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This is the central chapter of this book. It criticizes belief revision theory for providing only a non-iterable account of belief change and thus only an incomplete dynamics of belief. An analysis of the incompleteness motivates the basic notion of this book: ranking functions. The chapter introduces some variants of this notion and develops its basic theory. It explains how ranks represent belief, and by defining conditional ranks, it is able to adequately explicate conditional belief. The latter notion finally allows stating a complete dynamics of belief by specifying various rules of conditionalization. Expansion, revision, and contraction turn out to be special cases of those rules. An appendix discusses the existing insufficient attempts at iterated belief change, and a further appendix explicates so-called multiple contraction in ranking-theoretic terms.

Conditional ranks also allow explicating a subjective notion of (deductive or non-deductive) reason, i.e., positive relevance, which is at the base of all current notions of (theoretical) reasons. The chapter introduces and defends this explication; it distinguishes sufficient, necessary, insufficient, and supererogatory reasons (in an unconditional and a conditional version); it states the formal behavior of reasons thus explicated; it explains how such reasons can be weighed; and it shows that it is reasons precisely in this sense that drive the dynamics of belief. Moreover, it explains what maximal certainty and unrevisability mean in ranking-theoretic terms and thus provides a dynamic approach to two notions of apriority: (traditional) unrevisable apriority and so-called defeasible apriority.

Sets up parameters for the book's approach — focuses on epistemic (rather than pragmatic) rationality; looks at conditions on simultaneous rational beliefs (rather than on rational changes of belief); and concentrates on global rationality—conditions for an agent's whole system of beliefs (rather than on local conditions for the rationality of particular beliefs). These choices are designed to focus the inquiry where formal logic is most likely to be useful in characterizing ideal rationality.

This chapter examines several kinds of evidence about reactions to reading a novel based on a study conducted by Wayne Booth which surveyed readers of different ages and backgrounds about the novels that had led them to make a change in their behavior or beliefs. It discusses readers' experiences related to narrative empathy and explains a set of working hypotheses about the qualities of novels that evoke empathy in readers. It also analyzes the result of empirical studies concerning the effects of reading and discusses ideas about readers' empathy.

This chapter considers the “vertical” relationship between theory and evidence. In particular, it considers the impact of the conception of “partial” truth on the dynamics of belief change. A new basis for a logic of induction is developed which is faithful to the central principles of induction as set down by Russell, and which can handle various well-known problems that are taken to beset standard Bayesian approaches. It is shown that the standard, but implausible, assumption of “logical omniscience” can be appropriately weakened through a formal modification of the notion of “quasi truth”.

Does radical probabilism have enough structure to say anything interesting? Structure is provided by coherent belief change. Coherence imposes the Martingale property, which gives convergence theorems and theorems about the value of knowledge.

This chapter attempts to add to the literature on the psychological mechanisms underlying perpetrator behavior by looking at the possibility that a specific form of self-deception may play an important role. Specifically, adopting lies and communicating them to others may enable perpetrators to carry out their evil tasks on a daily basis and may even enable them to live out the remainder of their lives with a clear conscience. The chapter examines what Hannah Arendt (1965) calls “lying self-deception”: the effects of telling lies repeatedly on subsequent belief change. The present analysis focuses heavily on how such processes may have operated on Adolf Eichmann, one of the main perpetrators of the Holocaust. In addition, the chapter offers speculations on how such an analysis may extend to other perpetrators, bystanders, and, to some extent, victims of genocide.

This chapter identifies the diverse cultural contexts that shaped the future members of the X Club: gentlemanly London science (Busk, Hooker and Lubbock), Balliol College, Oxford (Spottiswoode), radical provincial Dissent (Spencer and Huxley), and the mechanics institutes and mutual improvement societies of the industrial north (Frankland, Tyndall and Hirst). The variety of their social backgrounds, scientific ambitions, and religious beliefs opens windows onto early Victorian science more generally. The future X-men included wealthy amateurs pursuing their scientific interests, medically trained men seeking to make reputations and careers in science, and social outsiders seeking to rise in the world through scientific employment. Most saw specialist expertise as the route to scientific recognition. They were all aware of the subtle distinctions of social status and religious belief that shaped Victorian life. Even scientific societies, it is shown, marked their status by the level of their fees. Religious skeptics were expected to constrain their conversation in polite society to avoid giving offence to orthodox believers. The changing religious beliefs of the nine are investigated: varieties of Anglicanism; reinterpretations of religion that rejected dogmatic formulations and associated “true” religion with deep feeling; the politics of Church reform and disestablishment.

The chapter studies how norms emerge or come to be abandoned. It argues how norm change always entails a change in social expectations. It also addresses which expectations must first change for a norm to be abandoned, and which expectations have to be created for a norm to develop. It explains how social dilemmas can be solved by norms, as well as how cognitive biases affect the possibility of norm change. The chapter examines the role of scripts and schemata in norm change, and to illustrate these roles it takes examples from the field: sanitation and child marriage.

The chapter discusses which tools can be employed to bring about norm change. It examines the limits of legislative interventions and economic incentives. It thereafter explores the role of the media and collective deliberation in initiating norm change. It identifies the marks of a successful intervention both within media and community deliberation. Along the way, it questions the purported utility of economic incentives for norm change, showing how incentives can backfire. Against the background of this critique, the chapter argues for the centrality of involving the target community in understanding the reasons for abandoning a traditional norm. However, it also raises cautionary flags about the use of deliberative practices in effecting norm change. An integrated approach, operating at the level of media, legal, and communal discussions, is recommended.

Propositions are the bearers of truth and falsity and the objects of belief associated with sentences. Two views about propositions are temporalism, the view that some propositions can change truth value over time, and eternalism, the view that no proposition can do so. Eternalism is defended over temporalism. It is shown that temporalism is false, as it commits us to incorrect semantics for ascriptions of belief. A weakened version of temporalism is also considered and shown to be wanting.

Chapter 4 explores the mechanisms of reflection and internal deliberation: how citizens assess deliberative inputs and update their beliefs in light of them. It discusses, first, how epistemic weights are assigned to the claims encountered in public deliberation. Epistemic weights alone should determine what citizens believe to be true. It discusses, second, how democratic weights (derived proportionally to the stakes citizens have in collective decisions) are allocated to the same deliberative inputs. Both epistemic and democratic weights should bear on the question of what citizens collectively should do. The chapter finally discusses how the epistemic and democratic weights of the same claim should be balanced against each other in internal deliberation.