Brian Weatherson

There is a natural view of the relationship between preference and choice: an option is choiceworthy if and only if no alternative is strictly preferred to it. I argue against this view on two grounds. First, it makes false predictions about which options are choiceworthy in games and in multidimensional choice settings. Second, it conflates two distinct attitudes: choiceworthiness, which is assessed ex ante, and preference, which is assessed ex post. I explore the consequences of rejecting this natural view, including how it simplifies the relationship between game theory and decision theory, and how it complicates debates about what Ruth Chang calls “parity” between options.

Three recent results about probabilistic deference, due to Zhang, Geanakoplos, and Dorst et al,. each hold for all finite probability frames but fail when frames are allowed to be infinite. Zhang's result, that a novice cannot defer to two experts while planning to always have a credence strictly between them when they disagree, requires a finite range of possible expert credences; a counterexample using normal distributions shows it fails otherwise. Geanakoplos's result, that more informative experiments are more valuable when experiments are reflexive, transitive, and nested, does not extend to uncountable frames with discontinuous payoffs, nor does it extend when both the state space and the option set are infinite. The equivalence Dorst et al. establish between Total Trust and Value breaks down in both directions on infinite frames: Total Trust can hold without Value (when utilities are unbounded), and Value can hold without Total Trust (when the option set is finite but the state space is countably infinite). These failures raise questions about the philosophical significance of results that hold only in the finite case, though the paper largely sets those questions aside in favour of establishing the formal results.

There is a natural view of the relationship between preference and choice: an option is choiceworthy if and only if no alternative is strictly preferred to it. I argue against this view on two grounds. First, it makes false predictions about which options are choiceworthy in games and in multidimensional choice settings. Second, it conflates two distinct attitudes: choiceworthiness, which is assessed ex ante, and preference, which is assessed ex post. I explore the consequences of rejecting this natural view, including how it simplifies the relationship between game theory and decision theory, and how it complicates debates about what Ruth Chang calls “parity” between options.

Some writers have said that academic freedom should extend to giving academics complete freedom over what they choose to research. I argue against this: it is consistent with academic freedom for universities to hire people to research particular subjects, and to make continued employment conditional on at least some of the academic’s research being in the areas they were hired to work in. In practice, many academics think that their fellow academics should be free to choose to work on anything that’s within the disciplinary boundaries of the department they were hired into. I argue that’s both too narrow and too broad. Academic freedom implies that researchers should be allowed to have their research focus drift over time. But the boundaries of permissible drift do not correspond to anything like the boundaries of contemporary academic departments.

In this book the author argues for a groundbreaking perspective that knowledge is inherently interest-relative. This means that what one knows is influenced not just by belief, evidence, and truth, but crucially by the purposes those beliefs serve. Drawing from classical Nyāya epistemologies, the book asserts that knowledge rationalizes action: if you know something, it is sensible to act on it—and the best way to square this with an anti-sceptical epistemology is to say that knowledge is interest-relative. While versions of this view have been debated, they haven’t gained wide acceptance. The author addresses common objections with a refined formulation and explores how this perspective elucidates the role of knowledge in inquiry, daily life, and the history of thought. Key distinctions include the impact of “long odds” situations on knowledge, the distinctive role knowledge has a starting point for inquiry, and the importance of using non-ideal models in theorising about knowledge. Building on decades of scholarship, the author offers a cohesive theory that integrates and clarifies previous works, demonstrating that not only knowledge but also belief, rational belief, and evidence are interest-relative. This book is essential for those seeking a deeper understanding of the intricate relationship between knowledge and practical interests.

