Equivocation

In logic, equivocation ('calling two different things by the same name') is an informal fallacy resulting from the use of a particular word/expression in multiple senses throughout an argument leading to a false conclusion. Abbott and Costello's "Who's on first?" routine is a well known example of equivocation.

It is a type of ambiguity that stems from a phrase having two distinct meanings, not from the grammar or structure of the sentence.

Some examples of equivocation in syllogisms (a logical chain of reasoning) are below:

• Since only man [human] is rational,

and no woman is a man [male],

Therefore, no woman is rational.

• A feather is light [not heavy].

What is light [bright] 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 simple-minded or obnoxious person instead of a male donkey.

See also

• Antanaclasis, a related purposeful rhetorical device
• Circumlocution
• Etymological fallacy
• Evasion (ethics)
• Fallacy of four terms
• False equivalence
• If-by-whiskey
• Mental reservation
• Persuasive definition
• Plausible deniability
• Principle of explosion
• When a white horse is not a horse