normal modal logic
set of modal formulas containing all propositional tautologies and all instances of the Kripke schema ◻(A→B)→(◻A→◻B) and closed under modus ponens and necessitation
set of modal formulas containing all propositional tautologies and all instances of the Kripke schema ◻(A→B)→(◻A→◻B) and closed under modus ponens and necessitation