Fallacy

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).

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.

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.

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.

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.

See also

Logical Fallacy