Fallacy (Aristotle)

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Fallacy (Aristotle)

A fallacy is an argument which appears to be conclusive when it is not [1]. The earliest classification, and for a long time the generally accepted, is the one given by Aristotle in his Sophistici Elenchi (Sophistical Refutations). Aristotle divides fallacies into two main groups: fallacies in dictione, or those which arise through some ambiguity of language, and fallacies extra dictionem, sometimes known as 'material fallacies', namely those which have a source other than in language.

There are thirteen fallacies in Aristotle's classification, six in dictione and seven extra dictionem, as follows:

Fallacies in dictione

  • Equivocation
  • Amphiboly
  • Composition
  • Division
  • Accent
  • Figure of speech (figura dictionis)

Fallacies extra dictionem

  • Accident
  • Secundum quid
  • Ignoratio Elenchi
  • Petitio principii
  • Non causa pro causa or False cause
  • Consequent
  • Many questions

Fallacies in dictione


Equivocation is a simple form of fallacy where the same word is used in different senses in different parts of the argument. To avoid the fallacy, all important terms to be used in an argument should be defined at the beginning, and the definition should be adhered to throughout the argument. For example, in his Essay on human understanding, the English philosopher John Locke defines an 'idea' as 'whatsoever the mind perceives in itself, or is the immediate object of perception, thought or understanding'. However, in the course of his work he often reverts to the ordinary English usage, which contrasts 'idea' with 'reality'.


Amphiboly (sometimes wrongly called 'amphibology') is the use of the same phrase in different parts of the argument, where the individual words have different meaning, but the meaning of the expression is different. Whately gives an example once used in the Form of Service for use on the anniversary of the execution of King Charles I. 'If this day shall happen to be Sunday, this form of prayer shall be used and the fast kept the next day following'. It is not clear whether the form of prayer shall be used on Sunday, and the fast kept on Monday, or whether both are to be deferred until Monday.


The Fallacy of composition is where words which are taken separately in the premisses of the argument, are taken together in the conclusion. It typically happens when the premiss that the parts of a whole are of a certain nature is improperly used to infer that the whole itself must also be of this nature. thus 'Atoms are colourless, cats are composed of atoms, therefore cats are colourless'.


The Fallacy of division is the converse of the fallacy of composition, i.e. things which are taken together in the premisses are taken separately in the conclusion.


The Fallacy of accent arises from the ambiguity of a word having different meanings when differently accented. In English, which does not distinguish words by tonic accent, the type applies to arguments that wrongly depend on the emphasis of a particular word in a sentence.

Figure of speech

The Fallacy of figure of speech or 'form of expression' is where the same verbal inflexion is used in different parts of the argument, but where the inflexions have different semantic analyses. The type is reserved for cases in which there is no equivovation, no amphiboloy, or composed versus divided readings, and no multiple meaning because of accents.

For example, in Utilitarianism, John Stuart Mill tries to prove that the one desirable thing is pleasure. 'The only proof capable of being given that an object is visible is that people actually see it. The only proof that a sound is audible, is that people hear it: and so of the other sources of our experience. In like manner, I apprehend, the sole evidence it is possible to produce that anything is desirable, is that people do actually desire it'.

However, the inflexion '-ible' has a different semantic analysis in the premisses than in the conclusion. Visible and audible mean what can be seen or heard: the inflexion implies mere possibility. But desirable means that a thing ought to be desired, or that it is intrinsically valuable or worthwhile. Taken properly, the argument proves only that people can desire pleasure, not that they ought to.

Fallacies extra dictionem


Secundum quid

Ignoratio Elenchi

Petitio principii

Non causa pro causa or False cause


Many questions


  1. ^ Joseph p.525