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)

In earlier papers (Lindström & Rabinowicz, 1989. 1990), we proposed a generalization of the AGM approach to belief revision. Our proposal was to view belief revision as a relation rather thanas a function on theories (or belief sets). The idea was to allow for there being several equally reasonable revisions of a theory with a given proposition. In the present paper, we show that the relational approach is the natural result of generalizing in a certain way an approach to belief (...) revision due to Adam Grove. In his (1988) paper, Grove presents two closely related modelings of functional belief revision, one in terms of a family of "spheres" around the agent's theory G and the other in terms of an epistemic entrenchment ordering of propositions. The "sphere"-terminology is natural when one looks upon theories and propositions as being represented by sets of possible worlds. Grove's spheres may be thought of as possible "fallback" theories relative to the agent's original theory: theories that he may reach by deleting propositions that are not "sufficiently" entrenched (according to standards of sufficient entrenchment of varying stringency). To put it differently, fallbacks are theories that are closed upwards under entrenchment The entrenchment ordering can be recovered from the family of fallbacks by the definition: A is at least as entrenched as B iff A belongs to every fallback to which B belongs. To revise a theory T with a proposition A, we go to the smallest sphere that contain A-worlds and intersect it with A. The relational notion of belief revision that we are interested in, results from weakening epistemic entrenchment by not assuming it to be connected. I.e., we want to allow that some propositions may be incomparable with respect to epistemic entrenchment. As a result, the family of fallbacks around a given theory will no longer have to be nested. This change opens up the possibility for several different ways of revising a theory with a given proposition. (shrink)

In this article we present a new class of multiple contraction functionswhich are a generalization of the epistemic entrenchment-based contractions (Grdenfors & Makinson, 1988) to the case of contractions by (possibly nonsingleton) sets of sentences and provide an axiomatic characterization for that class of functions. Moreover, we show that the class of epistemic entrenchment-based multiple contractions coincides with the class of system of spheres-based multiple contractions introduced in Fermé & Reis (2012).

A sentence A is epistemically less entrenched in a belief state K than a sentence B if and only if a person in belief state K who is forced to give up either A or B will give up A and hold on to B. This is the fundamental idea of epistemic entrenchment as introduced by Gärdenfors (1988) and elaborated by Gärdenfors and Makinson (1988). Another distinguishing feature of relations of epistemic entrenchment is that they permit (...) particularly simple and elegant construction recipes for minimal changes of belief states. These relations, however, are required to satisfy rather demanding conditions. In the present paper we liberalize the concept of epistemic entrenchment by removing connectivity, minimality and maximality conditions. Correspondingly, we achieve a liberalization of the concept of rational belief change that does no longer presuppose the postulates of success and rational monotony. We show that the central results of Gärdenfors and Makinson are preserved in our more flexible setting. Moreover, the generalized concept of epistemic entrenchment turns out to be applicable also to relational and iterated belief changes. (shrink)

In this paper it is argued that, in order to solve the problem of iterated belief change, both the belief state and its input should be represented as epistemic entrenchment (EE) relations. A belief revision operation is constructed that updates a given EE relation to a new one in light of an evidential EE relation. It is shown that the operation in question satisfies generalized versions of the Gärdenfors revision postulates. The account offered is motivated by Spohn's ordinal (...) conditionalization functions, and can be seen as the Jeffrization of a proposal considered by Rott. (shrink)

Formal models of theory contraction entered the philosophicalliterature with the prototype model by Alchourrón, Gärdenfors,and Makinson (Alchourrón et al. 1985). One influential modelinvolves theory contraction with respect to a relation calledepistemic entrenchment which orders the propositions of a theoryaccording to their relative degrees of theoretical importance.Various postulates have been suggested for characterizingepistemic entrenchment formally. I argue here that threesuggested postulates produce inappropriately bizarre results whenapplied to scientific theories. I argue that the postulates callednoncovering, continuing up, and continuing down, (...) implyrespectively that, (i) no scientific law is more epistemicallyentrenched than any of its instances, (ii) two distinct instances ofthe same scientific law must have different degrees of epistemicentrenchment, and (iii) any two scientific laws must have differentdegrees of epistemic entrenchment. I also argue that continuingup and continuing down each lead to incoherency. (shrink)

