dialectica Book VII.
• Francis Bacon, the doctrine of the idols in Novum Organum Scientiarum, Aphorisms concerning The Interpretation of Nature and the Kingdom of Man, XXIIIff Archived 2020-02-14 at the Wayback Machine. fly.hiwaay.net
• Arthur Schopenhauer, The Art of Controversy | Die Kunst, Recht zu behalten - The Art Of Controversy (bilingual), (also known as "Schopenhauers 38 stratagems"). gutenberg.net
• John Stuart Mill, A System of Logic - Raciocinative and Inductive. Book 5, Chapter 7, Fallacies of Confusion. la.utexas.edu

External links

• Hansen, Hans. "Fallacies". In Zalta, Edward N. (ed.). Stanford Encyclopedia of Philosophy.
• Zalta, Edward N. (ed.). "Informal logic". Stanford Encyclopedia of Philosophy.
• "Fallacy". Internet Encyclopedia of Philosophy.
• Fallacy at PhilPapers
• Humbug! The skeptic's field guide to spotting fallacies in thinking – textbook on fallacies. scribd.com
• List of fallacies with clear examples, infidels.org
• Interactive Syllogistic Machine A web based syllogistic machine for exploring fallacies, figures, and modes of syllogisms.
• Logical Fallacies and the Art of Debate, csun.edu
• Stephen Downes Guide to the Logical Fallacies, onegoodmove.org
• Explain fallacies, what they are and how to avoid them
• Fallacy Files