= Normal modal distribution axiom
{title2=$\Box(A\to B)\to(\Box A\to\Box B)$}
= K axiom of modal logic
{c}
{synonym}
The normal distribution axiom says that a boxed implication and its boxed antecedent give the boxed consequent. Together with the <necessitation rule>, it permits boxed versions of propositional deductions. Under an arithmetic interpretation it is the internal modus-ponens condition among the <Hilbert-Bernays-Löb derivability conditions>. It does not permit dropping a box to assert the enclosed sentence.
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