In this paper, it is argued that both the belief state and its input should be represented as epistemic entrenchment (EE) relations. A belief revision operation is constructed that updates a given EE relation to a new one in light of an evidential EE relation, and an axiomatic characterization of this operation is given. Unlike most belief revision operations, the one developed here can handle both multiple belief revision and iterated belief revision.

Formal models of theory contraction entered the philosophicalliterature with the prototype model by Alchourrón, Gärdenfors,and Makinson (Alchourrón et al. 1985). One influential modelinvolves theory contraction with respect to a relation calledepistemic entrenchment which orders the propositions of a theoryaccording to their relative degrees of theoretical importance.Various postulates have been suggested for characterizingepistemic entrenchment formally. I argue here that threesuggested postulates produce inappropriately bizarre results whenapplied to scientific theories. I argue that the postulates callednoncovering, continuing up, and continuing down, (...) implyrespectively that, (i) no scientific law is more epistemicallyentrenched than any of its instances, (ii) two distinct instances ofthe same scientific law must have different degrees of epistemicentrenchment, and (iii) any two scientific laws must have differentdegrees of epistemic entrenchment. I also argue that continuingup and continuing down each lead to incoherency. (shrink)

We show that Gabbay’s nonmonotonic consequence relations c an be reduced to a new family of relations, called entrenchment relations. Entrenchment relations provide a direct generalization of epistemic entrenchment and expectation ordering introduced by G ̈ardenfors and Makinson for the study of belief revision and expectation inference, respectively.

In contrast to other prominent models of belief change, models based on epistemic entrenchment have up to now been applicable only in the context of very strong packages of requirements for belief revision. This paper decomposes the axiomatization of entrenchment into independent modules. Among other things it is shown how belief revision satisfying only the 'basic' postulates of Alchourrón, Gärdenfors and Makinson can be represented in terms of entrenchment.

We describe the relation between coherence and foundations approaches to belief change in terms of a correspondence between epistemic entrenchment relations(Gärdenfors and Makinson, 1988; Rott, 1992) and dependence consequence relations from Bochman (1999, 2000a).The general conclusion of the study is that dependence consequence relations are sufficiently expressive to subsume the notion of an epistemic entrenchment and its generalizations.

We introduce a simple generalization of Gardenfors and Makinson’s epistemic entrenchment called partial entrenchment. We show that preferential inference can be generated as the sceptical counterpart of an inference mechanism defined directly on partial entrenchment.

We distinguish the set of explicit beliefs of a reasoner, his "belief base", from the beliefs that are merely implicit. Syntax-based belief change governed by the structure of the belief base and the ranking ("prioritization") of its elements is reconstructed with the help of an epistemic entrenchment relation in the style of Gärdenfors and Makinson. Though priorities are essentially different from entrenchments, distinguished relations of epistemic entrenchment may be obtained from prioritized belief bases by a number (...) of different constructions. An approximate reconstruction of syntax-based belief change is possible, which can be strengthened to a strict identity in some important special cases. A competitive interpretation and a minimal change interpretation of the basic idea of entrenchment are discussed. It is argued that entrenchment essentially involves multiple belief changes, i.e., changes by sets of sentences. (shrink)

