Two theses are central to recent work on the epistemology of disagreement: Equal Weight (‘EW’): In cases of epistemic peer disagreement, one should give equal weight to the attitude of a peer and to one’s own attitude.1 Uniqueness (‘U’): For any given proposition and total body of evidence, some doxastic attitude is the one the evidence makes rational (justifies) toward that proposition.

: There are many reasons why scientific experts may mask disagreement and endorse a position publicly as "jointly accepted." In this paper I consider the inner workings of a group of scientists charged with deciding not only a technically difficult issue, but also a matter of social and political importance: the maximum acceptable dose of radiation. I focus on how, in this real world situation, concerns with credibility, authority, and expertise shaped the process by which this group negotiated the competing (...) virtues of reaching consensus versus reporting accurately the nature and degree of disagreement among them. (shrink)

This paper analyses conceptual change. A rejection of pure experience has prompted philosophers of science to adopt a certain perspective from which to view changes of belief. Popper, Kuhn, and others have analysed conceptual change in terms of problems or anomalies, that is, in terms of contingent reasoning about issues posed in the context of an inherited web of belief. This paper explores a more general analysis of conceptual change in dialogue with these philosophers of science. Because changes of belief (...) are not all changes in scientific belief, we seek to unpack conceptual change in terms of dilemmas, as opposed to anomalies or problems. For a start, the notion of a dilemma has to be broader than that of an anomaly since it purports to apply to conceptual change as a whole, not just the transition from one era of normal science to another. In addition, we should detach the notion of a dilemma from the objectivism of Popper's world-3 problems. (shrink)

How much should your confidence in your beliefs be shaken when you learn that others – perhaps 'epistemic peers' who seem as well-qualified as you are – hold beliefs contrary to yours? This article describes motivations that push different philosophers towards opposite answers to this question. It identifies a key theoretical principle that divides current writers on the epistemology of disagreement. It then examines arguments bearing on that principle, and on the wider issue. It ends by describing some outstanding questions (...) that thinking about this issue raises. (shrink)

To appear in Richard Feldman and Ted Warfield (eds.) Disagreement, forthcoming from Oxford University Press.

1. The Question, and Some Preliminaries Suppose you trust someone – call him Adam – to be your epistemic peer with regard to a certain topic, for instance philosophy. If asked to evaluate the probability of you giving a correct answer to an unspecified philosophical question and the probability of Adam doing so, you give roughly the same answer. You treat Adam as your philosophical peer (and for now we can safely assume that he is indeed your peer, and that (...) you are justified in so treating him). You then find out that you disagree with Adam about a given philosophical question – for some philosophical p, you believe p, and Adam believes not- p. How should you update your belief with regard to p given this further evidence (Adam's view regarding p)? Should you be less confident now in p than you were before finding out about Adam’s view? If so, how much less confident? One natural reply is the Equal Weight View, according to which you should give equal weight to your belief and to that of the one you take to be your peer, and so in our case suspend judgment about p. Adam Elga’s (2007, 490) official presentation of the view – more precise and general than as just stated – runs, for instance, as follows1. (shrink)

Suppose two agents, S1 and S2, are epistemic peers regarding a proposition p: that is, suppose S1 and S2 are equally competent, equally impartial, and equally able to evaluate and assess the relevant evidence regarding p (we will call such propositions p peer-propositions for S1 and S2). After carefully reflecting on the salient evidence for p, suppose S1 and S2 discover that they disagree about p. For instance, S1 might believe the defendant is guilty, while S2 believes the defendant is (...) innocent. Or S1 might believe that free will and determinism are incompatible, while S2 believes that the two views are compatible. More generally, S1 and S2 might assign different credences to p. Examples of peer disagreement (in each of these senses) are common in everyday life, in philosophy, and in many other disciplines. (shrink)

The epistemological consequences of paradox are paradoxical. They can be usefully generated by telling a series of once-upon-a-time stories that make various philosophical points, starting out innocent and ending up, well, paradoxical.

