Sven Ove Hansson

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.

Changing preferencesis a phenomenonoften invoked but rarely properlyaccounted for. Throughout the history of the social sciences, researchers have come against the possibility that their subjects’ preferenceswere affected by the phenomenato be explainedor by otherfactorsnot taken into accountin the explanation.Sporadically, attempts have been made to systematically investigate these in uences, but none of these seems to have had a lasting impact. Today we are still not much further with respect to preference change than we were at the middle of the last century. This anthology hopes to provide a new impulse for research into this important subject. In particular, we have chosen two routes to amplify this impulse. First, we stress the use of modellingtechniquesfamiliar from economicsand decision theory. Instead of constructing complex, all-encompassing theories of preference change, the authors of this volume start with very simple, formal accounts of some possible and hopefully plausible mechanism of preference change. Eventually, these models may nd their way into larger, empirically adequate theories, but at this stage, we think that the most importantwork lies in building structure.Secondly,we stress the importance of interdisciplinary exchange. Only by drawing together experts from different elds can the complex empirical and theoretical issues in the modelling of preference change be adequately investigated.

ABSTRACT John Rawls proposed two criteria for the delimitation of acceptable inequalities. The universal gain principle requires inequalities to be beneficial for all, and the difference principle requires them to be beneficial for the least advantaged. These principles are commonly believed to have originated in Rawls’s work, but they were both clearly expressed in the writings of Nicolas de Condorcet. Contrary to Rawls, Condorcet did not imbed them in the framework of a social contract, but instead sought their foundations in natural rights. Whereas Rawls recommends us to find out what social arrangements rational reasoners would choose in a hypothetical pre-social situation, Condorcet proposes that we ask the underprivileged in our society whether or not they consider themselves to benefit from the prevailing social and economic inequalities. Thus, Condorcet’s original version of the difference principle puts social inequalities to a different test than its latter-day, hypothetical version.

Full meet contraction, that was devised by Carlos Alchourrón and David Makinson in the early 1980' s, has often been overlooked since it is not in itself a plausible contraction operator. However, it is a highly useful building-block in the construction of composite contraction operators. In particular, all plausible contraction operators can be reconstructed so that the outcome of contracting a belief set K by a sentence p is defined as K ∼ f, where ∼ is full meet contraction and f a sentential selector, i.e. a function to and from sentences. This paper investigates the logic of full meet contraction. Seven properties of this operation are presented that contribute to making it useful as a building-block: Full meet contraction is a purely logical operation. It retains finitebasedness of the belief set. It is the inclusion-maximal contraction that removes all sentences that can contribute to implying the input sentence. It is the inclusion-maximal contraction that removes all non-tautologous consequences of the input sentence. Almost all contractions can be reconstructed as full meet contraction. Full meet contraction allows for recovery of the input sentence. Full meet contraction provides a unified account of multiple and singleton contraction. La llamada full meet contraction, creada por Carlos Alchourrón y David Makinson en los comienzos de los ' 80, ha sido a menudo desestimada puesto que ella no constituye un operador de contracción plausible. De todas formas ella es altamente útil en la construcción de operadores de contracción compuestos. En particular, todos los operadores de contracción plausibles pueden ser reconstruidos de forma tal que la contracción de un conjunto de creencias K por una sentencia p sea definida como K ∼ f, donde ∼ es una full meet contraction y f un selector de sentencias, i.e., una función de sentencias a sentencias. En este trabajo investigamos la lógica de la full meet contraction. Se presentan siete propiedades de esta operación que contribuyen a hacerla útil como building-block: Full meet contraction es una operación puramente lógica. Ella retiene la finit- basednes del conjunto de creencias. Ella es la máxima-inclusiva de las contracciones que elimina todas las sentencias que pueden contribuir a implicar la input-sentence. Es la contracción maximal inclusiva que elimina todas las consecuencias no tautológicas de la input-sentence. Casi todas las contracciones pueden ser reconstruidas como full-meet contractions. Full meet contraction permite la recuperación de la input-sentence. Full meet contracción da cuenta en forma unificada de las contracciones múltiples y singulares

An agent can usually hold a very large number of beliefs. However, only a small part of these beliefs is used at a time. Efficient operations for belief change should affect the beliefs of the agent locally, that is, the changes should be performed only in the relevant part of the belief state. In this paper we define a local consequence operator that only considers the relevant part of a belief base. This operator is used to define local versions of the operations for belief change. Representation theorems are given for the local operators.

Safety is a concern in almost all branches of engineering. Whereas safety was traditionally introduced by applying safety factors or margins to the calculated maximum load, this approach is increasingly replaced with probabilistic risk assessment (PRA) as a tool for dimensioning safety measures. In this paper, the two approaches are compared in terms of what they aim at and what they can, in fact, achieve. The outcome of this comparison suggests that the two approaches should be seen as complementary rather than mutually exclusive. PRA is particularly useful for priority setting and for the effect evaluation of safety measures; however, in most applications, uncertainties prevent PRA from providing an objective probability of failure or value of damage. Safety factors are indispensible for dealing with dangers that cannot be assigned meaningful probabilities.

The precautionary principle has often been described as an extreme principle that neglects science and stifles innovation. However, such an interpretation has no support in the official definitions of the principle that have been adopted by the European Union and by the signatories of international treaties on environmental protection. In these documents, the precautionary principle is a guideline specifying how to deal with certain types of scientific uncertainty. In this contribution, this approach to the precautionary principle is explicated with the help of concepts from the philosophy of science and comparisons with general notions of practical rationality. Three major problems in its application are discussed, and it is concluded that to serve its purpose, the precautionary principle has to (1) be combined with other decision principles in cases with competing top priorities, (2) be based on the current state of science, which requires procedures for scientific updates, and (3) exclude potential dangers whose plausibility is too low to trigger meaningful precautionary action.

Systems of urban transportation are largely shaped through planning practices. In transport economics, the benefits of infrastructure investments consist mainly of travel time savings calculated using monetary values of time. The economic interpretation of the value of travel time has significantly shaped our urban environment and transportation schemes. However, there is often an underlying assumption of transferability between time and money, which arguably does not sufficiently take into account the specific features of time. In this paper, we analyze the various properties of time as an economic resource using findings in behavioral economics and psychology. Due to limitations in the standard model, it is proposed that an alternative model value should be investigated in which time rather than money is the primary carrier of and the basic features of such a model are outlined. An improved understanding the nature of time as a source of utility puts us in a better position to determine what aspects of time matter. Additionally, the analysis can be applied to further develop modeling where value of time plays a significant role; such as new models for the planning of urban transport.