Postulates for revising BDI structures

The process of rationally revising beliefs in the light of new information is a topic of great importance and long-standing interest in artificial intelligence. Moreover, significant progress has been made in understanding the philosophical, logical, and computational foundations of belief revision. However, very little research has been reported with respect to the revision of other mental states, most notably propositional attitudes such as desires and intentions. In this paper, we present a first attempt to formulate a general framework for understanding the revision of mental states. We develop an abstract belief-desire-intention model of agents, and introduce a notion of rationality for this model. We then present a series of formal postulates characterizing the processes of adding beliefs, desires, and intentions, updating costs and values, and removing beliefs, desires, and intentions. We also investigate the computational complexity of several problems involving the abstract model and comment on algorithms for revision.     

If You Can't Change What You Believe,You Don't Believe It

I develop and defend the view that subjects are necessarily psychologically able to revise their beliefs in response to relevant counter-evidence. Specifically, subjects can revise their beliefs in response to relevant counter-evidence, given their current psychological mechanisms and skills. If a subject lacks this ability, then the mental state in question is not a belief, though it may be some other kind of cognitive attitude, such as a supposition, an entertained thought, or a pretense. The result is a moderately revisionary view of belief: while most mental states we thought were beliefs are beliefs, some mental states which we thought were beliefs are not beliefs. The argument for this view draws on two key claims: First, subjects are rationally obligated to revise their beliefs in response to relevant counter-evidence. Second, if some subject is rationally obligated to revise one of her mental states, then that subject can revise that mental state, given her current psychological mechanisms and skills. Along the way to defending these claims, I argue that rational obligations can govern activities which reflect on one's rational character, whether or not those activities are under one's voluntary control. I also show how the relevant version of epistemic ‘ought’ implies ‘can’ survives an objection which plagues other variants of the principle.     

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     

“He Cursed, and I Got Angry:” Beliefs About Anger Among Adolescent Male Offenders in India

Cultural influences in the experience and expression of emotions have been widely recognized, although systematic studies of emotion-related beliefs in culturally diverse families have been scarce. The purpose of the present exploratory study was to examine beliefs about anger among a group of adolescent male offenders in India temporarily residing in a pre-sentencing institution. In particular, adolescent offenders (n = 14) were individually interviewed about their beliefs concerning causes and concomitants of, and behavioral responses to, one’s own and others’ anger, as well as family patterns of anger expression that are crucial in understanding socialization processes. Although some of the themes reflected in their narratives parallel the beliefs of educated, middle-class, non-offender youth in India (e.g., social inappropriateness of anger), as well as those of offenders in other parts of the world (e.g., aggressive behavior as a common response to anger), beliefs about various aspects of anger specific to this subculture of offender youth also emerged. In particular, perceived violations of family honor were cited as the most common elicitors of anger, and although anger was considered ‘bad’ it was expressed through aggression. The findings of this study highlight the need to develop a culturally informed theory of emotions, and relatedly, to develop culturally sensitive interventions for anger management that can be incorporated as a part of rehabilitation efforts for offender youth in India.     

The role of beliefs in goal dynamics: prolegomena to a constructive theory of intentions

In this article we strive to provide a detailed and principled analysis of the role of beliefs in goal processing—that is, the cognitive transition that leads from a mere desire to a proper intention. The resulting model of belief-based goal processing has also relevant consequences for the analysis of intentions, and constitutes the necessary core of a constructive theory of intentions, i.e. a framework that not only analyzes what an intention is, but also explains how it becomes what it is. We discuss similarities and differences between our approach and other standard accounts of intention, in particular Bratman’s planning theory. The aim here is to question and refine the conceptual foundations of many theories of intentional action: as a consequence, although our analysis is not formal in itself, it is ultimately meant to have deep consequences for formal models of intentional agency.     

Interrogative Belief Revision in Modal Logic

The well known AGM framework for belief revision has recently been extended to include a model of the research agenda of the agent, i.e. a set of questions to which the agent wishes to find answers (Olsson & Westlund in Erkenntnis, 65, 165–183, 2006). The resulting model has later come to be called interrogative belief revision. While belief revision has been studied extensively from the point of view of modal logic, so far interrogative belief revision has only been dealt with in the metalanguage approach in which AGM was originally presented. In this paper, I show how to model interrogative belief revision in a modal object language using a class of operators for questions. In particular, the solution I propose will be shown to capture the notion of K-truncation, a method for agenda update in the case of expansion constructed by Olsson & Westlund. Two case studies are conducted: first, an interrogative extension of Krister Segerberg’s system DDL, and then a similar extension of Giacomo Bonanno’s modal logic for belief revision. Sound and complete axioms will be provided for both of the resulting logics.     

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.     