What should you do when you discover that someone firmly disagrees with you on some claim? Suppose you know that someone has seen all your evidence and you’ve seen all hers. Suppose further that you know that both of you have evaluated that common body of evidence for about the same length of time. You also know that she’s about as clever, thorough, and open-minded as you are, both generally and with respect to the issues at hand. You know that (...) you have about the same relevant biases. At this point, before you find out her opinion on some claim P relevant to the topic, you fully admit that you can’t think of any epistemic advantage you have over her when it comes to the topic in question; you admit that she’s just as likely to get P’s truth-value right as you are (whether or not you’re right about that won’t matter). Let’s say that under these conditions she is your recognized epistemic peer with regard to P (I’ll relax some of these conditions below). And then after learning all this about her you find out that she thinks P is false, whereas you had already concluded to yourself that P is true. (shrink)

Many of the best philosophers endorse purely philosophical error theories, theories that do not have much empirical support and reject large swaths of our most commonsensical beliefs. Often enough those of us who are philosophers of average abilities know full well that we are no experts on the topics in question even though we think all the admittedly superior philosophers are wrong. I argue that in this situation either (a) the average philosopher’s true commonsensical beliefs don’t amount to knowledge, or (...) (b) a large portion of philosophy is bunk even though its arguments are no worse than those in non-bunk areas of philosophy, and knowledge is not an epistemically impressive state. In sum: we can conclude that either novel kinds of radical skepticism are contingently true or in a real sense we know that knowledge isn’t impressive and large portions of philosophy are bunk despite being argumentatively and evidentially as good as or superior to other areas of philosophy. (shrink)

Philosophers often find themselves in disagreement with contemporary philosophers they know full well to be their epistemic superiors on the topics relevant to the disagreement. This looks epistemically irresponsible. I offer a detailed investigation of this problem of the reflective epistemic renegade. I argue that although in some cases the renegade is not epistemically blameworthy, and the renegade situation is significantly less common than most would think, in a troublesome number of cases in which the situation arises the renegade is (...) blameworthy in her disagreement with recognized epistemic superiors. I also offer some thoughts on what it would mean for philosophical practice for us to refrain from being renegades. Finally, I show how a new kind of radical skepticism emerges from modest theses regarding the renegade. (shrink)

This is a short essay that presents what I take to be the main questions regarding the epistemology of disagreement.

Those of us who take skepticism seriously typically have two relevant beliefs: (a) it’s plausible (even if false) that in order to know that I have hands I have to be able to epistemically neutralize, to some significant degree, some skeptical hypotheses, such as the brain-in-a-vat (BIV) one; and (b) it’s also plausible (even if false) that I can’t so neutralize those hypotheses. There is no reason for us to also think (c) that the BIV hypothesis, for instance, is plausible (...) or probably true. In order to take skepticism seriously it’s sufficient to hold (a) and (b); one need not hold (c). Indeed, philosophers who accept (a) and (b) never endorse (c). Show me a philosopher who suspects that he is a brain in a vat and I’ll show you someone who is deranged! That’s one thing that bothers undergraduates in philosophy. They object: why on earth do some philosophers take the BIV hypothesis to pose any threat at all to our beliefs given that those very same philosophers think that there’s no real chance that the BIV hypothesis is true? Sure, the BIV hypothesis is formally inconsistent with my belief that I have hands, so if the former is true then my belief is false. But so what? Why should that bare inconsistency matter so much? Is this strange attitude amongst philosophers the result of some logic fetish infecting the philosophical community? It is sometimes said that the skeptical hypotheses are not only inconsistent with our beliefs but are explanatory of our experiences, which is supposed to make them more of a threat. But students aren’t fooled: although the skeptical hypotheses may attempt to explain why our experience is as it is, it’s the kind of attempt appropriate for science fiction movies that are all special effects and virtually no plot. No one with any sense of reality will take the evil demon hypothesis to be even tenuously explanatory. (shrink)

