CHAPTER 17 DISAGREEMENT: IDEALIZED AND EVERYDAY Jonathan Matheson I've never met an epistemic peer I didn't like. I've never met an epistemic peer I've disagreed with either. Epistemic peers are hard to come by. I think that I've encountered exactly one – myself. By no means is this situation unique to me. I imagine the same is true of you – that you are the only epistemic peer of yourself that you have ever encountered, and that you have never found yourself to disagree with yourself, at least not at a single time. I have changed my mind about various things, but my earlier selves are not epistemic peers of my current self, just as your earlier selves are not epistemic peers of your current self. Often my current self has thought about the matter more than my earlier self, has attained more evidence on the matter, and so forth. Other times my current self has forgotten relevant bits of information or how they fit together. Given this situation, it might seem puzzling that almost all of the literature on the epistemic significance of disagreement concerns disagreement with an epistemic peer.1 While the issue of the epistemic significance of disagreement is often motivated by pointing out the widespread and persistent disagreement that we encounter regarding a number of topics in morality, politics, religion, and philosophy in general, the discussion often quickly turns to a particular kind of discovered disagreement – an idealized disagreement with an epistemic peer. 1 For a notable exception, and someone who raises this problem as well, see Nathan King (2011). 2 However, this is a kind of disagreement that we simply don't encounter. So, while the question of what we should believe in cases of idealized disagreement is intrinsically interesting, we should want more from an account of the epistemology of disagreement. We should want an account that tells us what we should believe in the everyday cases of disagreement that we are all too familiar with. At this stage in the debate, the epistemic impact of the disagreements that we are aware of is far from obvious. In this essay I want to go some way towards rectifying this matter. I will begin by briefly discussing cases of idealized peer disagreement. First, I will set up what an evidentially symmetric disagreement looks like. I will then briefly explain and motivate one popular account of the epistemic significance of disagreement, the Equal Weight View, and examine its claims about cases of idealized peer disagreement. I will then proceed to extend my conclusions to be made about cases of idealized disagreement to the more everyday cases of disagreement. In doing so it will become apparent both why the focus in the literature has been on the idealized cases of disagreement and why this is a good thing. 1. Idealized Disagreements Let's begin by looking at evidentially symmetric cases of disagreement. While much of the literature on disagreement has focused on evidentially symmetrical disagreements, such disagreements have often been mischaracterized, resulting in a case where the evidence is not symmetrical after all. As I am understanding them, an evidentially symmetric case of disagreement between S1 and S2 meets each of the following conditions: (i) S1 and S2 are justified in believing that they are epistemic peers at t. 3 (ii) S1 and S2 are justified in believing that they have adopted competitor doxastic attitudes, D1 and D2, toward a proposition p at t. (iii) S1 and S2 are each as justified in believing that S2 has adopted D2 toward p at t as that S1 has adopted D1 toward p at t. (iv) S1 and S2 are justified in believing that there are no circumstantial factors that make it the case that either S1 or S2 is more likely to be correct about p at t. Some clarifications are in order. So understood, an evidentially symmetrical case of disagreement need not actually be a case of disagreement at all, it must simply be a case where the parties are reasonable in taking there to be a particular kind of disagreement. That is, it may be that S1 and S2 in fact have adopted the same doxastic attitude toward p. One's interlocutor can mislead, and one's evidence can mislead, so cases where one is rational in taking there to be a disagreement need not be cases where there is in fact a disagreement. All four conditions can be met even when S1 and S2 have in fact adopted the same doxastic attitude toward p. What's important is that one's evidence supports that there is a disagreement. Conditions (i) through (iv) each claim that the parties to the disagreement are justified in believing a particular proposition. Meeting these conditions does not entail that either of them actually believes these propositions, just that they are propositions that it is reasonable for them to believe at that time. So, the focus in evidentially symmetrical disagreements is on propositional justification. Condition (i) requires the parties to be justified in believing that they are epistemic peers. While there have been slightly different takes on what constitutes an epistemic peer, the central 4 component is that epistemic peers are equally likely to be correct – that they are in an equally good epistemic position regarding the disputed proposition. We can subdivide factors which contribute to the likelihood of being correct as follows: (a) Faculty factors: S1 and S2 are equally intelligent, equal in terms of reasoning ability, perceptual ability, etc. (b) Evidential factors: S1 and S2 have the same, or equally good, evidence. (c) Virtue factors: S1 and S2 are equally intellectually virtuous (open-minded, intellectually