A logical calculus created by adding operators ‘O p ’ (it ought to be the case that p ) and ‘P p ’ (it is permissible that p ) to a basic system such as the propositional calculus, together with rules of inference for them. A deontic logic will study inferences between these forms, telling for instance whether Op & p →q yield Oq, or whether Op → ¬O¬p . Principles such as these have proved controversial and there is no one ‘classical’ system of deontic logic. See also gentle murder, paradox of.
Philosophy dictionary. Academic. 2011.