Disagreement Bryan Frances Revised version in Routledge Companion to Epistemology, Duncan Pritchard and Sven Bernecker editors, 2010 What should you do when you discover that someone firmly disagrees with you on some claim P? Suppose you know that someone has seen all your evidence and you have 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 and with the same care. You also know that she is 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 P, you fully admit that you cannot think of any epistemic advantage you have over her when it comes to the topic in question; you admit that she is just as likely to get P's truth-value right as you are. Let us say that under these conditions she is your recognized epistemic peer with regard to P (I will 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. Two conflicting responses immediately suggest themselves. First, there is the thought that respectful disagreement is quite common and should be expected among intelligent, reflective people. We all know that everyone makes many mistakes, so there is nothing at all odd in thinking that the one who disagrees with you has just made a mistake this time around. But second, why should you think that your cranium is any more accurate than another's-especially since you just admitted that you have no epistemic advantage over her, that she is just as likely as you to get P's truth-value right (on trust see Foley 2001)? When you take a "third-person view" of the matter, all you see are two people who are equally placed to determine P's truth-value, and so you should see no reason to think that one of them (viz. you) are the one who got things right this time around. 2 Here is another interesting case. I initially believe P but then learn about the famous Professor Smith. I fully admit that she is a genius and knows much more than I do about the issues relevant to P. I know that she has all my evidence if not much more. I also know that she is smarter than I am and has thought about and investigated P much more than I have. I know full well that when it comes to the topics germane to P she is not my peer but significantly exceeds me. Prior to finding out her opinion on P, I would have insisted that she is much more likely than I am to get P's truth-value right. Let us say that under these conditions she is my recognized epistemic superior with regard to P. Then I find out that she firmly believes ~P. In this case, it seems as though you would be pretty foolish to not significantly diminish your confidence in P's truth. And yet, if this reasoning were right could we have any epistemically responsible yet even slightly controversial beliefs? The application to philosophical belief is particularly interesting (see Goldberg 2009, Frances 2005a, Frances forthcoming A, and Fumerton 2010). There are many philosophers who are genuine experts on material composition who flatly deny that baseballs and other ordinary composite things exist. Other philosophers truly believe that there are no beliefs. Some believe that nothing is morally wrong (or right). Many think that fire engines aren't red (or any other color). Some of these philosophers are among the best in the world. They look at the evidence as carefully and expertly and competently as anyone, and then contravene common sense. And often enough their claims are based on mostly a posteriori evidence and have the endorsement of some expert scientists (e.g., error theories about color or character traits). So when faced with their opinion are we supposed to suspend judgment on the claims that fire engines are red-or even that they exist? I have described just two kinds of disagreement cases: the recognized extreme peer one and the recognized superior genius one. But there is a whole range of philosophically interesting cases of disagreement, which can be introduced in the following illuminating way. I say to myself that P is true, where P might concern any subject matter. In case 1 my five-year-old daughter says ~P. I'm not too worried that I might be mistaken. The fact that she disagrees with me gives me no good reason to doubt my belief. In case 2 a sharp undergraduate who majors in the relevant subject matter says ~P. Provided I know that I know the subject matter significantly better than undergraduates I'm still not too worried that my belief in P is mistaken. In case 3 I discover that one of my colleagues says ~P-but I don't know any details regarding what evidence she has seen or how long she has investigated the matter; all I know is that she is generally about as sharp and careful as I am. This discovery gives me 3 pause. In case 4 I discover that one of my recognized epistemic peers regarding P and the topics surrounding P says that ~P. Now I'm more worried but not mortified. In case 5 a large group of people I recognize to be genii on the topic all announce that they firmly believe ~P for a variety of reasons and have done so for many years. Now I'm feeling pretty insecure in my belief in P. In case 6 I die, knowingly come face