Sven Ove Hansson

Blockage contraction is an operation of belief contraction that acts directly on the outcome set, i.e. the set of logically closed subsets of the original belief set K that are potential contraction outcomes. Blocking is represented by a binary relation on the outcome set. If a potential outcome X blocks another potential outcome Y, and X does not imply the sentence p to be contracted, then Y ≠ K ÷ p. The contraction outcome K ÷ p is equal to the (unique) inclusion-maximal unblocked element of the outcome set that does not imply p. Conditions on the blocking relation are specified that ensure the existence of such a unique inclusion-maximal set for all sentences p. Blockage contraction is axiomatically characterized and its relations to AGM-style operations are investigated. In a finite-based framework, every transitively relational partial meet contraction is also a blockage contraction

A model of coherentist belief contraction is constructed. The outcome of belief contraction is required to be one of the coherent subsets of the original belief set, and a set of plausible properties is proposed for this set of coherent subsets. The contraction operators obtained in this way are shown to coincide with well-known belief base operations. This connection between coherentist and "foundationalist" approaches to belief change has important implications for the philosophical interpretation of models of belief change

The postulate of recovery is commonly regarded to be the intuitively least compelling of the six basic Gärdenfors postulates for belief contraction. We replace recovery by the seemingly much weaker postulate of core-retainment, which ensures that if x is excluded from K when p is contracted, then x plays some role for the fact that K implies p. Surprisingly enough, core-retainment together with four of the other Gärdenfors postulates implies recovery for logically closed belief sets. Reasonable contraction operators without recovery do not seem to be possible for such sets. Instead, however, they can be obtained for non-closed belief bases. Some results on partial meet contractions on belief bases are given, including an axiomatic characterization and a non-vacuous extension of the AGM closure condition.

Theoria , the international Swedish philosophy journal, was founded in 1935. Its contributors in the first 75 years include the major Swedish philosophers from this period and in addition a long list of international philosophers, including A. J. Ayer, C. D. Broad, Ernst Cassirer, Hector Neri Castañeda, Arthur C. Danto, Donald Davidson, Nelson Goodman, R. M. Hare, Carl G. Hempel, Jaakko Hintikka, Saul Kripke, Henry E. Kyburg, Keith Lehrer, Isaac Levi, David Lewis, Gerald MacCallum, Richard Montague, Otto Neurath, Arthur N. Prior, W. V. Quine, Nicholas Rescher, Ernest Sosa, Robert C. Stalnaker, P. F. Strawson, Patrick Suppes, Johan van Benthem, Georg Henrik von Wright and many others. Hempel's confirmation paradoxes, Ross's deontic paradox, Montague's universal grammar and Lindström's theorem are among the contributions to philosophy that were first published in Theoria.

In order to explore public views on nanobiotechnology (NBT), convergence seminars were held in four places in Europe; namely in Visby (Sweden), Sheffield (UK), Lublin (Poland), and Porto (Portugal). A convergence seminar is a new form of public participatory activity that can be used to deal systematically with the uncertainty associated for instance with the development of an emerging technology like nanobiotechnology. In its first phase, the participants are divided into three “scenario groups” that discuss different future scenarios. In the second phase, the participants are regrouped into three “convergence groups”, each of which contains representatives from each of the three groups from the first phase. In the final third phase, all participants meet for a summary discussion. This pilot project had two aims: (1) to develop and assess the new methodology and (2) to gather advice and recommendations from the public that may be useful for future decisions on nanobiotechnology (NBT). Participants emphasized that they wanted the technology to focus on solutions to environmental and medical problems and to meet the needs of developing countries. The need for further public participation and deliberation on NBT issues seemed to be acknowledged by all participants. Many of them also raised equality concerns. Views on the means by which NBT should be steered into socially useful directions were more divided. In particular, different views were expressed on how much regulation of company activities is needed to curb unwanted developments. The participants’ responses in a questionnaire indicate that the methodology of the convergence seminars was successful for decision-making under uncertainty. In particular, the participants stated that their advice was influenced both by access to different possible future developments and by the points of view of their co-participants, which is what the method is specifically intended to achieve.

A new equivalent presentation of AGM revision is introduced, in which a preference-based choice function directly selects one among the potential outcomes of the operation. This model differs from the usual presentations of AGM revision in which the choice function instead delivers a collection of sets whose intersection is the outcome. The new presentation confirms the versatility of AGM revision, but it also lends credibility to the more general model of direct choice among outcomes of which AGM revision is shown here to be a special case

A formal language is introduced that contains expressions for the dependency of a legal relation on the claims that the concerned individuals make and on the permissions that they grant. It is used for a classification of legal relations into six major categories: categorical obligation, categorical permission, claimable obligation, grantable permission, claim-dependent obligation and grant-dependent permission. Legal rights may belong to any of these six categories, but the characteristics of a right-holder are shown to be different in each of the six types.

The 1985 paper by Carlos Alchourrón, Peter Gärdenfors, and David Makinson, “On the Logic of Theory Change: Partial Meet Contraction and Revision Functions” was the starting-point of a large and rapidly growing literature that employs formal models in the investigation of changes in belief states and databases. In this review, the first twenty-five years of this development are summarized. The topics covered include equivalent characterizations of AGM operations, extended representations of the belief states, change operators not included in the original framework, iterated change, applications of the model, its connections with other formal frameworks, computatibility of AGM operations, and criticism of the model.

Receiving information about threats to one’s health can contribute to anxiety and depression. In contemporary medical ethics there is considerable consensus that patient autonomy, or the patient’s right to know, in most cases outweighs these negative effects of information. Worry about the detrimental effects of information has, however, been voiced in relation to public health more generally. In particular, information about uncertain threats to public health, from—for example, chemicals—are said to entail social costs that have not been given due consideration. This criticism implies a consequentialist argument for withholding such information from the public in their own best interest. In evaluating the argument for this kind of epistemic paternalism, the consequences of making information available must be compared to the consequences of withholding it. Consequences that should be considered include epistemic effects, psychological effects, effects on private decisions, and effects on political decisions. After giving due consideration to the possible uses of uncertain information and rebutting the claims that uncertainties imply small risks and that they are especially prone to entail misunderstandings and anxiety, it is concluded that there is a strong case against withholding of information about uncertain threats to public health.