Equivocation is a logical fallacy that occurs when a key word or phrase in an argument is used in an ambiguous way, with one meaning in one part of the argument and then another meaning in another part of the argument. This fallacy is also sometimes referred to as "shifting the meaning" or "the bait-and-switch". This fallacy often takes the form of intentionally using one definition of a word in one part of an argument and then switching to another definition of the same word in another part of the argument. Equivocation is a type of fallacy that can easily be used to deceive or mislead an audience, since the audience may not notice the shift in meaning of the key word or phrase.
The equivocation fallacy is often used in political debates or in advertising. Politicians will sometimes equivocate in order to make their policies seem more palatable to the public. For example, a politician might argue that we need to support "freedom" (meaning free markets and deregulation) and then conclude that opponents of their policy are against "freedom" (now meaning personal liberty and civil rights). Similarly, an advertisement might claim a product will help you "lose weight fast" — where "fast" first implies speed but is then quietly redefined to mean a period of fasting or dietary restriction.
Equivocation is an informal fallacy, meaning that the error lies not in the formal logical structure of the argument but in the imprecise use of language. The argument may appear logically valid on the surface, but it is unsound because the key term shifts meaning between premises, effectively making the argument about two different things. For this reason, the equivocation fallacy can be difficult to recognize, since it is often subtle and may go unnoticed. It is important to be aware of this fallacy in order to avoid being deceived or misled. Additionally, it is important to recognize when someone is using equivocation in order to point out the fallacy and expose the manipulation of language.
