List of Fallacies and Reasoning

Lecture

A fallacy is a piece of reasoning that is logically incorrect, undermines the logical validity of an argument, or is recognized as unsound. All forms of human communication can contain fallacies.

Fallacies are difficult to classify because of their variety. They can be classified by structure (formal fallacies) or by content (informal fallacies). Informal fallacies, a larger group, can then be subdivided into categories such as improper presumption, faulty generalization, error in establishing a causal connection, and relevance, among others.

The use of fallacies is common when the speaker's goal of achieving general agreement is more important to them than the use of sound reasoning. When fallacies are used, the premise should be recognized as unsupported, the conclusion as unproven (but not necessarily false), and the argument as unsound.

Formal fallacies Formal error

A formal fallacy is an error in the form of an argument. All formal fallacies lack meaning.

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

Propositional fallacies

A propositional fallacy is an error related to compound propositions. For a compound proposition to be true, the truth values of its constituent parts must satisfy the corresponding logical connectives that occur in it (most often: [and], [or], [not], [only if], [if and only if]). The fallacies below concern relations whose truth is not guaranteed and therefore does not guarantee that true conclusions will be obtained.
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 a logical error in which the quantifiers of the premises contradict 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 are logical fallacies that occur in syllogisms.

Affirmative conclusion from a negative premise (illicit negative) - a categorical syllogism has an affirmative 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 made up of four terms.
Illicit major - a categorical syllogism that is invalid because its major term is not distributed in the major premise but is distributed in the conclusion.
Illicit minor - a categorical syllogism that is invalid because its minor term is not distributed in the minor premise but is 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 necessity with sufficiency. Condition X is necessary for Y if X is required even for the possibility of Y. X does not cause Y by itself, but if there is no X, there will be no Y. For example, oxygen is necessary for fire. But one cannot assume that wherever there is oxygen, there is fire. Condition X is sufficient for Y if X alone is enough to cause Y. For example, taking the bus is a sufficient means of transportation to get to work. But there are other modes of transport - a car, a taxi, a bicycle, walking - that can be used.
Modal scope fallacy - the conclusion contains some degree of unwarranted necessity.

Informal fallacies: Informal error

Informal fallacies are arguments that are logically unsound due to a lack of well-founded premises.

