Fallacy
A
fallacy is a component of an
argument that is demonstrably flawed in its
logic or form, thus rendering the argument
invalid (except in the case of begging the question) in whole.In
logical arguments, fallacies are either
formal or
informal. Because the validity of a deductive argument depends on its form, a
formal fallacy (or
logical fallacy) is a deductive argument that has an invalid form, whereas an
informal fallacy is any other invalid mode of reasoning whose flaw is not in the form of the argument.
Beginning with
Aristotle, informal fallacies have generally been placed in one of several categories, depending on the source of the fallacy. There are fallacies of relevance, fallacies involving causal reasoning, and fallacies resulting from ambiguities. A similar approach to understanding and classifying fallacies is provided by
argumentation theory. In this approach, an argument is regarded as part of an interactive
protocol between individuals who are attempting to resolve a disagreement. The protocol is regulated by certain rules of interaction and violations of these rules are fallacies.
Recognizing fallacies in actual arguments may be difficult since arguments are often structured using
rhetorical patterns that obscure the logical connections between assertions. As we illustrate with various examples, fallacies may also exploit the
emotions or intellectual or
psychological weaknesses of the interlocutor. Having the capability of recognizing logical fallacies in arguments will hopefully reduce the likelihood of such an occurrence.
Material fallacies
The classification of
material fallacies widely adopted by modern logicians and based on that of Aristotle, Organon (Sophistici elenchi), is as follows:
*
Fallacy of Accident (also called destroying the exception or a dicto simpliciter ad dictum secundum quid) meaning to argue erroneously from a general rule to a particular case, without proper regard to particular conditions that vitiate the application of the general rule; e.g. if manhood suffrage be the law, arguing that a criminal or a lunatic must, therefore, have a vote.
*
Converse Fallacy of Accident (also called reverse accident, destroying the exception, or a dicto secundum quid ad dictum simpliciter) meaning to argue from a special case to a general rule.
*
Irrelevant Conclusion (also called Ignoratio Elenchi), wherein, instead of proving the fact in dispute, the arguer seeks to gain his point by diverting attention to some extraneous fact (as in the legal story of "No case. Abuse the plaintiff's attorney"). The fallacies are common in platform oratory, in which the speaker obscures the real issue by appealing to his audience on the grounds of
**purely personal considerations (
argumentum ad hominem)
**popular sentiment (
argumentum ad populum, appeal to the majority)
**fear (
argumentum ad baculum)
**conventional propriety (
argumentum ad verecundiam):This fallacy has been illustrated by ethical or theological arguments wherein the fear of punishment is subtly substituted for abstract right as the sanction of moral obligation.
*
Begging the question (also called Petitio Principii or Circulus in Probando--arguing in a circle) consists in demonstrating a conclusion by means of premises that pre-suppose that conclusion.
Jeremy Bentham points out that this fallacy may lurk in a single word, especially in an epithet, e.g. if a measure were condemned simply on the ground that it is alleged to be "un-English".
* Fallacy of the Consequent, really a species of Irrelevant Conclusion, wherein a conclusion is drawn from premises that do not really support it.
* Fallacy of False Cause, or
Non Sequitur (L., it does not follow), wherein one thing is incorrectly assumed as the cause of another, as when the ancients attributed a public calamity to a meteorological phenomenon (a special case of this fallacy also goes by the Latin term
post hoc ergo propter hoc; the fallacy of believing that temporal succession implies a causal relation).
*
Fallacy of Many Questions (Plurium Interrogationum), wherein several questions are improperly grouped in the form of one, and a direct categorical answer is demanded, e.g. if a prosecuting counsel asked the prisoner " What time was it when you met this man? " with the intention of eliciting the tacit admission that such a meeting had taken place. Another example is the classic line, "Is it true that you no longer beat your wife?"
Verbal fallacies
Verbal fallacies are those in which a false conclusion is obtained by improper or ambiguous use of words. They are generally classified as follows.
*
Equivocation consists in employing the same word in two or more senses, e.g. in a
syllogism, the middle term being used in one sense in the major and another in the minor premise, so that in fact there are four not three terms ("All fair things are honourable; This woman is fair; therefore this woman is honourable," the second "fair" being in reference to complexion).
