信念修正视域下的悖论研究初探

悖论研究是一个古老的研究领域,信念修正理论则是最近三十年发展而成的新型逻辑理论。悖论的形成、发现与解决是一种典型而复杂的信念修正过程。虽然这两个领域的亲缘关系非同一般,但迄今为止学界对这种亲缘关系缺乏系统的研究。本文从信念修正理论的角度提出一种重新审视悖论相关论题的新思路,进而提出一种基于信念修正理论的新的解悖方法论,最后依据这种解悖方法论对罗素悖论给出了一种新的解决方案。这种交叉研究的新思路不仅能推动悖论研究的发展,也能为信念修正理论指出新的研究方向。     

信念修正中的一种新型评价算子研究

本文考察了评价算子,即刻画认知主体如何借助评价依据来理性评价新信息的算子,它放弃新信息中部分不可信信息,但是与传统收缩算子不同,它不指定收缩的信息而只要求评价结果与评价依据相一致。S.O.Hansson认为以单个句子作为新信息的非优先信念修正具有三种模式:决策–修正(Decision-Revision)、整合选择(Integrated Choice)和膨胀–巩固(Expansion-Consolidation)。评价算子单独刻画了非优先复合修正决策–修正模式的决策模块,对于修正模块这里不作探讨。我们先按AGM信念修正模式对评价算子进行了公理性刻画,接着通过不一致核心集和一致保留集分别构造了核心评价算子和部分交评价算子,然后分别证明了这两种算子与公理性刻画之间的表达定理,最后对评价算子和其他相关工作进行了比较。     

一个描述现实主体信念的信息宣告觉知逻辑

对现实主体信念的研究是认知科学和人工智能研究的重要内容.一个现实主体的信念有两个重要特征:动态的和非逻辑全知的.描述主体的动态特征的逻辑主要有两个途径,其一是表达信息更新的逻辑,其中公开宣告逻辑PAL([Plaza,1989],[Gerbrandy,Groeneveld,1997])受到了广泛关注;其二是表达信念修正的逻辑AGM(Gardenfors,Rott,1995).本文的逻辑是用公开宣告逻辑的思想来建立的.     

社会网络中信念修正的几个问题

本文首先在传统信念修正理论和动态认知逻辑的框架上提出了社会网络的信念修正模型,将主体之间的社会关系纳入到新的模型中来,介绍并研究了"有穷自动机"模型从众心理的信念修正模式;其次,引入证据、信任度两个概念来刻画基于理由的信念修正;最后,指出社会网络中信念修正的研究如何与哲学其他领域相关联。     

信念修正的逻辑

人是如何修正他们的信念的?这是一个非常重要的认识论问题。信念修正理论领域经过三十多年的蓬勃发展,对这个问题作出了许多极富创见的回答。本文首先介绍了此领域的研究对象、问题意识和研究范式,揭示出信念修正理论研究热点变迁的演化模式;其次系统评述了学界对此认识论问题的各种回答;最后揭示出信念修正理论与悖论研究、动态认知逻辑和人工智能等诸多学科领域进行交叉研究的重大理论意义和应用价值。     

信念修正的理论与方法

信念修正的理论大约产生于20世纪70年代,最初是由哲学家和逻辑学家提出的,但很快就引起了计算机界和人工智能领域学者的浓厚兴趣,20世纪90年代成为人工智能领域的一个热点.在我国,计算机领域的学者从20世纪90年代初就开始介绍并研究信念修正的理论,近年来逻辑学界的学者也开始关注这一领域中的问题.     

冲突情境下幼儿的选择性信任和信念修正

幼儿如何选择性地采信他人提供的信息、获取知识, 是幼儿社会认知发展研究的重要问题。除客观的信息内容外, 信息传递者的特征也影响幼儿的选择性信任。另外, 在不确定情境下, 他人证言与幼儿已有信念可能存在冲突, 在二者冲突的情境下, 幼儿是否可以采信他人的证言, 并最终改变幼儿的已有判断是以往研究忽略的问题。本研究考察了当母亲证言与幼儿已有信念冲突时, 不同程度的冲突情境(面对不同比例的合成动物时)对幼儿选择性信任和信念修正的影响。研究采用冲突信息源范式, 向74名4~6岁幼儿呈现对不同比例合成动物(50%-50%任务 vs 75%-25%任务)命名的证言, 考察幼儿对信息提供者的询问意愿、对证言的信任情况和在证言前后对合成动物的判断(信念修正)。信息提供的一方为母亲(提供相似度低的动物名称), 另一方为陌生人(提供相似度高的动物名称)。结果发现, 幼儿的选择性信任和信念修正受到母亲证言与已有信念冲突程度的影响。在低冲突情境下, 幼儿对母亲证言的询问意愿和外显信任均高于高冲突情境。幼儿的信念修正存在年龄差异, 在低冲突情境下, 年长幼儿比年幼幼儿更倾向于改变已有信念, 在高冲突情境下, 年长的幼儿比年幼幼儿更不愿意改变已有信念。本研究结果表明, 当母亲的证言与幼儿已有信念冲突时, 中国幼儿可以区分不同程度的冲突情境, 并且可以根据冲突的程度进行选择性信任和信念修正。     

