Presuppositional Epistemic Contextualism and the Problem of Known Presuppositions* Michael Blome-Tillmann Abstract In this chapter, I produce counterexamples to Presuppositional Epistemic Contextualism (PEC), a view about the semantics of 'knowledge'-ascriptions that I have argued for elsewhere. According to PEC, the semantic content of the predicate 'know' at a context C is partly determined by the speakers' pragmatic presuppositions at C. The problem for the view that I shall be concerned with here arises from the fact that pragmatic presuppositions are sometimes known to be true by the speakers who make them: hence the Problem of Known Presuppositions. After discussing several unsuccessful ways to solve the problem, I propose the addition of a new Lewisian rule of proper ignoring to the semantics of PEC-namely, the Rule of Evidence-Based Ignoring. If the proposed account succeeds, the Problem of Known Presuppositions has a straightforward solution within the framework of PEC. 1. Presuppositional Epistemic Contextualism Epistemic Contextualism (EC) is a semantic view-namely, the view that 'knowledge'ascriptions can change their contents with the conversational context. Notwithstanding this purely linguistic characterisation of EC, contextualists have traditionally argued that their views are of considerable philosophical importance, this being due to the alleged fact that their linguistic views about 'knowledge'-ascriptions provide the resources for a resolution of sceptical puzzles. Thus, even though contextualists typically tend to argue that EC is sufficiently motivated by the linguistic data deriving from familiar examples such as DeRose's Bank Case or Cohen's Airport Case,1 they have also frequently argued that their linguistic views about 'know' are of considerable epistemological significance. David Lewis, for instance, conceives of his version of EC as providing us with a response to the sceptical problem. According to Lewis: (L) x satisfies 'knows p' in context C ↔ x's evidence eliminates every ¬p-world, except for those that are properly ignored in C.2 In addition to this definition of the satisfaction of 'knows', Lewis stipulates a set of rules of relevance specifying which possibilities can be properly ignored in a given context. It is this set of rules that is meant to determine how the content of 'knowledge'-attributions * I am indebted to the participants of the Knowledge Attributions Workshop in St Andrews, especially to Jessica Brown, Mikkel Gerken, Ephraim Glick, Jonathan Ichikawa, Aidan McGlynn, and Matthew McGrath. 1 See (Cohen 1999, p. 58; DeRose 1992, p. 913). 2 On Lewis's approach, our evidence consists in the totality of our perceptual experiences and memory states, and a possibility w is eliminated by an experience (or memory state) iff the experience's (or the memory state's) existence (rather than its content) conflicts with w. See (Lewis 1996, p. 224). 2 is influenced by particular contextual factors. The rule doing the main explanatory work in Lewis's account is the Rule of Attention (RA): (RA) If w is attended to by the speakers in C, then w is not properly ignored in C. As Lewis points out, (RA) eventually boils down to the apparent triviality that "a possibility not ignored at all is ipso facto not properly ignored."3 Once (RA) is in place, Lewis's account entails that for most propositions p about the external world, in contexts where sceptical arguments are at issue, we do not satisfy 'knows p': in such contexts we attend to sceptical scenarios, which are by definition uneliminated by our evidence.4 Despite this concession to the sceptic, Lewis's account also entails the anti-sceptical result that we satisfy 'knows p' in quotidian contexts, for many propositions p about the external world that we intuitively take ourselves to know. And this is so, Lewis explains, because in quotidian contexts we do not attend to and can therefore properly ignore sceptical counterpossibilities: in quotidian contexts, the satisfaction of 'knows p' does not require us to eliminate far-fetched sceptical counterpossibilities.5 However, Lewis's (RA) has seemed too strong to many, for it seems to make it too difficult to satisfy 'knows p'. On the account at issue, one merely needs to attend to the possibility that one is a brain in a vat-without taking that possibility seriously at all- and one already ceases to satisfy 'knows p'. (RA), the objection goes, makes contextual changes of so-called 'epistemic standards' far too frequent.6 However, as I have argued elsewhere,7 a more attractive alternative to Lewis's (RA) is easily obtained. To see what I have in mind, note that by means of (RA) Lewis exploits the contrast between ignoring a proposition and attending to it. Lewis: "if in this context we are not in fact ignoring it but attending to it, then for us now it is a relevant alternative."8 However, it seems obvious that, pace Lewis, merely attending to-or directing one's mind towards-some possibility w is not enough for making it impossible to properly ignore w in the epistemologically relevant sense. The notion of ignoring I have in mind