© LOGOS & EPISTEME, VI, 1 (2015): 129-139 DEFENDING THE UNIQUENESS THESIS: A REPLY TO LUIS ROSA Muralidharan ANANTHARAMAN ABSTRACT: The Uniqueness Thesis (U), according to Richard Feldman and Roger White, says that for a given set of evidence E and a proposition P, only one doxastic attitude about P is rational given E. Luis Rosa has recently provided two counterexamples against U which are supposed to show that even if there is a sense in which choosing between two doxastic attitudes is arbitrary, both options are equally and maximally rational. Both counterexamples work by exploiting the idea that 'ought implies can' and trying to spell out situations in which some inferences are beyond the capabilities of some reasoners. I argue that on a descriptive account of doxastic rationality, questions of whether 'epistemic ought implies can' can be bracketed and that at least one of the inferential moves that Rosa describes in his cases is irrational. I further argue that a descriptive account of doxastic rationality is the appropriate notion of rationality that is to be considered when evaluating U. If my argument for a descriptive account of rationality is successful, then we have reason to revise our use of the term rationality to fit this descriptive understanding. KEYWORDS: epistemology, uniqueness thesis, epistemic deontology Introduction We have many beliefs, and we would like to think, for any given belief, that not only is it true, but also that we are justified in believing this to be the case. However, when we meet others who are just as rational as ourselves and who possess the same evidence, but take a different doxastic attitude, we may be concerned about what we should do, whether one or more of us should or should not revise our beliefs so as to be aligned with that of others'. On the one hand, it might seem that if rational disagreement were possible, then the fact that we have different beliefs given the same evidence, may not be too disquieting. Conversely, it would seem inappropriate to so easily dismiss the concern that perhaps one of the parties has indeed made a mistake while forming his beliefs. After all, the question may arise as to why we hold one particular belief rather than another. To this, the only answer which would be consistent with taking that belief to be fully determined by the reasons we have is that this belief is more appropriate than any other. This could only be the case if something like the Uniqueness Thesis were true. Muralidharan Anantharaman 130 According to the Uniqueness Thesis: Uniqueness Thesis (U): 'Given a body of evidence, [at most one doxastic attitude1] is the rationally justified one'2 Roger White defends U by showing that alternatives to U are untenable. White calls all these alternatives 'permissive theses' and defines them as follows. The first one is Extreme Permissiveness (EP): (EP): 'There are possible cases in which you rationally believe P, yet it is consistent with your being fully rational and possessing your current evidence that you believe not-P instead'3 Luis Rosa defends EP by offering a counterexample in which either P or not-P is allegedly permissible if the relevant evidence contains, unknown to oneself, inconsistent premises.4 The second is Moderate Permissiveness, (MP) which does not sanction such vastly opposed doxastic attitudes, but still sanctions a narrower range of such attitudes. Rosa presents one version: (MP): 'There are cases in which a certain body of evidence E makes believing that P rational, but E could also make suspending judgment about P rational'5 Rosa defends MP by offering a counterexample to U in which both suspending judgment and believing P are permissible, if in one case, an agent is incapable of making a particular inference.6 Of course, the leeway in doxastic attitudes sanctioned by MP may be much smaller.7 In this paper, I will defend the Uniqueness Thesis against Rosa's counterexamples,8 by appealing to a non-deontic account of rationality. I shall specifically defeat the counterexamples that defend some version of either EP or 1 To be clear, I am only concerning myself with the degree of confidence that a person can have with respect to a particular proposition. I do not take up whether it is permissible to use a given proposition as a premise in subsequent reasoning nor am I, in this paper, concerned with pragmatic encroachment. 2 Richard Feldman, "Reasonable Religious Disagreements," in Philosophers Without Gods, ed. Louise M. Antony (New York: Oxford University Press, 2007), 205. 3 Roger White, "Epistemic Permissiveness," Philosophical Perspectives, 19, Epistemology (2005): 447. 4 Luis Rosa, "Justification and the Uniqueness Thesis," Logos & Episteme III, 4 (2012): 572-574. 5 Rosa, "Justification and the Uniqueness Thesis," 572. 