to face with the infallible and truth-telling God, and He says that the truth is definitely ~P. At this point only an idiot would retain his belief in P. Surely at this point I have to admit I was wrong-or at least withhold judgment! It seems that there is a scale of degree of blameworthiness. With the five-year-old, I'm not blameworthy in persisting with my belief (degree zero); with God I'm an idiot if I retain my belief (the highest degree of blameworthiness). Our issue is whether people in the various "middle" situations, cases 2-5 as well as similar ones, are in a bad enough position among this scale to be blameworthy. Epistemologists have just begun to thoroughly explore these and similar cases, with the main works on the topic published in just the last few years (on the epistemic peer cases, see: Christensen 2007; Elga 2007; Feldman 2005, 2006, 2007; Kelly 2006, 2008; on the epistemic superior cases, see Frances 2010).). Often the best way to introduce a new topic is to articulate what one takes to be some of the central questions concerning that topic. That is the approach I'll take here, focusing primarily on recognized peers and recognized superiors. 1. In what situations, if any, in which I have discovered a disagreement with a recognized epistemic peer or superior (or one of the other "middle" situations) am I epistemically permitted to not at all alter my confidence in my belief in P? Under what conditions can I "stick to my guns"? 2. When I am not epistemically permitted to retain my confidence level in P, how is my confidence level supposed to change in response to the discovery of disagreement? (Disagreement isn't always one person believing P while another believes ~P: all we need are different levels of confidence in P's truth.) For instance, do I have to suspend judgment on P or can I merely lower my confidence in P a bit? If the latter, what factors dictate what my new level of confidence in P must be? Moreover, consider two cases. In each I'm fairly confident in P but not certain. In the first case the person who disagrees with me says that she is about as confident in P's falsehood as I am in its truth. In the second case everything is as it was in the first case except she says she is completely certain that P is false. If I am required in the first case to lower my confidence in P, 4 am I required to lower my confidence even more in the second case? And how does the level of expertise of the ~P proponent figure in to what I'm supposed to do (e.g., I know that she's a peer, I know that she's a genius, etc.)? Generally speaking, will there be mathematical epistemic principles governing how my confidence levels should change (see White 2005 for discussion)? 3. When I am epistemically required to alter my confidence in P, what has happened to the epistemic characteristics of my belief that makes this alteration required? For instance, when I learn that the peer or superior disagrees with me, has my level of overall warrant decreased enough that I am no longer warranted to have my previous confidence level-where warrant is what needs to be added to true belief in order for it to become knowledge? Or is it that my level of justification was lowered enough that my previous confidence level would be unjustified-where justification is the thing that is present in Gettier cases but insufficient for true belief to amount to knowledge? Or do I have to lower my confidence level for some other reason entirely? 4. Does it matter who was on the right track in the first place? For instance, suppose I have made some epistemological blunder in coming to believe P, whereas my opponent has not (whether or not P happens to be true). Do these facts regarding the epistemic statuses of our past matter to what we are supposed to do in reacting to the present discovery of the disagreement? 5. When I am epistemically required to alter my confidence in P, am I also required to alter the way I behave regarding whether P is true? Can I still act on the assumption that P is true or must I do something different? And might moral principles come into play here? For instance, if I'm epistemically permitted to not alter my confidence in P, might I nevertheless have a moral obligation to act differently regarding P-perhaps due to a moral obligation to respect others and, if the conditions are right, their opinions? In fact, might I have a moral obligation to not just act differently but alter my confidence in P-so a moral obligation gives birth to an epistemological one? 6. Does it matter what topics the disagreement is about? For instance, are the principles governing how we need to react to disagreements in science different from those regarding morals, religion, philosophy, or art (for the case of religion see van Inwagen 1996, Feldman 5 2007, and McKim 2001)? Or is it rather that different data gets plugged into the same disagreement principles? Furthermore, will it matter how difficult or simple the question 'Is P true?' is (e.g., 'Is there dark matter?' vs. 'What is 56 x 7?')