Editing Modal logic (section)

===Structural proof theory===
[[sequent calculus|Sequent calculi]] and systems of natural deduction have been developed for several modal logics, but it has proven hard to combine generality with other features expected of good [[structural proof theories]], such as purity (the proof theory does not introduce extra-logical notions such as labels) and analyticity (the logical rules support a clean notion of [[analytic proof]]). More complex calculi have been applied to modal logic to achieve generality.{{Citation needed|date=September 2024}}