Many voices and stories have been systematically silenced in interpersonal conversations, political deliberations and historical narratives. Recalcitrant and interrelated patterns of epistemic, political, cultural and economic marginalisation exclude individuals as knowers, citizens, agents. Two questions lie at the centre of this article, which focuses on the epistemically – but also politically, culturally and economically – dominant: How can we sabotage the dominant’s investment in their own ignorance of unjust silencing? How can they be seduced to become acute perceivers of (...) others’ experiences of oppression and reckon with their own participation in it? Situated at the intersection between political theory, aesthetics and epistemology, this article contributes a so-far-unexplored suggestion: that certain literary works create epistemic friction between shared, entrenched prejudices on the one hand, and representations of epistemic exclusion or authority, on the other. Their power to illuminate ideational, moral and experiential limitations makes them valuable tools in problematising, rendering visible and dislocating epistemic injustice, as well as other marginalisations it intersects with. To advance this argument, the article relies on insights from aesthetics, unpacking fiction’s multidimensional epistemic potential. Audre Lorde exemplifies literary works’ ability to seductively sabotage bias and provide audiences with prosthetic visions of unfamiliar experiences of marginalisation. (shrink)

Disrespect for the truth, the rise of conspiracy thinking, and a pervasive distrust in experts are widespread features of the post-truth condition in current politics and public opinion. Among the many good explanations of these phenomena there is one that is only rarely discussed: that something is wrong with our deeply entrenched intellectual standards of (i) using our own critical thinking without any restriction and (ii) respecting the judgment of every rational agent as epistemically relevant. In this paper, I will (...) argue that these two enlightenment principles—the Principle of Unrestricted Critical Thinking and the Principle of Democratic Reason—not only conflict with what is rationally required from a purely epistemic point of view, but also have bad cognitive consequences in furthering the spread of conspiracy theories and undermining trust in experts. I will then explain in more detail why we should typically defer to experts without using any of our own reasons regarding the subject matter. Moreover, I will show what place this leaves for critical thinking and why it does not have the crazy consequences that the critics expect. (shrink)

The debate about whether misoprostol should be distributed to low resource communities to prevent post-partum haemorrhage, recognised as a major cause of maternal mortality, is deeply polarised. This is in spite of stakeholders having access to the same evidence about the risks and benefits of misoprostol. To understand the disagreement, we conducted a qualitative analysis of the values underpinning debates surrounding community distribution of misoprostol. We found that different moral priorities, epistemic values, and attitudes towards uncertainty were the main (...) factors sustaining the debate. With this understanding, we present a model for ethical discourse that might overcome the current impasse. (shrink)

Testimonial injustice occurs when hearers attribute speakers a credibility deficit because of an identity prejudice and consequently dismiss speakers’ testimonial assertions. Various philosophers explain testimonial injustice by appealing to interpersonal norms arising within testimonial exchanges. When conversational participants violate these interpersonal norms, they generate second-personal epistemic harms, harming speakers as epistemic agents. This focus on testimony, however, neglects how systematically misevaluating speakers’ knowledge affects conversational participants more generally. When hearers systematically misevaluate speakers’ conversational competence because of entrenched assumptions (...) about what speakers know, I call these conversational epistemic injustices. I argue the same epistemic harm in testimonial injustice arises for non-assertoric speech acts, generating conversational epistemic injustices. For across speech acts, deflated knowledge attributions create second-personal harms that prevent speakers from using their knowledge in linguistic exchanges, limiting their epistemic agency. These harms however are not reducible to linguistic harms, (e.g.,) silencing or discursive injustice. This article applies insight from how second-personal epistemic harm arises in testimonial exchanges to conversational exchanges more generally, demonstrating that epistemic injustices arise beyond testimonial exchanges and contexts of inquiry because deflated knowledge attributions undermine general conversational norms requiring participants assume each other’s conversational competence, generating conversational epistemic injustices. (shrink)

This paper explores the intersection between affect, emotion, social imaginaries, and institutions through the lens of epistemic power in the academy. It argues that attending to this intersection is critical for a fuller understanding of how affective and emotional dynamics can assist to entrench, but also disrupt, asymmetries of epistemic privilege that cut across lines of race, sex, and other markers of social difference. As part of this discussion the paper reflects on the possibility of intervening in dominant (...) social imaginaries that become sedimented in the routine operations of the modern university, and which produce affective ecologies that sustain epistemic exclusions within academic institutions. (shrink)