We all can identify many contemporary philosophy professors we know to be theists of some type or other. We also know that often enough their nontheistic beliefs are as epistemically upstanding as the non-theistic beliefs of philosophy professors who aren’t theists. In fact, the epistemic-andnon-theistic lives of philosophers who are theists are just as epistemically upstanding as the epistemic-and-non-theistic lives of philosophers who aren’t theists. Given these and other, similar, facts, there is good reason to think that the pro-theistic beliefs (...) of theistic philosophers are frequently epistemically upstanding. Given their impeccable epistemic credentials on non-theistic matters, the amount of careful thought that lies behind their theism, the large size of the community of philosophical theists, as well as other, similar facts, it would be surprising if all or even most of their pro-theistic beliefs were epistemically blameworthy in some or other significant sense tied to charges such as ‘He should know better than to believe that’ (so mere false belief need not be blameworthy in this sense; the use of ‘blameworthy’ will be clarified below). Of course some of the pro-theistic beliefs of some theistic philosophers are epistemically blameworthy; the mere large numbers of fallible theistic philosophers almost guarantees it. My point here is that it would be unexpected if most of the pro-theistic beliefs of theistic philosophers were epistemically blameworthy. (shrink)

I’m going to argue for a set of restricted skeptical results: roughly put, we don’t know that fire engines are red, we don’t know that we sometimes have pains in our lower backs, we don’t know that John Rawls was kind, and we don’t even know that we believe any of those truths. However, people unfamiliar with philosophy and cognitive science do know all those things. The skeptical argument is traditional in form: here’s a skeptical hypothesis; you can’t epistemically neutralize (...) it, you have to be able to neutralize it to know P; so you don’t know P. But the skeptical hypotheses I plug into it are “real, live” scientific-philosophical hypotheses often thought to be actually true, unlike any of the outrageous traditional skeptical hypotheses (e.g., ‘You’re a brain in a vat’). So I call the resulting skepticism Live Skepticism. Notably, the Live Skeptic’s argument goes through even if we adopt the clever anti-skeptical fixes thought up in recent years such as reliabilism, relevant alternatives theory, contextualism, and the rejection of epistemic closure. Furthermore, the scope of Live Skepticism is bizarre: although we don’t know the simple facts noted above, many of us do know that there are black holes and other amazing facts. (shrink)

I once overheard a telling conversation between two of my colleagues. One asked the other about a new book on a topic of some importance to both of them. He asked whether they would have to do anything different because of the book. The second colleague said not, so the first colleague said he would not read the book. The conversation encapsulates an excellent test of the worth of a philosophical work: an idea is important if as a result of (...) it experts will have to change what they do when they work on the idea’s topic. It’s not good enough to be right, or to choose an important topic, or to choose a topic of contemporary interest, or to be original; it isn’t even enough to have all of those qualities. I know now that much of the work I have done, especially as a graduate student, failed that test—even work that found its way into leading philosophy journals. (shrink)

Academic debates are so frequent and omnipresent in most disciplines, particularly the social sciences and humanities, it seems obvious that disagreements are bound to occur. The aim of this paper is to show that whereas the agent who perceives his/her contribution as being misunderstood locates the origin of the communication problem on the side of the receiver who "misinterprets" the text, the emitter is in fact also contributing to the possibility of this misunderstanding through the very manner in which his/her (...) text is written. In other words, I propose a symmetric approach to understanding misunderstandings: taking simultaneously into account the position of the reader in the scientific field and the structure of the texts of the writers. The paper thus proposes to complement the sociological analysis of controversies in a scientific field with the close reading of texts, a practice usually found in studies of argumentation, in order to explain the occurrence of misunderstandings. The debate surrounding the charge of "relativism" among sociologists of scientific knowledge provides us with a case study to analyse in detail the argumentative context of misunderstanding. (shrink)

The following three propositions appear to be individually defensible but jointly inconsistent: (1) reliability is a necessary condition on epistemic justification; (2) on contested matters in philosophy, my beliefs are not reliably formed; (3) some of these beliefs are epistemically justified. I explore the nature and scope of the problem, examine and reject some candidate solutions, compare the issue with ones arising in discussions about disagreement, and offer a brief assessment of our predicament.

But is it not possible, that men who really love truth, and are open to conviction, may differ about first principles? I think it is possible, and that it cannot, without great want of charity, be denied to be possible. (Thomas Reid, Essays on the Intellectual Powers of Man, Essay 6, Chapter..

