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In logic and rhetoric, a fallacy is a misconception resulting from incorrect reasoning in argumentation. By accident or design, fallacies may exploit emotional triggers in the listener or interlocutor (e.g. appeal to emotion), or take advantage of social relationships between people (e.g. argument from authority). Fallacious arguments are often structured using rhetorical patterns that obscure the logical argument, making fallacies more difficult to diagnose. Also, the components of the fallacy may be spread out over separate arguments.


Material fallacies

The taxonomy of material fallacies is widely adopted by modern logicians and is based on that of Aristotle, Organon (Sophistici elenchi). This taxonomy is as follows:

  • Fallacy of Accident: a generalization that disregards exceptions
    • Example
      Argument: Cutting people is a crime. Surgeons cut people. Therefore, surgeons are criminals.
      Problem: Cutting people is only sometimes a crime.
      Argument: It is illegal for a stranger to enter someone's home uninvited. Firefighters enter people's homes uninvited, therefore firefighters are breaking the law.
      Problem: The exception does not break nor define the rule.
    • Also called destroying the exception, a dicto simpliciter ad dictum secundum quid
  • Converse Fallacy of Accident: argues from a special case to a general rule
    • Example
      Argument: Every swan I have seen is white, so it must be true that all swans are white.
      Problem: What one has seen is a subset of the entire set. One cannot have seen all swans.
    • Also called reverse accident, destroying the exception, a dicto secundum quid ad dictum simpliciter
  • Affirming the Consequent: draws a conclusion from premises that do not support that conclusion by assuming Q implies P on the basis that P implies Q
    • Example:
      Argument: If a person runs barefoot, then their feet hurt. Billy's feet hurt. Therefore, Billy ran barefoot.
      Problem: Other things, such as tight sandals, can result in sore feet.
      Argument: If it rains, the ground gets wet. The ground is wet, therefore it rained.
      Problem: There are other ways by which the ground could get wet (i.e. dew).
  • Denying the antecedent: draws a conclusion from premises that do not support that conclusion by assuming Not P implies Not Q on the basis that P implies Q
    • Example
      Argument: If it is raining out, it must be cloudy. It is not raining out. Therefore, it is not cloudy.
      Problem: There does not have to be rain in order for it to be cloudy.
  • Begging the question: demonstrates a conclusion by means of premises that assume that conclusion.
    • Example
      Argument: The Bible says that God exists and the Bible is always right because it was inspired by God, therefore God exists.
      Problem: The premises are circular in nature because each premise is assuming the other.
    • Also called Petitio Principii, Circulus in Probando, arguing in a circle, assuming the answer. It is worth noting that a circular argument may actually be both logically and factually correct. Circularity itself has no bearing on the truth or falseness of the argument at all, the fallacy is to use a circular argument as a proof of truth.
  • Fallacy of False Cause or Non Sequitur: incorrectly assumes one thing is the cause of another. Non Sequitur is Latin for "It does not follow."
    • Example
      Argument: Our nation will prevail because God is great.
      Problem: There is no necessary cause and effect between God's greatness and a nation prevailing. Simply because God can be considered great does not mean a nation will prevail.
    • Special cases
      • post hoc ergo propter hoc: believing that temporal succession implies a causal relation.
        • Example
          Argument: After Billy had his vaccine, he developed autism. Therefore, the vaccine caused autism.
          Problem: The characteristics of autism may generally become noticeable at the age just following the typical age children receive vaccinations.
      • cum hoc ergo propter hoc: believing that happenstance implies causal relation (aka fallacy of causation versus correlation: assumes that correlation implies causation).
        • Example
          Argument: More cows die in India in the summer months. More ice cream is consumed in summer months. Therefore, the consumption of ice cream in the summer months is killing Indian cows.
          Problem: It is hotter in the summer, resulting in both the death of cows and the consumption of ice cream.
  • Fallacy of Many Questions or loaded question: groups more than one question in the form of a single question
    • Example
      Argument: Is it true that you no longer beat your wife?
      Problem: A yes or no answer will still be an admission of guilt to beating your wife at some point. (See also Mu.)
    • Also called Plurium Interrogationum and other terms
  • Straw man: A straw man argument is an informal fallacy based on misrepresentation of an opponent's position.
    • Example
      Person A claims: Sunny days are good.
      Argument Person B: If all days were sunny, we'd never have rain, and without rain, we'd have famine and death. You are obviously wrong.
      Problem: B has falsely framed A's claim to imply that A says that only sunny days are good, and has argued against that assertion instead of the assertion A has made.