courageous, etc.). One quick note is in order regarding 'equally good' evidence. Two bodies of evidence are equally good with respect to a proposition when they each provide the same degree of justification for that proposition. Richard Feldman's (2006) Dean on the Quad case is an example of a disagreement where the parties have distinct but equally good bodies of evidence. In this case, two individuals look across the quad. One sees the Dean, and the other does not. Both disagreeing parties have distinct perceptual bodies of evidence since they have distinct perceptual experiences. While these are distinct bodies of evidence, they each support their possessor's conclusion equally well since each party has equally good reasons to believe that they are perceptually adept. Another example of distinct but equally good bodies of evidence is given by David Christensen (2007). Christensen imagines a case where the two disagreeing parties had each conducted their own poll on the issue at hand with populations of the same size, equally representative, etc. Upon discovering the disagreement, each party knows that the other has a distinct body of evidence, but one that is just as good as her own. 5 Regarding (ii), competitor doxastic attitudes are rival alternative doxastic attitudes. A single body of evidence cannot support each of two competitor doxastic attitudes.2 So, a competitor doxastic attitude to D1 is a distinct doxastic attitude that is not simply related in a nesting way to D1. If we adopt a tripartite doxastic taxonomy, then believing, disbelieving, and suspending judgment are all competitor doxastic attitudes. On a more fine-grained doxastic taxonomy believing to degree 0.7 and believing to degree 0.2 would be competitor doxastic attitudes. It might be that not all distinct doxastic attitudes are competitors. For instance, it may be that all-out believing, and believing to degree 0.7 are not in fact competitor doxastic attitudes, but different descriptions of the same doxastic attitude on two distinct levels of appraisal. I include 'competitor' to not rule out this possibility. Condition (iii) is a condition of an evidentially symmetrical disagreement that is often ignored. This condition requires that S1 have just as good of reason to believe that S2 has adopted D2 toward p at t, as S1 does regarding the claim that S1 has adopted D1 toward p at t, and the same for S2. Typically we have introspective evidence of our own doxastic attitudes and we have testimonial evidence of the doxastic attitudes of others. To meet condition (iii) in such cases, the introspective evidence that S1 has that S1 believes p must be just as good (provide just as much justification for believing) as the testimonial evidence that S1 has that S2 disbelieves p. If this condition is not met, then S1 will have at least some reason to favor either S1 or S2's conclusion (depending on where the better reasons point). For there to be the perfect evidential symmetry between S1 and S2, meeting condition (iii) is crucial. 2 Here I am assuming the Uniqueness Thesis. For a richer defense of the Uniqueness Thesis see Roger White (2005) and Matheson (2011). 6 Finally condition (iv) is included to make sure that neither party's evidence gives him or her any reason to think that on this particular occasion either of the parties is more likely to be correct on the matter, even if in general they are equally good at such matters and are equally informed on this issue. Epistemic peers need not be equally likely to be correct regarding every proposition on every occasion. Condition (iv) is there to rule out cases where one of the parties has good reason to think that one of the parties has been compromised (S1 or S2 is drunk, overly sleepy, biased on this topic, etc.), as well as cases where one of the parties has good reason to think that one of the parties is particularly adept on this occasion (had a peppermint, is a morning person, etc.). 2. The Equal Weight View Suppose that there is a two party case that meets (i) through (iv). The question at the heart of most of the literature on the epistemic significance of disagreement concerns what S1 and S2 are justified in believing at t', the time immediately following the discovered disagreement at t. Perhaps the most discussed answer to this question is the Equal Weight View. According to an Equal Weight View, having encountered an evidentially symmetrical case of disagreement S1 and S2 ought to give each other's conclusion equal weight as his or her own. According to Equal Weight Views, in such an idealized case of peer disagreement, no one peer opinion counts for more or less than any other peer opinion. While this seems plausible, this answer naturally invites the question, what does it mean to give a conclusion 'equal weight'? Equal Weight Views have often been thought to entail splitting the difference between the disparate doxastic attitudes – that is, adopting the doxastic 7 attitude halfway between the two competitor doxastic attitudes.3 Let's suppose that D1, S1's doxastic attitude toward p at t, is believing to degree 0.7, and that D2, S2's doxastic attitude toward p at t, is believing to degree 0.3. A split the difference view has it that if conditions (i) through (iv) are met, then S1 and S2 should each believe p to degree 0.5 at t'. Believing p to degree 0.5 is the doxastic attitude which splits the difference between D1 and D2. Holding an Equal Weight View, however, does not entail holding a 'split the difference' view. For one thing, it is consistent with giving another's conclusion equal weight that one