I argue that Open Science as currently conceptualized and implemented does not take sufficient account of epistemic diversity within research. I use three case studies to exemplify how Open Science threatens to privilege some forms of inquiry over others, thus exasperating divides within and across systems of practice, and overlooking important sources and forms of epistemic diversity. Building on insights from pluralist philosophy, I then identify four aspects of diverse research practices that should serve as reference points for (...) debates around Open Science: (1) specificity to local conditions, (2) entrenchment within repertoires, (3) permeability to newcomers, and (4) demarcation strategies. (shrink)

Arguing that ecological thinking can animate an epistemology capable of addressing feminist, multicultural, and other post-colonial concerns, this book critiques the instrumental rationality, hyperbolized autonomy, abstract individualism, and exploitation of people and places that western epistemologies of mastery have legitimated. It proposes a politics of epistemic location, sensitive to the interplay of particularity and diversity, and focused on responsible epistemic practices. Starting from an epistemological approach implicit in Rachel Carson’s scientific projects, the book draws, constructively and critically, on (...) ecological theory and practice, on (post-Quinean) naturalized epistemology, and on feminist and post-colonial theory. Analyzing extended examples from developmental psychology, from medicine and law, and from circumstances where vulnerability, credibility, and public trust are at issue, the argument addresses the constitutive part played by an instituted social imaginary in shaping and regulating human lives. The practices and examples discussed invoke the responsibility requirements central to this text’s larger purpose of imagining, crafting, articulating a creative, innovative, instituting social imaginary, committed to interrogating entrenched hierarchical social structures, en route to enacting principles of ideal cohabitation. (shrink)

Recent years have witnessed growing controversy over the “wisdom of the multitude.” As epistemic critics drawing on vast empirical evidence have cast doubt on the political competence of ordinary citizens, epistemic democrats have offered a defense of democracy grounded largely in analogies and formal results. So far, I argue, the critics have been more convincing. Nevertheless, democracy can be defended on instrumental grounds, and this article demonstrates an alternative approach. Instead of implausibly upholding the epistemic reliability of (...) average voters, I observe that competitive elections, universal suffrage, and discretionary state power disable certain potent mechanisms of elite entrenchment. By reserving particular forms of power for the multitude of ordinary citizens, they make democratic states more resistant to dangerous forms of capture than non-democratic alternatives. My approach thus offers a robust defense of electoral democracy, yet cautions against expecting too much from it—motivating a thicker conception of democracy, writ large. (shrink)

This paper observes that in the midst of a thickening debate over the concept of “epistemic possibility,” nearly every philosopher assumes that the concept is equivalent to a mere absence of epistemic impossibility, that a proposition is epistemically possible if and only if our knowledge does not entail that it is false. I suggest that it is high time that we challenge this deeply entrenched assumption. I assemble an array of data that singles out the distinctive meaning and (...) function of epistemic possibility, which suggest it to be distinct from other modals and an attitude toward a proposition, not a part of the content of a proposition. I suggest that this data is best explained by a positive evidentialist conception of epistemic possibility, one which maintains that a proposition is epistemically possible to a subject only if there is evidence specifically in support of that proposition that is cognitively available to that subject. I suggest that this view not only offers a superior explanation of the data, but also offers a unique and straightforward strategy for undermining skeptical arguments. (shrink)

This article examines Wilfrid Sellars's views on the epistemic status of philosophical propositions. It suggests that according to Sellars philosophical propositions are normative and practically oriented. They do not form a theory for the description of reality; their function is, rather, that of motivating actions which aim at changing reality. The article argues that the role of philosophical propositions can be illuminated if they are understood as a special kind of (proposed) “material” rules of inference, provided that the latter (...) are construed as being firmly entrenched in practice. To this end, a distinction between “theoretical” and “practical” anomalies is drawn to better elucidate—and in some cases criticize and further expand—Sellars's position on the relation between the theoretical and practical dimensions of philosophical activity. In this connection, the Weberian notion of the “disenchantment of the world” is used to throw light on the relation between these two dimensions. (shrink)

