Dual axioms in modal logic

Axioms in modal logic often say that one sequence of boxes and diamonds in front of a proposition p implies another sequence of boxes and diamonds in front of p. For example, Axiom 4 says □ p → □ □ p and Axiom 5 says ◇p → □◇p. Every axiom has a dual form. The […] The post Dual axioms in modal logic first appeared on John D. Cook....

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