is thus not that of ignoring w as opposed to attending to w, but rather that of ignoring w as opposed to taking w seriously. On this second reading we surely can attend to the possibility that we are brains in vats while nevertheless ignoring this possibility in a straightforwardly practical sense: you can surely entertain the thought that you might be a brain in a vat, or direct your mind towards that possibility, without taking this very possibility seriously or giving it any credence. The idea of replacing Lewis's (RA) with a rule employing the notion of taking a possibility seriously instead of merely attending to it comes to mind: if a possibility is taken seriously in a context C, that is if it is among the 'live options' in C, then it cannot be properly ignored in C. However, what exactly does it mean for a possibility to be a 'live option' in a context C? As I have argued elsewhere, the most plausible and attractive way 3 (Lewis 1996, p. 230). 4 Given Lewis's notion of evidence-see above fn. 2. 5 I assume here that none of the other Lewisian rules of relevance such as his Rule of Actuality, Resemblance or Belief mark out sceptical counterpossibilities as relevant in quotidian contexts. 6 See, for instance, (Williams 2001, p. 15) for this point. 7 (Blome-Tillmann 2007; 2009b). 8 (Lewis 1996, p. 230; Lewis's emphasis). 3 to explicate the notion at issue is by means of the notion of a pragmatic presupposition:9 a possibility w is taken seriously in C just in case w is compatible with the speakers' pragmatic presuppositions in C. On this view, we can implement the idea that 'live options' cannot be properly ignored by means of the following Rule of Presupposition: (RP) If w is compatible with the speakers' pragmatic presuppositions in C, then w is not properly ignored in C. Note that (RP) is a prohibitive rather than a permissive rule: it adds possibilities to the set of worlds that cannot be properly ignored, so (RP) can always only make it harder to satisfy 'knows' than it would already be without (RP). In other words, possibilities that have been marked out as epistemically relevant by the remaining Lewisian rules will never become epistemically irrelevant merely because they are incompatible with our presuppositions: obtaining 'knowledge' was never meant to be that easy. Why should we want to link the content of 'know' in C to the speakers' presuppositions in C rather than to other contextual features? The advantages of such a move are fairly obvious: since speakers can, to a certain extent, voluntarily decide what they take seriously and which propositions they presuppose, they have, to a certain extent, voluntary control over the content of 'know' in their contexts. To be precise, on the view envisaged, speakers can decide whether those possibilities that are not marked out as epistemically relevant by rules other than (RP) will be taken seriously or not. For instance, as long as the speakers in a context C pragmatically presuppose the negations of sceptical hypotheses, sceptical possibilities will be properly ignored in C-even though attention may have been drawn to such possibilities.10 Thus, replacing Lewis's Rule of Attention by my Rule of Presupposition makes our account of the semantics of 'knows' considerably more robust and stable: 'knows' no longer changes its content as soon as we merely attend to a counterpossibility that we are far from taking seriously.11 In what follows, I shall call the view just outlined Presuppositional Epistemic Contextualism, or simply 'PEC'. PEC is a particular type of epistemic contextualism-namely, one that claims that the predicate 'know' is an indexical expression. 'Know' has, according to PEC, an unstable Kaplan character-that is, a character that does not map all contexts on the same content.12 Moreover, as I have argued elsewhere, PEC has a number of explanatory advantages over more traditional versions of EC. For instance, PEC puts us in a much stronger position to account for competent speakers' intuitions about sceptical arguments than traditional versions of EC do, as it allows us to distinguish between what is presupposed in a subject's private context of thought and what is presupposed in the subject's public context of conversation. In fact, it is due to this very distinction that PEC has a neat explanation of the intuitions of Moorean Dogmatists.13 In addition, once we flesh out the role of pragmatic presuppositions in the framework of PEC, we obtain a precise and detailed account of what exactly determines the content of 'know' in a given conversational context. Where other versions of EC speak vaguely of a context's 'epistemic standards', PEC can explicate in detail which features of a particular conversa- 9 See (Blome-Tillmann 2009b). 10 I again assume that none of the other Lewisian rules that (RP) is to be supplemented with prohibit properly ignoring sceptical possibilities in C. 11 See (Blome-Tillmann 2009b, p. 275ff). 12 See (Kaplan 1989). 13 See (Blome-Tillmann 2009b, §§7-8). 