Understanding the Brandenburger-Keisler Paradox

Adam Brandenburger and H. Jerome Keisler have recently discovered a two person Russell-style paradox. They show that the following configurations of beliefs is impossible: Ann believes that Bob assumes that Ann believes that Bob’s assumption is wrong. In [7] a modal logic interpretation of this paradox is proposed. The idea is to introduce two modal operators intended to represent the agents’ beliefs and assumptions. The goal of this paper is to take this analysis further and study this paradox from the point of view of a modal logician. In particular, we show that the paradox can be seen as a theorem of an appropriate hybrid logic. Special Issue Formal Epistemology II. Edited by Branden Fitelson     

Iterated Belief Revision and Conditional Logic

In this paper we propose a conditional logic called IBC to represent iterated belief revision systems. We propose a set of postulates for iterated revision which are a small variant of Darwiche and Pearl's ones. The conditional logic IBC has a standard semantics in terms of selection function models and provides a natural representation of epistemic states. We establish a correspondence between iterated belief revision systems and IBC-models. Our representation theorem does not entail Gärdenfors' Triviality Result.     

When Mental States Matter,When They Don't,and What That Means for Morality

Research has shown that moral judgments depend on the capacity to engage in mental state reasoning. In this article, we will first review behavioral and neural evidence for the role of mental states (e.g., people's beliefs, desires, intentions) in judgments of right and wrong. Second, we will consider cases where mental states appear at first to matter less (i.e., when people assign moral blame for accidents and when explicit information about mental states is missing). Third, we will consider cases where mental states, in fact, matter less, specifically, in cases of “purity” violations (e.g., committing incest, consuming taboo foods). We will discuss how and why mental states do not matter equivalently across the multi‐dimensional space of morality. In the fourth section of this article, we will elaborate on the possibility that norms against harmful actions and norms against “impure” actions serve distinct functions – for regulating interpersonal interactions (i.e., harm) versus for protecting the self (i.e., purity). In the fifth and final section, we will speculate on possible differences in how we represent and reason about other people's mental states versus our own beliefs and intentions. In addressing these issues, we aim to provide insight into the complex structure and distinct functions of mental state reasoning and moral cognition. We conclude that mental state reasoning allows us to make sense of other moral agents in order to understand their past actions, to predict their future behavior, and to evaluate them as potential friends or foes.     

Neither Fish nor Fowl: Implicit Attitudes as Patchy Endorsements

Implicit attitudes are mental states that appear sometimes to cause agents to act in ways that conflict with their considered beliefs. Implicit attitudes are usually held to be mere associations between representations. Recently, however, some philosophers have suggested that they are, or are very like, ordinary beliefs: they are apt to feature in properly inferential processing. This claim is important, in part because there is good reason to think that the vocabulary in which we make moral assessments of ourselves and of others is keyed to folk psychological concepts, like ‘belief’, and not to concepts that feature only in scientific psychology: if implicit attitudes are beliefs there is a prima facie case for thinking that they can serve as the basis for particular kinds of moral assessment. In this paper I argue that while implicit attitudes have propositional structure, their sensitivity and responsiveness to other mental representations is too patchy and fragmented for them to properly be considered beliefs. Instead, they are a sui generis kind of mental state, a state I dub patchy endorsements.     

Making a Start with the <Emphasis Type="Italic">stit</Emphasis> Logic Analysis of Intentional Action

This paper studies intentional action in stit logic. The formal logic study of intentional action appears to be new, since most logical studies of intention concern intention as a static mental state. In the formalization we distinguish three modes of acting: the objective level concerning the choices an agent objectively exercises, the subjective level concerning the choices an agent knows or believes to be exercising, and finally, the intentional level concerning the choices an agent intentionally exercises. Several axioms constraining the relations between these different modes of acting will be considered and discussed. The side effect problem will be analyzed as an interaction between knowingly doing and intentionally doing. Non-successful action will be analyzed as a weakening of the epistemic attitude towards action. Finally, the notion of ‘attempt’ will be briefly considered as a further weakening in this direction.     

It’s in your nature: a pluralistic folk psychology

I suggest a pluralistic account of folk psychology according to which not all predictions or explanations rely on the attribution of mental states, and not all intentional actions are explained by mental states. This view of folk psychology is supported by research in developmental and social psychology. It is well known that people use personality traits to predict behavior. I argue that trait attribution is not shorthand for mental state attributions, since traits are not identical to beliefs or desires, and an understanding of belief or desire is not necessary for using trait attributions. In addition, we sometimes predict and explain behavior through appeal to personality traits that the target wouldn’t endorse, and so could not serve as the target’s reasons. I conclude by suggesting that our folk psychology includes the notion that some behavior is explained by personality traits—who the person is—rather than by beliefs and desires—what the person thinks. Consequences of this view for the debate between simulation theory and theory theory, as well as the debate on chimpanzee theory of mind are discussed.     

