It is argued that a subject's evidence consists of all and only the propositions that the subject knows.

Formally inclined epistemologists often theorize about ideally rational agents—agents who exemplify rational ideals, such as probabilistic coherence, that human beings could never fully realize. This approach can be defended against the well-known worry that abstracting from human cognitive imperfections deprives the approach of interest. But a different worry arises when we ask what an ideal agent should believe about her own cognitive perfection (even an agent who is in fact cognitively perfect might, it would seem, be uncertain of this fact). (...) Consideration of this question reveals an interesting feature of the structure of our epistemic ideals: for agents with limited information, our epistemic ideals turn out to conflict with one another. This suggests that we must revise the way we see ideal agents in epistemic theorizing. (shrink)

I advocate Time-Slice Rationality, the thesis that the relationship between two time-slices of the same person is not importantly different, for purposes of rational evaluation, from the relationship between time-slices of distinct persons. The locus of rationality, so to speak, is the time-slice rather than the temporally extended agent. This claim is motivated by consideration of puzzle cases for personal identity over time and by a very moderate form of internalism about rationality. Time-Slice Rationality conflicts with two proposed principles of (...) rationality, Conditionalization and Reflection. Conditionalization is a diachronic norm saying how your current degrees of belief should fit with your old ones, while Reflection is a norm enjoining you to defer to the degrees of belief that you expect to have in the future. But they are independently problematic and should be replaced by improved, time-slice-centric principles. Conditionalization should be replaced by a synchronic norm saying what degrees of belief you ought to have given your current evidence and Reflection should be replaced by a norm which instructs you to defer to the degrees of belief of agents you take to be experts. These replacement principles do all the work that the old principles were supposed to do while avoiding their problems. In this way, Time-Slice Rationality puts the theory of rationality on firmer foundations and yields better norms than alternative, non-time-slice-centric approaches. (shrink)

I outline a number of parallels between trust and distrust, emphasising the significance of situations in which both trust and distrust would be an imposition upon the (dis)trustee. I develop an account of both trust and distrust in terms of commitment, and argue that this enables us to understand the nature of trustworthiness. Note that this article is available open access on the journal website.

When it comes to epistemic normativity, should we take the good to be prior to the right? That is, should we ground facts about what we ought and ought not believe on a given occasion in facts about the value of being in certain cognitive states (such as, for example, the value of having true beliefs)? The overwhelming answer among contemporary epistemologists is “Yes, we should.” This essay argues to the contrary. Just as taking the good to be prior to (...) the right in ethics often leads one to sanction implausible trade-offs when determining what an agent should do, so too, this essay argues, taking the good to be prior to the right in epistemology leads one to sanction implausible trade-offs when determining what a subject should believe. Epistemic value—and, by extension, epistemic goals—are not the explanatory foundation upon which all other normative notions in epistemology rest. (shrink)

On the face of it, in ordinary practices of rational assessment, we criticize agents both for the combinations of attitudes, like belief, desire, and intention, that they possess at particular times, and for the ways that they behave cognitively over time, by forming, reconsidering, and updating those attitudes. Accordingly, philosophers have proposed norms of rationality that are synchronic—concerned fundamentally with our individual time-slices, and diachronic—concerned with our temporally extended behaviour. However, a recent movement in epistemology has cast doubt on the (...) very existence of requirements of the latter type. My aim in this paper is to address what I take to be the most direct and general recent attack on diachronic epistemic rationality, the arguments for so-called ‘time-slice epistemology’ by Brian Hedden. I argue that Hedden's attempt to motivate the rejection of diachronic rational norms ultimately fails, and in particular that an independently attractive view about the nature of such norms, namely one on which such norms govern processes, escapes his assault unscathed. (shrink)

Rationality Through Reasoning answers the question of how people are motivated to do what they believe they ought to do, built on a comprehensive account of normativity, rationality and reasoning that differs significantly from much existing philosophical thinking. Develops an original account of normativity, rationality and reasoning significantly different from the majority of existing philosophical thought Includes an account of theoretical and practical reasoning that explains how reasoning is something we ourselves do, rather than something that happens in us Gives (...) an account of what reasons are and argues that the connection between rationality and reasons is much less close than many philosophers have thought Contains rigorous new accounts of oughts including owned oughts, agent-relative reasons, the logic of requirements, instrumental rationality, the role of normativity in reasoning, following a rule, the correctness of reasoning, the connections between intentions and beliefs, and much else. Offers a new answer to the ‘motivation question’ of how a normative belief motivates an action. (shrink)

