A Sequent Formulation of Conditional Logic Based on Belief Change Operations

Peter Gärdenfors has developed a semantics for conditional logic, based on the operations of expansion and revision applied to states of information. The account amounts to a formalisation of the Ramsey test for conditionals. A conditional A > B is declared accepted in a state of information K if B is accepted in the state of information which is the result of revising K with respect to A. While Gärdenfors's account takes the truth-functional part of the logic as given, the present paper proposes a semantics entirely based on epistemic states and operations on these states. The semantics is accompanied by a syntactic treatment of conditional logic which is formally similar to Gentzen's sequent formulation of natural deduction rules. Three of David Lewis's systems of conditional logic are represented. The formulations are attractive by virtue of their transparency and simplicity.     

General belief in a just world and resilience: Evidence from a collectivistic culture

Previous research showed that in the individualistic culture, adults endorse the personal more than the general belief in a just world (PBJW vs. GBJW). Comparatively little is known about the prevalence character and adaptive functions of GBJW, especially in the collectivistic culture. We conducted three surveys among the Chinese adults and adolescents. We found that (1) Chinese adults and adolescents endorsed more GBJW than PBJW; (2) Adult survivors with high exposure to post‐earthquake trauma and adolescents in the poverty‐stricken area maintained high GBJW, with relatively lower PBJW. (3) GBJW predicted the psychological resilience in all the three samples independent of PBJW. The results imply that in contrast to populations from the individualistic culture, people from the collectivistic culture endorse a robust GBJW, which allows them to resiliently confront harsh realities. Copyright © 2010 John Wiley & Sons, Ltd.     

Levels of modality for BDI Logic

The use of rational agents for modelling real world problems has both been heavily investigated and become well accepted, with BDI (Beliefs, Desires, and Intentions) Logic being a widely used architecture to represent and reason about rational agency. However, in the real world, we often have to deal with different levels of confidence in the beliefs we hold, desires we have, and intentions that we commit to. This paper extends our previous framework that integrated qualitative levels of beliefs, desires, and intentions into BDI Logic. We describe an expanded set of axioms and properties of the extended logic. We present a modular structure for the semantics which involves a non-normal Kripke type semantics that may be used for other agent systems. Further, we demonstrate the usefulness of our framework with a scheduling task example.     

An analytic tableau calculus for a temporalised belief logic

A tableau is a refutation-based decision procedure for a related logic, and is among the most popular proof procedures for modal logics. In this paper, we present a labelled tableau calculus for a temporalised belief logic called TML⁺, which is obtained by adding a linear-time temporal logic onto a belief logic by the temporalisation method of Finger and Gabbay. We first establish the soundness and the completeness of the labelled tableau calculus based on the soundness and completeness results of its constituent logics. We then sketch a resolution-type proof procedure that complements the tableau calculus and also propose a model checking algorithm for TML⁺ based on the recent results for model checking procedures for temporalised logics. TML⁺ is suitable for formalising trust and agent beliefs and reasoning about their evolution for agent-based systems. Based on the logic TML⁺, the proposed labelled tableau calculus could be used for analysis, design and verification of agent-based systems operating in dynamic environments.     

Thinking about representations: the case of opaque contexts

To address the question of whether young children are differentially sensitive to referential opacity, an advanced Theory of Mind skill, we assessed 4-, 6-, and 8-year-olds on three types of opaque contexts: epistemic, quotational, and intentional. Children’s performance improved as a function of age and varied significantly by opacity type. Performance was best for epistemic opacity (using the verb “know”) and poorest for intentional opacity (using “mean to”), with quotational opacity (using “said”) falling in-between. Importantly, the current results suggest that children’s sensitivity to referential opacity is not an all-or-nothing competence but rather one that varies across the contexts examined. Possible reasons for this variability are discussed.     