gives neither peer conclusion any weight. Such a view about the epistemic significance of disagreement would be an Equal Weight View, but not a split the difference view. In addition, splitting the difference only appears to be a plausible way of giving another's conclusion equal weight when the two parties to the disagreement are of a certain sort. If S1 and S2 are both known to be unreliable in forming beliefs about p-like matters, then splitting the difference does not appear to be an epistemically appropriate response even when conditions (i) – (iv) are met. If neither party is likely to be right about the disputed matter, then splitting the difference would not be a rational response to the discovery of the disagreement. Rather, it is only in cases where S1 and S2 are not only justified in believing that they are epistemic peers, but are also justified in believing that they are reliable in forming beliefs about p-like matters, that splitting the difference is called for. Indeed, the literature on the epistemology of disagreement has focused on this very type of case (although typically without explicitly noting it). It has been disagreement between rational individuals – reliable evidence evaluators – that has been of principle interest in the literature, not philosophical disagreements between unreliable children 3 See Kelly (2010) and Christensen (2007). 8 (even if the children are epistemic peers). Not all ways of being equals have the same epistemic significance. The discovery of a two-party evidentially idealized peer disagreement between individuals that are reliable in forming beliefs about matters like p does seem to call for both parties to split the difference. If both parties are justified in believing that they are equally likely to be correct about p on this occasion and yet have adopted competitor doxastic attitudes toward p, then to adopt a doxastic attitude toward p other than the one which splits the difference would be to show preference or bias toward one of the competing attitudes. So, splitting the difference seems to be the appropriate way to give each peer conclusion equal weight in such circumstances. When understanding Equal Weight Views as a split the difference views, we should therefore add the following condition to our conditions for evidentially symmetrical disagreements: (v) S1 and S2 are justified in believing that they are reliable evaluators of the evidence regarding p-like matters. To meet this condition, S1 and S2 must be such that it is reasonable for them to think that they are good at judging the evidence regarding matters like p and subsequently forming the doxastic attitude toward such propositions which fits their evidence. Let's then call a case that meets conditions (i) – (v) a case of rationally idealized peer disagreement (an RIPD). Notice that this label does not imply that both parties are justified in having adopted their respective doxastic attitudes at t, but only that it is an apparent disagreement between individuals that are a certain sort of epistemic peers – rational peers – individuals who are likely to evaluate the relevant type of evidence correctly. 9 In what follows I will be taking Equal Weight Views in a two-person RIPD to call for splitting the difference between the two competitor doxastic attitudes. While this isn't the only way to give peer opinions equal weight, this seems to be the view that defenders of Equal Weight Views have had in mind in these cases.4 So, in what follows I will be understanding the Equal Weight View as follows: EWV: In a two-person RIPD, S1 and S2 should split the difference and each adopt the doxastic attitude toward p that is midway between D1 and D2. The following case given by Thomas Kelly (2010) can help us unpack and apply EWV: Case 4: Despite having access to the same substantial body of evidence E, you and I arrive at very different opinions about some hypothesis H: while I am quite confident that H is true, you are quite confident that it is false. Indeed, at time t0, immediately before encountering one another, my credence for H stands at .8 while your credence stands at .2. At time t1, you and I meet and compare notes. How, if at all should we revise our respective beliefs? (Kelly 2010, 122) Understanding this case as a two-party RIPD, you and I should each assign a credence of .5 to H at t1. A credence of .5 is the attitude which splits the difference between us. This verdict is plausible since in meeting the RIPD conditions, the evidence is symmetrically balanced between you and I having adopted the correct doxastic attitude toward p given our evidence. Although we are both likely to be right about H, according to our evidence, neither of us is more likely to be right than the other. Given conditions (i) – (v) it is reasonable to believe that there exists an evidential symmetry between us. It is as though I have gone through the reasoning twice having 4 See Elga (2007), Christensen (2007), and Feldman (2006). 