6 Rosa, "Justification and the Uniqueness Thesis," 574-575. 7 White, "Epistemic Permissiveness," 453. 8 Rosa, "Justification and the Uniqueness Thesis," 571-577. Defending The Uniqueness Thesis: A Reply to Luis Rosa 131 MP. If no counterexample to U can be constructed, it may be because U is necessarily true. Motivating U By definition, if a given belief B is based on extremely permissive evidence, E, then one could have rationally based the opposite belief on E. White's objection to EP is that if this is the case, then inferring B from E is no better than using an arbitrary process like taking a belief inducing pill or flipping a coin. However, if one's belief is arrived at via such an arbitrary process, it is irrational. The point about arbitrariness is crucial as a body of evidence, as a whole, cannot be said to support a proposition if it does not support the proposition more than its negation. It could be said that MP exhibits this same arbitrariness, but only to a lesser degree; only that the intuitive force of the point is not as strong as with EP. According to Kelly,9 in cases where the permissible range of views is so narrow that all permissible doxastic attitudes are only minutely different from one another, choosing one of those attitudes over another does not seem viciously arbitrary. One way of resisting U is to show via counterexamples, that having multiple doxastic attitudes from E is not arbitrary. Another strategy is to show via counterexamples, that those multiple doxastic attitudes, even if arbitrary, are not irrational. That is to say, that even if reasoning from the same piece of evidence leads different people to different conclusions, they may still be instantiating good types of reasoning. The focus of this paper will be the second strategy. This second approach10 is to invoke certain deontic features of reasoning, namely the idea that 'ought implies can,' that are prominent in internalist accounts of epistemic justification.11 Implicit in this strategy is the idea to say that some inference is rational implies that such an inference is either obligatory or permissible. Since real reasoners are incapable of thinking about all of their beliefs at the same time, they may fail to notice inconsistent beliefs that they may hold even when they make a sincere attempt to verify that all their beliefs are consistent with one another. I will call this way of using the term 'rational' d- 9 Thomas Kelly, "Can Evidence Be Permissive?" in Contemporary Debates in Epistemology, eds. Ernest Sosa, Matthias Steup, and John Turri (Oxford: Wiley-Blackwell, 2013): 298-311. 10 See Anthony Booth and Rik Peels, "Why Responsible Belief is Permissible Belief," Analytic Philosophy 55, 1 (2014): 75-88 and Rosa, "Justification and the Uniqueness Thesis," 571-577. 11 Richard Foley, "Conceptual Diversity in Epistemology," The Oxford Handbook of Epistemology, ed. Paul K Moser (Oxford: Oxford University Press, 2002), 179-180 Muralidharan Anantharaman 132 rational12 and contrast it with another way of using the term rational. If a given inference is beyond the capabilities of a reasoner, the inference is neither obligatory nor even permissible for that reasoner. If that is the case, then a person may have done the best that she was capable of, given her abilities, and still make different inferences from the same body of evidence due to chance or some other factors. For instance, limited reasoners may have to make tradeoffs between acquiring true beliefs and avoiding false beliefs. Different attitudes towards epistemic risk would make different inferences rational for different people. Since such a person could not have done more, she is not obligated to do more and cannot be called d-irrational. Since she has not failed her epistemic duties and even if she did have an epistemic duty, her failure to do so could not have been avoided; she is beyond criticism on this account. As such, both doxastic attitudes towards the evidence are rationally justified, though, perhaps, not simultaneously. Often, in such counterexamples, details about which inferences are made are not available. In such cases it becomes impossible to affirm or deny whether any of the reasoners' inferences are rationally defective. Luis Rosa13 presents counterexamples which are more detailed in this respect. When the exact inferences made are supplied, it is possible to assess the counterexample to see if Rosa is indeed correct about the rationality of both reasoners. If d-rationality was indeed the relevant way in which proponents of U think there can only be one rational response to the total evidence, then U is in trouble. I will argue, therefore, that there cannot be more than one rational response. I contend that there is another, non-deontic