从归因疗法到内隐理念：德韦克的心理学理论体系及影响

为更好地理解美国当代著名心理学家卡罗尔·德韦克(Carol S. Dweck)的心理学理论体系,对其学术成果进行了系统的整理与分析,发现可按时间维度将其理论划分为四个相继形成的主题：(1)习得性无助和归因的关系主题;(2)成就目标理论主题;(3)内隐智力理念主题;(4)内隐理念主题。这些主题促进了归因、智力、动机、人格等心理学理论的发展,已经被广泛地应用于健康、教育、人际关系及管理等实践领域,对学界与社会产生了深刻的影响。     

决策者-建议者系统模型的回顾与前瞻

自从决策者-建议者系统于1995年被提出以来,在决策领域引起了广泛的关注。通过总结决策者-建议者系统的研究范式和过程模型,比较了其与群体决策和团队决策的异同。目前在该系统模型中的主要研究变量涉及信任、建议者信心、专门知识、报酬、任务难度和相似性,已有的理论解释主要包括心理契约理论、态度改变理论、信念修正理论和沉没成本理论。未来的研究应当从变量关系、信任机制、建议提出和任务类型的角度进行专题探讨,并应当开展跨文化研究。     

基础生成的多元部分收缩的一个公理化刻画(英文)

这篇论文结合了两种信念收缩的 AGM 框架的推广,分别为:(1)基础生成收缩,其中信念集的变化是从某个信念基的变化生成的;(2)多元收缩,其中几个句子一次过同时被消去。本文引入了一个结合以上两种推广的运算,"基础生成的多元部分收缩",并将其进行了公理化刻画。     

Infinitary Belief Revision

This paper extends the AGM theory of belief revision to accommodate infinitary belief change. We generalize both axiomatization and modeling of the AGM theory. We show that most properties of the AGM belief change operations are preserved by the generalized operations whereas the infinitary belief change operations have their special properties. We prove that the extended axiomatic system for the generalized belief change operators with a Limit Postulate properly specifies infinite belief change. This framework provides a basis for first-order belief revision and the theory of revising a belief state by a belief state.     

On AGM for Non-Classical Logics

The AGM theory of belief revision provides a formal framework to represent the dynamics of epistemic states. In this framework, the beliefs of the agent are usually represented as logical formulas while the change operations are constrained by rationality postulates. In the original proposal, the logic underlying the reasoning was supposed to be supraclassical, among other properties. In this paper, we present some of the existing work in adapting the AGM theory for non-classical logics and discuss their interconnections and what is still missing for each approach.     

Recovery Recovered

The most controversial condition that the AGM theory of rational belief change places on belief contraction is the recovery condition. The condition is controversial because of a series of putative counterexamples due (separately) to I. Levi and S. O. Hansson. In this paper we show that the conflicts that Levi and Hansson arrange between AGM contraction and our intuitions about how to give up beliefs are merely apparent. We argue that these conflicts disappear once we attend more closely to the identification of the beliefs contracted away in each counterexample case. Since, on our view, speakers" belief contraction intentions are often more complicated than they may first appear, we are led to develop apparatus for thinking about the communication and identification of those intentions. Our argument refocuses attention on the difficult question of how to apply the AGM theory to particular cases.     

Verisimilitude and Belief Change for Conjunctive Theories

Theory change is a central concern in contemporary epistemology and philosophy of science. In this paper, we investigate the relationships between two ongoing research programs providing formal treatments of theory change: the (post-Popperian) approach to verisimilitude and the AGM theory of belief change. We show that appropriately construed accounts emerging from those two lines of epistemological research do yield convergences relative to a specified kind of theories, here labeled “conjunctive”. In this domain, a set of plausible conditions are identified which demonstrably capture the verisimilitudinarian effectiveness of AGM belief change, i.e., its effectiveness in tracking truth approximation. We conclude by indicating some further developments and open issues arising from our results.     

