Mattias Skipper

Guessing is a familiar activity, one we engage in when we are uncertain of the answer to a question under discussion. It is also an activity that lends itself to normative evaluation: some guesses are better than others. The question that interests me here is what makes for a good guess. In recent work, Dorst and Mandelkern have argued that good guesses are distinguished from bad ones by how well they optimize a tradeoff between accuracy and specificity. Here I argue that Dorst and Mandelkern’s implementation of this idea fails to satisfy some plausible constraints on good guesses, and I develop an alternative implementation that satisfies the relevant constraints. The result is a new account of good guesses which retains the positive aspects of Dorst and Mandelkern’s proposal, but without the drawbacks.

This paper is about a problem that can arise when we try to harness the “wisdom of the crowd” from groups comprised of individuals who exhibit a certain kind of epistemic humility in the way they respond to testimonial evidence. I begin by setting out the problem and then make some initial steps toward solving it. The solution I develop is tentative and may not apply in all circumstances, but it promises to alleviate what seems to me to be a problem of both theoretical interest and practical importance.

Many theories of rational action are predicated on the idea that what it is rational to do in a given situation depends, in part, on what it is rational to believe in that situation. In short: they treat epistemic rationality as explanatorily prior to practical rationality. If they are right in doing so, it follows, on pain of explanatory circularity, that epistemic rationality cannot itself be a form of practical rationality. Yet, many epistemologists have defended just such a view of epistemic rationality. According to them, there is no such thing as a distinctively epistemic form of rationality which could be explanatorily prior to practical rationality. Rather, they maintain, there is just one form of rationality—practical rationality—of which epistemic rationality is a species. What to make of this conflict? The aim of this paper is to motivate a view about the relationship between epistemic and practical rationality which resolves the conflict in a way that should be attractive to both sides. The central idea is to ground both epistemic and practical rationality in an independently motivated notion of evidential probability which is itself to be understood in non-normative terms. Doing so, I argue, allows us to unify epistemic and practical rationality in a way that does justice to the idea that what it is rational to do depends, in part, on what it is rational to believe; and to do so in a way that avoids explanatory circularity.

When a belief has been influenced, in part or whole, by factors that, by the believer's own lights, do not bear on the truth of the believed proposition, we can say that the belief has been, in a sense, arbitrarily formed. Can such beliefs ever be rational? It might seem obvious that they can't. After all, belief, supposedly, “aims at the truth.” But many epistemologists have come to think that certain kinds of arbitrary beliefs can, indeed, be rational. In this paper, I want to do two things. First, I want to show that the claim that arbitrary beliefs can be rational is inconsistent with the conjunction of two other attractive claims: one saying that rationality requires a certain kind of epistemic immodesty, and one saying that rationality forbids certain kinds of self-ascriptions of epistemic luck. Second, I want to evaluate different ways one might respond to this inconsistent triad. I won't defend any response in particular, but I'll draw out some notable costs and benefits of each response, which may help shed light on the question of whether arbitrary beliefs can be rational.

Our aim in this chapter is to draw attention to what we see as a disturbing feature of conciliationist views of disagreement. Roughly put, the trouble is that conciliatory responses to in-group disagreement can lead to the frustration of a group's epistemic priorities: that is, the group's favoured trade-off between the "Jamesian goals" of truth-seeking and error-avoidance. We show how this problem can arise within a simple belief aggregation framework, and draw some general lessons about when the problem is most pronounced. We close with a tentative proposal for how to solve the problem raised without rejecting conciliationism.

