Deontic Logic

Deontic logic is the formal study of the normative concepts of obligation, permission, and prohibition. These concepts and their logical relationships to one another are distinguished from value concepts such as goodness and badness (or evil), as well as from such agent-based concepts as act, choice, decision, desire, freedom, and will.

Studies in Fuzziness and Soft Computing, 2011

Deontic logic or logic of norms is a kind of special logics, so-called 'extended logics'. 1 This branch of logics tries to analyze the formal relations established among obligations, permissions, and prohibitions. To this end, the language of logic is supplemented with a new vocabulary that consists of three operators which refer to the above deontic qualifications: 'o' (obligation, duty), 'a' (allowed, permission) and 'v' (interdiction, forbidden). As Sánchez-Mazas says ([21], p. 25), the term 'Deontic Logic' is intended to cover today, in a general way, all studies on the peculiar logical structure of systems of norms of any kind or, if you will, on the sets of values, laws, and deduction rules that govern those systems. For example, if it is an obligation to vote for any political party, then is it allowed? If I have the right to move across the European Union, are prohibited to impede me? Is there a duty to provide the means to such places? If I am required to hold choice to do this or that, how will fulfil that duty, joining the first, or the second, or both requirements? If I have the obligation to attend the institutional acts of my university and I also have the duty not to lose any of my graduate lessons, am I subject to the joint obligation of both actions? Are the causal consequences of an allowed action lawful too? Etc. Many issues of this kind arise when we think about the framework of deontic qualifications or regulations that appear in all human relationships. In sum, the terms that contain such qualifications are norms (moral, legal) whose structure and inferential relations analyzes deontic logic. Thus, we can say that deontic logic is the theory of valid inference rules, that is, the analysis of the conditions and rules in which reasoning including qualifications of prohibition, duty, or permission, is correct. We assume, therefore, that there are structural relations among expressions that include qualifications as required, prohibited, permissible, right, duty, etc. That is, there is a principle of inference between the norms so that, from a structured set of norms, it is possible to establish deductive inferences (logical consequences). In this way, we treat norms as entities like propositions, which can be negated and 1 The term 'deontic logic' is generalized from von Wright's work (1951)[25] in order to refer to the study of inferential relations among norms. The word 'deontik' has been previously used by Mally (1926)[16] related to his 'logic of will' and by Broad (1950)[6], speaking about 'deontic propositions'. Bentham also used the term 'deontology' referring to ethics. The source of that expression is greek word 'tò deón', translated as 'duty' or 'obligation'.

A. Introduction. Two key concepts and three perspectives in deontic logic. Situation, agency and agent oriented deontic theories. B. Concept of norm and its structure revisited. Norms as atomic and molecular entities. C. Two approaches to deontic logic: deterministic, focusing on alethic \ deontic regularities, and indeterministic, viewing agentive choice and alternative lines of behavior. D. Conclusion. Three faces of deontic logic pursue different perspective of normative codes' analysis, reasoning about norms and agentive behavior with preferences \ priorities accordingly.

Ratio Juris, 1991

The paper offers a critical survey of two main sorts of problems hindering the possibility of conceiving deontic logic as a suitable account of the logical behaviour of (sentences expressing) legal norms. The notion of "legal norm" is viewed as the main source of the first sort of problems: (a) the typological variety of legal norms requires an account both of the differing logical behaviour of (sentences expressing) differing legal norms, and of the relations which might hold amon them; (b) the ontologic, figure out a logical analysis of (sentences expressing) legal norms. The notion of "systemic legal validity" is viewed as the main source of the second sort of problems: Deontic logic does not provide suitable logical tools to account for legal phenomena like enactment, derogation, and conflicts between legal norms which rely on systemic legal validity. semantic, and epistemic features of legal norms shed dou % t on the very attempt to

Normative Multi-agent …, 2007

The paper discusses ten philosophical problems in deontic logic: how to formally represent norms, when a set of norms may be termed 'coherent', how to deal with normative conflicts, how contraryto-duty obligations can be appropriately modeled, how dyadic deontic operators may be redefined to relate to sets of norms instead of preference relations between possible worlds, how various concepts of permission can be accommodated, how meaning postulates and counts-as conditionals can be taken into account, and how sets of norms may be revised and merged. The problems are discussed from the viewpoint of input/output logic as developed by van der Torre & Makinson. We argue that norms, not ideality, should take the central position in deontic semantics, and that a semantics that represents norms, as input/output logic does, provides helpful tools for analyzing, clarifying and solving the problems of deontic logic.

Ratio Juris, 2002

A recent series of papers, sparked off by a note by Robert Walter (1996), has rekindled the debate over the possibility of creating a logic of normative concepts. The debate correctly centres on ways in which Jørgensen’s dilemma might be resolved (Jørgensen 1937–8), since a means of resolving that dilemma is the only apparently available way in which to establish that a logic of norms is possible. Two separate questions require answers: (i) what is the correct way in which to regard Jørgensen’s dilemma; and (ii) how should one face that dilemma? I shall argue that traditional responses to the first question are inadequate, and I shall then try to expose as flawed two recent attempts to resolve the dilemma. Finally, I shall relate my conclusions in the earlier part of the paper to the wider question of whether a logic of normative concepts is, after all, a possibility.

Deontic logic enjoys increasing popularity. First and foremost, there are the biennial DEON conferences dedicated to deontic logic and related topics (since 1991). Moreover, Handbook of Deontic Logic and Normative Systems came into existence in 2013. The crucial importance of this publication for further rise of deontic logic is beyond question. But let us move three years forward. The 13 th DEON conference took place in Bayreuth (Germany) on July 18-21, 2016. The reviewed book contains the proceedings of this conference. Interestingly enough, the special focus was "Reasons, Argumentation and Justification". The clever choice of special focus has led to an interesting cooperation between argumentation theory and deontic logic. The conference had four keynote speakers, namely John Broome, Janice Dowell, Xavier Parent, and Gabriella Pigozzi.

Lecture Notes in Computer Science, 2004

The ESSLLI course material has been compiled by Leon van der Torre and Jörg Hansen. Unless otherwise mentioned, the copyright lies with the individual authors of the material. Leon van der Torre and Jörg Hansen declare that they have obtained all necessary permissions for the distribution of this material. ESSLLI 2008 and its organizers take no legal responsibility for the contents of this booklet.

Handbook of Deontic Logic and Normative Systems, 2021

This chapter is a light-weighted overview of significant contributions to legal logic insofar as they involve deontic reasoning and related methods. A special emphasis is given to defeasible reasoning, which has been the major topic for legal reasoning in the last decades. The chapter is divided into three parts and the layout is as follows. Part 1 provides an introductory outline. In particular, we briefly recall an issue that was discussed in the context of deontic logic and that has been as well a hot research theme in legal reasoning, i.e., the very possibility of the use of logic in the law. Part 2 reconstructs the contribution of the literature about some classic topics or methods in deontic logic as relevant for the law: normative positions, the concept of permission, contrary-to-duty reasoning, input/output logic, algebras for normative systems, norm change, defeasibility in law. Part 3 is the largest one and offers, from our previous work, a unifying formal framework, based on Defeasible Logic, re-addressing some of the topics that we have already discussed in Part 2: legal hierarchies and dynamics, institutional agency and normative positions, and deontic aspects of legal interpretation.

1981

In a recent paper, Sven Danielsson argued that the 'original paradoxes' of deontic logic, in particular Ross's paradox and Prior's paradox of derived obligation, can be solved by restricting the modal inheritance rule. I argue that this does not solve the paradoxes.