Awareness Growth and Belief Revision

The problem of awareness growth, also known as the problem of new hypotheses, is a persistent challenge to Bayesian theories of rational belief and decision making. Cases of awareness growth include coming to consider a completely new possibility (called expansion), or coming to consider finer distinctions through the introduction of a new partition (called refinement). Recent work has centred on Reverse Bayesianism, a proposal for rational awareness growth due to Karni and Vierø. This essay develops a "Reserve Bayesian" position and defends it against two challenges. The first, due to Anna Mahtani, says that Reverse Bayesian approaches yield the wrong result in cases where the growth of awareness constitutes an expansion relative to one partition, but a refinement relative to a different partition. The second, due to Steele and Stefánsson, says that Reverse Bayesian approaches cannot deal with new propositions that are evidentially relevant to old propositions. I argue that these challenges confuse questions of belief revision with questions of awareness change. Mahtani’s cases reveal that the change of awareness itself requires a model which specifies how propositions in the agent’s old algebra are identified with propositions in the new algebra. I introduce a lattice-theoretic model for this purpose, which resolves Mahtani’s problem cases and some of Steele and Stefánsson’s cases. Applying my model of awareness change, then Reverse Bayesianism, and then a generalised belief revision procedure, resolves Steele and Stefánsson’s remaining cases. In demonstrating this, I introduce a simple and general model of belief revision in the face of new information about previously unknown propositions.

How Confident Should the Religious Believer Be in the Face of Religious Pluralism?

Chapter 3 explores the prospects for resisting the sorts of arguments in which religious diversity or disagreement seem to support skepticism regarding justified (or rational) religious belief. Those religious believers who would resist can (i) argue that the principles that convict the faithful of irrationality overreach, and would establish a more widespread skepticism about rational belief; (ii) downgrade their disagreeing interlocutor(s); (iii) appeal to epistemic permissivism; or (iv) argue that the believer is no worse off, epistemically speaking, than the atheist or agnostic non-believer. After presenting what the present author regards as the best version of the argument from diversity or disagreement, the chapter argues that any believer who hopes for truth will not get much solace from any of these responses.

Rational Belief

This chapter generalizes the modal theory of subjective reasons to the epistemic domain and combines it with the first-order commitment that truth is the sole right-maker for belief. The result is a modal account of epistemic rationality, according to which there is a safety condition on rational belief distinct from but mirroring the more familiar safety condition on knowledge. The chapter shows that the account delivers plausible closure principles on rational belief and offers a straightforward resolution of the lottery paradox. It also explores the implications of the view for whether it is rational to believe necessary propositions, preface propositions, and Moorean propositions.

An Epistemological Study of Theory Change

Belief Revision is a well-established field of research that deals with how agents rationally change their minds in the face of new information. The milestone of Belief Revision is a general and versatile formal framework introduced by Alchourrón, Gärdenfors and Makinson, known as the AGM paradigm, which has been, to this date, the dominant model within the field. A main shortcoming of the AGM paradigm, as originally proposed, is its lack of any guidelines for relevant change. To remedy this weakness, Parikh proposed a relevance-sensitive axiom, which applies on splittable theories; i.e., theories that can be divided into syntax-disjoint compartments. The aim of this article is to provide an epistemological interpretation of the dynamics (revision) of splittable theories, from the perspective of Kuhn's inuential work on the evolution of scientific knowledge, through the consideration of principal belief-change scenarios. The whole study establishes a conceptual bridge between rational belief revision and traditional philosophy of science, which sheds light on the application of formal epistemological tools on the dynamics of knowledge.

Learning from Our Mistakes

In Learning from Our Mistakes: Epistemology for the Real World, William J. Talbott provides a new framework for understanding the history of Western epistemology and uses it to propose a new way of understanding rational belief that can be applied to pressing social and political issues.