way in which we use the term 'rational' which is appropriate in at least some situations and more importantly, is the relevant sense in which U is meant and in which U is true. One way of talking about rationality which, arguably, cannot have deontic connotations is when we talk about defects in a person's reasoning.14 One of the counterintuitive implications about using d-rationality in such a situation is that 12 D-rationality as such seems to assume some significant level of doxastic voluntarism. I am, for the purposes of this paper, willing to grant this assumption. If this assumption seems unfounded, then that is one more reason to think that d-rationality is the wrong way to talk about epistemic rationality. Objections to U which rely on d-rationality being the right account of epistemic rationality will likewise be unsuccessful. 13 Rosa, "Justification and the Uniqueness Thesis," 571-577. 14 See Gideon Rosen, "Nominalism, Naturalism, Epistemic Relativism," Philosophical Perspectives, 15, Metaphysics (2001): 85, Booth and Peels, "Why Responsible Belief is Permissible Belief," 79, and David M. Holley, "Religious Disagreements and Epistemic Rationality," International Journal of the Philosophy of Religion 74 (2013): 41, for examples of such usage. Defending The Uniqueness Thesis: A Reply to Luis Rosa 133 to say that some instance of reasoning is without rational defect is to ordinarily imply that it is perfect. Consider the example of a person, Amanda, who is unable to use modus tollens.15 While we may in some circumstances be unwilling to call her irrational when she fails to use modus tollens to arrive at what seems to us a fairly obvious conclusion, we would be hesitant to say that her reasoning on the issue lacked rational defect. Since, as according to Rosa's description of the case, the inference that Amanda failed to make would have been obvious to us if we were in those circumstances even if it was not so to her, it seems intuitively obvious that her failure in this case is rationally defective. Yet, per definition, since she was unable to use modus tollens, she had no obligation to do so and her reasoning thus lacked any d-rational defect. In order to account for the above intuition, the term 'rationality' must be used in some other sense in which either 'ought' does not imply 'can' or in which it is not the case that one ought to make an inference which is rational. In order to bracket the question of whether 'ought implies can' applies to the epistemic ought, I will opt to use the term 'rationality' in the second way, namely, by taking rationality to not imply 'ought' or even 'may.' Then, even if 'ought' does imply 'can,' it does not apply when I use the term rational in this second sense. For clarity, I will use the term 'p-rational' to refer to the sense in which 'rational' is used in these cases. The question of whether a given inference is obligatory or permissible can be evaluated separately. We may say that an inference is p-rational if and only if no performance errors are made. A person makes a performance error in reasoning about a proposition P if the inference she makes is invalid or if she fails to make an inference that would have been valid had it been made and that inference bears on whether P. After all, if making that valid inference would not have resulted in a different doxastic attitude about P there are at least some cases where it would be unclear if such an error was relevant or significant.16 The preceding account of performance errors is not necessarily complete. Moreover, it is so demanding that all of us can be expected to fall short of its demands most of the time. However, this should not surprise us. Except in particularly simple reasoning tasks we cannot expect to avoid entirely any performance errors in our reasoning. Moreover, since 'ought implies can' does not apply to p-rationality, the fact that it 15 Rosa, "Justification and the Uniqueness Thesis," 574-575. 16 There are also some cases where such a failure would be relevant but I need not explore those instances in order to make my point in this paper. See John Turri, "On the Relationship between Propositional and Doxastic Justification," Philosophy and Phenomenological Research LXXX, 2 (2010): 312-326, for an excellent discussion of some of these cases. Muralidharan Anantharaman 134 is a demanding account of rationality is not a criticism that is applicable. After all, demanding-ness matters only if 'ought' implies can. It is adequate for my purposes if making an invalid inference as well as the failure to make a valid inference are performance errors. However, how do we characterise a valid inference? For the purposes of this paper, it is adequate to note that modus ponens and modus tollens are valid