 Deontic logic has been regularly influenced by reflection on the logic of modal notions, such as necessity (in varying senses of the term). In particular, analogies between alethic (truth-implicating) modal notions and deontic notions were noticed before the fourteenth century in Europe, where we might say that the rudiments of formal (though not symbolic) deontic logic experienced its initial European stirrings. In Islamic thought, such analogies go back at least as far as the tenth century.