*
Amphibology is the result of ambiguity of grammatical structure, e.g. of the position of the adverb "only" in careless writers ("He only said that," in which sentence, as experience shows, the adverb has been intended to qualify any one of the other three words).
*
Fallacy of Composition is a species of Amphibology that results from the confused use of collective terms. e.g. "The angles of a triangle are less than two right angles" might refer to the angles separately or added together.
*
Division, the converse of the preceding, which consists in employing the middle term distributively in the minor and collectively in the major premise.
*
Proof by verbosity, sometimes colloquially referred to as
argumentum verbosium - a rhetorical technique that tries to persuade by overwelming those considering an argument with such a volume of material that the argument sounds plausible, superficially appears to be well-researched, and it is so laborious to untangle and check supporting facts that the argument might be allowed to slide by unchallenged.
* Accent, which occurs only in speaking and consists of emphasizing the wrong word in a sentence. e.g., "He is a fairly good pianist," according to the emphasis on the words, may imply praise of a beginner's progress, or an expert's depreciation of a popular hero, or it may imply that the person in question is a deplorable violinist.
* Figure of Speech, the confusion between the metaphorical and ordinary uses of a word or phrase.
Logical fallacies
The standard Aristotelian
logical fallacies are:
*
Fallacy of Four Terms (Quaternio terminorum)
*
Fallacy of Undistributed Middle* Fallacy of Illicit process of the
major or the
Illicit minor term;
*
Fallacy of Negative Premises.
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.
Fallacies are used frequently by
pundits in the
media and
politics. When one politician says to another, "You don't have the moral authority to say
X", this could be an example of the
argumentum ad hominem or
personal attack fallacy; that is, attempting to disprove
X, not by addressing validity of
X but by attacking the person who asserted
X. Arguably, the politician is not even attempting to make an argument against
X, but is instead offering a moral rebuke against the interlocutor. For instance, if
X is the assertion:
The military uniform is a symbol of national strength and honor.
Then ostensibly, the politician is not trying to prove the contrary assertion. If this is the case, then there is no logically fallacious argument, but merely a personal opinion about moral worth. Thus identifying logical fallacies may be difficult and dependent upon context.
In the opposite direction is the fallacy of
argument from authority. A classic example is the
ipse dixit—"He himself said it" argument—used throughout the
Middle Ages in reference to
Aristotle. A modern instance is "celebrity spokespersons" in advertisements: a product is good and you should buy/use/support it because your favorite celebrity endorses it.
An appeal to authority is always a logical fallacy, though it can be an appropriate form of
rational argument if, for example, it is an appeal to
expert testimony. In this case, the expert witness must be recognized as such and all parties must agree that the testimony is appropriate to the circumstances. This form of argument is common in legal situations.
By definition, arguments with logical fallacies are
invalid, but they can often be (re)written in such a way that they fit a valid
argument form. The challenge to the interlocutor is, of course, to discover the
false premise, i.e. the premise that makes the argument
unsound.
The entries in the following list are neither exhaustive nor mutually exclusive; that is, several distinct entries may refer to the same pattern. As noted in the introduction, these fallacies describe erroneous or at least suspect patterns of argument in general, not necessarily argument based on formal logic. Many of the fallacies listed are traditionally recognized and discussed in works on critical thinking; others are more specialized.