Permissivism in epistemology is a family of theses, each of which says that rationality is compatible with a number of distinct attitudes. This paper argues that thinking about symmetric games gives us new reason to believe in permissivism. In some finite games, if permissivism is false then we have to think that a player is more likely to take one option rather than another, even though each option has the same expected return given that player’s credences. And in some infinite games, if permissivism is false there is no rational way to play the game, although intuitively the games could be rationally played. The latter set of arguments rely on the recent discovery that there are symmetric games with only asymmetric equilibria. It was long known that there are symmetric games with no pure strategy symmetric equilibria; the surprising new discovery is that there are symmetric games with asymmetric equilibria, but no symmetric equilibria involving either mixed or pure strategies.

A very simple contextualist treatment of a sentence containing an epistemic modal, e.g. a might be F, is that it is true iff for all the contextually salient community knows, a is F. It is widely agreed that the simple theory will not work in some cases, but the counterexamples produced so far seem amenable to a more complicated contextualist theory. We argue, however, that no contextualist theory can capture the evaluations speakers naturally make of sentences containing epistemic modals. If we want to respect these evaluations, our best option is a relativist theory of epistemic modals. On a relativist theory, an utterance of a might be F can be true relative to one context of evaluation and false relative to another. We argue that such a theory does better than any rival approach at capturing all the behaviour of epistemic modals.

A very simple contextualist treatment of a sentence containing an epistemic modal, e.g. a might be F, is that it is true iff for all the contextually salient community knows, a is F. It is widely agreed that the simple theory will not work in some cases, but the counterexamples produced so far seem amenable to a more complicated contextualist theory. We argue, however, that no contextualist theory can capture the evaluations speakers naturally make of sentences containing epistemic modals. If we want to respect these evaluations, our best option is a relativist theory of epistemic modals. On a relativist theory, an utterance of a might be F can be true relative to one context of evaluation and false relative to another. We argue that such a theory does better than any rival approach at capturing all the behaviour of epistemic modals.

There is a lot that we don’t know. That means that there are a lot of possibilities that are, epistemically speaking, open. For instance, we don’t know whether it rained in Seattle yesterday. So, for us at least, there is an epistemic possibility where it rained in Seattle yesterday, and one where it did not. It’s tempting to give a very simple analysis of epistemic possibility: • A possibility is an epistemic possibility if we do not know that it does not obtain. But this is problematic for a few reasons. One issue, one that we’ll come back to, concerns the first two words. The analysis appears to quantify over possibilities. But what are they? As we said, that will become a large issue pretty soon, so let’s set it aside for now. A more immediate problem is that it isn’t clear what it is to have de re attitudes towards possibilities, such that we know a particular possibility does or doesn’t obtain. Let’s try rephrasing our analysis so that it avoids this complication

This paper contributes to the project of articulating and defending the supra-Bayesian approach to judgment aggregation. I discuss three cases where a person is disposed to defer to two different experts, and ask how they should respond when they learn about the opinion of each. The guiding principles are that this learning should go by conditionalisation, and that they should aim to update on the evidence that the expert had updated on. But this doesn’t settle how the update on pairs of experts should go, because we also need to know how the experts are related. I work through three examples showing how the results change given different prior beliefs about this relationship.

