Plausible inference: A multi-valued logic for problem solving

A new logic is developed which permits continuously variable strength of belief in the truth of assertions. Four inference rules result, with formal logic as a limiting case. Quantification of belief is defined. Propagation of belief to linked assertions results from dependency-based techniques of truth maintenance so that local consistency is achieved or contradiction discovered in problem solving. Rules for combining, confirming, or disconfirming beliefs are given, and several heuristics are suggested that apply to revising already formed beliefs in the light of new evidence. The strength of belief that results in such revisions based on conflicting evidence are a highly subjective phenomenon. Certain quantification rules appear to reflect an orderliness in the subjectivity. Several examples of reasoning by plausible inference are given, including a legal example and one from robot learning. Propagation of belief takes place in directions forbidden in formal logic and this results in conclusions becoming possible for a given set of assertions that are not reachable by formal logic

Advances on belief base dynamics

The main goal underlying the research area of belief change consists in finding appropriate ways of modelling the belief state of a rational agent and, additionally, the changes which occur in such a state when the agent receives new information. The most important model of belief change is the so-called AGM model, proposed in [AGM85]. In this model, the belief state of an agent is represented by a belief set—a deductively closed set of sentences. A change consists in adding or removing a specific sentence from a belief set to obtain a new belief set. Two of the main shortcomings pointed out to the AGM model of belief change are the use of belief sets to represent belief states and the (unrealistic) acceptance of any new piece of information. In this thesis we address both those issues. We present axiomatic characterizations for ensconcement-based contractions and for brutal contractions, two kinds of belief bases contraction operators introduced in [Wil94b] that are based on the concept of ensconcement, which is a generalization to the case of belief bases of the concept of epistemic entrenchment introduced in [Ga¨r88, GM88]. We compare the axiomatic characterizations of these operators with those of other well-known base contraction operators and study the interrelations among the former and the contraction operators based on epistemic entrenchments. We study non-prioritized base change operators, namely shielded base contractions and credibility-limited base revisions. We propose several different classes of shielded base contractions and obtain axiomatic characterizations for each one of them. Additionally we thoroughly investigate the interrelations (in the sense of inclusion) among all those classes. Afterwards we perform a similar study for credibility-limited base revisions. Finally, we study the interrelation between the different proposed classes of operators of credibility-limited base revision and of shielded contraction by means of the consistency-preserving Levi identity and the Harper identity.O objetivo principal da a´rea de revis˜ao de cren¸cas ´e encontrar modelos que permitam modelar o estado de cren¸cas de um agente racional, bem como as mudan¸cas que ocorrem nesse estado de cren¸cas quando o agente recebe novas informa¸co˜es. O modelo mais influente desta ´area ´e o chamado modelo AGM proposto em [AGM85]. Neste modelo, o estado de cren¸cas de um agente ´e representado por um conjunto de cren¸cas—conjunto de f´ormulas dedutivamente fechado. Uma mudan¸ca consiste em adicionar ou remover uma fo´rmula espec´ıfica de um conjunto de cren¸cas para obter um novo conjunto de crenc¸as. Dois dos principais problemas apontados ao modelo AGM sa˜o o uso de conjuntos de cren¸cas para representar estados de cren¸ca e a aceita¸ca˜o (irrealista) de qualquer nova informa¸ca˜o. Nesta tese abordamos ambas as quest˜oes. Apresentamos caracteriza¸co˜es axiom´aticas para contra¸c˜oes baseadas em ensconcements e para contra¸c˜oes brutais, dois tipos de operadores de contrac¸˜ao em bases de cren¸cas introduzidos em [Wil94b] e que se baseiam no conceito de ensconcement— generaliza¸ca˜o em bases de cren¸cas, do conceito de epistemic entrenchment introduzido em [Ga¨r88, GM88]. Comparamos as caracteriza¸c˜oes axiom´aticas destes operadores com as de outros operadores de contrac¸˜ao em bases bem conhecidos e estudamos as inter-rela¸co˜es entre os primeiros e os operadores de contra¸ca˜o baseados em epistemic entrenchments. Estudamos operadores de mudanc¸as de crenc¸as na˜o-priorizados em bases, nomeadamente contra¸c˜oes protegidas e revis˜oes com limite de credibilidade. Propomos v´arias classes de operadores de contra¸c˜oes protegidas e obtemos teoremas de representa¸ca˜o para cada uma dessas classes. Investigamos, igualmente, as inter-rela¸co˜es (no sentido de inclusa˜o) entre todas essas classes. Posteriormente, realizamos um estudo semelhante para reviso˜es com limite de credibilidade. Finalmente, estudamos a inter-relac¸˜ao entre as diferentes classes propostas de operadores (definidos em bases de cren¸cas) de revis˜ao com limite de credibilidade e de contra¸co˜es protegidas atrav´es da identidade de Levi conservadora-da-consistˆencia e da identidade de Harper