*
Ad hominem (also called
argumentum ad hominem or
personal attack) including:
**
ad hominem abusive (also called
argumentum ad personam)
**
ad hominem circumstantial (also called
ad hominem circumstantiae)
**
ad hominem tu quoque (also called
you-too argument)
*
Amphibology (also called
amphiboly)
*
Appeal to authority (also called
argumentum ad verecundiam or
argument by authority)
*
Appeal to emotion including:
**
Appeal to consequences (also called
argumentum ad consequentiam)
**
Appeal to fear (also called
argumentum ad metum or
argumentum in terrorem)
**
Appeal to flattery**
Appeal to pity (also called
argumentum ad misericordiam)
**
Appeal to ridicule**
Appeal to spite (also called
argumentum ad odium)
**
Two wrongs make a right**
Wishful thinking*
Appeal to the majority (also called
Appeal to belief, Argumentum ad numerum, Appeal to popularity, Appeal to the people, Bandwagon fallacy, Argumentum ad populum, Authority of the many, Consensus gentium, Argument by consensus)
*
Appeal to motive*
Appeal to novelty (also called
argumentum ad novitatem)
*
Appeal to probability*
Appeal to tradition (also called
argumentum ad antiquitatem or
appeal to common practice)
*
Argument from fallacy (also called
argumentum ad logicam)
*
Argument from ignorance (also called
argumentum ad ignorantiam or
argument by lack of imagination)
*
Argument from silence (also called
argumentum ex silentio)
*
Appeal to force (also called
argumentum ad baculum)
*
Appeal to wealth (also called
argumentum ad crumenam)
*
Appeal to poverty (also called
argumentum ad lazarum)
*
Argument from repetition (also called
argumentum ad nauseam)
*
Base rate fallacy*
Begging the question (also called
petitio principii,
circular argument or
circular reasoning)
*
Conditional probability fallacy*
Conjunction fallacy*
Continuum fallacy (also called
fallacy of the beard)
*
Correlative based fallacies including:
**
Fallacy of many questions (also called
complex question,
fallacy of presupposition,
loaded question or
plurium interrogationum)
**
False dilemma (also called
false dichotomy or
bifurcation)
**
Denying the correlative**
Suppressed correlative*
Definist fallacy*
Dicto simpliciter, including:
**
Accident (also called
a dicto simpliciter ad dictum secundum quid)
**
Converse accident (also called
a dicto secundum quid ad dictum simpliciter)
*
Equivocation*
Engineering Fallacy*
Fallacies of distribution:
**
Composition**
Division**
Ecological fallacy*
Fallacies of Presumption*
False analogy*
False premise*
False compromise*
Faulty generalization including:
**
Biased sample**
Hasty generalization (also called
fallacy of insufficient statistics,
fallacy of insufficient sample,
fallacy of the lonely fact,
leaping to a conclusion,
hasty induction,
secundum quid)
**
Overwhelming exception**
Statistical special pleading*
Gambler's fallacy/
Inverse gambler's fallacy*
Genetic fallacy*
Guilt by association*
Historian's fallacy*
Homunculus fallacy*
If-by-whiskey (argues both sides)
*
Ignoratio elenchi (also called
irrelevant conclusion)
* Inappropriate interpretations or applications of statistics including:
**
Biased sample**
Correlation implies causation**
Gambler's fallacy**
Prosecutor's fallacy**
Screening test fallacy*
Incomplete comparison*
Inconsistent comparison*
Invalid proof*
Judgemental language*
Juxtaposition*
Loki's Wager*
Lump of labour fallacy (also called
the fallacy of labour scarcity)
*
Meaningless statement*
Middle ground (also called
argumentum ad temperantiam)
*
Misleading vividness*
Naturalistic fallacy*
Negative proof*
Non sequitur including:
**
Affirming the consequent**
Denying the antecedent*
No true Scotsman*
Package deal fallacy*
Perfect solution fallacy*
Poisoning the well*
Potent directors fallacy - a common example would be any popular press article on
Macroeconomics which asserts or (more often, merely) assumes that the US Fed has learned to control our money and our economy.
*
Proof by assertion*
Proof by verbosity (also called
argumentum verbosium)
*
Questionable cause (also called
non causa pro causa) including:
**
Correlation implies causation (also called
cum hoc ergo propter hoc)
**
Fallacy of the single cause**
Joint effect**
Post hoc (also called
post hoc ergo propter hoc)
**
Regression fallacy **
Texas sharpshooter fallacy **
Wrong direction *
Red herring (also called
irrelevant conclusion)
*
Reification (also called
hypostatization)
*
Relativist fallacy (also called
subjectivist fallacy)
*
Retrospective determinism (it happened so it was bound to)
* Shifting the
burden of proof*
Slippery slope*
Special pleading*
Straw man*
Style over substance fallacy*
Sunk cost fallacy*
Syllogistic fallacies, including:
**
Affirming a disjunct**
Affirmative conclusion from a negative premise**
Existential fallacy**
Fallacy of exclusive premises**
Fallacy of four terms (also called
quaternio terminorum)
**
Fallacy of the undistributed middle**
Illicit major**
Illicit minorFallacious arguments involve not only
formal logic but also
causality.Others involve psychological ployssuch as use of power relationships between proposer and interlocutor,appeals to patriotism and morality, appeals to ego etc., to establishnecessary intermediate (explicit or implicit) premises for an argument.Indeed, fallacies very often lay in unstated assumptions or
impliedpremises in arguments that are not always obvious at first glance.One way to obscure a premise is through
enthymeme.
