Equivocation ("to call by the same name") is an informal logical fallacy. It is the misleading use of a term with more than one meaning or sense (by glossing over which meaning is intended at a particular time). It generally occurs with polysemic words (words with multiple meanings).
Albeit in common parlance it is used in a variety of contexts, when discussed as a fallacy, equivocation only occurs when the arguer makes a word or phrase employed in two (or more) different senses in an argument appear to have the same meaning throughout.
It is therefore distinct from (semantic) ambiguity, which means that the context doesn't make the meaning of the word or phrase clear, and amphiboly (or syntactical ambiguity), which refers to ambiguous sentence structure due to punctuation or syntax.
A common case of equivocation is the fallacious use in a syllogism (a logical chain of reasoning) of a term several times, but giving the term a different meaning each time.
- A feather is light.
- What is light cannot 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 have long ears.
- Carl is a jackass.
- Therefore, Carl has long ears.
Here the equivocation is the metaphorical use of "jackass" to imply a stupid or obnoxious person instead of a male donkey.
- Etymological fallacy
- Persuasive definition
- Principle of explosion
- Evasion (ethics)
- Fallacy of four terms
- False equivalence
- Mental reservation
- Plausible deniability
- When a white horse is not a horse
- Antanaclasis, a similar usage for stylistic or rhetorical purposes
- Damer, T. Edward (2009), Attacking Faulty Reasoning: A Practical Guide to Fallacy-free Arguments (6th ed.), Wadsworth, p. 121, ISBN 978-0-495-09506-4
- Fischer, D. H. (June 1970), Historians' fallacies: toward a logic of historical thought, Harper torchbooks (first ed.), New York: HarperCollins, p. 274, ISBN 978-0-06-131545-9, OCLC 185446787
- Damer, T. Edward (2009), Attacking Faulty Reasoning: A Practical Guide to Fallacy-free Arguments (6th ed.), Wadsworth, p. 123, ISBN 978-0-495-09506-4
- Logical Fallacy: Equivocation The Fallacy Files