inferences as is replacing a conditional (If P then Q) with the disjunction (not-p or Q) containing the negated antecedent. I will now use this account of p-rationality to demonstrate that the alleged counterexamples to U, provided by Rosa that attempt to show that there is more than one rational doxastic response to some given evidence, are unsuccessful. If it can be shown that one or more of those inferences are invalid, then it would disqualify those inferences from being rational. Rosa's defence of Extreme Permissiveness (EP) To defend EP, Rosa uses the example of Michelle who draws conclusions from a body of evidence E which, unknown to her, contain inconsistent premises. Michelle believes about George, the following: 1. George is tired, but willing. 2. If George is tired he will rest or sleep. 3. George is not willing or it is not the case that he will rest or sleep.17 From the first and second premises, Michelle can conclude that George will rest and (or) sleep. From the first and third, she can conclude that he will not. Given Rosa's description, it should be obvious to the reader that the three premises are inconsistent even if it is much less apparent to Michelle. Abstracting from the particular content of the beliefs in question, the case can be described in the following way: Michelle could, using some of her premises found in E, rationally infer a conclusion C. Michelle could also rationally infer from some other premises found in E that not-C. Since, according to Rosa, either of the inferences would be rationally warranted, and Michelle, by stipulation and given the circumstances, could not have known that E contained inconsistent premises, both C and not-C are rational inferences from E for Michelle. Rosa further bolsters this conclusion by appealing to the intuition that we would be reluctant to call Frege irrational just because he 17 Rosa, "Justification and the Uniqueness Thesis," 572. Defending The Uniqueness Thesis: A Reply to Luis Rosa 135 failed to notice the contradictions inherent in his logical axioms. By such an exacting standard, Rosa argues, none of us are rational.18 This bullet is a tough one to bite, only if the appropriate sense of rational used is d-rational. But, if p-rationality is the appropriate notion of rationality in this situation, it is not so difficult to think that reasoning from inconsistent premises is not rational even if it was unknowingly done. However, how could this be the case? The permissivist may argue that even if there is still a mistake made in reasoning from inconsistent premises, it is not a performance error as no invalid inferences are made, and only a performance error can implicate the quality of a given inference. Consider a variant of the above situation where Michelle has misleading evidence E' instead. E' is consistent, but at least one of its premises, unknown to her, is wrong. There is further nothing that Michelle could reasonably have done to figure out that E' contained a false premise. In this case, there is no sense in which Michelle is irrational when she derives C' by applying modus ponens to E'. Likewise, there is no performance error when carrying out modus ponens even when the premises are false. Michelle might be mistaken in thinking that E' was appropriate to base her reasoning on, but we cannot necessarily attribute any performance error on her part. After all, if E' had been true, using modus ponens on E' would necessarily have yielded a true conclusion. If one's premises are inconsistent, there are valid inferences that one could make from one's premises that would show that this is indeed the case. The only way in which one could be unaware that this is the case is if one failed to make a particular valid inference from one's own premises. Even if this lapse is excusable, unavoidable and thus often committed by all human reasoners, it is still a performance error. Thus, a person makes a performance error in failing to notice that she has inconsistent premises. A permissivist may still argue that even if the failure to infer that E contains inconsistent premises is some sort of performance error, it is not necessarily a performance error that is relevant to whether C or not-C. Let me illustrate: If there is only one pair of inconsistent premises one of which is true, E can be made consistent by eliminating the one premise, A, to yield E' or eliminating the other one, not-A, to yield E''. Presumably, C can be validly inferred from E' and not-C from E''. Even if the fact that E contains inconsistent premises was inferred, since either A or not-A could be rejected to make the set of beliefs consistent, it seems that not only is either way of resolving the contradiction equally rational, identifying that a contradiction exists still