Use–mention distinction

The use–mention distinction is a foundational concept of analytic philosophy, according to which it is necessary to make a distinction between using a word (or phrase) and mentioning it, and many philosophical works have been "vitiated by a failure to distinguish use and mention". The distinction is disputed by non-analytic philosophers.

The distinction between use and mention can be illustrated for the word cheese:

The first sentence is a statement about the substance called "cheese"; it uses the word "cheese" to refer to that substance. The second is a statement about the word "cheese" as a signifier; it mentions the word without using it to refer to anything other than itself.

In written language, mentioned words or phrases often appear between quotation marks (as in "'Chicago' contains three vowels") or in italics (as in "When I say honey, I mean the sweet stuff that bees make"), and style authorities such as Strunk and White insist that mentioned words or phrases must always be made visually distinct in this manner. Used words or phrases (much more common than mentioned ones) do not bear any typographic distinction. In spoken language, or in absence of the use of stylistic cues such as quotation marks or italics in written language, the audience must identify mentioned words or phrases through semantic and pragmatic cues.

If quotation marks are used, it is sometimes the practice to distinguish between the quotation marks used for speech and those used for mentioned words, with double quotes in one place and single in the other:

Many authorities recommend against such a distinction, and prefer one style of quotation mark to be used for both purposes, which is a much more common practice.

The general phenomenon of a term's having different references in different contexts was called suppositio (substitution) by medieval logicians. It describes how one has to substitute a term in a sentence based on its meaning—that is, based on the term's referent. In general, a term can be used in several ways. For nouns, they are:

The last sentence contains a mention example.

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