Editing Use–mention distinction (section)

== Overview ==

In written language, {{em|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.<ref>For example, ''Butcher's Copy-Editing: The Cambridge Handbook for Editors, Copy-editors and Proofreaders,'' 4th edition, by Judith Butcher, Caroline Drake, and Maureen Leach. Cambridge University Press, 2006. ''Butcher's'' recommends against the practice, but ''The Chicago Manual of Style,'' section 7.58 (15th edition, 2003), indicates that philosophers use single quotes for a similar distinction, though it is not explained in these terms.</ref> Some style authorities, such as [[Strunk and White]], emphasize that mentioned words or phrases should be visually distinct. On the other hand, {{em|used}} words or phrases do not carry typographic markings.<ref>{{cite web |last=Wilson |first=Shomir |year=2011 |title=A Computational Theory of the Use-Mention Distinction in Natural Language |url=http://drum.lib.umd.edu/handle/1903/11694 |access-date=16 February 2013 |publisher=PhD Dissertation, University of Maryland}}</ref>

The phenomenon of a term having different [[references]] in various contexts was referred to as ''[[Supposition Theory|suppositio]]'' (substitution) by medieval logicians.<ref>See Read, Stephen (2006). [http://plato.stanford.edu/entries/medieval-terms Medieval Theories: Properties of Terms]. In [[Stanford Encyclopedia of Philosophy]].</ref> 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 {{em|concrete and real referent}}:{{efn|This use of the word ''concrete'' is explained at [[Abstract and concrete]].}} "That is my ''pig''." (personal supposition) 
* With a {{em|concrete but unreal referent}}: "Santa Claus's ''pig'' is very big." (personal supposition)
* With a {{em|generic referent}}: "Any ''pig'' breathes air." (simple supposition)
* Metaphorically: "Your grandfather is a ''pig''." (improper supposition)
* As a {{em|pure term}}: "''Pig'' has only three letters." (material supposition)

The use–mention distinction is particularly significant in [[analytic philosophy]].<ref>{{cite encyclopedia |title=Quotation |encyclopedia=The Stanford Encyclopedia of Philosophy |url=http://plato.stanford.edu/entries/quotation/#2.2 |access-date=5 October 2009 |date=16 July 2005}}</ref> Confusing use with mention can lead to misleading or incorrect statements, such as [[category error]]s.

[[Self-reference|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.