Possible Worlds Semantics for Partial Meet Multiple Contraction

In the logic of theory change, the standard model is AGM, proposed by Alchourrón et al. (J Symb Log 50:510–530, 1985). This paper focuses on the extension of AGM that accounts for contractions of a theory by a set of sentences instead of only by a single sentence. Hansson (Theoria 55:114–132, 1989), Fuhrmann and Hansson (J Logic Lang Inf 3:39–74, 1994) generalized Partial Meet Contraction to the case of contractions by (possibly non-singleton) sets of sentences. In this paper we present the possible worlds semantics for partial meet multiple contractions.     

Minimal Belief Change and the Pareto Principle

This paper analyzes the notion of a minimal belief change that incorporates new information. I apply the fundamental decision-theoretic principle of Pareto-optimality to derive a notion of minimal belief change, for two different representations of belief: First, for beliefs represented by a theory – a deductively closed set of sentences or propositions – and second for beliefs represented by an axiomatic base for a theory. Three postulates exactly characterize Pareto-minimal revisions of theories, yielding a weaker set of constraints than the standard AGM postulates. The Levi identity characterizes Pareto-minimal revisions of belief bases: a change of belief base is Pareto-minimal if and only if the change satisfies the Levi identity (for “maxichoice” contraction operators). Thus for belief bases, Pareto-minimality imposes constraints that the AGM postulates do not. The Ramsey test is a well-known way of establishing connections between belief revision postulates and axioms for conditionals (“if p, then q”). Pareto-minimal theory change corresponds exactly to three characteristic axioms of counterfactual systems: a theory revision operator that satisfies the Ramsey test validates these axioms if and only if the revision operator is Pareto-minimal. This revised version was published online in June 2006 with corrections to the Cover Date.     

Symmetry and Belief Revision

This paper continues the recent tradition of investigating iterated AGM revision by reasoning directly about the dynamics for total pre-order (“implausibility ordering”) representations of AGM revision functions. We reorient discussion, however, by proving that symmetry considerations, almost by themselves, suffice to determine a particular, AGM-friendly implausibility ordering dynamics due to Spohn 1988, which we call “J-revision”. After exploring the connections between implausibility ordering dynamics and the social choice theory of Arrow 1963, we provide symmetry arguments in the social choice-theoretic framework for an interesting generalization of J-revision due to Nayak 1994. We conclude by arguing that the symmetry principles that uniquely favor J-revision and its generalizations are importantly expressive of the purely qualitative framework for representing beliefs that distinguishes the AGM program. Our results therefore comprehensively vindicate Spohn's 1988 conjecture that essentially J-revision is the best that can be done by way of a purely qualitative model of belief revision. This revised version was published online in August 2006 with corrections to the Cover Date.     

Resource Bounded Belief Revision

The AGM paradigm for belief revision provides a very elegant and powerful framework for reasoning about idealized agents. The paradigm assumes that the modeled agent is a perfect reasoner with infinite memory. In this paper we propose a framework to reason about non-ideal agents that generalizes the AGM paradigm. We first introduce a structure to represent an agent's belief states that distinguishes different status of beliefs according to whether or not they are explicitly represented, whether they are currently active and whether they are fully accepted or provisional. Then we define a set of basic operations that change the status of beliefs and show how these operations can be used to model agents with different capacities. We also show how different operations of belief change described in the literature can be seen as special cases of our theory.     

Systematic Withdrawal

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).     

Severe Withdrawal (and Recovery)

The problem of how to remove information from an agent's stock of beliefs is of paramount concern in the belief change literature. An inquiring agent may remove beliefs for a variety of reasons: a belief may be called into doubt or the agent may simply wish to entertain other possibilities. In the prominent AGM framework for belief change, upon which the work here is based, one of the three central operations, contraction, addresses this concern (the other two deal with the incorporation of new information). Makinson has generalised this work by introducing the notion of a withdrawal operation. Underlying the account proffered by AGM is the idea of rational belief change. A belief change operation should be guided by certain principles or integrity constraints in order to characterise change by a rational agent. One of the most noted principles within the context of AGM is the Principle of Informational Economy. However, adoption of this principle in its purest form has been rejected by AGM leading to a more relaxed interpretation. In this paper, we argue that this weakening of the Principle of Informational Economy suggests that it is only one of a number of principles which should be taken into account. Furthermore, this weakening points toward a Principle of Indifference. This motivates the introduction of a belief removal operation that we call severe withdrawal. We provide rationality postulates for severe withdrawal and explore its relationship with AGM contraction. Moreover, we furnish possible worlds and epistemic entrenchment semantics for severe withdrawals.