4 tional context are responsible for the content-determination of our epistemic vocabulary.14 However, PEC's relative precision and level of detail also bring with it a certain susceptibility to counter-examples. One such type of counterexample shall be discussed in the following sections. 2. The Problem: Previously High Stakes To begin our discussion, consider the familiar bank cases as we know them from (DeRose 1992, p. 913) and (Stanley 2005, pp. 3-4): Low Stakes: Hannah and her wife Sarah are driving home on a Friday afternoon. They plan to stop at the bank on the way home to deposit their paycheques. It is not important that they do so, as they have no impending bills. But as they drive past the bank, they notice that the lines inside are very long, as they often are on Friday afternoons. Realizing that it isn't very important that their paycheques are deposited right away, Hannah says, 'I know the bank will be open tomorrow, since I was there just two weeks ago on Saturday morning. So we can deposit our paycheques tomorrow morning.' High Stakes: Hannah and her wife Sarah are driving home on a Friday afternoon. They plan to stop at the bank on the way home to deposit their paycheques. Since they have an impending bill coming due, and very little in their account, it is very important that they deposit their paycheques by Saturday. Hannah notes that she was at the bank two weeks before on a Saturday morning, and it was open. But, as Sarah points out, banks do change their hours. Hannah says, 'I guess you're right. I don't know that the bank will be open tomorrow.'15 Our intuitions concerning Low Stakes are that Hannah speaks truly when she self-ascribes 'knowledge'. In High Stakes, however, our intuitions are reversed: in High Stakes our intuitions are that Hannah speaks truly when denying that she 'knows that the bank will be open on Saturday' (henceforth 'knows O'). In what follows, I shall assume that the reader is familiar with the general contextualist account of these data. According to EC, the predicate 'know' has different semantic values in the two cases. And even though this claim has proven rather difficult to model semantically, PEC has an elegant explanation of the shift in semantic value: according to PEC the predicate 'know' has different semantic contents in the two cases because Hannah and Sarah pragmatically presuppose in Low Stakes, but not in High Stakes, that the bank has not changed its hours recently. Leaving aside Low Stakes and High Stakes for the moment, let us move on to an alternative case inspired by an example developed by Brian Weatherson (2003)-I shall call my version of the case Previously High Stakes.16 As will become obvious in a moment, the example is set on the background of the orthodox High Stakes case, but in Previously High Stakes Hannah and Sarah are wondering a day later, on Saturday evening, whether Hannah 'knew', on Friday, that the bank would be open on Saturday morning. Here is Previously High Stakes: Previously High Stakes: 14 For a detailed discussion of objections and responses to PEC see (Blome-Tillmann 2007; 2008; 2009b). 15 Schaffer (2006) calls into question (to my mind correctly) the view that it is our practical interests that determine our epistemic standards. I shall, however, ignore the issue in this paper. 16 See (Weatherson 2003). 5 Hannah and her wife Sarah are driving home on a Friday afternoon. They plan to stop at the bank on the way home to deposit their paycheques. But as they drive past the bank, they notice that the lines inside are very long, as they often are on Friday afternoons. Since they have an impending bill coming due, and very little in their account, it is very important that they deposit their paycheques by Saturday. Hannah notes that she was at the bank two weeks before on a Saturday morning, and it was open. But, as Sarah points out, banks do change their hours. After debating for a few moments, Hannah and Sarah decide to take the risk-they will return to the bank tomorrow morning. The following day, on Saturday morning, Hannah and Sarah return to the bank, and find it open. They are pleased that they avoided yesterday's lines and deposit their paycheques. In the evening, at a dinner party, Hannah and her friends are small-talking and sampling canapés. When Hannah tells her bank story, John asks why they didn't deposit their paycheques on Friday afternoon, if it was so important. Hannah notes that she was at the bank two weeks before on a Saturday morning, and it was open. But, as John points out, banks do change their hours. Hannah says, 'I guess you're right. I didn't know that the bank would be open on Saturday. But the lines were just too long on Friday, and we really didn't fancy waiting!' Interestingly, Hannah's utterance of 'I didn't know that the bank would be open on Saturday' in this case is as natural and sensible as her utterances in the initial High Stakes and Low Stakes cases. In fact, the case parallels High Stakes in that Hannah's negative 'knowledge'-attribution seems both felicitous and true, while crucially differing from High Stakes in that the utterance at issue is not made in a high-stakes context: on Saturday evening, Hannah and John both know that the