In logic, equivocation ("calling two different things by the same name") is an

informal fallacy Informal fallacies are a type of incorrect argument in natural language. The source of the error is not just due to the ''form'' of the argument, as is the case for formal fallacies, but can also be due to their ''content'' and ''context''. Fallac ...

resulting from the use of a particular word/expression in multiple

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within an argument. It is a type of

ambiguity Ambiguity is the type of meaning in which a phrase, statement or resolution is not explicitly defined, making several interpretations plausible. A common aspect of ambiguity is uncertainty. It is thus an attribute of any idea or statement ...

that stems from a phrase having two or more distinct meanings, not from the grammar or structure of the sentence.

Fallacy of four terms

Equivocation in a syllogism (a chain of reasoning) produces a

fallacy of four terms The fallacy of four terms ( la, quaternio terminorum) is the formal fallacy that occurs when a syllogism has four (or more) terms rather than the requisite three, rendering it invalid. Definition Categorical syllogisms always have three terms ...

(). Below are some examples: : Since only man

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is rational. : And no woman is a man

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: Therefore, no woman is rational. The first instance of "man" implies the entire human species, while the second implies just those who are male. : A feather is light ot heavy : What is light rightcannot be dark. : Therefore, a feather cannot be dark. In the above example, distinct meanings of the word "light" are implied in contexts of the first and second statements. : All jackasses ale donkeyhave long ears. : Carl is a jackass nnoying person : Therefore, Carl has long ears. Here, the equivocation is the metaphorical use of "jackass" to imply a simple-minded or obnoxious person instead of a male donkey.

Motte-and-bailey fallacy

Equivocation can also be used to conflate two positions which share similarities, one modest and easy to defend and one much more controversial. The arguer advances the controversial position, but when challenged, they insist that they are only advancing the more modest position.

References

{{Fallacies Verbal fallacies Ambiguity

Fallacy of four terms

Motte-and-bailey fallacy

See also

References