10 come up with a different conclusion on each occasion (one being given by me, and the other being given by you). Having met (i) – (v) it appears that the only difference lies in who has adopted each competing opinion, but this factor seems to be an epistemically inert piece of information.5 So, given this scenario, it seems plausible that we should meet each other halfway and split the difference. Any other alternative answer appears to be either arbitrary or prejudiced.6 3. Everyday Disagreements While EWV appears to be a plausible account of how idealized cases of peer disagreement should be handled, it is reasonable to want more from an account of the epistemic significance of disagreement. While the question of how idealized cases of disagreement should be handled is intrinsically interesting, the epistemic significance of disagreement extends beyond these idealized cases. Conditions (i) – (v) are rarely (if ever) met, yet it seems that the disagreements that we are aware of should still have some effect on what we believe about disputed matters. The people we find ourselves disagreeing with are simply never exactly as intelligent as us, exactly as informed, exactly as open-minded, etc. Epistemic peerhood simply does not obtain.7 That said, can we learn anything about how to rationally handle everyday cases of disagreement from how idealized cases should be handled? Suppose EWV is correct about RIPDs. What could we learn from this about how we should respond to the everyday disagreements that we encounter? In what follows I want to examine what consequences 5 One other difference which has been cited by some to be relevant is which attitude is supported by our shared firstorder evidence. See Kelly (2009) and (2011) for defenses of this claim, and Matheson (2009) for a sound argument for the conclusion that this difference does not have an epistemic effect. 6 In what follows I will be taking it that EWV gives the correct verdicts about RIPDs, however much of the argument that follows does not hang on this. 7 For a more detailed argument for this conclusion see King (2011). 11 stripping off the various idealizations of two-party RIPDs would have for what the parties of the disagreement should believe having encountered it. Fortunately, what we can learn from twoparty RIPDs can teach us something about how to respond everyday disagreements. So, what I hope to offer is a way of moving from verdicts about idealized cases of disagreement to verdicts about everyday disagreements. Recall that a RIDP met the following conditions: (i) S1 and S2 are justified in believing that they are epistemic peers at t. (ii) S1 and S2 are justified in believing that they have adopted competitor doxastic attitudes, D1 and D2, toward a proposition p at t. (iii) S1 and S2 are each as justified in believing that S2 has adopted D2 toward p at t as that S1 has adopted D1 toward p at t. (iv) S1 and S2 are justified in believing that there are no circumstantial factors that make it the case that either S1 or S2 is more likely to be correct about p at t. (v) S1 and S2 are justified in believing that they are reliable evaluators of the evidence regarding p-like matters. I want to now consider the justificatory effects of stripping away these idealizations. Condition (ii) is not an idealized condition at all. It is met in our everyday cases of disagreement. We are often justified in believing that other people disagree with us about various propositions. Meeting (ii) only requires that we are reasonable in believing that there is a disagreement. Similarly, condition (v) is not overly idealized. Most of us are justified in believing this most of the time. We are often justified in believing that we are reliable evaluators of the evidence, and 12 that we are pretty good at evaluating the evidence regarding the matter under dispute. Recall, that this condition is only in place to ignore cases where the party of a disagreement is justified in believing that he is likely to be mistaken on the matter. That is not a feature shared by many of the everyday disagreements that we are interested in. The idealizations, therefore, lie in (i), (iii), and (iv). Let's begin with condition (i). Condition (i) can be met even when S1 and S2 are not in fact epistemic peers – it only requires that they are justified in believing that they are. That said, one's evidence rarely (if ever) supports that another individual is one's epistemic peer. For S1's evidence to support that S2 is his peer, it must support that they are equals in their evidence, faculties, and intellectual virtues. Let's first consider equality in faculties and the effects of stripping away the idealization here. If S1 is justified in believing that he is superior to S2 in terms of reasoning ability or intelligence, then this will give S1 some reason to favor S1's conclusion regarding the disputed proposition – this will give S1 a reason to make more modest concessions to S2 (to not give S2's conclusion equal weight). The degree to which S1 is justified in believing that he is superior to S2 in terms of reasoning ability and intelligence will typically affect how much conciliation is to be made. If S1 is justified in believing that he is only slightly superior to S2 in this way, then everything else being equal, S1 will not have to give S2's conclusion equal weight, but he will still have to make quite significant conciliation toward S2. Everything else being equal, the more superior in terms of reasoning ability and intelligence that S1 is justified in believing that he is, the less conciliation will be required of him from the discovery of the disagreement with S2. So, being justified in believing oneself superior to one's interlocutor in terms of reasoning ability and intelligence is a reason to make less conciliation. 