The axiom of recovery, while capturing a central intuition regarding belief change, has been the source of much controversy. We argue briefly against putative counterexamples to the axiom—while agreeing that some of their insight deserves to be preserved—and present additional recovery-like axioms in a framework that uses epistemic states, which encode preferences, as the object of revisions. This makes iterated revision possible and renders explicit the connection between iterated belief change and the axiom of recovery. We provide a representation theorem (...) that connects the semantic conditions we impose on iterated revision and our additional syntactical properties. We show interesting similarities between our framework and that of Darwiche–Pearl (Artificial Intelligence 89:1–29 1997). In particular, we show that intuitions underlying the controversial (C2) postulate are captured by the recovery axiom and our recovery-like postulates (the latter can be seen as weakenings of (C2)). We present postulates for contraction, in the same spirit as the Darwiche–Pearl postulates for revision, and provide a theorem that connects our syntactic postulates with a set of semantic conditions. Lastly, we show a connection between the contraction postulates and a generalisation of the recovery axiom. (shrink)

Although AGM theory contraction (Alchourrón et al., 1985; Alchourrón and Makinson, 1985) occupies a central position in the literature on belief change, there is one aspect about it that has created a fair amount of controversy. It involves the inclusion of the postulate known as Recovery. As a result, a number of alternatives to AGM theory contraction have been proposed that do not always satisfy the Recovery postulate (Levi, 1991, 1998; Hansson and Olsson, 1995; Fermé, 1998; Fermé and Rodriguez, 1998; (...) Rott and Pagnucco, 1999). In this paper we present a new addition, systematic withdrawal, to the family of withdrawal operations, as they have become known. We define systematic withdrawal semantically, in terms of a set of preorders, and show that it can be characterised by a set of postulates. In a comparison of withdrawal operations we show that AGM contraction, systematic withdrawal and the severe withdrawal of Rott and Pagnucco (1999) are intimately connected by virtue of their definition in terms of sets of preorders. In a future paper it will be shown that this connection can be extended to include the epistemic entrenchment orderings of Gärdenfors (1988) and Gärdenfors and Makinson (1988) and the refined entrenchment orderings of Meyer et al. (2000). (shrink)

We examine the equity valuation effect of press releases of upgrades or downgrades reflected in the Covalence Ethical Quote, an index ranking the ethical performance of multinational firms. The index is updated quarterly and is comprehensive enough to include 45 criteria reflecting working conditions, impact of product, impact of production, and company institutional impact. Thus, it captures many dimensions of firms’ ethical performance that are not accounted for in previous research. Our research encompasses a joint test of the value relevance (...) of the index itself and the impact of ethical reputation on a firm’s value. We find first a significant causal relationship between stock market reactions and changes in the CEQ. Specifically, disclosures of positive changes in firm ethical performance cause increases in firm value. Second, cross-sectional analysis indicates a positive association between changes in firm ethical performance and both its financial performance and its financial reporting quality. Collectively, these results suggest that the CEQ conveys information that is useful to investors. Further, corporate measures taken to increase ethical performance are associated with positive benefits to shareholders. Finally, investors have concluded that good news about their firms’ efforts to be ethical is worth the cost. (shrink)

Traditional accounts of belief change have been criticized for placing undue emphasis on the new belief provided as input. A recent proposal to address such issues is a framework for non-prioritized belief change based on default theories (Ghose and Goebel, 1998). A novel feature of this approach is the introduction of disbeliefs alongside beliefs which allows for a view of belief contraction as independently useful, instead of just being seen as an intermediate step in the process of belief revision. This (...) approach is, however, restrictive in assuming a linear ordering of reliability on the received inputs. In this paper, we replace the linear ordering with a preference ranking on inputs from which a total preorder on inputs can be induced. This extension brings along with it the problem of dealing with inputs of equal rank. We provide a semantic solution to this problem which contains, as a special case, AGM belief change on closed theories. (shrink)