Many theories of rational belief give a special place to logic. They say that an ideally rational agent would never be uncertain about logical facts. In short: they say that ideal rationality requires "logical omniscience." Here I argue against the view that ideal rationality requires logical omniscience on the grounds that the requirement of logical omniscience can come into conflict with the requirement to proportion one’s beliefs to the evidence. I proceed in two steps. First, I rehearse an influential line of argument from the "higher-order evidence" debate, which purports to show that it would be dogmatic, even for a cognitively infallible agent, to refuse to revise her beliefs about logical matters in response to evidence indicating that those beliefs are irrational. Second, I defend this "anti-dogmatism" argument against two responses put forth by Declan Smithies and David Christensen. Against Smithies’ response, I argue that it leads to irrational self-ascriptions of epistemic luck, and that it obscures the distinction between propositional and doxastic justification. Against Christensen’s response, I argue that it clashes with one of two attractive deontic principles, and that it is extensionally inadequate. Taken together, these criticisms will suggest that the connection between logic and rationality cannot be what it is standardly taken to be—ideal rationality does not require logical omniscience.

Should you always be certain about what you should believe? In other words, does rationality demand higher-order certainty? First answer: Yes! Higher-order uncertainty can’t be rational, since it breeds at least a mild form of epistemic akrasia. Second answer: No! Higher-order certainty can’t be rational, since it licenses a dogmatic kind of insensitivity to higher-order evidence. Which answer wins out? The first, I argue. Once we get clearer about what higher-order certainty is, a view emerges on which higher-order certainty does not, in fact, license any kind of insensitivity to higher-order evidence. The view as I will describe it has plenty of intuitive appeal. But it is not without substantive commitments: it implies a strong form of internalism about epistemic rationality, and forces us to reconsider standard ways of thinking about the nature of evidential support. Yet, the view put forth promises a simple and elegant solution to a surprisingly difficult problem in our understanding of rational belief.

People don't always speak the truth. When they don't, we do better not to trust them. Unfortunately, that's often easier said than done. People don't usually wear a ‘Not to be trusted!’ badge on their sleeves, which lights up every time they depart from the truth. Given this, what can we do to figure out whom to trust, and whom not? My aim in this paper is to offer a partial answer to this question. I propose a heuristic—the “Humility Heuristic”—which is meant to help guide our search for trustworthy advisors. In slogan form, the heuristic says: people worth trusting admit to what they don't know. I give this heuristic a precise probabilistic interpretation, offer a simple argument for it, defend it against some potential worries, and demonstrate its practical worth by showing how it can help address some difficult challenges in the relationship between experts and laypeople.

Don’t form beliefs on the basis of coin flips or random guesses. More generally, don’t take belief gambles: if a proposition is no more likely to be true than false given your total body of evidence, don’t go ahead and believe that proposition. Few would deny this seemingly innocuous piece of epistemic advice. But what, exactly, is wrong with taking belief gambles? Philosophers have debated versions of this question at least since the classic dispute between William Clifford and William James near the end of the nineteenth century. Here I reassess the normative standing of belief gambles from the perspective of epistemic decision theory. The main lesson of the paper is a negative one: it turns out that we need to make some surprisingly strong and hard-to-motivate assumptions to establish a general norm against belief gambles within a decision-theoretic framework. I take this to pose a dilemma for epistemic decision theory: it forces us to either make seemingly unmotivated assumptions to secure a norm against belief gambles, or concede that belief gambles can be rational after all.

Orthodox Bayesianism is a highly idealized theory of how we ought to live our epistemic lives. One of the most widely discussed idealizations is that of logical omniscience: the assumption that an agent’s degrees of belief must be probabilistically coherent to be rational. It is widely agreed that this assumption is problematic if we want to reason about bounded rationality, logical learning, or other aspects of non-ideal epistemic agency. Yet, we still lack a satisfying way to avoid logical omniscience within a Bayesian framework. Some proposals merely replace logical omniscience with a different logical idealization; others sacrifice all traits of logical competence on the altar of logical non-omniscience. We think a better strategy is available: by enriching the Bayesian framework with tools that allow us to capture what agents can and cannot infer given their limited cognitive resources, we can avoid logical omniscience while retaining the idea that rational degrees of belief are in an important way constrained by the laws of probability. In this paper, we offer a formal implementation of this strategy, show how the resulting framework solves the problem of logical omniscience, and compare it to orthodox Bayesianism as we know it.