My aim in this paper is to develop and defend a novel answer to a question that has recently generated a considerable amount of controversy. The question concerns the normative significance of peer disagreement. Suppose that you and I have been exposed to the same evidence and arguments that bear on some proposition: there is no relevant consideration which is available to you but not to me, or vice versa. For the sake of concreteness, we might picture..

Suppose that you and I disagree about some non-straightforward matter of fact (say, about whether capital punishment tends to have a deterrent effect on crime). Psychologists have demonstrated the following striking phenomenon: if you and I are subsequently exposed to a mixed body of evidence that bears on the question, doing so tends to increase the extent of our initial disagreement. That is, in response to exactly the same evidence, each of us grows increasingly confident of his or her original (...) view; we thus become increasingly polarized as our common evidence increases. I consider several alternative models of how people reason about newly-acquired evidence which seems to disconfirm their prior beliefs. I then explore the normative implications of these models for the phenomenon in question. (shrink)

Looking back on it, it seems almost incredible that so many equally educated, equally sincere compatriots and contemporaries, all drawing from the same limited stock of evidence, should have reached so many totally different conclusions—and always with complete certainty.

Contemporary Western culture is experiencing a heightened awareness of religious diversity. This article surveys a range of possible responses to such diversity, and distinguishes between responses that concern the salvation or moral transformation of persons (soteriological views) and those that concern the alethic or epistemic status of religious beliefs (doctrinal views). After providing a brief taxonomy of these positions and their possible relations to one another, the article focuses primarily on competing views about the truth and rationality of religious beliefs (...) (e.g., pluralism, exclusivism, and skepticism). Here a heavy emphasis is placed on arguments for and against the rationality and moral propriety of retaining one's religious beliefs in the face of disagreement. The article surveys some of the more prominent arguments from the literature on this topic and closes with suggestions for further research. (shrink)

This paper assesses the comparative reliability of two beliefrevision rules relevant to the epistemology of disagreement, the Equal Weight and Stay the Course rules. I use two measures of reliability for probabilistic belief-revision rules, Calibration and Brier Scoring, to give a precise account of epistemic peerhood and epistemic reliability. On the Calibration measure of reliability, epistemic peerhood is easy to come by, and employing the Equal Weight rule in the case of peer disagreement generally renders you less reliable than Staying (...) the Course. On the Brier-Score measure of reliability, epistemic peerhood is much more difficult to come by, but employing the Equal Weight rule in the case of peer disagreement always renders you more reliable than Staying the Course. I conclude with some lessons we can draw from these formal results for the normative issue of rational belief-change in the face of peer disagreement, foreshadowing part II of my work on this topic, “On the Rationality of Belief-Invariance in Light of Peer Disagreement.”. (shrink)

This paper considers two questions. First, what is the scope of the Equal Weight View? Is it the case that meeting halfway is the uniquely rational method of belief-revision in all cases of known peer disagreement? The answer is no. It is sometimes rational to maintain your own opinion in the face of peer disagreement. But this leaves open the possibility that the Equal Weight View is indeed sometimes the uniquely rational method of belief revision. Precisely what is the skeptical (...) import of this fact; is it the case that some form of skepticism triumphs in such cases? The answer to this question is also no. As it turns out, the situations in which it is most plausible that the Equal Weight view is a rational requirement are the ones in which meeting halfway with a disagreeing peer brings you closer to, and not farther from, knowledge. I argue for these theses in a novel way; by looking at the comparative reliability of belief-invariance and meeting halfway using measures of reliability for degrees of belief, and by drawing normative conclusions from such results. The conclusions here can have the effect of reframing the entire debate in the epistemology of disagreement. (shrink)

In this article I argue that the prevalence of intersubjective disagreement in epistemology poses a serious problem for Epistemic Externalism. I put the problem in the form of a dilemma: either Epistemic Externalism is not a complete account of epistemic justification or it’s implausible to claim that the belief that Epistemic Externalism is true is itself an externalistically justified belief.

