# Use–mention distinction

In analytic philosophy, a fundamental distinction is made between the use of a term and the mere mention of it. Many philosophical works have been "vitiated by a failure to distinguish use and mention." The distinction can sometimes be pedantic, especially in simple cases where it is obvious.
The distinction between use and mention can be illustrated with the word "cheese":
* Cheese is derived from milk.
* "Cheese" is derived from the Old English word ċēse.
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.

## Overview

In written language, mentioned words or phrases often appear between single or double quotation marks or in italics. In philosophy, single quotation marks are typically used, while in other fields (such as linguistics) italics are more common. Some style authorities, such as Strunk and White, emphasize that mentioned words or phrases should be visually distinct. On the other hand, used words or phrases do not carry typographic markings.
The phenomenon of a term having different references in various contexts was referred to as suppositio (substitution) by medieval logicians. A substitution describes how a term is substituted in a sentence based on its referent. For nouns, a term can be used in different ways:
* With a concrete and real referent: "That is my pig." (personal supposition)
* With a concrete but unreal referent: "Santa Claus's pig is very big." (personal supposition)
* With a generic referent: "Any pig breathes air." (simple supposition)
* Metaphorically: "Your grandfather is a pig." (improper supposition)
* As a pure term: "Pig has only three letters." (material supposition)
The use–mention distinction is particularly significant in analytic philosophy. Confusing use with mention can lead to misleading or incorrect statements, such as category errors.
Self-referential statements also engage the use–mention distinction and are often central to logical paradoxes, such as Quine's paradox. In mathematics, this concept appears in Gödel's incompleteness theorem, where the diagonal lemma plays a crucial role.

## Commentary

Stanisław Leśniewski extensively employed this distinction, noting the fallacies that can result from confusing it in Russell and Whitehead's Principia Mathematica.
Donald Davidson argued that quotation cannot always be treated as mere mention, giving examples where quotations carry both use and mention functions.
Douglas Hofstadter explains the distinction between use and mention as follows:
   When a word is used to refer to something, it is being used. When a word is quoted, the focus is on its surface aspects, such as typography or phonetics, and it is being mentioned.
Issues arise when a mention itself is mentioned. Notating this with italics or repeated quotation marks can lead to ambiguity.
Some analytic philosophers have said the distinction "may seem rather pedantic".
In a 1977 response to analytic philosopher John Searle, Jacques Derrida mentioned the distinction as "rather laborious and problematical".