We now give a few examples illustrating common errors in reasoning. Note that providing a critique of an argument has no relation to the truth of the conclusion. The conclusion could very well be true, while the argument itself is not valid. See
argument from fallacy.
In the following, we view an argument as a dialogue between a
proposer and an
interlocutor.
Example 1: Material Fallacy
James argues:
# Cheese is food. # Food is delicious.# Therefore, cheese is delicious.
This argument claims to prove that cheese is delicious. This particular argument has the form of a
categorical syllogism. Any argument must have
premises as well as a conclusion. In this case we need to ask what the premises are, that is the set of assumptions the proposer of the argument can expect the interlocutor to grant. The first assumption is almost true by definition:
cheese is a foodstuff edible by humans. The second assumption is less clear as to its meaning. Since the assertion has no
quantifiers of any kind, it could mean any one of the following:
* All food is delicious.
* Most food is delicious.
* To me, all food is delicious.
* Some food is disgusting.
In all but the first interpretation, the above syllogism would then fail to have validated its second premise. James may try to assume that his interlocutor believes that all food is delicious; if the interlocutor grants this then the argument is valid. In this case, the interlocutor is essentially conceding the point to James. However, the interlocutor is more likely to believe that some food is disgusting, such as a sheep's liver white chocolate torte; and in this case James is not much better off than he was before he formulated the argument, since he now has to prove the assertion that cheese is a unique type of universally delicious food, which is a disguised form of the original thesis. From the point of view of the interlocutor, James commits the logical fallacy of
begging the question.
Example 2: Verbal Fallacy
Barbara argues:
# Andre is a good tennis player.# Therefore, Andre is 'good', that is to say a
morally good person.
Here the problem is that the word
good has different meanings, which is to say that it is an
ambiguous word. In the premise, Barbara says that Andre is good at some particular activity, in this case tennis. In the conclusion, she says that Andre is a morally good person. These are clearly two different senses of the word "good". The premise might be true but the conclusion can still be false: Andre might be the best tennis player in the world but a rotten person morally. However, it is not legitimate to infer he is a bad person on the ground there has been a fallacious argument on the part of Barbara. Nothing concerning Andre's moral qualities is to be inferred from the premise. Appropriately, since it plays on an ambiguity, this sort of fallacy is called the fallacy of
equivocation, that is, equating two incompatible terms or claims.
Example 3: Verbal Fallacy
Ramesh argues:
# Nothing is better than eternal happiness.# Eating a hamburger is better than nothing.# Therefore, eating a hamburger is better than eternal happiness.
This argument has the appearance of an inference that applies
transitivity of the two-placed relation
is better than, which in this critique we grant is a valid property. The argument is an example of
syntactic ambiguity. In fact, the first premise semantically does not predicate an attribute of the subject, as would for instance the assertion
A potato is better than eternal happiness.
In fact it is semantically equivalent to the following
universal quantification:
Everything fails to be better than eternal happiness.
So instantiating this fact with
eating a hamburger, it logically follows that
Eating a hamburger fails to be better than eternal happiness.
Note that the premise
A hamburger is better than nothing does not provide anything to this argument. This fact really means something such as
Eating a hamburger is better than eating nothing at all.
Thus this is a
fallacy of composition.
Example 4: Logical Fallacy
In the strictest sense, a logical fallacy is the incorrect application of a valid logical principle or an application of a nonexistent principle:
# Some drivers are men.# Some drivers are women.# Therefore, some drivers are both men and women.
This is fallacious. Indeed, there is no logical principle that states
# For some x, P(x).# For some x, Q(x).# Therefore for some x, P(x) and Q(x).
An easy way to show the above inference is invalid is by using
Venn diagrams. In logical parlance, the inference is invalid, since under at least one interpretation of the predicates it is not validity preserving.
*
Logical fallacy