Most approaches to iterated belief revision are accompanied by some motivation for the use of the proposed revision operator (or family of operators), and typically encode enough information in the epistemic state of an agent for uniquely determining one-step revision. But in those approaches describing a family of operators there is usually little indication of how to proceed uniquely after the first revision step. In this paper we contribute towards addressing that deficiency by providing a formal framework which goes beyond (...) the first revision step in two ways. First, the framework is obtained by enriching the epistemic state of an agent starting from the following intuitive idea: we associate to each world x two abstract objects x⁺ and x⁻, and we assume that, in addition to preferences over the set of worlds, we are given preferences over this set of objects as well. The latter can be considered as meta-information encoded in the epistemic state which enables us to go beyond the first revision step of the revision operator being applied, and to obtain a unique set of preferences over worlds. We then extend this framework to consider, not only the revision of preferences over worlds, but also the revision of this extended structure itself. We look at some desirable properties for revising the structure and prove the consistency of these properties by giving a concrete operator satisfying all of them. Perhaps more importantly, we show that this framework has strong connections with two other types of constructions in related areas. Firstly, it can be seen as a special case of preference aggregation which opens up the possibility of extending the frame-work presented here into a full-fledged framework for preference aggregation and social choice theory. Secondly, it is related to existing work on the use of interval orderings in a number of different contexts. (shrink)

In studies of multi-agent interaction, especially in game theory, the notion of equilibrium often plays a prominent role. A typical scenario for the belief merging problem is one in which several agents pool their beliefs together to form a consistent "group" picture of the world. The aim of this paper is to define and study new notions of equilibria in belief merging. To do so, we assume the agents arrive at consistency via the use of a social belief removal function, (...) in which each agent, using his own individual removal function, removes some belief from his stock of beliefs. We examine several notions of equilibria in this setting, assuming a general framework for individual belief removal due to Booth et al. We look at their inter-relations as well as prove their existence or otherwise. We also show how our equilibria can be seen as a generalisation of the idea of taking maximal consistent subsets of agents. (shrink)

Epistemic entrenchment, as presented by Gärdenfors and Makinson (1988) and Gärdenfors (1988), is a formalisation of the intuition that, when forced to choose between two beliefs, an agent will giveup the less entrenched one. While their formalisation satisfactorilycaptures the intuitive notion of the entrenchment of beliefs in a number ofaspects, the requirement that all wffs be comparable has drawn criticismfrom various quarters. We define a set of refined versions of theirentrenchment orderings that are not subject to the same criticism, andinvestigate (...) the relationship between the refined entrenched orderings,the entrenchment orderings of Gärdenfors and Makinson, and AGM theorycontraction (Alchourrón et al., 1985). To conclude, we compare refinedentrenchment with two related approaches to epistemic entrenchment. (shrink)

Intelligent agents are often faced with the problem of trying to combine possibly conflicting pieces of information obtained from different sources into a coherent view of the world. We propose a framework for the modelling of such combination operations with roots in the work of Spohn [Spo88, Spo91]. We construct a number of combination operations and we measure them against various properties that such operations ought to satisfy. We conclude by discussing the connection between combination operations and the use of (...) infobases [Mey99, MLH00]. (shrink)

We provide a formal study of belief retraction operators that do not necessarily satisfy the postulate. Our intuition is that a rational description of belief change must do justice to cases in which dropping a belief can lead to the inclusion, or ‘liberation’, of others in an agent's corpus. We provide two models of liberation via retraction operators: ρ-liberation and linear liberation. We show that the class of ρ-liberation operators is included in the class of linear ones and provide axiomatic (...) characterisations for each class. We show how any retraction operator can be ‘converted’ into either a withdrawal operator ) or a revision operator via the Harper Identity and the Levi Identity respectively. (shrink)

This article analyzes Leo Strauss’s early and mature political philosophy in unusual ways. It offers a new reading of known and unknown texts and documents and shows how Leo Strauss became Leo Strauss.

Generalisations of theory change involving arbitrary sets of wffs instead of belief sets have become known as base change. In one view, a base should be thought of as providing more structure to its generated belief set, and can be used to determine the theory change operation associated with a base change operation. In this paper we extend a proposal along these lines by Meyer et al. We take an infobase as a finite sequence of wffs, with each element in (...) the sequence being seen as an independently obtained bit of information, and define appropriate infobase change operations. The associated theory change operations satisfy the AGM postulates for theory change. Since an infobase change operation produces a new infobase, it allows for iterated infobase change. We measure iterated infobase change against the postulates proposed by Darwiche et al. and Lehmann. (shrink)

