aequivocatio

Aequivocatio is a Latin term describing the logical fallacy known in English as equivocation. It refers to the use of a single word with two or more meanings within an argument, such that the conclusion seems to follow while the issue actually rests on shifting senses of the term. The word derives from Latin roots often linked to equal voices or calls of the same term.

In scholarly use, aequivocatio is discussed as a kind of ambiguity at the level of a single word, not merely a sentence. It is distinguished from grammatical ambiguity (amphiboly), which arises from syntax, and from benign polysemy, where related meanings coexist but are not intentionally exploited to mislead. Aequivocatio typically involves switching between senses in different premises or in a conclusion, producing a superficially valid argument that collapses under scrutiny.

Example: Premise 1 asserts that all banks lend money (bank in the financial sense). Premise 2 states that the river bank is a bank. Conclusion: the river bank lends money. The apparent inference rests on treating “bank” in two senses as the same; the fallacy lies in the equivocation of the term.

Significance: Recognizing aequivocatio helps in critical thinking and logical analysis by demanding clear definitions of key terms and consistent application of a chosen sense throughout an argument. It remains a common reference point in discussions of formal and informal fallacies.

See also: equivocation, ambiguity, fallacy, logic, rhetoric.