In modal logic, the axiom scheme named after mathematician Martin Löb (1921–2006):
When is interpreted as a provability operator, i.e., when is read ‘ is provable’, Löb’s axiom aligns with Löb’s theorem in arithmetic:
From a semantic perspective, Löb’s axiom corresponds to transitive and converse well-founded Kripke frames. That is, the accessibility relation, , is such that if and then , and there is no infinite sequence of worlds such that .