13 One might worry at this point that if one has any epistemic reason to prefer one's own conclusion she should not make any doxastic conciliation. Support for this thought might come from the Uniqueness Thesis.8 If the Uniqueness Thesis is true, a body of evidence justifies at most one competitor attitude toward a proposition given. Applied to our case, if the evidence supports only one doxastic attitude, and our subject has a little more reason to think that he adopted that attitude, then it might seem that no conciliation would be called for. If only one of the doxastic attitudes toward p is justified by the evidence, and S1 has some reason to think that it is his over his interlocutor's, then why should S1 make any conciliation at all? After all, neither party adopted an attitude between the two, so there might seem to be little reason to make conciliation and adopt one of those attitudes. While there is some pull to this theoretical worry, when it is applied to cases it can be seen to give the wrong verdicts. Suppose that you have two thermometers in the same room, and that the room has only one temperature at a time. Suppose further that one of the thermometers is slightly more reliable than the other, though both thermometers are reliable. Let's say that you find out that the slightly more reliable thermometer read '80' at t and then later discover that the slightly less reliable thermometer read '74' at t. In such a case it seems that you shouldn't simply stick with believing that the temperature in the room was 80 at t with the same level of confidence, even if that is what the more reliable thermometer says. You have acquired some powerful evidence that the temperature in the room is not 80 degrees – evidence from the other reliable (though slightly less so) thermometer. Though this other evidence is not as strong as the evidence that it is 80 degrees in the room, it is evidence that makes a difference as to how 8 For a more detailed discussion and defense of the Uniqueness Thesis, see Feldman (2006), White (2005), and Matheson (2011). For criticism, see Ballantyne and Coffman (2011). 14 justified you are in believing that it is 80 degrees in the room, and thus which attitude you should adopt toward that proposition. So, even when S1 is justified in believing that he is more intelligent than S2, S1 might in still in the end be epistemically required to make quite significant doxastic conciliation toward S2. Further, while having reason to believe that you are intellectually superior gives you a reason to make less conciliation, reasons can be defeated. This bit of evidence concerning one's intellectual superiority is only one piece of the evidential puzzle, and this bit of evidence may be supplemented with other bits of evidence which create inequalities between S1 and S2 in the other direction and which in turn require more conciliation of S1. In addition, some disagreements may make the impact of inequality along intellectual lines quite insubstantial. If the disagreement pertains to the color of ordinary sized objects in good light, the day of the week, the location of the nearest gas station, etc., then even if S1 is justified in believing that she is in general more intelligent or that she has superior reasoning abilities, this may not factor in at all, or at least not very significantly, regarding what she should believe in this case having discovered the disagreement. Such an asymmetry may not make S1 any more likely to be right on the disputed matter, and so long as that is the case, then there is no reason for S1 to privilege her own conclusion even if she is justified in believing that she is more intelligent. A physicist may be no more likely to be correct about the location of the nearest Starbucks than a 5th grader, even though the physicist is more intelligent. If S1 is still justified in believing that S2 is just as likely to be correct about such matters, despite the inequality in terms of intellectual faculties, then the discovered disagreement will have the same epistemic effect in the non-idealized case as it would have in the idealized case. 15 The second factor in epistemic peerhood is evidential equality – that S1 and S2 have the same, or equally good, evidence. It is plausible that no two individuals ever actually have the same body of evidence, and it is only slightly less idealized for them to have distinct but equally good bodies of evidence. What are we to say about the epistemic significance of disagreement when this evidential equality condition is not met? Cases in which the parties of the disagreement differ only with respect to evidence which does not affect their justification for believing the disputed proposition (whether in quantity or quality), will make the discovery of the disagreement have precisely the same epistemological effect as cases where there is equality in these matters (holding all the other factors fixed, that is). So long as S1 is justified in believing that S2's evidence regarding the disputed proposition p is just as good as S1's, then evidential differences (in either quantity or quality) unrelated to the justification of p will not affect how S1 ought to respond to the discovery of the disagreement. Using the same example, though the physicist has a lot of evidence that the 5th grader lacks about physics, if they have equally good evidence about the location of the Starbucks, this evidential difference won't affect what is epistemically required of the disputants. It is also important to remember here that the evidence pertaining to one's justification for believing p does not simply include evidence directly pertaining to p, but also any relevant higher-order evidence such as evidence about the nature of evidence and the significance of disagreements.9 Differences in the evidence possessed by the parties that are relevant to the justification of the disputed proposition, however, can make for conciliatory differences between the idealized case and the everyday case. If S1 is justified in believing that he has more evidence on the issue (i.e. all the evidence S2 has on the matter, plus some additional evidence), then he will 9 For more on higher-order evidence see Kelly (2010) and Matheson (2009). 