The term Fallacy denotes any mistaken statement used in an argument. In Logic, it specifically means an argument that violates the rules of formal demonstration. Beginning with Aristotle, Fallacies have generally been placed in one of three catagories. Under the Aristotelian system a fallacy may be a Material fallacy (mistatement of facts), a Verbal fallacy (improper use of words), or a Logical Fallacy (also called a Formal Fallacy--a mistake in the process of inference). The latter two fallacies are called fallacies in dictione (L., in delivery) or in voce (L., in expression), as opposed to material fallacies in re (L. in fact/cause/property) or extra dictionem (outside of/beside delivery). Logic (from ancient Greek λόγος (logos), originally meaning the word, or what is spoken, but coming to mean thought or reason) is the study of arguments. ... Aristotle (sculpture) Aristotle (Greek: Αριστοτέλης Aristotelēs) (384 BC – March 7, 322 BC) was an ancient Greek philosopher. ... A logical fallacy is an error in logical argument which is independent of the truth of the premises. ...

Aristotelian Fallacies

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 which 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 which 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 which do not really support it

• Fallacy of False Cause, or Non Sequitur (L., it does not follow), wherein one thing is in-correctly assumed as the cause of another, as when the ancients attributed a public calamity to a meteorological phenomenon;

• 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.

The logical fallacy of accident, also called destroying the exception or a dicto simpliciter ad dictum secundum quid, is a deductive fallacy occurring in statistical syllogisms (an argument based on a generalization) when an exception to the generalization is ignored. ... The logical fallacy of converse accident (also called reverse accident, destroying the exception or a dicto secundum quid ad dictum simpliciter) is a deductive fallacy that can occur in a statistical syllogism when an exception to a generalization is wrongly called for. ... Ignoratio elenchi (also known as irrelevant conclusion) is the logical fallacy of presenting an argument that may in itself be valid, but which proves or supports a different proposition than the one it is purporting to prove or support. ... An ad hominem argument, also known as argumentum ad hominem ( Latin, literally argument to the man), is a logical fallacy that involves replying to an argument or assertion by addressing the person presenting the argument or assertion rather than the argument itself or an argument pointing out an inconsistency between... An appeal to the majority (also called argumentum ad populum) is the Americans support the death penalty as an argument for the death penalty is an appeal to the majority and does not logically support the argument. ... In logic, begging the question (also called petitio principii) has traditionally described a type of logical fallacy (classified as a material fallacy in the Aristotelian System) in which the proposition to be proved is assumed implicitly or explicitly in one of the premises ([1] [2] [3] [4] [5] [6]). Begging... Jeremy Bentham (February 15, 1748–June 6, 1832) was an English gentleman, jurist, philosopher, eccentric, and legal and social reformer. ... This article is about the logical fallacy. ... Many questions, also known as complex question, loaded question, or plurium interrogationum (Latin, of many questions), is a logical fallacy. ...

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 (" Be 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, which 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.
• 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.

The fallacy of equivocation is committed when someone uses the same word in different meanings in an argument, implying that the word means the same each time round. ... Amphibology or amphiboly (from the Greek ampibolia) is, in logic, a verbal fallacy arising from ambiguity in the grammatical structure of a sentence. ... A fallacy of composition arises when one claims the whole is true because its part is true. ... A fallacy of division occurs when someone reasons logically that something that is true of a thing must also be true of its constituents. ...

Aristotelian Logical Fallacies

The standard logical fallacies are:

• Fallacy of Four Terms (Qualernio terminorum)
• Fallacy of Undistributed Middle
• Fallacy of Illicit process of the major or the Illicit minor term;
• Fallacy of Negative Premises.

The fallacy of four terms (Latin: quaternio terminorum) is a logical fallacy that occurs when a three-part syllogism has four terms. ... The fallacy of the undistributed middle is a logical fallacy that is committed when the middle term in a categorical syllogism isnt distributed. ... Illicit major is a logical fallacy committed in a categorical syllogism that is invalid because its major term is undistributed in the major premise but distributed in the conclusion. ... Illicit minor is a logical fallacy committed in a categorical syllogism that is invalid because its minor term is undistributed in the minor premise but distributed in the conclusion. ... Affirmative conclusion from a negative premise is a logical fallacy that is committed when a categorical syllogism has a positive conclusion, but one or two negative premises. ...

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 text-books. Sir Francis Bacon Francis Bacon, 1st Viscount St Albans (January 22, 1561 – April 9, 1626) was an English philosopher, statesman, spy and essayist. ... John Stuart Mill (May 20, 1806 – May 8, 1873), aka JS Mill, an English philosopher and political economist, was an influential liberal thinker of the 19th century. ...

See also

Logical Fallacy A logical fallacy is an error in logical argument which is independent of the truth of the premises. ...