Sven Ove Hansson

A probabilistic explication is offered of equipoise and uncertainty in clinical trials. In order to be useful in the justification of clinical trials, equipoise has to be interpreted in terms of overlapping probability distributions of possible treatment outcomes, rather than point estimates representing expectation values. Uncertainty about treatment outcomes is shown to be a necessary but insufficient condition for the ethical defensibility of clinical trials. Additional requirements are proposed for the nature of that uncertainty. The indecisiveness of our criteria for cautious decision-making under uncertainty creates the leeway that makes clinical trials defensible.

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

We prove that four theses commonly associated with coherentism are incompatible with the representation of a belief state as a logically closed set of sentences. The result is applied to the conventional coherence interpretation of the AGM theory of belief revision, which appears not to be tenable. Our argument also counts against the coherentistic acceptability of a certain form of propositional holism. We argue that the problems arise as an effect of ignoring the distinction between derived and non-derived beliefs, and we suggest that the kind of coherence relevant to epistemic justification is the coherence of non-derived beliefs.

This article is an attempt at a systematic account of decision making under greater uncertainty than what traditional, mathematically oriented decision theory can cope with. Four components of great uncertainty are distinguished: (1) the identity of the options is not well determined (uncertainty of demarcation) ; (2) the consequences of at least some option are unknown (uncertainty of consequences); (3) it is not clear whether information obtained from others, such as experts, can be relied on (uncertainty of reliance); and (4) the values relevant for the decision are not determined with sufficient precision (uncertainty of values). Some possible strategy types are proposed for each of these components. Decisions related to environmental issues are used to illustrate the proposals

Two types of measures of probabilistic uncertainty are introduced and investigated. Dispersion measures report how diffused the agent’s second-order probability distribution is over the range of first-order probabilities. Robustness measures reflect the extent to which the agent’s assessment of the prior (objective) probability of an event is perturbed by information about whether or not the event actually took place. The properties of both types of measures are investigated. The most obvious type of robustness measure is shown to coincide with one of the major candidates for a dispersion measure, the mean square deviation measure.

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.

The maximin rule can be used as a formal version of the precautionary principle. This paper evaluates the feasibility and the intuitive plausibility of this decision rule. The major conclusions are: (1) Precaution has to be applied symmetrically. (2) Precaution is only possible when outcomes are comparable in terms of value, so that it can be determined which outcome is worst. (3) Precaution is sensitive to standards of possibility. Far-away scenarios have to be excluded, and it is difficult to find a principled way to draw the line. (4) Precaution is sensitive to the framing of decision problems. Local cautiousness may add up to global incautiousness.

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

Research is subject to more stringent ethical requirements than most other human activities, and a procedure that is otherwise allowed may be forbidden in research. Hence, risk-taking is more restricted in scientific research than in most non-research contexts, and privacy is better protected in scientific questionnaires than in marketing surveys. Potential arguments for this difference are scrutinized. The case in its favour appears to be weak. A stronger case can be made in favour of a difference in the opposite direction: If perilous or otherwise problematic activities have to be performed it is usually better to perform them in a research context where they are properly evaluated so that guidance is obtained for the future. However, retreating from current ethical demands on research is not a desirable direction to go. Instead, research ethics can serve to inspire the introduction of more stringent ethical principles in other social sectors

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.

Multiple contraction (simultaneous contraction by several sentences) and iterated contraction are investigated in the framework of specified meet contraction (s.m.c.) that is extended for this purpose. Multiple contraction is axiomatized, and so is finitely multiple contraction (contraction by a finite set of sentences). Two ways to reduce finitely multiple contraction to contraction by single sentences are introduced. The reduced operations are axiomatically characterized and their properties are investigated. Furthermore, it is shown how iterated contraction can be reduced to single-step, single-sentence contraction. However, in this framework the outcome of iterated contraction depends unavoidably on the order in which the inputs are received. This order-dependence makes it impossible to treat two inputs on an equal footing. Therefore it is often preferable to perform changes involving several pieces of information as multiple rather than iterated change.

abstract Even though much research has been devoted to studies of safety, the concept of safety is in itself under‐theorised, especially concerning its relation to epistemic uncertainty. In this paper we propose a conceptual analysis of safety. The paper explores the distinc‐tion between absolute and relative safety, as well as that between objective and subjective safety. Four potential dimensions of safety are discussed, viz. harm, probability, epistemic uncertainty, and control. The first three of these are used in the proposed definition of safety, whereas it is argued that control should not be included in a reasonable definition of safety. It is shown that strictly speaking, an objective safety concept is not attainable. Instead, an intersubjective concept is proposed that brings us as close as possible to an objective concept.

Healthcare depends increasingly on advanced medical technology. In addition, other forms of technology contribute to determine how our lives are influenced by disease and disability. The extent to which persons with impaired bodily functions are forced to live their lives differently than other people depends to a large part on a variety of technologies, from wheelchairs to computer interfaces, from hearing aids to garage doors. This wide-ranging influence of technology has important ethical aspects, but has seldom been discussed in bioethics, the ethics of technology, or other branches of applied ethics

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.

A possible world semantics for preference is developed. The remainder operator () is used to give precision to the notion that two states of the world are as similar as possible, given a specified difference between them. A general structure is introduced for preference relations between states of affairs, and three types of such preference relations are defined. It is argued that one of them, actual preference, corresponds closely to the concept of preference in informal discourse. Its logical properties are studied and shown to be plausible.

Implant ethics is defined here as the study of ethical aspects of the lasting introduction of technological devices into the human body. Whereas technological implants relieve us of some of the ethical problems connected with transplantation, other difficulties arise that are in need of careful analysis. A systematic approach to implant ethics is proposed. The major specific problems are identified as those concerning end of life issues (turning off devices), enhancement of human capabilities beyond normal levels, mental changes and personal identity, and cultural effects