Over the years I’ve written many papers defending an idiosyncratic version of interest-relative epistemology. This book collects and updates the views I’ve expressed over those papers. Interest-relative epistemologies all start in roughly the same way. A big part of what makes knowledge important is that it rationalises action. But for almost anything we purportedly know, there is some action that it wouldn’t rationalise. I know what I had for breakfast, but I wouldn’t take a bet at billion to one odds about it. Knowledge has practical limits. The first idiosyncratic feature of my version of interest-relative epistemology is how those limits are identified. Other interest-relative philosophers typically say that the limits have to do with stakes; in high stakes situations knowledge goes away. That’s no part of my view. I think knowledge goes away in long odds situations. High stakes situations are almost always are long odds situations, for reasons to do with the declining marginal utility of money. But the converse isn’t true. On my view, knowledge often goes away in cases where it is trivial to check before action. This idea, that interests matter in long odds cases, and not just in high stakes cases, is the main constant in what I’ve written on interest-relativity over the years. But there are three other respects in which the view I’m going to set out and defend in this book is very different from the view I set out in older papers. I used to identify the practical limits on knowledge with cases where relying on the purported knowledge would get the wrong answer. I focused, that is, on the outputs of inquiry. Knowledge goes away if relying on it would lead one to make a mistake. I now think I was looking at the wrong end of inquiry. Knowledge goes away if the thinker starts conducting an inquiry where the purported knowledge is an inappropriate starting point, and inappropriate for the special reason that it might be false. Now one way we can tell that something is a bad starting point is that starting there will mean we end up at the wrong place. But it’s not the only way. Sometimes a bad starting point will lead to the right conclusion for the wrong reasons. As the Nyāya philosophers argued, rational inquiry starts with knowledge. If it would be irrational to start this inquiry with a particular belief, that belief isn’t knowledge. Not all inquiries are practical inquiries, but many are. And practical inquiries are usually going to be at the center of attention in this book. But what is someone trying to figure out when they conduct a practical inquiry? I used to think that they were trying to figure out which option maximised expected utility, and to a first approximation identified knowledge with those things one could conditionalise on without changing the option that maximised expected utility. As noted in the previous paragraph, I no longer think that we can identify knowledge with what doesn’t change our verdicts. But more importantly, I no longer think that expected utility maximisation is as central to practical inquiry as I once did. There are some theoretical reasons from game theory that raise some doubts about expected utility maximisation. Weak dominance reasoning is part of our theory of rational choice, and can’t be modelled as expected utility maximisation. Perhaps some kinds of equilibrium seeking are parts of practical inquiry, and can’t be modelled as expected utility maximisation. But there are also very practical reasons to think that practical inquiry doesn’t aim at expected utility maximisation. When there are a lot of very similar options - think about selecting a can from a supermarket shelf - and it’s more trouble than it’s worth to figure out which of them maximises expected utility, it’s best to ignore the differences between them and just pick. As I’ll argue in Chapter 6, this makes a big difference to how interests and knowledge interact. In the version of interest-relativity that I’m defending here, everything in epistemology is interest-relative. Knowledge, rational belief, and evidence are all interest-relative. But they are all interest-relative in slightly different ways. The main aim here is to defend the interest-relativity of knowledge. A common objection to interest-relative theories of knowledge is that they can’t be extended into theories of all the things we care about in epistemology. Here I try to meet that challenge. The way I do so is a little messy. It would be nice if there was some part of epistemology that’s interest-invariant, as I used to think, or if all the interest-relative notions were interest-relative in the same way, as other interest-relative epistemologists argue. For better or worse, that’s not the view I’m defending. Interests matter throughout epistemology, and we just have to go case by case to figure out how and why they matter.

What question are decision theorists trying to answer, and why is it worth trying to answer it? A lot of philosophers talk as if the aim of decision theory is to describe how we should make decisions, and the reason to do this is to help us make better decisions. I disagree on both fronts. The aim of the decision theory is to describe how a certain kind of idealised decider does in fact decide. And the reason to do this is that this idealisation, like many other idealisations, helps generate explanations of real-world behaviour. We shouldn't do what these ideal deciders do, or try to be more like them, because a lot of what they do only makes sense because of the differences between us and them. Still, sometimes those differences are small enough that they can be ignored in explanations, and that's when decision theory is useful.