Conciliatory views of disagreement maintain that discovering a particular type of disagreement requires that one make doxastic conciliation. In this paper I give a more formal characterization of such a view. After explaining and motivating this view as the correct view regarding the epistemic significance of disagreement, I proceed to defend it from several objections concerning higher-order evidence (evidence about the character of one’s evidence) made by Thomas Kelly (2005).

As Hammond has argued, traditional explanations for disagreement among experts (incompetence, venality, and ideology) are inadequate. The character and fallibilities of the human judgement process itself lead to persistent disagreements even among competent, honest, and disinterested experts. Social Judgement Theory provides powerful methods for analysing such judgementally based disagreements when the experts' judgement processes can be represented by additive models involving the same cues. However, the validity and usefulness of such representations depend on several conditions: (a) experts must agree on (...) a problem definition, (b) experts must have access to the same information, and (c) experts must use the same organising principles. When these conditions are not met, methods for diagnosing and treating disagreement are poorly understood. As a start towards developing such an understanding, sources of expert disagreement are discussed and categorised. (shrink)

I introduce an alternative framework for thinking about peer disagreement -- one that distinguishes sharply between epistemic rationality and evidential support. I then defend the view that conciliationism provides the right answer to, "What credences is it rational to adopt in cases of peer disagreement?" and that non-conciliationism provides the right answer to, "What credences does the evidence support in cases of peer disagreement?" I then spend the second half of the paper applying some distinctions within rationality -- global vs. (...) local rational norms, wide-scope vs. narrow-scope rational norms -- to a defense of conciliationism against recent challenges by Tom Kelly and Brian Weatherson. I conclude by introducing what I think is an underdiscussed problem but a potentially fruitful one to think about: what is it rational to do relative to a set of mental states, some of which are beliefs or credences about rationality itself?

NOTE: Not only is the content rough, but I couldn't get the thing to upload without "blanking out" parts of some of the pages. Overall, it's still pretty readable, but e-mail me if you want a better copy. (shrink)

This paper is about the question of what to do under fundamental normative uncertainty. More specifically, it is about a problem that seems to confront all of the plausible answers to that question -- that it is impossible to compare the values of actions across different normative views or theories. I present a solution to that problem in 3 stages.

Comments EXTREMELY welcome.

The proportional weight view in epistemology of disagreement generalizes the equal weight view and proposes that we assign to judgments of different people weights that are proportional to their epistemic qualifications. It is shown that if the resulting degrees of confidence are to constitute a probability function, they must be the weighted arithmetic means of individual degrees of confidence, while if the resulting degrees of confidence are to obey the Bayesian rule of conditionalization, they must be the weighted geometric means (...) of individual degrees of confidence. The double bind entails that the proportional weight view (and its moderate adjustment in favor of one’s own judgment) is inconsistent with Bayesianism. (shrink)

We begin with a subsidiary question: Is reasonable disagreement ever possible? Opposing answers to one and the same question can both be reasonable, of course, if at least one of them is based on evidence that is persuasive but misleading. This much is uncontroversial. In a more interesting case, Pro and Con share all their evidence. Can they still assess the shared evidence differently? Can one affirm what the other denies, though each proceeds reasonably enough? For each to be reasonable, (...) each needs positive justification. Unlike ethics, epistemology repels arbitrariness. Facing a choice between bringing it about that p and bringing it about that not-p, you may have no sufficient reason to prefer either over the other, in which case you might well be free to take your pick. That’s how it is for practical choices or actions. By contrast, with no more reason for believing either a proposition or its negation in preference to the other, you are definitely not free to proceed either way. Here you must withhold, if you are to proceed reasonably at all, epistemically. If two opponents are both to be reasonable, then, each needs a balance of reason favoring his side.[2] But is this compatible with their sharing all of their evidence? Not if any reason they may have, for or against believing, would have to be found in the evidence that they share. We are supposing they share all their evidence. Since the evidence cannot point in two opposite directions at once, Pro and Con cannot each have substantial positive reason for affirming what the other denies. Based on such reasoning, you may well conclude that reasonable disagreement with full disclosure is just impossible. But others will no doubt disagree. Suppose you all pool your evidence, and they remain unimpressed. On one view with substantial support in the literature, if you encounter opposition from an apparent peer, then, absent independent reason to downgrade him, you must lower your confidence, perhaps below the threshold of belief.. (shrink)