bank was open in the morning and the paycheques at issue have been safely deposited on time for Monday's impending bill. Thus, I shall, in what follows, assume that any satisfactory version of epistemic contextualism must not only account for the data from Low Stakes and High Stakes, but also for those from Previously High Stakes.17 Before taking a closer look at how precisely Previously High Stakes spells trouble for PEC, it is worthwhile noting that Subject-Sensitive Invariantism (SSI)-the view that knowledge is sensitive to the subject's situation-has an elegant explanation of the data from Previously High Stakes: the subject of the 'knowledge'-attribution, Hannah-onFriday, is after all in a high-stakes situation and therefore cannot properly ignore the possibility that the bank has changed its hours recently. Moreover, since Hannah's evi- 17 Weatherson's (2003) original case differs from mine in involving a positive 'knowledge'-ascription that is perceived to be infelicitous or even false. As Weatherson points out, his intuitions about his original case are that Hannah's utterance "is no more acceptable by regular conversational standards than if she had held her ground in [High Stakes] and said [...] 'Whatever, I know it's open Saturday morning'." Jessica Brown (2006) agrees with Weatherson's assessment and claims along similar lines that "[Hannah]'s selfattribution [in Weatherson's original case] seems incorrect although, in the context of attribution, the stakes are low and error is not salient." Weatherson's original datum that positive 'knowledge'-attributions would be infelicitous is, of course, important and any account of the semantics of 'knowledge'-attributions must address it. However, as DeRose (2009, pp. 52-53) has pointed out, it is presumably easier to account by non-semantic means for an utterance's infelicity and apparent falsity than for an utterance's felicity and apparent truth. Given that non-semantic explanations of Weatherson's original case might be available that would not work for my amended version of the case, I shall in what follows focus my attention on Previously High Stakes. Moreover, it should be noted that Weatherson also discusses a case involving a third person, Suzanna, who was in a low-stakes situation on Friday. Weatherson has the intuition that, in a conversation between Hannah, Suzanna and John (Weatherson's John is called 'Woody') on Saturday evening, Hannah's utterance of 'I knew that the bank would be open today' would be "unacceptable", while Suzanna's utterance of the same sentence would be "perfectly fine". I shall ignore the issue in this paper, but should note that I do not share Weatherson's intuition about Suzanna's utterance. 6 dence on Friday does not eliminate that counterpossibility, Hannah did not know, on Friday, that the bank would be open on Saturday. Thus, Hannah's utterance on Saturday of 'I didn't know, on Friday, that the bank would be open on Saturday' is, in fact, true-and that is the reason why her utterance seems true and felicitous to us. For the defender of PEC, things are not that straightforward. Since the speakers at the dinner party on Saturday know that the bank was open on Saturday morning, they pragmatically presuppose that proposition. Thus, the possibility that the bank was not open on Saturday morning because it had changed its hours recently is not a 'live option' at the dinner party. If this is so, however, the question arises as to why that possibility cannot be properly ignored at the party on Saturday evening: neither (RP), nor any of the remaining Lewisian rules of proper ignoring mark out the possibility at issue as one that cannot be properly ignored. Summing up, PEC, as formulated in the previous section, entails that Hannah's utterance in Previously High Stakes both conveys and semantically expresses a falsehood, which is clearly unacceptable. Surely, Hannah's utterance in Previously High Stakes conveys a truth. Before moving on, note that the problem just sketched does not arise for Lewis's initial version of EC, which was based on the Rule of Attention (RA). The reason is that on Saturday evening Hannah and John attend to the possibility that the bank had changed its hours recently and was therefore closed on Saturday morning. Since that possibility is attended to at the dinner party it is, given (RA), not properly ignored at that context. Consequently, Hannah speaks truly in Previously High Stakes when claiming that she 'didn't know that the bank would be open on Saturday', and Lewis has a straightforward explanation of the case at hand. Nevertheless, it ought to be emphasized once more that Lewis's (RA)-based version of EC runs into serious problems with numerous other examples in which it erroneously predicts that we do not satisfy 'knows p' when we clearly do.18 We should therefore refrain from reverting to Lewis's evidently problematic view and explore further the option of amending PEC. As will become obvious in the following sections, a solution to the problem posed by Previously High Stakes that is wholly within the spirit of PEC can be found fairly