Verbal fallacies

Verbal fallacies are those in which a 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
Example Argument: All heavy things have a great mass; this is heavy fog; therefore this fog has a great mass.
Problem: Heavy describes more than just weight. In the case of fog, it means that the fog is dense, not that it has a great mass.
  • Connotation fallacies occur when a dysphemistic word is substituted for the speaker's actual quote and used to discredit the argument. It is a form of attribution fallacy.
  • Argument by innuendo involves implicitly suggesting a conclusion without stating it outright. For example, a job reference that says a former employee "was never caught taking money from the cash box" implies that the employee was a thief, even though it does not make (or justify) a direct negative statement.[1]
  • Amphibology is the result of ambiguity of grammatical structure
Example: The position of the adverb "only" in the a sentence starting with "He only said that" results in a sentence in which it is uncertain as to which of the other three words the speaker is intending to modify with the adverb.
  • Fallacy of Composition "From Each to All". Arguing from some property of constituent parts, to the conclusion that the composite item has that property. This can be acceptable (i.e., not a fallacy) with certain arguments such as spatial arguments (e.g. "all the parts of the car are in the garage, therefore the car is in the garage")
Example Argument: All the band members (constituent parts) are highly skilled, therefore the band (composite item) is highly skilled.
Problem: The band members may be skilled musicians but not in the same styles of music.
  • Division, the converse of the preceding, arguing from a property of the whole, to each constituent part
Example Argument: "The university (the whole) is 700 years old, therefore, all the staff (each part) are 700 years old".
Problem: Each and every person currently on staff is younger than 200 years. The university continues to exist even when, one by one, each and every person on the original staff leaves and is replaced by a younger person. See Theseus's Ship paradox.
Example Argument: "This cereal is part of a nutritious breakfast therefore the cereal is nutritious."
Problem: Simply because the breakfast taken as a whole is nutritious does not necessarily mean that each part of that breakfast is nutritious.
  • Proof by verbosity, sometimes colloquially referred to as argumentum verbosium - a rhetorical technique that tries to persuade by overwhelming 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 insult of an expert pianist.[citation needed]
  • Figure of Speech, the confusion between the metaphorical and ordinary uses of a word or phrase.
Example: The sailor was at home on the sea.
Problem: The expression 'to be at home' does not literally mean that one's domicile is in that location.

Example 1

Tom argues:

  1. Billy is a good tennis player.
  2. Therefore, Billy 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, Timmy says that Billy is good at some particular activity, in this case tennis. In the conclusion, Timmy states that Billy 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: Billy 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 Timmy. Nothing concerning Billy'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 2

One posits the argument:

  1. Nothing is better than eternal happiness.
  2. Eating a hamburger is better than nothing.
  3. 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 equivocation.

Example 3

Deductive fallacy

In philosophy, the term logical fallacy properly refers to a formal fallacy: a flaw in the structure of a deductive argument which renders the argument invalid.

However, it is often used more generally in informal discourse to mean an argument which is problematic for any reason, and thus encompasses informal fallacies as well as formal fallacies. – valid but unsound claims or bad nondeductive argumentation – .

The presence of a formal fallacy in a deductive argument does not imply anything about the argument's premises or its conclusion (see fallacy fallacy). Both may actually be true, or even more probable as a result of the argument (e.g. appeal to authority), 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.

Formalisms and frameworks used to understand fallacies

A different approach to understanding and classifying fallacies is provided by argumentation theory; see for instance the van Eemeren, Grootendorst reference below. In this approach, an argument is regarded as an interactive protocol between individuals which attempts to resolve a disagreement. The protocol is regulated by certain rules of interaction, and violations of these rules are fallacies. Many of the fallacies in the list below are best understood as being fallacies in this sense.

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.

See also


  1. ^ Damer, T. Edward (2008). Attacking Faulty Reasoning: A Practical Guide to Fallacy-free Arguments (6 ed.). Cengage Learning. pp. 130. ISBN 9780495095064. 

External links

1911 encyclopedia

Up to date as of January 14, 2010
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From LoveToKnow 1911

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Simple English

A logical fallacy or simply a fallacy is some logical transition that people think can be done, but that really cannot be done. It is like an error in thinking. Aristotle and other philosophers identified several such kinds of fallacies:

Aristotelian Fallacies

Material Fallacies

The list is based on the Organon by Aristotle and is widely accepted in scientific literature. The terms used are those commonly used in English.

In practice, modern 'Behavioral Cognitive Therapy' contains many of these same abstractions.

  • Fallacy of the Accident, also known as a dicto simpliciter ad dictum secundum quid. In this fallacy a general rule is improperly applied to some special situation. Example:
    1. Grass is green
    2. This parched plot is grass
    3. Therefore this parched plot is green.
  • Converse Fallacy of the Accident
  • Fallacy of the Irrelevant Conclusion (Ignoratio Elechi): Instead of proving or disproving the fact, the attention is drawn to something irrelevant to the argument:
    • Purely personal considerations: Argumentum Ad hominem. For instance:
      • The speaker said something wrong yesterday;
      • Therefore he cannot be right today.
    • Popular sentiment: Argumentum Ad populum, appeal to the majority
    • Fear: Argumentum Ad baculum (against the stick)
    • Propriety: Argumentum Ad verecundiam
  • Fallacy of Begging the Question
  • Fallacy of the Consequent
  • Fallacy of the False Cause, also known as Non Sequitur, or Post Hoc Ergo Propter Hoc
  • Fallacy of the Many Questions: Many questions are improperly grouped to just represent one question.


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