Generalisations of theory change involving operations on arbitrary sets ofwffs instead of on belief sets (i.e., sets closed under a consequencerelation), have become known as base change. In one view, a base should bethought of as providing more structure to its generated belief set, whichmeans that it can be employed to determine the theory contraction operationassociated with a base contraction operation. In this paper we follow suchan approach as the first step in defining infobase change. We think of an infobase (...) as a finite set of wffs consisting of independently obtainedbits of information. Taking AGM theory change (Alchourrón et al. 1985) as the general framework, we present a method that uses the structure of aninfobase B to obtain an AGM theory contraction operation for contractingthe belief set Cn(B). Both the infobase and the obtained theory contraction operation then play a role in constructing a unique infobasecontraction operation. Infobase revision is defined in terms of an analogueof the Levi Identity, and it is shown that the associated theory revisionoperation satisfies the AGM postulates for revision. Because every infobaseis associated with a unique infobase contraction and revision operation, the method also allows for iterated base change. (shrink)

In this paper, we will discuss Peter van Inwagen’s contribution to the epistemological debate about revealed peer disagreement. Roughly, this debate focuses on situations in which at least two participants disagree on a certain proposition based on the same evidence. This leads to the problem of how one should react rationally when peer disagreement is revealed. Van Inwagen, as we will show, discusses four possible reactions, all of which he rejects as unsatisfying. Our proposal will be to point to hidden (...) assumptions in van Inwagen’s reasoning and ask whether he is willing to reject at least one of these to get rid of the problem. In short, our thesis amounts to the following: Of the two epistemological claims, which we call “Weak” and “Full-blown Fallibilism”, van Inwagen cannot simultaneously accept the first and reject the latter, while this is what he seems to suggest. Revealing this potential dilemma for van Inwagen’s position will lead to a more detailed discussion of how “rationality”, “truth”, “evidence” and “justification” interrelate and how a closer look at their relation might help solving the puzzle of revealed peer disagreement. (shrink)

Most belief change operators in the AGM tradition assume an underlying plausibility ordering over the possible worlds which is transitive and complete. A unifying structure for these operators, based on supplementing the plausibility ordering with a second, guiding, relation over the worlds was presented in Booth et al. (Artif Intell 174:1339-1368, 2010). However it is not always reasonable to assume completeness of the underlying ordering. In this paper we generalise the structure of Booth et al. (Artif Intell 174: 1339-1368, 2010) (...) to allow incomparabilities between worlds. We axiomatise the resulting class of belief removal functions, and show that it includes an important family of removal functions based on finite prioritised belief bases. (shrink)

In this paper we present a brief overview of logic-based belief change, a research area concerned with the question of how a rational agent ought to change its mind in the face of new, possibly conflicting, information. Our intention is to provide the reader with a basic introduction to the work done in this area over the past 30 years. In doing so we hope to sketch the main historical results, provide appropriate pointers to further references, and discuss some current (...) developments. We trust that this will spur on the interested reader to learn more about the topic, and perhaps to join us in the further development of this exciting field of research. (shrink)

herent and rational way. Several proposals have been made for information merging in which it is possible to encode the preferences of sources (Benferhat, Dubois, Prade, & Williams, 1999; Benferhat, Dubois, Kaci, & Prade, 2000; Lafage & Lang, 2000; Meyer, 2000, 2001; Andreka, Ryan, & Schobbens, 2001). Information merging has much in common with social choice theory, which aims to define operations reflecting the preferences of a society from the individual preferences of the members of the society. Given this connection, (...) frameworks for information merging should provide satisfactory resolutions of problems raised in social choice theory. We investigate the link between the merging of epistemic states and two important results in social choice theory. We show that Arrow’s well-known impossibility theorem (Arrow, 1963) does not hold in merging frameworks when the preferences of sources are represented in terms of epistemic states. This is achieved by providing a consistent set of properties for merging from which Arrow-like properties can be derived. Similarly, by extending these to a consistent framework which includes properties corresponding to the notion of being strategy-proof, we show that results due to Gibbard and Satterthwaite (Gibbard, 1973; Satterthwaite, 1973, 1975) and other (Benoit, 2000; Barber´a, Dutta, & Sen, 2000) do not hold in merging frameworks. (shrink)

Contextual learning pervades our perception and cognition and plays a critical role in adjusting to aversive and stressful events. Our ability to memorise spatial context has been studied extensive...