Recently many have argued that agents must sometimes have credences that are imprecise, represented by a set of probability measures. But opponents claim that fans of imprecise credences cannot provide a decision theory that protects agents who follow it from foregoing sure money. In particular, agents with imprecise credences appear doomed to act irrationally in diachronic cases, where they are called to make decisions at earlier and later times. I respond to this claim on behalf of imprecise credence fans. Once (...) we appreciate the complexity of our intuitions about rational decision making, we can see that diachronic cases are in fact evidence for the essential claims motivating imprecise credence models. I argue that our decision theory for imprecise agents should mirror our decision theory for agents in moral dilemmas, and I develop permissive norms that explain our intuitions about both sorts of agents. (shrink)

In this paper I discuss the kinds of idealisations invoked in normative theories—logic, epistemology, and decision theory. I argue that very often the so-called norms of rationality are in fact mere idealisations invoked to make life easier. As such, these idealisations are not too different from various idealisations employed in scientific modelling. Examples of the latter include: fluids are incompressible (in fluid mechanics), growth rates are constant (in population ecology), and the gravitational influence of distant bodies can be ignored (in (...) celestial mechanics). Thinking of logic, epistemology, and decision theory as normative models employing various idealisations of these kinds, changes the way we approach the justification of the models in question. (shrink)

Classical theories of epistemic rationality take an agent\\textquoteright{}s individual beliefs to be the only things that are rational or irrational. For them, rationality is wholly static. Recent work in epistemology take sets of individual beliefs and also changes of belief over time to be rational or irrational. For these theories, rationality is both static and dynamic. However, for both groups, static rationality is fundamental. In my dissertation, I argue to the contrary that, in fact, all rationality is dynamic rationality. Epistemic (...) reasons, rationality, and justi{}cation as applying only to changes of belief. This wholly dynamic view of rationality, which I call \\textquotedblleft{}Dynamicism\\textquotedblright has wide-ranging epistemological consequences. A small set of simple, elegant, and independently motivated principles of dynamic rationality can illuminate and solve otherwise interminable epistemological disputes. (shrink)

The proposition expressed by an utterance of a quantified sentence depends on a domain of discourse somehow determined by the context. How does the context of utterance determine the content of the domain of discourse? Many philosophers would approach this question from the point of view of an expressive theory of linguistic communication, according to which the primary function of language is to enable speakers to convey the propositional contents of their thoughts to hearers. This paper argues that from this (...) point of view there is no persuasive treatment of the determinants of the domain of discourse. The argument focuses on an abnormal case in which the domain the speaker has in mind is not evident to the hearer. In this way the question concerning the determinants of the domain of discourse is used to challenge the expressive theory of communication. (shrink)

This chapter defines and defends time-slice epistemology, according to which there are no essentially diachronic norms of rationality. The chapter begins by distinguishing two notions of time-slice epistemology, and ends by defending time-slice theories of action under indeterminacy, i.e. theories about how you should act when the outcome of your decision depends on some indeterminate claim. In a recent chapter, J. Robert G. Williams defends a theory of action under indeterminacy which is subject to several objections. An alternative theory is (...) proposed in its place. The resulting discussion highlights a more general moral about action under indeterminacy, namely that time-slice theories are supported by strong analogies with ethical theories. In particular, our understanding of agents torn between interpretations of a decision situation should be guided by our theories of agents torn between incommensurable values. (shrink)

This paper defines and defends time-slice epistemology, according to which there are no essentially diachronic norms of rationality. First I motivate and distinguish two notions of time-slice epistemology. Then I defend time-slice theories of action under indeterminacy, i.e. theories about how you should act when the outcome of your decision depends on some indeterminate claim. I raise objections to a theory of action under indeterminacy recently defended by Robbie Williams, and I propose some alternative theories in its place. Throughout this (...) discussion, I defend a more general moral about action under indeterminacy, namely that time-slice theories are supported by strong analogies with ethical theories. In particular, our understanding of agents torn between interpretations of a decision situation should be guided by our theories of agents torn between incommensurable values. (shrink)