? Finally, what about disagreements concerning how we should respond to disagreement itself? Will plausible principles regarding how we should respond to disagreement generate paradoxical results when applied to disagreements among epistemologists over those principles themselves (think of the trouble from "revenge sentences" concerning the liar paradox or verificationist principles about meaning applied to themselves)? 7. In the recognized peer case I started out with the view that my peer was just as likely as me to get P's truth-value right. I also began with the idea that we had seen the same evidence, we had gone over it just as carefully as one another, and she was about as intelligent and intellectually careful as me in general. After learning of the disagreement, in what situations am I epistemically permitted to retain those beliefs (so set aside what I'm supposed to do with my belief in P)? For instance, if I am epistemically permitted to retain my confidence level in P upon discovering the disagreement with the peer, then am I required to lower my confidence level in my beliefs about my peer's knowledge regarding the topics germane to P's truth-since it looks like I'm now accusing her of definitely making a mistake? And how do we answer these questions in the epistemic superior case? 8. How often do the various cases actually show up in practice? For instance, much of the literature seems to address the case in which we start out believing P but not knowing what others think about P. And then the focus is on what we are supposed to do when we actually encounter someone who believes ~P. But in many real cases we start knowing, at least dispositionally, that there are dozens if not thousands of intelligent people who will believe ~P. In such cases it isn't clear what role the actual encounter with the disagreeing person will play (see discussion below). Those who have published on the topic of disagreement have spent most of their energies on (1)-(4) and, to a lesser extent, (7). Furthermore, they have focused almost exclusively on the "recognized peer" case. 6 If the proponent of ~P is known by you to be the infallible and truth-telling God, then you should not only cease believing P but start to believe ~P. More realistically, if I start out believing P and not knowing what anyone else thinks about P, I then find out that there are 2,000 experts on the topics relevant to P all of whom I fully admit are my epistemic superiors on P and are much more likely than I am to get P's truth-value right, then I probably should give up my belief in P upon later discovery that 95% of them firmly believe ~P in mostly mutual independence from one another. So, in some cases we seem forced to significantly alter our opinions in response to the discovery of disagreement. However, even in the latter case matters are complicated by the details. For instance, what if P was some bit of fundamental philosophy, such as 'There are non-temporal, non-spatial objects' or 'Moral statements have truth-value'? One might think that even though Fred is aware that expert opinion is firmly against him on P, Fred is epistemically a-okay in sticking with his guns because the epistemic weight attached to relative expertise runs out in some sense when it comes to the truly fundamental claims that are beyond the reach of empirical investigation. Or suppose that P is the claim that 1 + 1 = 2: in such a case one should perhaps not lower one's opinion that P is true but instead either give up one's belief that the superiors are really superiors or give up the belief that they really believe that 1 + 1 ≠ 2. (However, even this can be challenged: what if the experts who deny that 1 + 1 = 2 are all the best philosophers of mathematics who have sophisticated error theories that attempt to account for the usefulness of arithmetic while holding that its positive claims are false?) Or suppose that the 5% of experts who don't believe ~P all believe P and are generally considered the epistemic superiors of the 95% who do believe ~P. In such a case it is hardly obvious that when apprised of all those facts I should give up my belief in P. It might be wise to separate the question Q1 'After discovering the disagreement what should his confidence level be?' from the question Q2 'Given that he has just discovered a recognized epistemic peer/superior who disagrees with him, how should his confidence level change in response to that discovery alone?' Here's an argument why. Suppose that before the discovery of the disagreement he has credence in P of 0.85 (roughly, credence x = 0 when one is perfectly certain P is false, x = 1 when one is perfectly certain P is true, and x = 0.5 when one thinks there is a 50/50 chance P is true). Suppose further that the evidence he had at that time, the evidence he based his credence on, was so weak that he should have had a credence of just 0.65. Also suppose that P is fairly theoretical in the sense that his credence is fixed by his evidence alone (and not other epistemic