Temporal Interaction of Information and Belief

The temporal updating of an agent’s beliefs in response to a flow of information is modeled in a simple modal logic that, for every date t, contains a normal belief operator B _t and a non-normal information operator I _t which is analogous to the ‘only knowing’ operator discussed in the computer science literature. Soundness and completeness of the logic are proved and the relationship between the proposed logic, the AGM theory of belief revision and the notion of plausibility is discussed. A first draft of this paper was presented at the Workshop on Belief Change in Rational Agents: Perspectives from Artificial Intelligence, Philosophy and Economics, Dagstuhl (Germany), August 2005. Special Issue Formal Epistemology II. Edited by Branden Fitelson     

Diagnostic reasoning with circumstantial evidence

Individuals often evaluate hypotheses about the cause of particular events on the basis of circumstantial evidence. This article describes a quantitative model of belief revision with circumstantial evidence. The model assumes that subjects revise belief on the basis of a cascaded reasoning process that combines beliefs about three premises—the association of a clue and a possible cause, and forward and backward implications of the clue—to revise belief in a causal hypothesis. Subjects in three experiments solved fictional murder mysteries, reporting on each trial a subset of the beliefs specified by the model. Experiment 1 demonstrates that the model provides a good account of the reasoning process, over several contexts in which clues are evaluated. Subjects appear to develop causal models that affect the interpretation of clues. Experiment 2 provides further evidence on the development of causal models and compares the present model with a model based on Bayes' theorem. Experiment 3 is a control experiment which demonstrates that the belief assessments used in Experiments 1 and 2 do not alter the process of belief revision. Tests of subjects' memory for suspect-clue associations provide further support for the hypothesis that subjects develop causal models of the true cause and demonstrate the contrast between reasoning with currently available information and retrospective access to the facts on which belief revision is based. The present view is compared with other theories of causal thinking and belief revision.     

A Simple Modal Logic for Belief Revision

We propose a modal logic based on three operators, representing intial beliefs, information and revised beliefs. Three simple axioms are used to provide a sound and complete axiomatization of the qualitative part of Bayes’ rule. Some theorems of this logic are derived concerning the interaction between current beliefs and future beliefs. Information flows and iterated revision are also discussed. Giacomo Bonanno: I am grateful to two anonymous reviewers for helpful and constructive comments. A first draft of this paper was presented at the Sixth Conference on Logic and the Foundations of Game and Decision Theory (LOFT6), Leipzig, July 2004.     

Von Wright’s <Emphasis Type="Italic">“The Logic of Preference”</Emphasis> revisited

Preference is a key area where analytic philosophy meets philosophical logic. I start with two related issues: reasons for preference, and changes in preference, first mentioned in von Wright’s book The Logic of Preference but not thoroughly explored there. I show how these two issues can be handled together in one dynamic logical framework, working with structured two-level models, and I investigate the resulting dynamics of reason-based preference in some detail. Next, I study the foundational issue of entanglement between preference and beliefs, and relate the resulting richer logics to belief revision theory and decision theory.     

Belief as emotion

It is commonly held that (i) beliefs are revisable in the face of counter-evidence and (ii) beliefs are connected to actions in reliable and predictable ways. Given such a view, many argue that if a mental state fails to respond to evidence or doesn't result in the kind of behavior typical or expected of belief, it is not a belief after all, but a different state. Yet, one finds seeming counter examples of resilient beliefs that fail to respond to evidence, or that do not connect to action in the way that is expected. I offer a view of belief that does not force us to exclude states as real beliefs that we pre-reflectively think of as beliefs, and that does not require us to “outsource” the work belief seems to do to other mental states. I propose that we view belief as a type of emotion where emotions are understood a irreducibly blended states, containing representational, motivational and phenomenological elements.     

Belief and contextual acceptance

I develop a strategy for representing epistemic states and epistemic changes that seeks to be sensitive to the difference between voluntary and involuntary aspects of our epistemic life, as well as to the role of pragmatic factors in epistemology. The model relies on a particular understanding of the distinction between full belief and acceptance, which makes room for the idea that our reasoning on both practical and theoretical matters typically proceeds in a contextual way. Within this framework, I discuss how agents can rationally shift their credal probability functions so as to consciously modify some of their contextual acceptances; the present account also allows us to represent how the very set of contexts evolves. Voluntary credal shifts, in turn, might provoke changes in the agent’s beliefs, but I show that this is actually a side effect of performing multiple adjustments in the total lot of the agent’s acceptance sets. In this way we obtain a model that preserves many pre-theoretical intuitions about what counts as adequate rationality constraints on our actual practices—and hence about what counts as an adequate, normative epistemological perspective.