Why Hope Cannot Be an Intellectual Virtue: Rationality of Hope Considered from an Analytic Perspective

There are two aims of the paper. The first is to critically analyse the claim that hope can be regarded as an intellectual virtue, as proposed by Nancy E. Snow (2013) in her recent account of hope set within the project of regulative epistemology. The second aim is to explore the problem of rationality of hope. Section one of the paper explains two different interpretations of the key notion of hope and discusses certain features to be found in hope-that and hope-in. Section two addresses the question of whether hope could be interpreted as an intellectual virtue. To develop an argument against that view, a brief account of the notion of epistemic virtue is provided. Section three analyses the problem of rationality of hope and the parallels between rational belief and rational hope; the section focuses on what exactly makes a particular hope-that a rational and justified hope. Belief that p is possible/probable is part of the meaning of hope that p; therefore, it is assumed that rationality of hope cannot be considered in isolation from rationality of belief. It is argued that the “standard account” of the reasonableness of hope, which is found in the analytic literature, does not meet the standards of epistemic responsibility and needs rectifying.

Conceptual Learning and Local Incommensurability: A Dynamic Logic Approach

In recent decades, the logical study of rational belief dynamics has played an increasingly important role in philosophy. However, the dynamics of concepts such as conceptual learning received comparatively little attention within this debate. This is problematic insofar as the occurrence of conceptual change (especially in the sciences) has been an influential argument against a merely logical analysis of beliefs. Especially Kuhn’s ideas about the incommensurability, i.e., untranslatability, of succeeding theories seem to stand in the way of logical reconstruction. This paper investigates conceptual change as model-changing operations similar to belief revision and relates it to the notion of incommensurability. I consider several versions of conceptual change and discuss their influences on the expressive power, translatability and the potential arising of incommensurability. The paper concludes with a discussion of animal taxonomy in Aristotle’s and Linnaeus’s work.

Rational belief and Dialetheism

It is usually maintained that a subject with manifestly contradictory beliefs is irrational. How can we account, then, for the intuitive rationality of dialetheists, who believe that some manifest contradictions are true? My paper aims to answer this question. Its ultimate goal is to determine a characterization of (or rather a constraint for) rational belief approvable by both the theorists of Dialetheism and its opponents. In order to achieve this goal, a two-step strategy will be adopted. First, a characterization of rational belief applicable to non-dialetheist believers will be determined; this characterization will involve the semantic apparatus of Nathan Salmon’s Millian Russellianism but will get rid of the problematic and obscure notion of mode of presentation (guise in his own terminology), replacing it with a couple of novel devices, belief subsystems and cognitive coordination. Second, using ideas from Graham Priest, the leading proponent of Dialetheism, such a characterization will be modified, so as to devise a new one able to account for the intuitive rationality of both dialetheist and non-dialetheist believers.

How to Believe Long Conjunctions of Beliefs: Probability, Quasi-Dogmatism and Contextualism

According to the so-called Lockean thesis, a rational agent believes a proposition just in case its probability is sufficiently high, i.e., greater than some suitably fixed threshold. The Preface paradox is usually taken to show that the Lockean thesis is untenable, if one also assumes that rational agents should believe the conjunction of their own beliefs: high probability and rational belief are in a sense incompatible. In this paper, we show that this is not the case in general. More precisely, we consider two methods of computing how probable must each of a series of propositions be in order to rationally believe their conjunction under the Lockean thesis. The price one has to pay for the proposed solutions to the paradox is what we call “quasi-dogmatism”: the view that a rational agent should believe only those propositions which are “nearly certain” in a suitably defined sense.

A Note on the Epistemological Value of Pretense Imagination

Pretense imagination is imagination understood as the ability to recreate rational belief revision. This kind of imagination is used in pretend-play, risk-assessment, etc. Some even claim that this kind of hypothetical belief revision can be grounds to justify new beliefs in conditionals, in particular conditionals that play a foundational role in the epistemology of modality. In this paper, I will argue that it cannot. I will first provide a very general theory of pretense imagination, which I formalise using tools from dynamic epistemic logic. As a result, we can clearly see that pretense imagination episodes are build up out of two kinds of imaginative stages, so I will present an argument by cases. This argument shows that pretense imagination might indeed provide us with justification for believing certain conditionals. Despite this, I will argue that these are not the kind of conditionals that allow pretense imagination to play a foundational role in the epistemology of modality.