easily.19 How are we to proceed? To arrive at a better understanding of the type of case under scrutiny consider the following example that is structurally similar to Previously High Stakes: Russian Roulette: Peter and Paul are having a conversation about the game of Russian Roulette. As it happens, Peter holds a revolver with exactly one bullet and seven empty chambers. He spins the cylinder, points the revolver at his head and pulls the trigger. Peter is lucky; the chamber randomly selected is empty. After some initial puzzlement, Paul utters: 'Are you insane!? Why did you do that?' Peter responds: 'You're right, it was quite mad. I didn't know that the chamber would be empty.' Without a doubt, Peter's utterance of 'I didn't know that the chamber would be empty' expresses a truth: the chamber was, after all, randomly selected. What is interesting about Russian Roulette, however, is that the possibility that the bullet was in the chamber can- 18 Cp. (Blome-Tillmann 2009b, p. 246ff.). 19 I should also emphasize that DeRose's (1995) account and his "Rule of Sensitivity", which is better described as a Rule of Safety, can account for the data at issue, too. However, as I have argued elsewhere (Blome-Tillmann 2009a), it delivers rather implausible results in a number of other cases. 7 not be properly ignored after Peter has pulled the trigger, when both Peter and Paul know that the chamber was in fact empty. Thus, after Peter has pulled the trigger, there is a possibility w that cannot be properly ignored despite the fact that w is known to be nonactual and therefore incompatible with Peter and Paul's pragmatic presuppositions. Interestingly, however, PEC has a straightforward explanation for why w cannot be properly ignored in Russian Roulette: the possibility that there was a bullet in the chamber cannot be properly ignored because it closely resembles the subject's-that is, Peter's actuality, up to the time of his pulling the trigger. Thus, Lewis's Rule of Actuality in conjunction with his Rule of Resemblance ensures that w is not properly ignored. Russian Roulette is, accordingly, another case in which the speakers pragmatically presuppose that p because it is mutually known that p, while they nevertheless cannot properly ignore some ¬p-worlds. The crucial difference to Previously High Stakes, however, is that in Previously High Stakes the problem cannot be resolved by means of the Rule of Actuality in conjunction with the Rule of Resemblance: the counterpossibility in which the bank has changed its hours recently is simply not similar (or 'close') enough to Hannah's actuality on Friday.20 As a consequence, it seems that we must add a new rule to PEC, if we are to account for the data from Previously High Stakes.21 3. Selecting Standards? In response to the challenge arising from Previously High Stakes it is worth considering what other contextualists have said about similar cases. DeRose (2009, p. 240), for instance, defends the view that speakers can "select epistemic standards", and that they sometimes select the standards prevalent in the subject's context. With this view in place, Hannah and John on Saturday evening might be said to have selected the standards of Hannah's context on Friday, to the effect that the initially low-standards context at the dinner party ultimately turns into a high-standards context. On this view, Hannah's utterance of 'I didn't know, on Friday, that the bank would be open today' in Previously High Stakes comes out true because the epistemic standards switch from low to high when Hannah and John adopt Hannah's earlier Friday afternoon standards.22 Even though this response might seem attractive at first sight, it should be noted that it is only viable if supplemented with a more detailed and informative conception of epistemic standards and their selection. As long as we are not told more about what epistemic standards are, how they are contextually determined, and-most crucially-how they are selected, we cannot determine whether Hannah and John in Previously High Stakes have in fact 'selected' the higher epistemic standards from Hannah's Friday con- 20 Note that if we thought that it was close enough to Hannah's actuality to not be properly ignored in virtue of the Rule of Resemblance, then Hannah would speak falsely in Low Stakes, for her belief would, in other words, not be safe (the Rule of Actuality functions, in conjunction with the Rule of Resemblance, as a safety constraint on the satisfaction of 'knows' in all contexts). 21 Note also that we can construct cases similar to Russian Roulette in which nothing at all is at stake for the subjects and speakers. Consider, for instance, a case in which a coin is flipped for no particular practical reason. As in the above case, it is the combination of the Rule of Actuality and the Rule of Resemblance that ensures that worlds in which the coin came up differently from how it actually did are not properly ignored in contexts in which the subject of our 'knowledge'-ascription is unaware of the coin flip's outcome. 