积极情景线索对内隐攻击性的影响

通过向被试呈现代表积极情景线索的材料(一段含有互助、和谐信息的公益短片),运用内隐联想测验(IAT)范式,从内隐社会认知的角度来研究积极情境线索对个体内隐攻击性的影响,并分析这种影响是否具有性别差异。结果表明:未观看积极情景线索材料的被试表现出显著的内隐攻击性,而观看积极情景线索材料的被试的内隐攻击性不显著;积极情景线索的主效应显著,且这一效应不存在性别差异。这说明,积极情景线索能有效抑制个体的内隐攻击性,并支持自我攻击信念IAT是测量个体内隐攻击性的有效工具。     

Towards a “Sophisticated” Model of Belief Dynamics. Part I: The General Framework

It is well-known that classical models of belief are not realistic representations of human doxastic capacity; equally, models of actions involving beliefs, such as decisions based on beliefs, or changes of beliefs, suffer from a similar inaccuracies. In this paper, a general framework is presented which permits a more realistic modelling both of instantaneous states of belief, and of the operations involving them. This framework is motivated by some of the inadequacies of existing models, which it overcomes, whilst retaining technical rigour in so far as it relies on known, natural logical and mathematical notions. The companion paper (Towards a “sophisticated” model of belief dynamics. Part II) contains an application of this framework to the particular case of belief revision. Presented by Hannes Leitgeb     

The over-generalization problem: predicates rigidly signifying the “unnatural”

According to the simple proposal, a predicate is rigid iff it signifies the same property across the different possible worlds. The simple proposal has been claimed to suffer from an over-generalization problem. Assume that one can make sense of predicates signifying properties, and assume that trivialization concerns, to the effect that the notion would cover any predicate whatsoever, can be overcome. Still, the proposal would over-generalize, the worry has it, by covering predicates for artifactual, social, or evaluative properties, such as ‘is a knife,’ ‘is a bachelor,’ or ‘is funny.’ In defense, it is argued that rigidity for predicates as characterized plays the appropriate theoretical role, and that the contention that “unnatural” properties are not to be rigidly signified is ungrounded.     

The virtues of epistemic conservatism

Although several important methodologies implicitly assume the truth of epistemic conservatism, the view that holding a belief confers some measure of justification on the belief, recent criticisms have led some to conclude that epistemic conservatism is an implausible view. That conclusion is mistaken. In this article, I propose a new formulation of epistemic conservatism that is not susceptible to the criticisms leveled at earlier formulations of epistemic conservatism. In addition to withstanding these criticisms, this formulation of epistemic conservatism has several benefits. First, this formulation has the benefits of earlier formulations of epistemic conservatism, that is to say it makes sense of our intuitions about justification in regard to both memory beliefs and beliefs for which we have forgotten our evidence. Second, it provides a good way of responding to the skeptic’s challenge concerning the possibility of possessing knowledge of the external world posed by the Alternative Hypotheses argument. Third, it provides responses to both forms of a new skeptical problem plaguing basic knowledge structure theories, the Problem of Easy Knowledge formulated by Stewart Cohen. I argue that given the many benefits of this formulation of epistemic conservatism and the fact that it is not vulnerable to the criticisms that undermine earlier formulations of epistemic conservatism, this formulation of epistemic conservatism is a plausible view to maintain.     

Evaluating dialectical structures with Bayesian methods

This paper shows how complex argumentation, analyzed as dialectical structures, can be evaluated within a Bayesian framework by interpreting them as coherence constraints on subjective degrees of belief. A dialectical structure is a set of arguments (premiss-conclusion structure) among which support- and attack-relations hold. This approach addresses the observation that some theses in a debate can be better justified than others and thus fixes a shortcoming of a theory of defeasible reasoning which applies the bivalence principle to argument evaluations by assigning them the status of being either defeated or undefeated. Evaluation procedures which are based on the principle of bivalence can, however, be embedded as a special case within the Bayesian framework. The approach developed in this paper rests on the assumptions that arguments can be reconstructed as deductively valid and that complex argumentation can be reconstructed such that premisses of arguments with equivalent conclusions are pairwise independent.