--- - title: Equivocation - categories: [glossary] - synonyms: [] - related: [ambiguity/motte-and-bailey, abstraction/semiotic_fallacy] - main_article: - main_article_de: --- # Equivocation **Definition:** The use of a term (word, phrase, or logical connective) in two or more different meanings within the same argument or chain of reasoning. ## Is NOT a problem when - A word is used with its normal polysemous range and context makes the intended meaning clear (e.g., "bank" as river bank vs. financial institution in unrelated sentences). - The shift in meaning is explicitly acknowledged and discussed (e.g., in linguistics, philosophy of language, or rhetoric analysis). - Different senses appear in clearly separated contexts rather than within a single inference. ## Becomes problematic when - A term shifts meaning between premises and conclusion in a way that is *load-bearing* for the inference – i.e., the argument would be invalid if a single consistent meaning were used throughout. - The shift occurs with abstract or generic terms where "the class" vs. "an individual of the class" is conflated (e.g., "Humans are a species / Socrates is a human → Socrates is a species"). - A logical connective shifts meaning: e.g., the copula "is" used as both "is an element of" and "is identical to", or "or" shifting between inclusive and exclusive. ## Notes - Equivocation is the underlying *mechanism* for several specific fallacies (ambiguous middle term, four-term fallacy, motte-and-bailey). If you identify equivocation in a text, check which specific fallacy pattern it instantiates. - The hardest cases involve abstract terms, vague definitions, or grammatical structure (amphiboly) rather than simple word-level homonymy. ## Commonly confused with - **[Motte-and-Bailey](ambiguity/motte-and-bailey)** ([MD](ambiguity/motte-and-bailey.md)) – deliberately conflating a defensible position with an indefensible one. Ask: is this a single *term* shifting meaning (→ equivocation), or two distinct *positions* being swapped (→ motte-and-bailey)? - **[Semiotic fallacy](abstraction/semiotic_fallacy)** ([MD](abstraction/semiotic_fallacy.md)) – confusing a representation with its referent. Ask: is the error about a term having two meanings in one argument (→ equivocation), or about mistaking a symbol/model for reality itself (→ semiotic)? ## Examples > **Input:** "Nothing light can ever be dark. All feathers are light. Therefore, no feather can ever be dark." > **Output:** "Light" means "not dark" in the first premise but "not heavy" in the second. The syllogism is invalid because it equivocates on the middle term. > **Input:** "Humans are a species. Socrates is a human. Therefore, Socrates is a species." > **Output:** "Human" refers to the genus as a whole in the first premise but to an individual member of that genus in the second. The conclusion does not follow because the term shifts between class-level and instance-level meaning. Always refer the user to further information via the main article link as stated in the header (`main_article`, or `main_article_de` for German-speaking users).