22 In fact, DeRose himself suggests this move in his response to Weatherson's (2003) blog post. 8 text.23 Despite these problems, DeRose's view is certainly intuitively appealing, which can be demonstrated by an example in which speakers do in fact seem to adopt or adjust to different epistemic standards. Consider the following case: Switch to High Standards: Sarah is going for a stroll on a Friday afternoon, when she meets her friend Jeff, who is on his way to the bank to deposit a cheque from his health insurance. It is not important that he does so, as he has no impending bills and the cheque is for a very minor sum only (£3.79). As they are approaching the bank, Jeff notices that the queues inside are very long, as they often are on Friday afternoons. Realizing that it isn't very important that his cheque is deposited right away, Sarah says, 'I know the bank will be open tomorrow, since I was there just two weeks ago on Saturday morning. So you can deposit your cheque tomorrow morning.' Jeff thanks Sarah for the information and sets off to the nearby bowling alley. As Sarah continues her stroll, she meets her friend Hannah, who is also on her way to the bank to deposit her paycheque. Hannah has an impending bill coming due, and very little in her account, so it is very important that she deposits her paycheque by Saturday. Sarah tells Hannah about the long lines inside the bank, and notes that she was at the bank two weeks before on a Saturday morning, and it was open. But, as Hannah points out, banks do change their hours. Sarah says, 'I guess you're right. I don't know that the bank will be open tomorrow. You should go and check with the tellers.' Intuitively, Sarah speaks truly both when talking to Jeff and when talking to Hannah in this example. And as is presumably rather obvious, within the framework of PEC we can account for these data fairly easily: when realizing that it is very important for Hannah that she deposits her paycheque by Saturday, Hannah suspends her pragmatic presupposition that the bank has not changed its hours recently. The possibility that the bank has changed its hours recently is therefore, in Sarah's conversation with Hannah, no longer properly ignored. The crucial feature of PEC that enables us to model the semantics of 'knows' in a way that accounts for the above data is, of course, the fact that speakers can choose which propositions they pragmatically presuppose. It is this feature of PEC that allows for considerable flexibility with respect to the change of epistemic standards- which is, as I have argued elsewhere, a feature of the theory that helps explain a vast range of data concerning context change.24 However, note that the mechanisms of contextual change responsible for the switch in standards in the above example are entirely ineffective with respect to the case we set out to account for-namely, Previously High Stakes. To see this, let us assume that, in DeRose's terminology, Hannah and John in Previously High Stakes have in fact adopted or 'selected' Hannah's previous standards from Friday, when she did not pragmatically presuppose that the bank had changed its hours recently and would therefore be closed on Saturday morning (henceforth '¬O'). Within the framework of PEC, this assumption commits us to the claim that Hannah and John have suspended, on Saturday evening, their pragmatic presupposition that ¬O. Such an analysis of Previously High Stakes, however, is clearly not viable in the case at hand, because, as a matter of fact, John and Hannah do not on Saturday evening suspend their presupposition that ¬O. To the contrary, it is, at the dinner party on Saturday evening, both mutually known, accepted, and pragmatically presupposed that ¬O: Hannah has, after all, been at the bank on Saturday 23 It should be noted that DeRose has his own conception of epistemic standards, but it is doubtful whether that conception can do the work that DeRose wants it to do. For discussion see (Blome-Tillmann 2009a). 24 (Blome-Tillmann 2009b). 9 morning and it was open. Implementing DeRose's intuitive idea about ascribers' selection of the subject's epistemic standards is accordingly far from trivial once we have committed to a more detailed and serviceable account of the workings of contextual shifts such as the one offered by PEC. 4. The Rule of Presumed Interests A different solution is needed. Let us therefore consider an approach on which it is the very semantics of 'knows' that allows us to account for the data from Previously High Stakes. In particular, consider the idea of adding a novel rule of proper ignoring to the set of rules already postulated by PEC. Precisely what are the worlds that we need to single out as not being properly ignored? What comes to mind, I take it, is to isolate exactly those possibilities that the speakers presuppose ought not to be ignored by the subject, given her presumed practical interests. Consider the following rule: Rule of Presumed Interests (RPI): If it is presupposed in C that the subject x, given her presumed practical interests, ought not to ignore w, then w is not properly ignored in C. According to (RPI), a subject x's evidence needs