INCLUSION CRITERIA
An entry belongs in this division if and only if its distinctive content is one or more intensional operators interpreted over a relational or neighborhood semantics.
Required: At least one of the following:
- Modal operators (□, ◇, or readings thereof) with Kripke frames and accessibility conditions
- Neighborhood or topological semantics for an intensional operator
- A correspondence between frame conditions and modal axioms
Not sufficient: A semantics that distinguishes necessarily equivalent formulas, because its points of evaluation are states, situations, or impossible worlds rather than possible ones (that belongs in Hyperintensional; a Kripke frame identifies a proposition with a set of worlds however fine its accessibility). A purely truth-functional many-valued matrix (that belongs in Algebraic). A type-theoretic modality presented as a term calculus (that belongs in Type). Dropping structural rules (that belongs in Structural).
Boundary: Temporal, deontic, epistemic, and dynamic readings all live here, subdivided by operator meaning. Provability and justification, though about proof, are modal operators over frames and belong here (Alethic); the proof calculi themselves belong in Metatheory/Proof-Systems, and the incompleteness results they internalize in Metatheory.