Abstract.The author gives a short survey of the different methods which have been proposed to deal with the logic of norm sentences on the basis of logical systems of descriptive language: deontic logic, logic of norms as an isomorphism of propositional logic, restriction of logical relations to the propositional content of norm sentences, transformation of norms into sanction sentences, preference interpretation of norm sentences, double interpretation of ought‐sentences and the use of the descriptive interpretation as a tool for establishing the (...) logic of norms, proposition about norms in the place of normative logic, the logic of admissible worlds, postulates addressed to the rational lawgiver and technical ought as a substitute for nor‐mological considerations. A critical analysis of these attempts may prove them inappropriate, but it is not sufficient to prove the impossibility of any method of founding normative logic on systems of a descriptive language. Therefore the author adds a general consideration on the chances of such approaches. (shrink)

Modern belief revision theory is based to a large extent on partial meet contraction that was introduced in the seminal article by Carlos Alchourrón, Peter Gärdenfors, and David Makinson that appeared in 1985. In the same year, Alchourrón and Makinson published a significantly different approach to the same problem, called safe contraction. Since then, safe contraction has received much less attention than partial meet contraction. The present paper summarizes the current state of knowledge on safe contraction, provides some new results (...) and offers a list of unsolved problems that are in need of investigation. (shrink)