Taking up Kimberlé Crenshaw's conclusion that black feminist theorists seem to continue to find themselves in many ways “speaking into the void” (Crenshaw 2011, 228), even as their works are widely celebrated, I examine intersectionality critiques as one site where power asymmetries and dominant imaginaries converge in the act of interpretation (or cooptation) of intersectionality. That is, despite its current “status,” intersectionality also faces epistemic intransigence in the ways in which it is read and applied. My aim is not (...) to suggest that intersectionality cannot (or should not) be critiqued, nor do I maintain that celebratory applications/interpretations are immune from epistemic distortion when it comes to interpreting intersectionality. Rather, my goal is to demonstrate that critiques of intersectionality are one important site to examine hermeneutic marginalization and interpretive violence; the politics of citation; and the impact of dominant expectations or established social imaginaries on meaning-making. In so doing, I aim to consider more fully how entrenched ways of thinking are frequently relied upon to interpret and critique intersectionality, even as these are often the very frameworks that intersectionality theorists have identified as highly problematic tools of misrepresentation, erasure, and violation. This slippage away from intersectionality's outlooks, whether in critical or laudatory contexts, is a pivotal site of epistemic negotiation we must examine more closely. (shrink)

Information received from different sources can be inconsistent. Even when the sources of information can be ordered on the basis of their trustworthiness, it turns out that extracting an acceptable notion of support for information is a non-trivial matter, as is the question what information a rational agent should accept. Here it is shown how a support ordering on the information can be generated and how it can be used to decide what information to accept and what not to accept. (...) This ordering, it turns out, is closely related to notions such as Epistemic Entrenchment and Grove spheres studied in belief revision. (shrink)

The standard way of representing an epistemic state in formal philosophy is in terms of a set of sentences, corresponding to the agent’s beliefs, and an ordering of those sentences, reflecting how well entrenched they are in the agent’s epistemic state. We argue that this wide-spread representational view – a view that we identify as a “Quinean dogma” – is incapable of making certain crucial distinctions. We propose, as a remedy, that any adequate representation of epistemic states (...) must also include the agent’s research agenda, i.e., the list of question that are open or closed at any given point in time. If the argument of the paper is sound, a person’s questions and practical interests, on the one hand, and her beliefs and theoretical values, on the other, are more tightly interwoven than has previously been assumed to be the case in formal epistemology. (shrink)

In a recent article, Zhang and Foo generalized the AGM postulates for contraction to include infinite epistemic input. The new type of belief change is called set contraction. Zhang and Foo also introduced a constructive model for set contraction, called nicely ordered partition, as a generalization of epistemic entrenchment. It was shown however that the functions induced from nicely ordered partitions do not quite match the postulates for set contraction. The mismatch was fixed with the introduction of (...) an extra condition called the limit postulate. The limit postulate establishes a connection between contraction by infinite epistemic input and contraction by finite epistemic input (reducing the former to the latter) and it is appealing both on mathematical and on conceptual grounds. It is debatable however whether the limit postulate can be adopted as a general feature of rationality in set contraction. Instead we propose that the limit postulate is viewed as a condition characterizing an important special case of set contraction functions. With this reading in mind, in this article we introduce an alternative generalization of epistemic entrenchment, based on the notion of comparative possibility. We prove that the functions induced from comparative possibility preorders precisely match those satisfying the postulates for set contraction (without the limit postulate). The relationship between comparative possibility and epistemic entrenchment is also investigated. Finally, we formulate necessary and sufficient conditions under which the functions induced from comparative possibility preorders coincide with the special class of contraction functions characterized by the limit postulate. (shrink)

