Equivocation, from the Latin aequa vox meaning similar sound, is one of the main sources of fallacy, and may be defined as taking one meaning from a word, whereas another is intended or possible. Thus, it is the acceptance of one definite and particular signification of a term, with or without reflection, although the word in question permits a variety of interpretations. The result is usually a mistake in judgment. Equivocation itself is commonly the result of ambiguity in speech or writing.
The fallacy can arise both from an exact similarity of the word and from a sameness of sound (homonyms). A great number of words in the English language, similar in spelling but different in meaning, lend themselves to this fallacy, such as fire (to burn or to discharge), saw (looked or carpenter's tool), bill (invoice or lip), and rank (station or foul). Even more words are homonyms, such as one and won, soul and sole, fair and fare, nose and knows, steak and stake, might and mite, and bruise and brews.
It should also be remembered that meanings of words change with time or are regarded differently by people in other climates of opinion. A man labeled a liberal in the Victorian era would not pass for one in the 1960s. Words such as democracy, idealism, progress, education, and dictator change in significance with social movements and attitudes. This is why good logic requires that one define terms at the beginning of a debate.
Amphibology is an extension of equivocation in which a whole sentence (instead of one word) takes on a double meaning, usually because of an ambiguity in grammatical construction.
Equivocation has a primary role to play in logic when investigating the possible modes of predication. There are three modes of predication: the univocal, the analogical, and the equivocal. In the univocal mode, a term is applied to two or more objects in unvarying exactitude of meaning, such as human to Peter and to Pauline, fish to flounder and fluke, or quantity to mountain and mole. In analogical predication, the term is applied to two or more objects not because of an identity of nature, but for some resemblance in characteristics (see analogy). Thus, lamb is applied to Christ because of His resemblance in meekness, gentleness, and purity to a real lamb. In equivocal predication, however, there is neither identity nor resemblance, but only a similarity of word or sound. When the term match is attributed to a wedding and to a lighter, there is no common ground whatsoever in nature or resemblance.
See Also: term (logic); proposition.
Bibliography: j. a. oesterle, Logic: The Art of Defining and Reasoning (2d ed. Englewood Cliffs, N.J. 1963). s. j. hartman, Fundamentals of Logic (St. Louis 1949).
[p. c. perrotta]