16 have reason to make more modest concessions. In such a scenario, S1 will have reason to think that he is more likely to be correct on the matter, and thus has reason not to give S2's conclusion equal weight, and perhaps even reason to give S2's conclusion no weight at all. We can imagine here a case where S1 has in addition to all of S2's evidence an undercutting defeater which takes away all of the justification provided for p by S2's total evidence. So, even small differences in evidence may call for quite large deviations in terms of how much conciliation is called for from the idealized case. Alternatively, if S1 is justified in believing that S2's evidential position toward p is superior to S1's (in quantity or quality), then S1 will have reason to make even more conciliation to S2 than in the idealized case. In such a scenario S1 will have reason to believe that S2 is more likely than S1 to be correct on the matter, and thus has reason not to give S2's conclusion equal weight, but to give it even more weight than her own. Finally, the third condition of epistemic peerhood is equality in terms of epistemic virtues. To be epistemic peers, S1 and S2 must be equally intellectually virtuous – they must be equally open-minded, equally intellectually courageous, equally careful, and so forth. By now it should be clear how stripping away the idealizations will affect the significance of the disagreement. The more S1 has reason to believe that she is superior in terms of intellectual virtue, the less reason she has to make conciliation to S2, and the less reason she has to give S2's conclusion equal weight. The more S1 has reason to believe that S2 is superior in terms of intellectual virtue, the more reason S1 has to give even more deference to S2. As with evidential factors, it may be that some intellectual virtues are such that their possession does not figure into the likeliness of being correct regarding some matters. Perhaps if the disagreement pertains to the color of ordinary sized objects in good light, the day of the week, the location of the nearest 17 gas station, and so forth, being aware that one's interlocutor differs in terms of her intellectual courage will not affect how likely she is to be correct on the matter. So, some differences in intellectual virtue will seemingly make for no difference at all regarding the epistemic significance of disagreement. Let's turn now to condition (iii). Condition (iii) is idealized in that it is typically not met. Typically an individual will have better reason to believe that she believes what she does than she will have regarding what another believes. Plausibly, this is because introspection can provide better reasons than testimony typically does. Propositions that people believe from introspection are typically more justified than propositions that people believe from testimony.10 Eliminating this evidential symmetry between S1 and S2 will have epistemic effects. If S1 is more justified in believing that S1 has adopted D1 toward p at t1 than S1 is justified in believing that S2 has adopted D2 toward p at t1 (as S1 typically will be), then S1 will have some reason to favor his own conclusion. In such a scenario S1 has some reason to privilege D1 as a response to the evidence regarding p over D2.11 So here too, when the idealization is stripped away, S1 will typically have a reason to favor the doxastic attitude that S1 is more justified in believing is actually held by one of the parties.12 Like above, however, how such a reason will interact with the other asymmetrical reasons that S1 may have is a complicated matter that will depend on what those actual reasons are. 10 I say 'typically' since it can be the case that an individual has better reason to trust the testimony of another about the other's beliefs, than our subject has reason to trust her introspection about her own beliefs. The details of the particular case will matter. 11 Perhaps this is what Jennifer Lackey (2008) is tracking when she argues that 'personal information' can often be used to privilege one's own opinion. As I am understanding it, if one does have such privileging personal information, then one is not in an idealized case of disagreement. 12 S1 will only typically have such a reason since it is possible that the evidence one gains via testimony about S2's doxastic attitude regarding p is actually stronger that S1's evidence about which doxastic attitude S1 has himself adopted toward p. 18 The condition regarding circumstantial factors in RIPDs, condition (iv), is also idealized. In idealized cases of peer disagreement S1 has no reason coming from the circumstances to believe that S1 is more or less likely to be correct on this occasion than S2. S1 would have such a reason were he to have reason to believe that there was something about the disputed proposition or the encounter in general which made it more likely for S1 to be correct. For instance, if S1 had reason to believe that S2 is drunk (and that S1 is not), or that S2 is very tired (and that S1 is not), or that p is about the attractiveness of S2's spouse (and not S1's) or the usefulness of S2's occupation (and not S1's), then S1 would have reason to think that the balance tips in his favor. In such situations S1 would have reason to think that it is S2 that is mistaken due to some circumstantial factor. In typical