The formalist definition is that the history of "literature" foregrounds poetic effects; it is the "literariness" or "poeticity" of literature that distinguishes it from ordinary speech or other kinds of writing (e.g., journalism). Jim Meyer considers this a useful characteristic in explaining the use of the term to mean published material in a particular field (e.g., "scientific literature"), as such writing must use language according to particular standards. The problem with the formalist definition is that in order to say that literature deviates from ordinary uses of language, those uses must first be identified; this is difficult because "ordinary language" is an unstable category, differing according to social categories and across history.