Zusammenfassung. Gegenwärtige Fortschritte in den pharmakologischen Wissenschaften erlauben einen ersten Ausblick auf eine individuelle, genotyp-basierende Arzneimitteltherapie, durch die sich die Effektivität der Medikamentenbenutzung weiter verbessern ließe. Die genotypische Erfassung von genetischen Polymorphismen, die bei Medikamentenreaktionen beteiligt sind, verspricht die Arzneimitteltherapie grundlegend zu optimieren, wenn damit Patienten identifiziert werden, für die ein Medikament entweder nutzbringend und sicher angewandt oder aber aufgrund zu erwartender Nebenwirkungen nicht eingesetzt werden sollte. Die neuen pharmakogenomischen Behandlungsstrategien werfen komplexe ethische Fragestellungen auf, da durch ein genetisches Screening (...) für Arzneimittelzwecke asymptomatische Patienten mit erhöhtem Risiko für eine insgesamt schlechtere Prognose identifiziert werden könnten. Die Pharmakogenomik beeinflusst damit das Beziehungsverhältnis zwischen behandelnden Arzt und Patienten, das traditionell auf Diskretion, Vertraulichkeit und dem unbedingten Vorsatz, heilen und keinesfalls schaden zu wollen, beruht. Der vorliegende Aufsatz diskutiert einige ethische Aspekte im Bedeutungswandel der Arzt-Patienten-Beziehung, der durch diesen neuartigen pharmakogenomischen Behandlungsansatz ausgelöst wird. (shrink)

In this paper, we try to confront Robert Audis moral epistemology, namely his intuitionism, based on the concept of a self-evident moral proposition, with two main problems: disagreement and dogmatism within moral discourse. Although Audi can meet those classical objections in his theory, we think that some problems remain. We proceed – after an introduction – in five sections in order to pursue this end. After a short introductory section, we first reconstruct the classical intuitionist moral epistemology. We then discuss (...) the dogmatism and the disagreement objection and, in doing so, introduce Audi’s own version of a moral epistemology. After having proposed that the disagreement objection concerns an explanatory problem, we discuss a second version, namely disagreement as a problem of rationality. In the fourth section we present a third version, disagreement as a problem of moral discourse, understood as an intersubjective enterprise. In the fifth section we propose a solution to disagreement situations of this kind. (shrink)

The recent publication of The New Wittgenstein signals the arrival of a distinctive "therapeutic" reading of Ludwig Wittgenstein"s philosophical enterprise. As announced in its Preface, this collection presents the "nonsense" of philosophy as the subject of Wittgenstein"s therapeutic work. The simple, plain nonsense of many philosophical remarks is revealed under the scrutiny of Wittgenstein"s investigations, according to this interpretation, leading us to see that such remarks "fail to make any claim at all" (Crary 6). This view of Wittgenstein"s use of (...) "nonsense" as a term of criticism begins with the work of Stanley Cavell, on this account, and has extended more recently to work on a wide area of Wittgenstein"s concerns, elevating "nonsense" to a central position in his philosophy. This paper argues that, in at least one case of Wittgenstein"s talk of nonsense, this "therapeutic reading" (Crary 7) oversimplifies the subtlety of Wittgenstein"s writing. Indeed, one of the most prominent cases of "nonsense" in the later Wittgenstein concerns the remark "I know I am in pain". Though Wittgenstein repeatedly treats this remark as nonsense, this treatment is not final in his philosophy of psychology. Rather, though his rich discussion in the later manuscripts of the indeterminacy of psychological judgments, the relation of these judgments to knowledge, and the role of first-person psychological descriptions, Wittgenstein is able to find what sense a remark such as "I know I am in pain" might perhaps have. "I know I am in pain" may be called nonsense, but this is not the last word on the matter in Wittgenstein"s text: as Cavell says, ""it makes no sense to say these things" (in the way we think it does)" (Cavell 70). Wittgenstein is able to find what sense our remarks of first person psychological knowledge might have, contrary to what the therapeutic reading in The New Wittgenstein would have us suppose. Therefore, at least in one case, the therapeutic reading of Wittgenstein goes wrong. (shrink)