leaves us in a position of having to decide between inferring C and not-C via the intermediate step of resolving the 18 Rosa, "Justification and the Uniqueness Thesis," 573-574. Muralidharan Anantharaman 136 contradiction one way or the other. If identifying a contradiction necessarily resulted in one conclusion being identified as more rational than the alternative, the failure to identify the contradiction would be a relevant performance error. But, the permissivist could argue that this is not the case here since there is, according to the permissivist, no uniquely best way of resolving the contradiction. However, the permissivist is mistaken about this last claim. Identifying the existence of a contradiction is relevant because there is a uniquely rational way of resolving contradictions. In addition to rejecting A or not-A, there is also the option of suspending judgment on both premises to yield E'''. It is the case that either A has more support, less support or as much support as not-A. Let us suppose that Michelle possesses evidence T bearing on A or not-A. If the total evidence T supports either A over not-A or vice versa, then one or the other is to be rejected yielding either E' or E''. Given that one of the propositions enjoys greater support than the other, Michelle would be making a performance error if she rejected the proposition which enjoys greater support. Thus, if one of the propositions had more support than the other, there would be only one uniquely best response to the evidence E. However, what if both A and not-A were equally well supported by T? Might it not be the case that rejecting either one of A or not-A was equally good? If rejecting A was just as good as rejecting not-A, suspending judgment about A or not-A would be better than rejecting either proposition. This is easily demonstrable once we translate the degree of support for the statement A provided by T as the probability that A given T, p(A|T). Since, per assumption, T supports A and not-A to the same extent, p(A|T) = p((not-A)|T) ---------------------- (1) Since that A and not-A cannot both be true at the same time,19 the probability axioms cannot be violated. Since A and not-A are mutually exclusive and exhaust all logical possibilities, p(A|T) + p((not-A)|T) = 1 -------------------(2) Solving for (1) and (2), p(A|T) = p((not-A)|T) = 0.5 Since, according to the evidentialist, epistemic rationality just amounts to apportioning one's degree of belief in a proposition to the support for that proposition by the evidence that one has, suspending judgment about A and not-A is the only response that comes closest to being proportional to the support for 19 For the purposes of this paper, I will exclude non-standard logics. Defending The Uniqueness Thesis: A Reply to Luis Rosa 137 those propositions by the total evidence T. Thus, any response other than suspending judgment about A and not-not-A would be a performance error. I have thus shown that knowingly reasoning from inconsistent premises constitutes a performance error. EP is thus, absent a better counterexample, indefensible, at least when we use p-rationality. Having disarmed Rosa's EP counterexample with p-rationality, I will now turn to Rosa's counterexample defending MP. Rosa's Defence of Moderate Permissiveness (MP) The argument against MP is equally strong. Rosa defends MP by appealing to the example of Amanda who in possible world W1, is able to infer that she did not press a button from the following premises via modus tollens: 1. If Amanda presses the button, her computer will get infected with a virus. 2. Amanda's computer is not infected with a virus. Amanda has a counterpart in possible world W2 who is incapable of carrying out modus tollens and thus suspends judgment about whether she pressed the button. Moreover, since she does not believe she has good reason to believe that she pressed the button, according to Rosa, it would be absurd to say that she is irrational in suspending judgment about whether she pressed the button. Thus, if Rosa is right, both believing and suspending judgment about whether she pressed a button are fully rational responses to E in at least this case.20 However, the same criticism that was levelled against the EP case can also be levelled against the MP case. It may be that Amanda2 is not required to use modus tollens if she cannot and if she sees no reason to. Or even if she is required to, perhaps she is blameless because she lacks the capacity to do so. Yet, it is obvious that Amanda2's inability to use modus tollens means that she is predisposed to fail to make many valid inferences from her premises. This would constitute a performance error on Amanda2's part and she would not be p-rational. In fact, it is hard to say that Amanda2 possesses even a normal reasoning ability let alone a particularly good one. The only way out for Rosa here is if it were somehow the case that modus tollens was not valid in W2 but valid in W1. But this seems implausible. In both W1 and W2, using modus tollens on true premises necessarily gives us true conclusions. This means that modus tollens has to be valid in both worlds. 