Epistemic instrumentalists think that epistemic normativity is just a special kind of instrumental normativity. According to them, you have epistemic reason to believe a proposition insofar as doing so is conducive to certain epistemic goals or aims—say, to believe what is true and avoid believing what is false. Perhaps the most prominent challenge for instrumentalists in recent years has been to explain, or explain away, why one’s epistemic reasons often do not seem to depend on one’s aims. This challenge can arguably be met. But a different challenge looms: instrumental reasons in the practical domain have various properties that epistemic reasons do not seem to share. In this chapter, we offer a way for epistemic instrumentalists to overcome this challenge. Our main thesis takes the form of a conditional: if we accept an independently plausible transmission principle of instrumental normativity, we can maintain that epistemic reasons in fact do share the relevant properties of practical instrumental reasons. In addition, we can explain why epistemic reasons seem to lack these properties in the first place: some properties of epistemic reasons are elusive, or easy to overlook, because we tend to think and talk about epistemic reasons in an ‘elliptical’ manner.

When one has both epistemic and practical reasons for or against some belief, how do these reasons combine into an all-things-considered reason for or against that belief? The question might seem to presuppose the existence of practical reasons for belief. But we can rid the question of this presupposition. Once we do, a highly general ‘Combinatorial Problem’ emerges. The problem has been thought to be intractable due to certain differences in the combinatorial properties of epistemic and practical reasons. Here we bring good news: if we accept an independently motivated version of epistemic instrumentalism—the view that epistemic reasons are a species of instrumental reasons—we can reduce The Combinatorial Problem to the relatively benign problem of how to weigh different instrumental reasons against each other. As an added benefit, the instrumentalist account can explain the apparent intractability of The Combinatorial Problem in terms of a common tendency to think and talk about epistemic reasons in an elliptical manner.

People tend to think that they know others better than others know them. This phenomenon is known as the “illusion of asymmetric insight.” While the illusion has been well documented by a series of recent experiments, less has been done to explain it. In this paper, we argue that extant explanations are inadequate because they either get the explanatory direction wrong or fail to accommodate the experimental results in a sufficiently nuanced way. Instead, we propose a new explanation that does not face these problems. The explanation is based on two other well-documented psychological phenomena: the tendency to accommodate ambiguous evidence in a biased way, and the tendency to overestimate how much better we know ourselves than we know others.

Many epistemologists have endorsed a version of the view that rational belief is sensitive to higher-order defeat. That is to say, even a fully rational belief state can be defeated by misleading higher-order evidence, which indicates that the belief state is irrational. In a recent paper, however, Maria Lasonen-Aarnio calls this view into doubt. Her argument proceeds in two stages. First, she argues that higher-order defeat calls for a two-tiered theory of epistemic rationality. Secondly, she argues that there seems to be no satisfactory way of avoiding epistemic dilemmas within a two-tiered framework. Hence, she concludes that the prospects look dim for making sense of higher-order defeat within a broader theoretical picture of epistemic rationality. Here I aim to resist both parts of Lasonen-Aarnio’s challenge. First, I outline a way of accommodating higher-order defeat within a single-tiered framework, by amending epistemic rules with appropriate provisos for different kinds of higher-order defeat. Secondly, I argue that those who nevertheless prefer to accommodate higher-order defeat within a two-tiered framework can do so without admitting to the possibility of epistemic dilemmas, since epistemic rules are not always accompanied by ‘oughts’ in a two-tiered framework. The considerations put forth thus indirectly vindicate the view that rational belief is sensitive to higher-order defeat.