Argument to moderation (false compromise, golden mean fallacy, middle ground fallacy, argumentsum ad temperantiam) - assuming that a 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, decision-point fallacy) - improperly rejecting a statement for being imprecise.
Correlative-based fallacies
- Suppressed correlative - a correlative is redefined so that one alternative becomes impossible (for example, "I'm not fat, because I'm thinner than him").
Definist fallacy - the definition of a term used in an argument is biased (for example, through the use of "loaded terms"). The person making the argument expects the listener to accept the given definition, which makes it difficult to refute the argument.
Divine fallacy (argument from incredulity) - an argument that, since something is so improbable or amazing, it must be the result of a higher, divine, extraterrestrial, or paranormal power.
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 use of a term having more than one meaning in a statement, without specifying which meaning is intended.
- Ambiguous middle term - a middle term having several meanings.
- Definitional retreat - changing the meaning of a word when an objection is raised. Often combined with moving the goalposts (see below), for example when an argument is challenged using the common definition of a term in the argument, and the arguer presents a different definition of the term, thereby requiring different evidence to refute the argument.
- Motte-and-bailey fallacy - equating two positions with similar properties, one modest and easy to defend (the "motte") and another controversial one (the "bailey"). The arguer first states the controversial position, but when challenged, claims to be advancing the modest position.
- Fallacy of accent - changing the meaning of an utterance without clarifying which word bears the stress.
- Persuasive definition - using the "true" or "generally accepted" meaning of a term, while actually using an unusual or altered definition.
- (cf. the "if by whiskey" fallacy)
Ecological fallacy - drawing a conclusion about the nature of an object based solely on aggregate statistics collected for the group to which that object belongs.
Etymological fallacy - assuming that the original or historical meaning of a word or phrase is necessarily similar to its actual modern usage.
Fallacy of composition - assuming that something true of a part of a whole must also be true of the whole.
Fallacy of division - assuming that something true of a composite thing must also be true of all or some of its parts.
False attribution - an appeal to an irrelevant, unqualified, unidentified, biased, or fabricated source in support of an argument.
- Fallacy of quoting out of context (contextomy; quote mining) - selectively extracting words from their original context to distort the intended meaning.
False authority (single authority) - using an expert of dubious reputation, or using only one opinion to promote a product or idea. Related to appeal to authority.
False dilemma (false dichotomy, bifurcation fallacy, black-or-white fallacy) - two alternative statements are presented as the only possible options, when in fact there are more.
False equivalence - describing two or more statements as roughly equal, when they are not.
Feedback fallacy - believing in the objectivity of an evaluation that will be used as a basis for improvement, without confirming that the source of the evaluation is a disinterested party.
Historian's fallacy - assuming that decision-makers in the past possessed the same information as those who later analyzed the decision. This should not be confused with presentism, in which modern ideas and perspectives are anachronistically projected into the past.
Historian's fallacy (historicist fallacy) - the belief that a set of considerations carries force simply because a completed process is read back into the content of the process that led to that completed outcome.
- Baconian fallacy - the use of historical evidence without the aid of specific methods, hypotheses, or theories in an attempt to arrive at a general truth about the past. It sets historians "the impossible goal of an impractical method."
Homunculus fallacy - using a "middleman" for explanation; this sometimes leads to regressive middlemen. It explains a concept in terms of the concept itself without explaining its real nature (for example: explaining thought as something created by a little thinker - a homunculus - inside the head merely names an intermediary and does not explain the product or process of thinking).
Inflation of conflict - claiming that if experts in a field of knowledge disagree on a particular point in that field, it is impossible to reach a conclusion, or that the legitimacy of that field of knowledge is questionable.
"If by whiskey" - an argument that supports both sides of an issue by using emotionally sensitive and ambiguous terms.
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 overall comparison.
Intentionality fallacy - asserting that the ultimate meaning of an expression must correspond to the intent of the person from whom the message originates (for example, a work of art that is widely perceived as a blatant allegory need not be regarded as such if the author intended otherwise).
Kettle logic - using multiple mutually inconsistent arguments to defend a position.
Ludic fallacy - ignoring the fact that unregulated random events, unknown unknowns, can affect the probability of an event occurring.
Lump of labor fallacy - the misconception that there is a fixed amount of work to be done within an economy, which can be distributed to create more or fewer jobs.
McNamara fallacy (quantitative fallacy) - relying solely on quantitative observations (measurements, statistical or numerical values) and discounting subjective information that focuses on quality (traits, features, or attitudes).
Mind projection fallacy - assuming that a statement about an object describes an inherent property of the object rather than a personal perception.
Moralistic fallacy - drawing factual conclusions from evaluative premises in violation of the distinction between facts and values (for example: a conclusion is derived from "ought"). The moralistic fallacy is the opposite of the naturalistic fallacy.
Moving the goalposts - an argument in which evidence presented in response to a specific claim is rejected and some other (often more demanding) evidence is required instead.
Nirvana fallacy (perfect solution fallacy) - solutions to problems are rejected because they are imperfect.
Proof by assertion - a proposition is repeatedly restated regardless of contradiction; sometimes confused with the argument from repetition (argumentum ad nauseam, argumentum ad infinitum)
Prosecutor's fallacy - a low probability of a chance match does not mean a low probability that some chance match was found.
Proving too much - an argument that leads to an overly generalized conclusion (for example: claiming that drinking alcohol is bad because in some cases it has led to domestic or child abuse).
Psychologist's fallacy - an observer assumes the objectivity of their own point of view when analyzing a behavioral event.
Referential fallacy - assuming that all words refer to existing things and that the meaning of words lies within the things to which they refer, as opposed to words that may not refer to any real object (for example: Pegasus), or that meaning derives from how they are used (for example: "no one" was in the room).
Reification (concretism, hypostatization, or the fallacy of misplaced concreteness) - treating an abstract belief or hypothetical construct as if it were a concrete, real event or physical object (for example: claiming that evolution "selects" which traits are passed on to future generations; evolution is not a conscious entity with agency).
Retrospective determinism - the belief that, because an event occurred under certain circumstances, the circumstance must have made the event inevitable (for example: because someone won the lottery while wearing their lucky socks, wearing those socks made winning the lottery inevitable).
Slippery slope (thin end of the wedge, camel's nose) - asserting that a proposed, relatively small, first step will inevitably lead to a chain of related events resulting in a significant and negative event, and should therefore not be allowed.
Special pleading - an argument in which someone tries to cite something as an exception to a generally accepted rule or principle without justifying that exception (for example: a defendant who killed his parents asks for leniency because he is now an orphan).

