Sven Ove Hansson

The AGM (Alchourrón-Gärdenfors-Makinson) model of belief change is extended to cover changes on sets of beliefs that are not closed under logical consequence (belief bases). Three major types of change operations, namely contraction, internal revision, and external revision are axiomatically characterized, and their interrelations are studied. In external revision, the Levi identity is reversed in the sense that one first adds the new belief to the belief base, and afterwards contracts its negation. It is argued that external revision represents an intuitively plausible way of revising one's beliefs. Since it typically involves the temporary acceptance of an inconsistent set of beliefs, it can only be used in belief representations that distinguish between different inconsistent sets of belief

Situationist deontic logic is a model of that fraction of normative discourse which refers to only one situation and one set of alternatives. As we can see from a whole series of well-known paradoxes, standard deontic logic (SDL) is seriously mistaken even at the situationist level. In this paper it is shown how a more realistic deontic logic can be based on the assumption that prescriptive predicates satisfy the property of contranegativity. A satisfactory account of situation-specific norms is a necessary prerequisite for a successful treatment of more complex normative structures

By replacement is meant an operation that replaces one sentence by another in a belief set. Replacement can be used as a kind of Sheffer stroke for belief change, since contraction, revision, and expansion can all be defined in terms of it. Replacement can also be defined either in terms of contraction or in terms of revision. Close connections are shown to hold between axioms for replacement and axioms for contraction and revision. Partial meet replacement is axiomatically characterized. It is shown that this operation can have outcomes that are not obtainable through either partial meet contraction or partial meet revision.

The basic assumption of repertoire contraction is that only some of the logically closed subsets of the original belief set are viable as contraction outcomes. Contraction takes the form of choosing directly among these viable outcomes, rather than among cognitively more far-fetched objects such as possible worlds or maximal consistent subsets of the original belief set. In this first investigation of repertoire contraction, postulates for various variants of the operation are introduced. Necessary and sufficient conditions are given for when repertoire contraction coincides with AGM contraction or with operations generated by AGM-style contraction on a belief base. A close connection is shown to hold between repertoire contraction and specified meet contraction

This is a response to an article by Wade Allison in which he argues that we should accept drastically higher doses of ionizing radiation than what we currently do. He employs four arguments in defence of his position: comparisons with background radiation, the positive experiences of radiotherapy, the presence of biological defence mechanisms against radiation, and a concession by Swedish authorities that their approach to reindeer meat after the Chernobyl fallout was unnecessarily strict. It is shown that each of the four arguments is fallacious. In conclusion, the traditional weighing of risks against benefits in radiation protection is defended.

In order to shorten queues to healthcare, the Swedish government has introduced a yearly “queue billion” that is paid out to the county councils in proportion to how successful they are in reducing queues. However, only the queues for first visits are covered. Evidence has accumulated that queues for return visits have become longer. This affects the chronically and severely ill. Swedish physicians, and the Swedish Medical Association, have strongly criticized the queue billion and have claimed that it conflicts with medical ethics. Instead they demand that their professional judgments on priority setting and medical urgency be respected. This discussion provides an interesting illustration of some of the limitations of new public management and also more generally of the complicated relationships between medical ethics and public policy

J.S. Mill’s advocacy of liberty was based only in part on his harm principle. He also endorsed two other principles that considerably extend the scope of liberty: first, a principle of individual liberty that is based on the value of positive freedom and of developing individuality, and second, a principle of free trade or economic freedom that is based on the value of economic efficiency. An analysis is offered of how these three principles are combined in Mill’s account of liberty and how they connect with his antipaternalism. It is proposed that his appeal in On Liberty to positive freedom and the development of individuality provides a uniting principle that makes his view on liberty cohere with his utilitarianism.

A new possible world semantics for deontic logic is proposed. Its intuitive basis is that prohibitive predicates (such as "wrong" and "prohibited") have the property of negativity, i.e. that what is worse than something wrong is itself wrong. The logic of prohibitive predicates is built on this property and on preference logic. Prescriptive predicates are defined in terms of prohibitive predicates, according to the wellknown formula "ought" = "wrong that not". In this preference-based deontic logic (PDL), those theorems that give rise to the paradoxes of standard deontic logic (SDL) are not obtained. (E.g., O(p & q) → Op & Oq and Op → O(p v q)) are theorems of SDL but not of PDL.) The more plausible theorems of SDL, however, can be derived in PDL

The prescriptive has both an objective and a subjective interpretation. In the objective sense, what one ought to do depends on what is actually true. In the subjective sense it depends on what one believes to be true. Ordinary usage seems to vacillate between these two interpretations. An example (the indecisive terrorist) is used to show that a subjective ought statement can have a determinate truth-value in situations where the corresponding objective ought statement has no truth-value, not even an unknowable one. Therefore the subjective ought is not definable in terms of the objective ought. However, definability in the other direction is not excluded by this argument