20 Rosa, "Justification and the Uniqueness Thesis," 574-575. Muralidharan Anantharaman 138 It thus seems to be the case that Rosa's defence of MP is unsuccessful. If no better counterexample is available, MP is indefensible. Nevertheless, there might be other counter-examples to U that are even more refined than Rosa's. These counterexamples would have to unambiguously show instances where more than one conclusion can be inferred from a given body of evidence and that both inferences are impeccable. Conclusion The above discussion has rebutted counterexamples aiming to establish that even if two doxastic responses to some evidence are arbitrary, they can still be rational. In order to establish U, I need to rebut counterexamples that purport to show that sometimes, multiple responses to some given evidence are non-arbitrary. Even if I end up showing that U is true given p-rationality, the permissivist might still claim that using the word rationality to mean p-rationality is only appropriate in some circumstances and d-rationality fits better with the way we speak. Even if as a descriptive matter, this was true; there might be some reasons to revise the way we use the word rational to refer to p-rational instead. For one, anything we can say in terms of d-rationality can be said in terms of p-rationality. Since drationality refers to what inferences we are obligated or permitted to make, the set of d-rational inferences can be cashed out in terms of the set of inferences that most closely resemble p-rational inferences and which the reasoners in question are capable of making. On the other hand, there are some things that can be expressed in terms of p-rationality which cannot be expressed in terms of d-rationality. Suppose there are a set of inferences all of which are beyond the capabilities of a given agent, some of which contain fewer performance errors than others. For instance, suppose a large set, S, of statements exists such that some of them contradict one another. S also contains an indicative conditional C for which the consequent is also contained in S. Because S is very large, John, an ordinary but competent reasoner would not be able to identify that S contains inconsistent premises. It is also the case that because S is very large, John would not be able to affirm the consequent with respect to C. Since both inferences are beyond John's capabilities, it is not d-rational to make either inference. Thus, if d-rationality is the concept that is referred to by doxastic rationality, both inferences are on par. However, if p-rationality is the relevant notion of rationality, identifying a contradiction is clearly superior to affirming the consequent. Thus p-rationality cannot be cashed out in terms of d-rationality. This asymmetry means that using rationality to refer to p-rationality is more conducive Defending The Uniqueness Thesis: A Reply to Luis Rosa 139 to analytic clarity. This also means that it is in terms of p-rationality that the Uniqueness Thesis should be evaluated. Evaluating decision procedures for instances of peer-disagreement would be derivative of this. A second reason to think that p-rationality is the right way to use rationality in this instance is that p-rationality connects up more directly with the motivating intuition behind the Uniqueness Thesis. If all I am concerned about is whether I have violated my epistemic duties in some blameworthy manner, then meeting an epistemic peer who shares my evidence but who still disagrees with me is not necessarily troubling. Having done all I reasonably could have been expected to do in order to ensure that my beliefs are true, I would have no further epistemic duties. However, if I am concerned with acquiring true beliefs and avoiding false beliefs, then the presence of someone who is my epistemic peer and who shares my evidence, but disagrees with me is more worrying. More precisely, the worry is that since both beliefs cannot be true at the same time and since the evidence is, by assumption, true, at least one person has made a performance error in reasoning and that person may very well be me! If this is the case, then any attempt to justify epistemic permissiveness by appealing to our cognitive limitations is mistaken.21 21 I would like to thank Axel Gelfert, Tang Weng Hong, Chetan Cetty, Yeo Shang Long, Peter Kung and Luis Rosa for instructive comments on the paper.