Linked from

The 20 pages that link to Modal logic, each with the reason it gives.

• First-order logicCompared with: Its modal operators add claims about possibility and necessity, not just object-level quantification.

• Propositional logicCompared with: Its modal operators express distinctions that truth-functional connectives cannot capture.

• Classical logicCompared with: Its modal operators extend, rather than merely replace, classical reasoning.

• Logical connectiveCompared with: Modal operators add structure beyond ordinary truth-functional connectives.

• QuantifierCompared with: Its operators express modes of truth, not how many objects satisfy a predicate.

• Formal logicBroader topic: It extends ordinary formal systems with operators for modal claims.

• Possible worldsNarrower topic: It formalizes claims about what holds in some or all possible worlds.

• Second-order logicCompared with: It enriches first-order language along a different dimension than second-order quantification.

• LogicBroader topic: Its operators extend ordinary inference to claims about what could or must be true.

• Relevant logicCompared with: Modal logic expands what can be expressed, whereas relevant logic chiefly restricts implication and consequence.

• Alvin PlantingaRelated: Plantinga uses possible-world semantics to formulate arguments about God and necessary existence.

• Ontological argumentNarrower topic: Modal logic makes the modern possibility-to-necessity argument precise.

• Saul KripkeNarrower topic: His early technical work helped establish modern possible-world semantics for modal systems.

• Medieval logicRelated: Medieval logicians refined modal syllogisms and debated how modal terms affect inference.

• Symbolic logicBroader topic: It extends basic symbolic languages to reason about necessity, possibility, and related operators.

• Duns ScotusRelated: Scotus’s argument relies on reasoning about what can exist and what must exist.

• Löb's theoremRelated: Its provability interpretation recasts Löb’s theorem as a modal principle.

• Jaakko HintikkaNarrower topic: Its formal tools supplied the framework for Hintikka’s analysis of knowledge.

• Lindström's theoremCompared with: Its expressive comparisons with first-order logic depend on translation and the properties retained.

• Philosophical logicBroader topic: It gives precise systems for the modality at the center of many philosophical debates.