We often have reason to doubt our own ability to form rational beliefs, or to doubt that some particular belief of ours is rational. Perhaps we learn that a trusted friend disagrees with us about what our shared evidence supports. Or perhaps we learn that our beliefs have been afflicted by motivated reasoning or other cognitive biases. These are examples of higher-order evidence. While it may seem plausible that higher-order evidence should impact our beliefs, it is less clear how and why. Normally, when evidence impacts our beliefs, it does so by virtue of speaking for or against the truth of theirs contents. But higher-order evidence does not directly concern the contents of the beliefs that they impact. In recent years, philosophers have become increasingly aware of the need to understand the nature and normative role of higher-order evidence. This is partly due to the pervasiveness of higher-order evidence in human life. But it has also become clear that higher-order evidence plays a central role in many epistemological debates, spanning from traditional discussions of internalism/externalism about epistemic justification to more recent discussions of peer disagreement and epistemic akrasia. This volume brings together, for the first time, a distinguished group of leading and up-and-coming epistemologists to explore a range of issues about higher-order evidence.

Evidentialism is the thesis, roughly, that one’s beliefs should fit one’s evidence. The enkratic principle is the thesis, roughly, that one’s beliefs should "line up" with one’s beliefs about which beliefs one ought to have. While both theses have seemed attractive to many, they jointly entail the controversial thesis that self-misleading evidence is impossible. That is to say, if evidentialism and the enkratic principle are both true, one’s evidence cannot support certain false beliefs about which beliefs one’s evidence supports. Recently, a number of epistemologists have challenged the thesis that self-misleading evidence is impossible on the grounds that misleading higher-order evidence does not have the kind of strong and systematic defeating force that would be needed to rule out the possibility of such self-misleading evidence. Here I respond to this challenge by proposing an account of higher-order defeat that does, indeed, render self-misleading evidence impossible. Central to the proposal is the idea that higher-order evidence acquires its normative force by influencing which conditional beliefs it is rational to have. What emerges, I argue, is an independently plausible view of higher-order evidence, which has the additional benefit of allowing us to reconcile evidentialism with the enkratic principle.

In this paper, we present a new semantic framework designed to capture a distinctly cognitive or epistemic notion of meaning akin to Fregean senses. Traditional Carnapian intensions are too coarse-grained for this purpose: they fail to draw semantic distinctions between sentences that, from a Fregean perspective, differ in meaning. This has led some philosophers to introduce more fine-grained hyperintensions that allow us to draw semantic distinctions among co-intensional sentences. But the hyperintensional strategy has a flip-side: it risks drawing semantic distinctions between sentences that, from a Fregean perspective, do not differ in meaning. This is what we call the ‘new problem’ of hyperintensionality to distinguish it from the ‘old problem’ that faced the intensional theory. We show that our semantic framework offers a joint solution to both these problems by virtue of satisfying a version of Frege’s so-called ‘equipollence principle’ for sense individuation. Frege’s principle, we argue, not only captures the semantic intuitions that give rise to the old and the new problem of hyperintensionality, but also points the way to an independently motivated solution to both problems.

Titelbaum Oxford studies in epistemology, 2015) has recently argued that the Enkratic Principle is incompatible with the view that rational belief is sensitive to higher-order defeat. That is to say, if it cannot be rational to have akratic beliefs of the form “p, but I shouldn’t believe that p,” then rational beliefs cannot be defeated by higher-order evidence, which indicates that they are irrational. In this paper, I distinguish two ways of understanding Titelbaum’s argument, and argue that neither version is sound. The first version can be shown to rest on a subtle, but crucial, misconstrual of the Enkratic Principle. The second version can be resisted through careful consideration of cases of higher-order defeat. The upshot is that proponents of the Enkratic Principle are free to maintain that rational belief is sensitive to higher-order defeat.

The traditional possible-worlds model of belief describes agents as ‘logically omniscient’ in the sense that they believe all logical consequences of what they believe, including all logical truths. This is widely considered a problem if we want to reason about the epistemic lives of non-ideal agents who—much like ordinary human beings—are logically competent, but not logically omniscient. A popular strategy for avoiding logical omniscience centers around the use of impossible worlds: worlds that, in one way or another, violate the laws of logic. In this paper, we argue that existing impossible-worlds models of belief fail to describe agents who are both logically non-omniscient and logically competent. To model such agents, we argue, we need to ‘dynamize’ the impossible-worlds framework in a way that allows us to capture not only what agents believe, but also what they are able to infer from what they believe. In light of this diagnosis, we go on to develop the formal details of a dynamic impossible-worlds framework, and show that it successfully models agents who are both logically non-omniscient and logically competent.