This dissertation looks at a set of interconnected questions concerning the foundations of probability, and gives a series of interconnected answers. At its core is a piece of old-fashioned philosophical analysis, working out what probability is. Or equivalently, investigating the semantic question of what is the meaning of ‘probability’? Like Keynes and Carnap, I say that probability is degree of reasonable belief. This immediately raises an epistemological question, which degrees count as reasonable? To solve that in its full generality would mean the end of human inquiry, so that won’t be attempted here. Rather I will follow tradition and merely investigate which sets of partial beliefs are coherent. The standard answer to this question, what is commonly called the Bayesian answer, says that degrees of belief are coherent iff they form a probability function. I disagree with the way this is usually justified, but subject to an important qualification I accept the answer. The important qualification is that degrees of belief may be imprecise, or vague. Part one of the dissertation, chapters 1 to 6, looks largely at the consequences of this qualification for the semantic and epistemological questions already mentioned. It turns out that when we allow degrees of belief to be imprecise, we can discharge potentially fatal objections to some philosophically attractive theses. Two of these, that probability is degree of reasonable belief and that the probability calculus provides coherence constraints on partial beliefs, have been mentioned. Others include the claim, defended in chapter 4, that chance is probability given total history. As well as these semantic and epistemological questions, studies of the foundations of probability usually include a detailed discussion of decision theory. For reasons set out in chapter 2, I deny we can gain epistemological insights from decision theory. Nevertheless, it is an interesting field to study on its own, and it might be expected that there would be decision theoretic consequences of allowing imprecise degrees of belief. As I show in part two, this expectation seems to be mistaken. Chapter 9 shows that there aren’t interesting consequences of this theory for decision theory proper, and chapters 10 and 11 show that Keynes’s attempt to use imprecision in degrees of belief to derive a distinctive theory of interest rates is unsound. Chapters 7 and 8 provide a link between these two parts. In chapter 7 I look at some previous philosophical investigations into the effects of imprecision. In chapter 8 I develop what I take to be the best competitor to the theory defended here – a constructivist theory of probability. On this view degrees of belief are precise, but the relevant coherence constraint is a constructivist probability calculus. This view is, I think, mistaken, but the calculus has some intrinsic interest, and there are at least enough arguments for it to warrant a chapter-length examination.

There is a lot that we don't know. That means that there are a lot of possibilities that are, epistemically speaking, open. For instance, we don't know whether it rained in Seattle yesterday. So, for us at least, there is an epistemic possibility where it rained in Seattle yesterday, and one where it did not. What are these epistemic possibilities? They do not match up with metaphysical possibilities - there are various cases where something is epistemically possible but not metaphysically possible, and vice versa. How do we understand the semantics of statements of epistemic modality? The ten new essays in this volume explore various answers to these questions, including those offered by contextualism, relativism, and expressivism.

Relativism is the view that the truth of a sentence is relative both to a context of utterance and to a context of assessment. That the truth of a sentence is relative to a context of utterance is uncontroversial in contemporary semantics. This chapter focuses on three points: whether the version of contextualism is vulnerable to the disagreement and retraction arguments, and if so, whether these problems can be avoided by a more sophisticated contextualist theory. The points include: whether relativism really does avoid the four problems posed for the other theories; and whether there are other theories that also avoid the problems, without running into the problems facing relativism or problems of their own. The chapter concentrates on two families of views that have been called relativist: Relativism about propositional truth; and Relativism about utterance truth. (Note that this paper only appears in the 2nd edition of A Companion to the Philosophy of Language; its original publication date is 2017.)

Humean supervenience is the conjunction of three theses: Truth supervenes on being, Anti‐haecceitism, and Spatiotemporalism. The first clause is a core part of Lewis's metaphysics. The second clause is related to Lewis's counterpart theory. The third clause says there are no fundamental relations beyond the spatiotemporal, or fundamental properties of extended objects. Supervenience is classified into strong modal Humean supervenience, local modal Humean supervenience and familiar modal Humean supervenience which states that: for any two "worlds like ours", if the spatiotemporal distribution of fundamental qualities is the same at each world, the contingent facts are also the same. The fact that quantum mechanics raises problems for Humean supervenience does not undercut the philosophical significance of Lewis's defense of Humean supervenience. Humean supervenience says that in a world like ours, the fundamental properties are local qualities: perfectly natural intrinsic properties of points, or of point‐sized occupants of points.