factors). Finally, suppose that 7 principles regarding disagreement discovery dictate that he should lower his credence by 0.20 upon discovery of the disagreement with the recognized peer or superior. The answer to Q1 might be 'His credence should have been 0.65 to begin with; upon disagreement discovery it should have dropped by 0.20; so he should end up at 0.45'. The answer to Q2 might be 'He started with credence 0.85 and upon disagreement discovery it should have dropped by 0.20; so he should end up at 0.65'. In any case, one must be careful in formulating the question one is trying to answer. Three relatively straightforward views address what we are supposed to do upon the discovery of disagreement with a single recognized peer (see the works of Christensen, Elga, Feldman, Frances, Kelly, Lackey, and White for motivation and further evaluation): (a) Always suspend judgment regarding P's truth-value. (b) Always stick to your guns, not altering your view one bit. (c) Always "split the difference" in the sense that if I actually gave P credence x before the discovery of disagreement and I know that my peer gave it y before the discovery, then I should change my credence to the average of x and y. There is reason to think (b) is incorrect. You start out believing P but not knowing what anyone else thinks about P. If you then encounter 100 recognized peers in succession each of whom firmly believes that P is false, then if (b) were correct you would be epistemically permitted to stick to your guns even while accumulating the knowledge that 100 out of 100 of your recognized peers think ~P. It would seem that in almost all realistic cases this is the wrong result. A similar yet weaker argument goes against (a). Suppose I encounter 10 recognized peers in succession each of whom firmly agrees with me that P is true. Then the very next recognized peer, the 11th, is discovered to think P is false. If (a) is true then I'm supposed to suspend judgment upon encountering the 11th peer-despite the fact that I've learned that 10 out of 11 of my peers agree with me. Once again, it is hard to imagine a scenario in which this holds. However, that argument ignores some important wrinkles that are important when working on the topic of disagreement. Consider my position after I have encountered the first ten recognized peers who agree with me. Next I meet Fred, whom I recognize as the eleventh peer regarding P. In order for me to 8 recognize him as what might be called an extreme peer, I have to know that we have all the same evidence concerning P. But part of my evidence concerning P is that ten of my recognized peers agree with P. (You might think it isn't strong evidence, but it does appear to be evidence and the person who advocates (a) will think it's evidence.) Thus, Fred has to be aware of that fact. That is, he has to know, at that moment just before we tell each other our opinions on P, that ten out of ten of his recognized epistemic peers think P is true. Furthermore, he can't have any evidence I lack. So the only thing he knows about peoples' opinions regarding P is what I know: ten out of ten of his (and my) peers think P is true. So how on earth can Fred be reasonable in retaining his belief in ~P? Keep in mind that he cannot think, for instance, that he has some stunning new evidence that the ten others have not seen: since these ten people who disagree with him are his recognized peers, he knows that they have seen all his evidence. After I learn of his opinion regarding P I will probably conclude that Fred has not fully appreciated the consequences of the fact that ten out of ten of his peers disagree with him. I am free to hold that he is still my peer with respect to the issues surrounding P, but I will conclude that he has made two errors: first, he got P's truth-value wrong; second, he did not adequately follow up on the epistemic consequences of the facts of disagreement. I seem epistemically permitted to retain my belief in P, thereby falsifying (a). And if he isn't my extreme peer but is a moderate peer-so he has all the evidence I have with the exception of the knowledge of the ten out of ten peers who believe P-then it still seems clear that I need not suspend judgment. Option (c), "always split the difference", appears more reasonable than the extreme (a) and (b). Even so, there is an argument against it. As indicated above, in many cases when I come to believe P I am not thinking about what anyone else thinks about P but I am disposed to admit that there are many people who will disagree with me on P-people who are my peers and superiors concerning the relevant topics. I don't have any dispositions regarding any percentages of them endorse or reject P. If you had asked me, right then while I was coming to accept P, 'Do you think there are other intelligent people who will disagree with you on this issue-people you are happy to admit know about as much or even more than you do on the relevant topics?', I would have responded affirmatively. If that's the situation I was