In classes that examine entrenched injustices like sexism or racism, students sometimes use “distancing strategies” to dissociate themselves from the injustice being studied. Education researchers argue that distancing is a mechanism through which students, especially students of apparent privilege, deny their complicity in systemic injustice. While I am sympathetic to this analysis, I argue that there is much at stake in student distancing that the current literature fails to recognize. On my view, distancing perpetuates socially sanctioned forms of ignorance and (...) unknowing, through which students misrecognize not only their complicity in injustice, but also the ways that injustice shapes the world, their lives, and their knowledge. Thus, distancing is pedagogically problematic because it prevents students from understanding important social facts, and because it prevents them from engaging with perspectives, analyses, and testimonies that might beneficially challenge their settled views and epistemic habits. To substantiate this new analysis, I draw on recent work on epistemologies of ignorance, especially José Medina’s account of “active ignorance.” In order to respond to student distancing, I argue, it is not sufficient for teachers to make students aware of injustice, or of their potential complicity in it. Beyond this, teachers should cultivate epistemic virtue in the classroom and encourage students to take responsibility for better ways of knowing. The article ends by outlining several classroom practices for beginning this work. (shrink)

It is becoming evident that failure to reconcile African Christians and Muslims is partly due to the misinterpretation of the African epistemology of peace. This work argues that Christian-Muslim peacemaking must be conceived apart from the Western epistemology whereby conferences, lectures, chart signing, religious fora, and systematic military strategies are common practices. For Africans, peacemaking involves creating a space where members of a community connect with each other at a deeper level. This paper explores the process of reconciling African Christians (...) and Muslims, not exclusively from a diplomatic tact and religious slant, but from intrinsic cultural constituents like the African ubuntu, Fulbe’s pulaaku, and the Ethiopian medemer which are entrenched in the notion of kinship. A Fulbe proverb constitutes a tool for illustrating kinship and peace. (shrink)

ABSTRACT The rise of social media has correlated with an increase in political polarization, which many perceive as a threat to public discourse and democratic governance. This paper presents a framework, drawing on social epistemology and the economic theory of public goods, to explain how social media can contribute to polarization, making us collectively poorer, even while it provides a preferable media experience for individual consumers. Collective knowledge and consensus is best served by having richly connected networks that are epistemically (...) integrated: individuals with diverse levels of expertise should be relatively well connected to each other. In epistemically segregated networks, by contrast, we have reason to predict collective epistemic failures. Expert knowledge will be isolated from the majority, leading average opinion to be less informed than is socially optimal, and entrenching disagreements. Because social media enables users to very easily adopt homophilous network connections – connections to those with similar opinions, education levels, and social backgrounds – it is likely to have increased epistemic segregation compared to older media platforms. The paper explains the theoretical foundations of these predictions, and sketches regulatory measures – such as taxes – that might be employed to preserve the public good of a well integrated social media network. (shrink)

What does it look like when a group of scientists set out to re-envision an entire field of biology in symbolic and formal terms? I analyze the founding and articulation of Numerical Taxonomy between 1950 and 1970, the period when it set out a radical new approach to classification and founded a tradition of mathematics in systematic biology. I argue that introducing mathematics in a comprehensive way also requires re-organizing the daily work of scientists in the field. Numerical taxonomists sought (...) to establish a mathematical method for classification that was universal to every type of organism, and I argue this intrinsically implicated them in a qualitative re-organization of the work of all systematists. I also discuss how Numerical Taxonomy’s re-organization of practice became entrenched across systematic biology even as opposing schools produced their own competing mathematical methods. In this way, the structure of the work process became more fundamental than the methodological theories that motivated it. (shrink)

This paper investigates the formal relationship between two prominent approaches to the logic of belief change. The first one uses the idea of "relational partial meet contractions" as developed by Alchourrón, Gärdenfors and Makinson (Journal of Symbolic Logic 1985), the second one uses the concept of "epistemic entrenchment" as elaborated by Gärdenfors and Makinson (in Theoretical Aspects of Reasoning about Knowledge, M. Y. Vardi, Los Altos 1988). The two approaches are shown to be strictly equivalent via direct links (...) between the underlying formal relations. The paper closes with observations about the application of epistemic entrenchment to simple and iterated revisions. (shrink)

