A deontic logic framework allowing for factual detachment

• Published in: Journal of applied logic 2011-03, Vol.9 (1), p.61-80
• Main Author: Strasser, Christian
• Format: Article
• Language: English
• Subjects: Adaptive logic; Conditional deontic logic; Dealing; Defeasible reasoning; Detachment; Dyadics; Editors; Ethical standards; Falling; Logic; Modus ponens; Norms; Tasks
• ISSN: 1570-8683; 1570-8691
• DOI: 10.1016/j.jal.2010.11.001

Since our ethical and behavioral norms have a conditional form, it is of great importance that deontic logics give an account of deontic commitments such as “ A commits you to do/bring about B”. It is commonly agreed that monadic approaches are suboptimal for this task due to several shortcomings, for instance their falling short of giving a satisfactory account of “Strengthening the Antecedent” or their difficulties in dealing with contrary-to-duty paradoxes. While dyadic logics are more promising in these respects, they have been criticized for not being able to model “detachment”: A and the commitment under A to do B implies the actual obligation to do B. “We seem to feel that detachment should be possible after all. But we cannot have things both ways, can we? This is the dilemma on commitment and detachment.” (Lennart Åqvis. Deontic logic. In D. Gabbay and F. Guenthner, editors, Handbook of Philosophical Logic, p. 199, Kluwer, Dordrecht, 2002). In this paper I answer Åqvist's question with “Yes, we can”. I propose a general method to turn dyadic deontic logics in adaptive logics allowing for a defeasible factual detachment while paying special attention to specificity and contrary-to-duty cases. I show that a lot of controversy about detachment can be resolved by analysing different notions of unconditional obligations. The logical modeling of detachment is paradigmatically realized on basis of one of Lou Goble's conflict tolerant CDPM logics.