Editing Structural rule (section)

{{Short description|Rule of mathematical logic}}
{{for|the type of rule used in linguistics|phrase structure rule}}
In the [[formal logic|logical]] discipline of [[proof theory]], a '''structural rule''' is an [[inference rule]] of a [[sequent calculus]] that does not refer to any [[logical connective]] but instead operates on the [[sequent]]s directly.<ref name=":0">{{Cite journal |last=Gentzen |first=Gerhard |date=1935 |title=Untersuchungen über das logische Schließen. I, Mathematische Zeitschrift |url=http://link.springer.com/10.1007/BF01201353 |journal=Mathematische Zeitschrift |language=de |volume=39 |issue=1 |pages=176–210 |doi=10.1007/BF01201353 |issn=0025-5874|url-access=subscription }}</ref><ref>{{Cite book |last=Szabo |first=M. E. |title=Collected papers of Gerhard Gentzen |date=1969 |publisher=Elsevier |isbn=978-0-444-53419-4 |location=Place of publication not identified}}</ref> Structural rules often mimic the intended meta-theoretic properties of the logic. Logics that deny one or more of the structural rules are classified as [[substructural logic]]s.