The debate on the epistemology of disagreement has so far focused almost exclusively on cases of disagreement between individual persons. Yet, many social epistemologists agree that at least certain kinds of groups are equally capable of having beliefs that are open to epistemic evaluation. If so, we should expect a comprehensive epistemology of disagreement to accommodate cases of disagreement between group agents, such as juries, governments, companies, and the like. However, this raises a number of fundamental questions concerning what it means for groups to be epistemic peers and to disagree with each other. In this paper, we explore what group peer disagreement amounts to given that we think of group belief in terms of List and Pettit’s ‘belief aggregation model’. We then discuss how the so-called ‘equal weight view’ of peer disagreement is best accommodated within this framework. The account that seems most promising to us says, roughly, that the parties to a group peer disagreement should adopt the belief that results from applying the most suitable belief aggregation function for the combined group on all members of the combined group. To motivate this view, we test it against various intuitive cases, derive some of its notable implications, and discuss how it relates to the equal weight view of individual peer disagreement.

While many philosophers have agreed that evidence of disagreement is a kind of higher-order evidence, this has not yet resulted in formally precise higher-order approaches to the problem of disagreement. In this paper, we outline a simple formal framework for determining the epistemic significance of a body of higher-order evidence, and use this framework to motivate a novel interpretation of the popular “equal weight view” of peer disagreement—we call it the Variably Equal Weight View (VEW). We show that VEW differs from the standard Split the Difference (SD) interpretation of the equal weight view in almost all cases of peer disagreement, and use our formal framework to explain why SD has seemed attractive but is in fact misguided. A desirable feature of VEW, we argue, is that it gives rise to plausible instances of synergy—an effect whereby the parties to a disagreement should become more (or less) confident in the disputed proposition than any of them were prior to disagreement. Lastly, we show how VEW may be generalized to cases of non-peer disagreement.

Epistemic logics based on the possible worlds semantics suffer from the problem of logical omniscience, whereby agents are described as knowing all logical consequences of what they know, including all tautologies. This problem is doubly challenging: on the one hand, agents should be treated as logically non-omniscient, and on the other hand, as moderately logically competent. Many responses to logical omniscience fail to meet this double challenge because the concepts of knowledge and reasoning are not properly separated. In this paper, I present a dynamic logic of knowledge that models an agent’s epistemic state as it evolves over the course of reasoning. I show that the logic does not sacrifice logical competence on the altar of logical non- omniscience.

One well-known objection to the traditional Lewis-Stalnaker semantics of counterfactuals is that it delivers counterintuitive semantic verdicts for many counterpossibles (counterfactuals with necessarily false antecedents). To remedy this problem, several authors have proposed extending the set of possible worlds by impossible worlds at which necessary falsehoods may be true. Linguistic ersatz theorists often construe impossible worlds as maximal, inconsistent sets of sentences in some sufficiently expressive language. However, in a recent paper, Bjerring (2014) argues that the “extended” Lewis-Stalnaker semantics delivers the wrong truth-values for many counterpossibles if impossible worlds are required to be maximal. To make room for non-maximal or partial impossible worlds, Bjerring considers two alternative world-ontologies: either (i) we construe impossible worlds as arbitrary (maximal or partial) inconsistent sets of sentences, or (ii) we construe them as (maximal or partial) inconsistent sets of sentences that are closed and consistent with respect to some non-classical logic. Bjerring raises an objection against (i), and suggests that we opt for (ii). In this paper, I argue, first, that Bjerring’s objection against (i) conflates two different conceptions of what it means for a logic to be true at a world. Second, I argue that (ii) imposes too strong constraints on what counts as an impossible world. I conclude that linguistic ersatzists should construe impossible worlds as arbitrary (maximal or partial) inconsistent sets of sentences.