INCLUSION CRITERIA
An entry belongs in this subdivision if and only if its modal operator reads as necessity or possibility (or a close cousin—provability, justification, counterfactual necessity), interpreted over a Kripke or neighborhood semantics.
Required: At least one of the following:
- Operators □/◇ read alethically, with frame conditions and a normal or classical modal system
- A provability, justification, or interpretability operator over frames
- A strict or counterfactual conditional with a modal or similarity semantics
Not sufficient: A conditional whose constraint is content containment, variable inclusion, or exact verification rather than a modal or similarity semantics (Hyperintensional). An essentialist operator advanced as an alternative to modal analysis rather than a form of it (Hyperintensional). An obligation reading (Deontic). A knowledge or belief reading (Epistemic). A temporal reading (Temporal). A program or action modality (Dynamic).
Boundary: Provability and justification, though about proof, are alethic-style operators over frames and stay here; the proof calculi are in Metatheory/Proof-Systems and the incompleteness results in Metatheory. Conditionals with a modal similarity semantics stay here; probabilistic conditionals go to Applications/Probabilistic.