cases, however, S1 will have at least some such reasons. Often such reasons will be minor and will not significantly mitigate the amount of conciliation required of S1 from the discovery of the disagreement. If S1 is justified in believing that S2 has had a beer or just finished teaching before adopting D2 toward p (while S1 had not), then this might give S1 some reason to discount S2's conclusion, but not a reason that significantly mitigates the justificatory effect of the discovery of the disagreement. In such a case S1 may not be required to give S2's conclusion precisely equal weight, but he will be required to give it something very close to it. The more significant the reason to discount the other's conclusion, the more mitigated the justificatory effect of the reason to make conciliation will be. S1 will typically also have some reasons to discount his own conclusion. Perhaps it is he who has ingested a moderate amount of alcohol before considering the disputed proposition, while his opponent has not. Here again, the reasons on both sides will need to be weighed against each other. If S1 has on balance stronger reasons to discount S2's conclusion due to circumstantial factors, then S1 has a reason to make less conciliation. If S1 has on balance 19 stronger reasons to discount his own conclusion due to circumstantial factors, then S1 has reason to make even more conciliation. Finally, the discussion of RIPDs has also focused on two-person cases of disagreement. Many of our everyday disagreements are not like this. Regarding most of our political, religious, ethical, and philosophical beliefs in general, we are aware of a multitude of people who disagree with us, as well as a number of people who agree with us. EWV has mistakenly been thought to imply that discovering a solitary peer disagreement can have dramatic effects on what it is rational for us to believe.13 This is perhaps the fault of defenders of EWV since their accounts typically state meeting a disagreeing peer as being a sufficient condition for making substantial doxastic conciliation.14 Doing so, however, would not amount to giving each peer opinion equal weight – something that EWV is committed to. Rather, such an account would give the opinions of disagreeing peers much more weight than the opinions of the agreeing peers in allowing for one disagreeing peer to call for significant doxastic revision in the face of widespread agreement.15 So, extrapolating from the two-party RIPDs, each opinion of a rational cognizer is to be given some weight. Evidence that S1 has regarding the existence of other agreeing parties will give additional evidential force to D1, whereas evidence that S1 has regarding the existence of other disagreeing parties will give evidential force that pushes away from D1 (possibly in the direction of D2, but possibly in the opposite direction). The weight to be given to each of these 13 See Lackey (2008). 14 For examples of this see Elga (2007) and Feldman (2006). 15 For more on this point see Carey and Matheson (2013). So understood, EWV also mishandles cases when disagreeing peers are discovered at different times. On this understanding of EWV, EWV has certain peer opinions counting for more depending upon when they were discovered. Clearly, the time of discovery should not affect the weight of the peer opinion – to do so would not be to give peer opinions equal weight. 20 opinions will depend on the information that S1 has about each of these individuals in ways that we have covered above. Plausibly, the weight to be given to an individual's opinion corresponds to how likely that individual is to be right on the matter. Clearly, the more individuals whose opinion on the matter S1 is aware of, the more complicated the evidential story will be. In particular, the independence of the various opinions (or lack thereof) will make a difference as to how much weight each opinion is to be given. Issues of independence are difficult indeed. The independence of opinions comes in degrees. Plausibly the more independent two agreeing opinions are, the more weight each individual opinion is to be given. In contrast, the less independent two agreeing opinions are, the less weight there is to be given to the second agreeing opinion.16 We have seen in quite broad strokes what justificatory effect would result from stripping away our idealized conditions in various ways. Stripping away the idealizations resulted in either no difference or giving S1 a reason to give either S1's or S2's conclusion more weight. Nothing has been said about how those reasons add up in everyday cases. Unfortunately, not much else can be truly said about such non-idealized cases in universal terms. How these reasons to favor one's own conclusion, or to make greater conciliation, add up will be a matter of what the particular bits of evidence are, and thus it will be unique to particular cases of disagreement. Sometimes a reason to think that there are circumstantial factors counting against S2 will be much more significant than the fact that S1 is justified in believing that S2 has a superior body of evidence regarding the disputed proposition; other times it will not. For instance, if I am justified in believing that S2 has much more evidence on the matter, but I am also justified in believing that S2 severely intoxicated, then I don't have much reason to make 16 For more on the consequences of the difficulty of determining independence, see Carey and Matheson (2013). 