in, then when I actually encounter Tom who I judge to be a peer or superior and then discover that he disagrees with me on P, I will probably not feel too much pressure to alter my view. After all, I already knew that there were many such people. So, bumping into one of the intelligent disagreeing folks doesn't really change anything for me. Under these conditions, which I 9 suspect are common, there doesn't seem to be much reason for me to change my view when I encounter Tom. If that is right, then (c) is false. Of course, when I encounter Tom I might become a little reflective. I might think to myself 'Come to think of it, I know perfectly well that there must be loads of people smarter than I am who think ~P. Why on earth should I think someone like me has got things right this time around?' If I have become that reflective, then suspending judgment looks reasonable if not required. But if this encounter with Tom means that I have to suspend judgment, it won't be because of the fact that Tom disagrees with me. Instead, it will be due to the fact that I've reflected on how there must be many people who disagree with me-people I would admit are my approximate peers and even superiors. Tom is fully dispensable: all I really needed in order for the epistemic challenge of recognized disagreement to arise was the reflection Tom happened to cause. I won't be adjusting my opinion based on the confidence level Tom happens to have; so (c) looks false. If one has never put a moment's thought into these matters then it is hard to see how one is under any epistemic obligation to go against one's strong natural propensity to follow one's own inclinations. The problem of disagreement doesn't arise unless one is both significantly reflective and respectful of the epistemic abilities and performances of others. But what if you have put some thought into these matters-like you are doing right now? What is stopping you from suspending judgment on P even when practical matters often force you to choose to act on either P or ~P? Are you so weak-willed that you have to put an irrational trust in the inclinations you find in your own head? Bibliography: Christensen, David. Forthcoming. Disagreement, question-begging and epistemic self-criticism. Philosophers' Imprint. Christensen, David. 2009. "Disagreement as Evidence: The Epistemology of Controversy", Philosophy Compass 4: 756-67. Christensen, David. 2007. "Epistemology of Disagreement: the Good News." Philosophical Review 116: 187-217. Elga, Adam. 2007. "Reflection and Disagreement." Noûs 41: 478-502. 10 Feldman, Richard. 2007. "Reasonable Religious Disagreements." In Philosophers Without Gods: Meditations on Atheism and the Secular Life, edited by Louise Antony. Oxford: Oxford University Press. Feldman, Richard. 2006. "Epistemological Puzzles About Disagreement." In Epistemology Futures, edited by Stephen Hetherington. Oxford: Oxford University Press. Feldman, Richard, 2005. "Respecting the Evidence", Philosophical Perspectives, 19: 95-119. Feldman, Richard and Ted Warfield (eds.). 2010. Disagreement, Oxford University Press. Foley, Richard, 2001. Intellectual Trust in Oneself and Others, Cambridge University Press: Cambridge. Frances, Bryan. Forthcoming A. "Philosophy Sabotages Knowledge" in an as yet untitled OUP volume on Disagreement edited by Jennifer Lackey and David Christensen. Frances, Bryan. Forthcoming B. "Discovering Disagreeing Epistemic Peers and Superiors" International Journal of Philosophical Studies. Frances, Bryan. 2010. "The Reflective Epistemic Renegade" Philosophy and Phenomenological Research. Frances, Bryan. 2005. Scepticism Comes Alive. Oxford: Oxford University Press. Fumerton, Richard. 2010. "You Can't Trust a Philosopher." In Feldman and Warfield. Goldberg, Sandy. 2009. "Reliabilism in Philosophy." Philosophical Studies 124: 105-17. Kornblith, Hilary. 2010. "Belief in the Face of Controversy." In Feldman and Warfield. Kelly, Thomas. 2008. "Disagreement, Dogmatism, and Belief Polarization", Journal of Philosophy 105: 611-33. Kelly, Thomas. 2006. "The Epistemic Significance of Disagreement." In Oxford Studies in Epistemology, v. 1, edited by John Hawthorne and Tamar Gendler Szabo. Oxford: Oxford University Press. Lackey, Jennifer. 2010a. "A Justificationist View of Disagreement's Epistemic Significance," in Adrian Haddock, Alan Millar, and Duncan Pritchard (eds.), Social Epistemology, Oxford: Oxford University Press. Lackey, Jennifer. 2010b. "What Should We Do When We Disagree?" in Tamar Szabó Gendler and John Hawthorne (eds.), Oxford Studies in Epistemology, v. 3, Oxford: Oxford University Press. McKim, Robert, 2001. Religious Ambiguity and Religious Diversity, Oxford University Press. van Inwagen, Peter. 1996. "Is It Wrong, Everywhere, Always, and for Anyone to Believe Anything on Insufficient Evidence?" In Faith, Freedom, and Rationality, edited by Jeff Jordan and Daniel Howard-Snyder. Lanham, MD: Rowman and Littlefield. White, Roger. 2005. "Epistemic Permissiveness." Philosophical Perspectives 19: 445-59.