Faulty premise

Begging the question (petitio principii) - using the conclusion of an argument to support the argument itself in the premise (for example: saying that smoking cigarettes is deadly because cigarettes can kill you; something that kills is deadly).
- Loaded label - although not inherently fallacious, the use of evocative terms to support a conclusion is a kind of question-begging fallacy. In its fallacious use, the connotations of a term are used to tilt an argument toward a particular conclusion. For example, an advertisement for organic products that states: "Organic products are safe and healthy products grown without any pesticides, herbicides, or other unhealthy additives." The use of the term "unhealthy additives" is used as confirmation of the idea of the product's safety.
Circular reasoning (circulus in demonstrando) - the reasoner begins with what they are trying to end up with (for example: all bachelors are unmarried men).
Fallacy of many questions (complex question, presumptuous inquiry, loaded question, plurium interrogationum) - someone asks a question that presupposes something that has not been proven or accepted by everyone involved. This fallacy is often used rhetorically, so that the question limits direct answers to those that fit the questioner's agenda.

Faulty generalizations

A faulty generalization is a conclusion drawn from weak premises.

Accident - an exception to a generalization is ignored.
- No true Scotsman - makes a generalization true by altering the generalization to exclude the counterexample.
Cherry picking (suppressed evidence, incomplete evidence) - using individual cases or data that support a particular position while ignoring 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 or unrepresentative sample.
Inductive fallacy - a more general name for the class of fallacies including hasty generalization and its relatives. An inductive fallacy occurs when a conclusion is drawn from premises that only weakly support it.
Misleading vividness - involves describing an event in vivid detail, even if it is an exceptional event, in order to convince someone that it is more significant; this also draws on the appeal-to-emotion fallacy.
Nutpicking (suppressed evidence, incomplete evidence) - using individual cases or data that misrepresent a particular position while ignoring related cases or data that might support it. Named as the opposite of cherry picking.
Overwhelming exception - an accurate generalization that comes with so many qualifications excluding cases that what remains looks far less impressive than the original statement would suggest.
Thought-terminating cliché - a commonly used phrase, sometimes passed off as folk wisdom, used to suppress cognitive dissonance, conceal a lack of forethought, change the subject, and so on - but in any case, to end the discussion with a cliché rather than a point.

Questionable cause

Questionable cause is a general type of error with many variants. Its primary basis is confusing associations with causation, either through improperly inferring (or rejecting) a causal connection, or through failing 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; false cause/effect, coincidental correlation, correlation without causation) - the erroneous 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 occurred, then Y occurred; therefore X caused Y.
- Wrong direction (reverse causation) - cause and effect are swapped. The cause is called the effect, and vice versa. The effect of a phenomenon is considered to be its root cause.
- Ignoring a common cause
Fallacy of the single cause (causal oversimplification) - assuming 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 - assuming that outcomes were caused by the misconduct of decision-makers.
Gambler's fallacy - the mistaken belief that individual independent events can influence the probability of another random event. If a fair coin comes up heads 10 times in a row, the belief that it is "due" to come up tails because of how many times it previously came up tails is incorrect.
- Inverse gambler's fallacy
Magical thinking - erroneously attributing causal relationships between actions and events. In anthropology this refers primarily to cultural beliefs according to which rituals, prayers, sacrifices, and taboos will have certain supernatural consequences. In psychology it refers to the irrational belief that thoughts alone can influence the world, or that thinking about something corresponds to it.
Regression fallacy - attributing a cause where there is none. The fallacy fails to account for natural fluctuation. It is often a special kind of post hoc fallacy.