21 much (or even any) conciliation toward S2. Sometimes S1 being justified in believing that he is more intelligent than S2 will be more significant than S1 having a reason to discount his own conclusion; other times it will not. In cases of non-idealized disagreement, the particular details matter. How each of these bits of evidence adds up will depend upon what exactly the reasons are and even what the disputed proposition concerns. Although we have seen how inequalities within the various factors contributing to epistemic peerhood give reasons to change one's opinion, how those reasons add up is a complicated matter that depends upon what those particular inequalities are. This is not to say that investigating idealized cases of peer disagreement is unimportant. Not only is such an investigation intrinsically interesting, but the verdicts in idealized cases of disagreement set the baseline for the verdicts to be given in everyday disagreement. It is important to see what the epistemically appropriate response is in two-party RIPDs since the epistemically appropriate response to everyday disagreements will depend upon the ways in which those everyday disagreements differ from the two-party idealized case. We have seen that we cannot derive true interesting and universal principles about these everyday disagreements, but how much conciliation should be made in everyday disagreements will depend on what the correct story is about idealized disagreements, coupled with how the asymmetrical reasons add up.17 4. An Ethical Analogy 17 For more on this point see Feldman (2009). 22 This account of the epistemic significance of disagreement bears some similarity to W.D. Ross's ethical theory that utilizes prima facie duties.18 Ross's theory is a particularist ethical theory in that what one is obligated to do is determined by the particular circumstances. Ross's theory gives seven prima facie duties which are features of an act which tend to make it one's actual duty (or duty proper). How these prima facie duties add up in any particular case, however, depends on the details of the particular case. One's actual duty (duty proper) is to follow the most stringent prima facie duty or duties, but what the most stringent prima facie duty or duties are is a feature of particular cases – different prima facie duties can be the most stringent based upon the particular details of the case at hand. So it is with our account of the epistemic significance of everyday disagreement. Regarding it, true and precise universal claims cannot be made about particular non-idealized cases of disagreement. We have seen in broad strokes various ways in which when one is in a non-idealized case of disagreement one thereby gets a reason to make more or less conciliation than in the idealized case, but how those reasons add up depends upon the details of the particular case and what those reasons consist of. Like Ross's account of what makes for one's actual obligation, which doxastic attitude one should adopt after discovering the disagreement will depend upon how the particular reasons add up. The result is a kind of epistemic particularism. We have seen how various pieces of evidence provide prima facie justification for believing that oneself is more or less likely to be correct on the matter, but whether one is on balance justified in so believing will depend upon how those bits of evidence intermingle and 18 See Ross (1930). 23 add up. The resulting picture for everyday disagreements is messy and perhaps less than we would like to have, but unfortunately it's all we can get.19 References Ballantyne, Nathan and Coffman, E. J. (2011). "Uniqueness, Evidence, and Rationality," Philosophers' Imprint 11(18). Carey, Brandon and Matheson, Jonathan. (2013). "How Skeptical is the Equal Weight View?" in Diego Machuca (Ed.), Disagreement and Skepticism. New York: Routledge, 131-149. Christensen, David. (2007). "Epistemology of Disagreement: The Good News," Philosophical Review 116: 187-218. Elga, Adam. (2007). "Reflection and Disagreement," Noûs 41: 478–502. Feldman, Richard. (2006). "Reasonable Religious Disagreements," in L. Antony (Ed.), Philosophers without Gods: Meditations on Atheism and the Secular Life. New York: Oxford University Press. Feldman, Richard. (2009). "Evidentialism, Higher-Order Evidence, and Disagreement," Episteme 6(3): 294-312. Kelly, Thomas (2005). "The Epistemic Significance of Disagreement," in T. Gendler and J. Hawthorne (Eds.), Oxford Studies in Epistemology, vol. 1. Oxford: Oxford University Press. Kelly, Thomas. (2010). "Peer Disagreement and Higher-Order Evidence," in R. Feldman and T. Warfield (Eds.), Disagreement. New York: Oxford University Press. King, Nathan. (2011). "Disagreement: What's the Problem? Or A Good Peer is Hard to Find," Philosophy and Phenomenological Research 85(2): 249-272. Lackey, Jennifer. (2008). "A Justificationalist View of Disagreement's Epistemic Significance," in Adrian Haddock, Alan Millar, and Duncan Pritchard (Eds.), Social Epistemology. Oxford: Oxford University Press. Matheson, Jonathan. (2009). "Conciliatory Views of Disagreement and Higher-Order Evidence," Episteme: A Journal of Social Philosophy 6(3): 269-279. 19 Special thanks to Tomas Bogardus, Brandon Carey, Earl Conee, Richard Feldman, Nate King, and Kevin McCain for helpful comments on earlier drafts. 24 Matheson, Jonathan. (2011). "The Case for Rational Uniqueness," Logos and Episteme: An International Journal of Epistemology 2(3): 359-73. Ross, W. D. (1930). The Right and the Good. Oxford: Oxford University Press. White, Roger. (2005). "Epistemic Permissiveness," in J. Hawthorne (Ed.), Philosophical Perspectives, vol. 19, Epistemology, Malden, MA: Blackwell, 445-459.