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 within an argument.

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

Below are some examples of equivocation in syllogisms (a logical chain of reasoning):


 * Since only man [human] is rational.
 * And no woman is a man [male].
 * 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 [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 [male donkey] have long ears.
 * Carl is a jackass [annoying 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.