This is a short version of Lindström & Rabinowicz 1991.In earlier papers, we proposed a generalization of the AGM approach to belief revision. The proposal was to view belief revision as a relation rather than as a function on theories (or belief sets). Going relational means that one allows for several equally reasonable revisions of a theory with a given proposition. In the present paper, we show that the relational approach is the natural result of generalizing in a certain way (...) an approach to belief revision due to Adam Grove. In his (1988) paper, Grove presented two closely related modelings of functional belief revision, one in terms of a family of "spheres" around the agent's theory G and the other in terms of an epistemic entrenchment ordering of propositions. The "sphere"-terminology is natural when one looks upon theories and propositions as sets of possible worlds. Grove's spheres may be thought of as possible "fallback" theories relative to the agent's original theory: theories that he may reach by deleting propositions that are not "sufficiently" entrenched (according to standards of sufficient entrenchment of varying stringency). The entrenchment ordering can be recovered from the family of fallbacks by the definition: A is at least as entrenched as B iff A belongs to every fallback to which B belongs. To revise a theory T with a proposition A, we go to the smallest sphere that contain A-worlds and intersect it with A. The relational notion of belief revision that we are interested in, results if one allows that some propositions may be incomparable with respect to epistemic entrenchment. As a result, the family of fallbacks around a given theory will no longer have to be nested. This change opens up the possibility for several different ways of revising a theory with a given proposition. (shrink)

Alchourrón, Gärdenfors and Makinson have developed and investigated a set of rationality postulates which appear to capture much of what is required of any rational system of theory revision. This set of postulates describes a class of revision functions, however it does not provide a constructive way of defining such a function. There are two principal constructions of revision functions, namely an epistemic entrenchment and a system of spheres. We refer to their approach as the AGM paradigm. We (...) provide a new constructive modeling for a revision function based on a nice preorder on models, and furthermore we give explicit conditions under which a nice preorder on models, an epistemic entrenchment, and a system of spheres yield the same revision function. Moreover, we provide an identity which captures the relationship between revision functions and update operators (as defined by Katsuno and Mendelzon). (shrink)

Using Gärdenfors's notion of epistemic entrenchment, we develop the semantics of a logic which accounts for the following points. It explains why we may generally infer `If ~A then B´ if all we know is AvB while must not generally infer `If ~A then B´ if all we know is {AvB, A}. More generally, it explains the nonmonotonic nature of the consequence relation governing languages which contain conditionals, and it explains how we can deduce conditionals from premise sets (...) without conditionals. Depending on the language at hand, our logic provides different ways of keeping the Ramsey test and getting round the Gärdenfors triviality theorem. I argue that consistent additions of new items of belief are not to be performed by transitions to logical expansions. (shrink)

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. (shrink)

This doctoral dissertation investigates what influence indicative conditionals have on belief updating and how learning from conditionals may be modelled in a probabilistic framework. Because the problem is related to the interpretation of conditionals, we first assess different semantics of indicative conditionals. We propose that conditionals should be taken as primary concepts. This allows us to defend a claim that learning a conditional is equivalent to learning that the relevant conditional probability is 1. This implies that learning a conditional can (...) be modelled as learning a material conditional. We then turn to a few competing approaches to the problem of learning from a conditional -- an approach that models these situations with regards to changes in the explanatory status of the antecedent, as minimising probability distances between the prior and posterior probability distributions, and, particularly, an approach based on epistemic entrenchment. It is argued that although all approaches are important for their pioneering contributions, none of them ultimately provides a fully satisfactory solution. We then formulate a proposal according to which learning a conditional may be modelled as learning a material conditional in conjunction with other contextually inferred or observed information. We show that the view has an intuitive appeal on the grounds of pragmatics and empirical research in psychology of reasoning. We also show that the proposed approach successfully resolves all standard cases from the literature. The proposal is then extended to left-nested conditionals. To do so, we first inspect some preliminary empirical data about actual reasoning with nested conditionals and then show that the proposed approach also successfully models these cases. We then investigate how the approach may be extended to the so-called imperative conditionals. We introduce a tripartite typology of imperative conditionals and argue that although imperatives cannot be probabilistically modelled in any straight-forward way, at least some general insights of the proposed method help us understand the influence that the three different types of imperative conditionals have on listeners’ beliefs. We conclude with a summary and some open questions that should be addressed in future work (e.g. the influence of counterfactuals on belief updating). (shrink)