Studies in credibility: limited base revision

In this paper we present axiomatic characterizations for several classes of credibility-limited base revision functions and establish the interrelation among those classes. We also propose and axiomatically characterize two new base revision functions.info:eu-repo/semantics/publishedVersio

Epistemically Pernicious Groups and the Groupstrapping Problem

Recently, there has been growing concern that increased partisanship in news sources, as well as new ways in which people acquire information, has led to a proliferation of epistemic bubbles and echo chambers: in the former, one tends to acquire information from a limited range of sources, ones that generally support the kinds of beliefs that one already has, while the latter function in the same way, but possess the additional characteristic that certain beliefs are actively reinforced. Here I argue, first, that we should conceive of epistemic bubbles and echo chambers as types of epistemically pernicious groups, and second, that while analyses of such groups have typically focused on relationships between individual members, at least part of what such groups epistemically pernicious pertains to the way that members rely on the groups themselves as sources of information. I argue that member reliance on groups results in groups being attributed a degree of credibility that outruns their warrant, a process I call groupstrapping. I argue that by recognizing the groupstrapping as an illicit method of forming and updating beliefs we can make progress on some of the open questions concerning epistemically pernicious groups

Evidence-Based Detection of Pancreatic Canc

This study is an effort to develop a tool for early detection of pancreatic cancer using evidential reasoning. An evidential reasoning model predicts the likelihood of an individual developing pancreatic cancer by processing the outputs of a Support Vector Classifier, and other input factors such as smoking history, drinking history, sequencing reads, biopsy location, family and personal health history. Certain features of the genomic data along with the mutated gene sequence of pancreatic cancer patients was obtained from the National Cancer Institute (NIH) Genomic Data Commons (GDC). This data was used to train the SVC. A prediction accuracy of ~85% with a ROC AUC of 83.4% was achieved. Synthetic data was assembled in different combinations to evaluate the working of evidential reasoning model. Using this, variations in the belief interval of developing pancreatic cancer are observed. When the model is provided with an input of high smoking history and family history of cancer, an increase in the evidential reasoning interval in belief of pancreatic cancer and support in the machine learning model prediction is observed. Likewise, decrease in the quantity of genetic material and an irregularity in the cellular structure near the pancreas increases support in the machine learning classifier’s prediction of having pancreatic cancer. This evidence-based approach is an attempt to diagnose the pancreatic cancer at a premalignant stage. Future work includes using the real sequencing reads as well as accurate habits and real medical and family history of individuals to increase the efficiency of the evidential reasoning model. Next steps also involve trying out different machine learning models to observe their performance on the dataset considered in this study

Credibility-limited base revision: new classes and their characterizations

In this paper we study a kind of operator —known as credibility-limited base revisions— which addresses two of the main issues that have been pointed out to the AGM model of belief change. Indeed, on the one hand, these operators are defined on belief bases (rather than belief sets) and, on the other hand, they are constructed with the underlying idea that not all new information is accepted. We propose twenty different classes of credibility limited base revision operators and obtain axiomatic characterizations for each of them. Additionally we thoroughly investigate the interrelations (in the sense of inclusion) among all those classes. More precisely, we analyse whether each one of those classes is or is not (strictly) contained in each of the remaining ones.info:eu-repo/semantics/publishedVersio

Levi and Harper identities for non-prioritized belief base change

In this paper, we investigate the relation between shielded base contraction postulates and credibility-limited (CL) base revision postulates. More precisely, we identify (i) the relation between the postulates satisfied by a shielded base contraction operator and the postulates satisfied by the CL base revision operator that is defined from it by means of the consistency-preserving Levi identity and (ii) the relation between the postulates satisfied by a CL base revision operator and the postulates satisfied by the shielded base contraction operator that is defined from it by means of the Harper identity. Furthermore, we show that the consistency-preserving Levi identity and the Harper identity establish a one-to one correspondence between the twenty classes of shielded base contractions presented in [21] and the twenty classes of credibility-limited base revisions presented in [22].info:eu-repo/semantics/publishedVersio

Belief Revision in Science: Informational Economy and Paraconsistency

In the present paper, our objective is to examine the application of belief revision models to scientific rationality. We begin by considering the standard model AGM, and along the way a number of problems surface that make it seem inadequate for this specific application. After considering three different heuristics of informational economy that seem fit for science, we consider some possible adaptations for it and argue informally that, overall, some paraconsistent models seem to better satisfy these principles, following Testa (2015). These models have been worked out in formal detail by Testa, Cogniglio, & Ribeiro (2015, 2017)