Fallacies of relevance

Appeal to the stone (argumentum ad lapidem) - dismissing a claim as absurd without demonstrating why it is absurd.
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 no one wants to discuss it anymore; 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 itself be valid but does not address the issue in question.

Fallacies of red herring

A red herring fallacy, one of the main subtypes of fallacies of relevance, is a logical error in which a proposition is, or is intended to be, misleading, in order to draw irrelevant or false conclusions. This includes any logical inference based on false arguments intended to replace the absence of real arguments or to implicitly change the subject under discussion.

Red herring - introducing a second argument in response to the first argument that is irrelevant and distracts attention from the original topic (for example: "If you want to complain about the dishes I leave in the sink, what about the dirty clothes you leave in the bathroom?"). See also irrelevant conclusion.

Ad hominem - attacking the arguer instead of the argument. (Note that "ad hominem" can also refer to a dialectical strategy of arguing from the opponent's own commitments. This type of ad hominem is not a fallacy.)
- Circumstantial ad hominem - stating that the arguer's personal situation or supposed benefit from advancing the conclusion means that their conclusion is incorrect.
- Poisoning the well - a subtype of ad hominem, presenting adverse information about a target person with the intent to discredit everything that person says.
- Appeal to motive - dismissing an idea by questioning the motives of its proponent.
- Kafkatrapping - a sophistical and unfalsifiable form of argumentation that attempts to overwhelm an opponent by inducing feelings of guilt and using the opponent's denial of guilt as further evidence of guilt.
- Tone policing - focusing on the emotion behind (or resulting from) a message rather than the message itself as a tactic to discredit it.
- Traitorous critic fallacy (ergo decedo, "thus leave") - the alleged affiliation of a critic is portrayed as the underlying reason for the criticism, and the critic is asked to stay out of the matter altogether. It is easily confused with the association fallacy ("guilt by association") below.
Appeal to authority (argument from authority, argumentum ad verecundiam) - a claim is considered true because of the position or authority of the person asserting it.
- Appeal to accomplishment - a claim is considered true or false based on the accomplishments of the person proposing it. This can also often carry elements of appeal to emotion (see below).
- Courtier's reply - criticism is dismissed by claiming that the critic lacks sufficient knowledge, credentials, or training to comment credibly on the subject.
Appeal to consequences (argumentum ad consequentiam) - the conclusion is supported by a premise that asserts positive or negative consequences of some course of action in an attempt to distract from the original discussion.
Appeal to emotion - manipulating the listener's emotions rather than using valid reasoning to obtain general agreement.
- Appeal to fear - generating anxiety, worry, cynicism, or prejudice toward an opponent in an argument.
- Appeal to flattery - using excessive or insincere praise to obtain general agreement.
- Appeal to pity (argumentum ad misericordiam) - generating feelings of sympathy or mercy in the listener to obtain general agreement.
- Appeal to ridicule (reductio ad ridiculum, reductio ad absurdum, ad absurdum) - mocking or claiming that an opponent's position is ridiculous in order to distract from the substance of the opponent's arguments. (Note that "reductio ad absurdum" can also refer to the classical form of argument that establishes a claim by showing that the opposite scenario would lead to absurdity or contradiction. This type of reductio ad absurdum is not a fallacy.)
- Appeal to spite - generating bitterness or hostility in the listener toward an opponent in an argument.
- Judgmental language - using offensive or derogatory language in an argument.
- Pooh-pooh - dismissing an opponent's argument as not worthy of consideration.
- Wishful thinking - arguing for a course of action according to what may be pleasant to imagine rather than according to evidence or reason.