Quine's holistic empiricist account of scientific inquiry can be characterized by three constitutive principles: *noncontradiction*, *universal revisability* and *pragmatic ordering*. We show that these constitutive principles cannot be regarded as statements within a holistic empiricist's scientific theory of the world. This claim is a corollary of our refutation of Katz's [1998, 2002] argument that holistic empiricism suffers from what he calls the Revisability Paradox. According to Katz, Quine's empiricism is incoherent because its constitutive principles cannot themselves be rationally revised. Using (...) Gärdenfors and Makinson's logic of belief revision based on epistemic entrenchment, we argue that Katz wrongly assumes that the constitutive principles are *statements* within a holistic empiricist's theory of the world. Instead, we show that constitutive principles are best seen as *properties* of a holistic empiricist's theory of scientific inquiry and we submit that, without Katz's mistaken assumption, the paradox cannot be formulated. We argue that our perspective on the status of constitutive principles is perfectly in line with Quinean orthodoxy. In conclusion, we compare our findings with van Fraassen's [2002] argument that we should think of empiricism as a stance, rather than as a doctrine. (shrink)

Since the early 1980s, logical theories of belief revision have offered formal methods for the transformation of knowledge bases or “corpora” of data and beliefs. Early models have dealt with unconditional acceptance and integration of potentially belief-contravening pieces of information into the existing corpus. More recently, models of “non-prioritized” revision were proposed that allow the agent rationally to refuse to accept the new information. This paper introduces a refined method for changing beliefs by specifying constraints on the relative plausibility of (...) propositions. Like the earlier belief revision models, the method proposed is a qualitative one, in the sense that no numbers are needed in order to specify the posterior plausibility of the new information. We use reference beliefs in order to determine the degree of entrenchment of the newly accepted piece of information. We provide two kinds of semantics for this idea, give a logical characterization of the new model, study its relation with other operations of belief revision and contraction, and discuss its intuitive strengths and weaknesses. (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)

When a new piece of information contradicts a currently held belief, one has to modify the set of beliefs in order to restore its consistency. In the case where it is necessary to give up a belief, some of them are less likely to be abandoned than others. The concept of epistemic entrenchment is used by some AI approaches to explain this fact based on formal properties of the belief set (e.g., transitivity). Two experiments were designed to test (...) the hypothesis that contrary to such views, (i) belief is naturally represented by degrees rather than in an all-or-nothing manner, (ii) entrenchment is primarily a matter of content and not only a matter of form, and (iii) consequently prior degree of belief is a powerful factor of change. The two experiments used Elio and Pelletier's (1997) paradigm in which participants were presented with full simple deductive arguments whose conclusion was denied, following which they were asked to decide which premise to revise. (shrink)

In a recent article, Peter Gärdenfors (1992) has suggested that the AGM (Alchourrón, Gärdenfors, and Makinson) theory of belief revision can be given an epistemic basis by interpreting the revision postulates of that theory in terms of a version of the coherence theory of justification. To accomplish this goal Gärdenfors suggests that the AGM revision postulates concerning the conservative nature of belief revision can be interpreted in terms of a concept of epistemic entrenchment and that there are (...) good empirical reasons to adopt this view as opposed to some form of foundationalist account of the justification of our beliefs. In this paper I argue that Gärdenfors’ attempt to underwrite the AGM theory of belief revision by appealing to a form of coherentism is seriously inadequate for several reasons. (shrink)