In written language, mentioned words or phrases often appear between single or double quotation marks or in italics.
[5] Some style authorities, such as Strunk and White, emphasize that mentioned words or phrases should be visually distinct.
In mathematics, this concept appears in Gödel's incompleteness theorem, where the diagonal lemma plays a crucial role.
Stanisław Leśniewski extensively employed this distinction, noting the fallacies that can result from confusing it in Russell and Whitehead's Principia Mathematica.
[2] In a 1977 response to analytic philosopher John Searle, Jacques Derrida mentioned the distinction as "rather laborious and problematical".