Appeal to nature - a judgment is based solely on whether the subject of the judgment is "natural" or "unnatural." (Sometimes also called the "naturalistic fallacy," but should not be confused with other fallacies under that name.)
Appeal to novelty (argumentum novitatis, argumentum ad antiquitatis) - a proposal is considered better or superior solely because it is new or modern. (the opposite of appeal to tradition)
Appeal to poverty (argumentum ad Lazarum) - supporting a conclusion because the arguer is poor (or refuting it because the arguer is rich). (The opposite of appeal to wealth.)
Appeal to tradition (argumentum ad antiquitatem) - a conclusion supported solely because it has long been considered true.
Appeal to wealth (argumentum ad crumenam) - supporting a conclusion because the arguer is wealthy (or refuting it because the arguer is poor). (Sometimes combined with appeal to poverty as a general appeal to the arguer's financial standing.)
Argumentum ad baculum (appeal to the stick, appeal to force, appeal to threat) - an argument made through coercion or threat of force in support of a position.
Argumentum ad populum (appeal to widespread belief, popular appeal, appeal to the majority, appeal to the people) - a claim is considered true or good solely because most or many people believe it to be so.
Association fallacy (guilt by association and honor by association) - claiming that, because two things share (or are said to share) some property, they are the same.
Ipse dixit (bare assertion fallacy) - a statement presented as true without support, as if self-evidently true or dogmatically true. This fallacy rests on the implied expertise of the speaker or on an unestablished truism.
Bulverism (psychogenetic fallacy) - concluding why an argument is being used, attributing it to some psychological cause, and then assuming that as a result it is invalid. The assumption that if an idea arose from a biased opinion, the idea itself must also be false.
Chronological snobbery - a thesis is considered incorrect because it was commonly held at a time when something else, known to be false, was also widely believed.
Relative privation fallacy (also known as "appeal to worse problems" or "not as bad as") - dismissing an argument or complaint because of what are considered to be more important issues. First World problems are a variety of this fallacy.
Genetic fallacy - a conclusion is drawn based solely on something's or someone's origin, rather than on its current meaning or context.
I'm entitled to my opinion - a person discredits any opposition by claiming that they are entitled to their opinion.
Moralistic fallacy - drawing factual conclusions from evaluative premises in violation of the fact-value distinction; for example, making claims about what is, based on claims about what should be. This is the opposite of the naturalistic fallacy.
Naturalistic fallacy - drawing evaluative conclusions from purely factual premises in violation of the fact-value distinction. The naturalistic fallacy (which is sometimes confused with the appeal to nature) is the reverse side of the moralistic fallacy.
- Is-ought fallacy - statements about what should be, based on what is.
Naturalistic fallacy fallacy (anti-naturalistic fallacy) - inferring the impossibility of deriving any instance of an ought from an is from the general invalidity of the is-ought fallacy mentioned above. For example, is genuinely implies ought for some proposition, although the naturalistic fallacy fallacy falsely declares such an inference invalid. The naturalistic fallacy fallacy is a kind of argument from fallacy.
Straw man fallacy - misrepresenting an opponent's argument by broadening or narrowing the scope of a premise and refuting a weaker version (for example: "You tell us that A is the right thing to do, but the real reason you want us to do A is that you personally will benefit from it").
Texas sharpshooter fallacy - incorrectly picking a cause to explain a cluster of data.
Tu quoque ("you too" - appeal to hypocrisy, what-about-that, what-about) - claiming that a position is false, incorrect, or should be ignored because its proponent cannot act consistently in accordance with it.
Two wrongs make a right - assuming that if one wrong is committed, another wrong will rectify it.
Vacuous truth - a statement that is technically true but meaningless, in the form of no B is C when there is no B. For example, stating that there are no mobile phones in the room when there are no mobiles in the room at all.