Version: v1, Published online: 1998
Retrieved May 21, 2019, from https://www.rep.routledge.com/articles/thematic/deontic-logic/v-1
Deontic logic is the investigation of the logic of normative concepts, especially obligation (‘ought’, ‘should’, ‘must’), permission (‘may’) and prohibition (‘ought not’, ‘forbidden’). Deontic logic differs from normative legal theory and ethics in that it does not attempt to determine which principles hold, nor what obligations exist, for any given system. Rather it seeks to develop a formal language that can adequately represent the normative expressions of natural languages, and to regiment such expressions in a logical system.
The theorems of deontic logic specify relationships both among normative concepts (for example, whatever is obligatory is permissible) and between normative and non-normative concepts (for example, whatever is obligatory is possible). Contemporary research beginning with von Wright treats deontic logic as a branch of modal logic, in so far as (as was noted already by medieval logicians) the logical relations between the obligatory, permissible and forbidden to some extent parallel those between the necessary, possible and impossible (concepts treated in ‘alethic’ modal logic).
Belzer, Marvin. Deontic logic, 1998, doi:10.4324/9780415249126-Y043-1. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/thematic/deontic-logic/v-1.
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