How to regard the weight we give to a proposition on the grounds of its being endorsed by an authority? I examine this question as it is raised within the epistemology of science, and I argue that “authority-based weight” should receive special handling, for the following reason. Our assessments of other scientists’ competence or authority are nearly always provisional, in the sense that to save time and money, they are not made nearly as carefully as they could be—indeed, they are (...) typically made on the basis of only a small portion of the available evidence. Consequently, we need to represent the authority-based elements of our epistemic attitudes in such a way as to allow the later revision of those elements, in case we decide in the light of new priorities that a more conscientious assessment is warranted. I look to the literature in confirmation theory, statistics, and economics for a semiformal model of this revision process, and make a particular proposal of my own. The discussion also casts some light on the question of why certain aspects of science’s epistemic state are not made public. (shrink)

Can known disagreement with our epistemic peers undermine or defeat the justification our beliefs enjoy? Much of the current literature argues for one of two extreme positions on this topic, either that the justification of each person's belief is (fully) defeated by the awareness of disagreement, or that no belief is defeated by this awareness. I steer a middle course and defend a principle describing when a disagreement yields a partial defeater, which results in a loss of some, but not (...) all, of the justification of a belief. I show that the 'no defeater' view is too strong. I also offer reasons for thinking that the 'full defeater' view is similarly mistaken. (shrink)

I argue with my friends a lot. That is, I offer them reasons to believe all sorts of philosophical conclusions. Sadly, despite the quality of my arguments, and despite their apparent intelligence, they don’t always agree. They keep insisting on principles in the face of my wittier and wittier counterexamples, and they keep offering their own dull alleged counterexamples to my clever principles. What is a philosopher to do in these circumstances? (And I don’t mean get better friends.) One popular (...) answer these days is that I should, to some extent, defer to my friends. If I look at a batch of reasons and conclude p, and my equally talented friend reaches an incompatible conclusion q, I should revise my opinion so I’m now undecided between p and q. I should, in the preferred lingo, assign equal weight to my view as to theirs. This is despite the fact that I’ve looked at their reasons for concluding q and found them wanting. If I hadn’t, I would have already concluded q. The mere fact that a friend (from now on I’ll leave off the qualifier ‘equally talented and informed’, since all my friends satisfy that) reaches a contrary opinion should be reason to move me. Such a position is defended by Richard Feldman (2006a, 2006b), David Christensen (2007) and Adam Elga (forthcoming). This equal weight view, hereafter EW, is itself a philosophical position. And while some of my friends believe it, some of my friends do not. (Nor, I should add for your benefit, do I.) This raises an odd little dilemma. If EW is correct, then the fact that my friends disagree about it means that I shouldn’t be particularly confident that it is true, since EW says that I shouldn’t be too confident about any position on which my friends disagree. But, as I’ll argue below, to consistently implement EW, I have to be maximally confident that it is true. So to accept EW, I have to inconsistently both be very confident that it is true and not very confident that it is true. This seems like a problem, and a reason to not accept EW.. (shrink)

Moral disagreement has long been thought to create serious problems for certain views in metaethics. More specifically, moral disagreement has been thought to pose problems for any metaethical view that rejects relativism—that is, for any view that implies that whenever two thinkers disagree about a moral question, at least one of those thinkers’ beliefs about the question is not correct. In this essay, I shall outline a solution to one of these problems. As I shall argue, it turns out in (...) the end that this problem is not really a special problem about moral disagreement at all: it is a general problem about disagreement as such. For this reason, in the later sections of this essay, I shall turn to some general questions in epistemology, about the epistemic significance of disagreement. (shrink)

How should we respond to cases of disagreement where two epistemic agents have the same evidence but come to different conclusions? Adam Elga has provided a Bayesian framework for addressing this question. In this paper, I shall highlight two unfortunate consequences of this framework, which Elga does not anticipate. Both problems derive from a failure of commutativity between application of the equal weight view and updating in the light of other evidence.