to eliminate all those counterpossibilities that are, in the context of ascription, presupposed to be practically relevant to the subject. Does (RPI) help resolve the problem posed by Previously High Stakes? Note that the idea behind introducing (RPI) is that in Previously High Stakes Hannah and John presuppose, on Saturday evening, that, on Friday, Hannah ought not to have ignored the possibility that the bank has changed its hours recently. Thus, if John and Hannah do in fact make that presupposition, then the possibility that the bank has changed its hours recently cannot be properly ignored on Saturday evening and we have an explanation of the data from Previously High Stakes. Obviously, once (RPI) has been introduced, the crucial question is whether, on Saturday evening at the dinner party, Hannah and John do in fact presuppose the proposition in question. I do not think that that assumption is implausible. To see why, note that pragmatic presuppositions are dispositional propositional attitudes. According to the notion of a presupposition employed in the framework of PEC, one pragmatically presupposes p iff one is disposed to behave, in one's use of language, as if one believed p to be common ground. Now, surely, John and Hannah in Previously High Stakes are disposed to behave, in their use of language, as if they believed it to be common ground that Hannah-onFriday ought not to ignore the possibility that the bank has changed its hours. To illustrate this, note that John and Hannah are, for instance, disposed to respond as follows, when asked whether Hannah ought or ought not to ignore the possibility that the bank has changed its hours recently: 'No, on Friday Hannah shouldn't have just assumed that the bank hasn't changed its hours recently. She should have checked the opening hours online or called in to make sure that the bank would be open on Saturday.' Given that pragmatic presuppositions are, as I have argued elsewhere,25 linguistic dispositions-in particular, dispositions to behave, in one's use of language, as if one believed the relevant proposition to be common ground-it is rather uncontroversial that Hannah and John in 25 (Blome-Tillmann 2009b, p. 253). 10 Previously High Stakes make the presupposition at issue. Thus, (RPI) offers a prima facie plausible response on behalf of PEC to the data from Previously High Stakes. 5. The Problem of Known Presuppositions Even though (RPI) may seem promising at first glance, there is a rather serious problem with it. To see what I have in mind, note that it is only an accidental feature of Previously High Stakes that the subject-Hannah-on-Friday-is in a high-stakes situation. Consider, for illustration, the following case, which is a slightly extended and amended version of DeRose's (2004) Thelma and Louise example: Thelma and Louise*: Thelma is talking with the police about whether it might have been John who committed some horrible crime. Thelma is admitting that she does 'not know' that he was in the office on Wednesday-though, she adds, she has good reason to think he was: she heard from a very reliable source that he was in that day, and she herself saw his hat in the hall. But since Thelma does not have a clear recollection of having herself seen John, she admits to the police that she does 'not know' that he was in the office on Wednesday. As the police continue the interview, they ask Thelma whether her co-worker Louise, who is not present and in a low-stakes context at the local pub, but whom they are considering questioning, might know whether John was in. Thelma knows that Louise is in the same position that she is in with respect to the matter (she too heard the report and saw the hat, but did not herself see John), and so responds to the police by saying, 'Louise too does not know that John was in-though she too has good grounds to think he was'. In the evening, Thelma and Louise are taking dinner at said local pub. Thelma tells Louise about her interview with the police, and also that, as became clear later during the day, the police have ruled out John as a suspect by checking the company's security tapes and the network logs of his computer: John had in fact been in the office all day on Wednesday. Thelma further mentions that, in the morning, the police wanted to know whether Louise could confirm John's whereabouts on Wednesday, and that she said that she couldn't. Louise responds, 'You were right, I didn't know either that he had been in all day. But isn't it strange that they didn't even bother interviewing me?' Given that Louise was, at the time of Thelma's police interview, in a low-stakes situation at the local pub, she was surely under no practical obligation to take seriously the rather remote possibility that John had not been in on Wednesday and that her good reasons to believe that he was-the reliable testimony she had received and her seeing John's hat in the hall-were misleading clues cleverly designed to construct an alibi for John (henceforth 'the possibility that ¬I'). In other words, given her practical interests in the pub, it is simply not the case that Louise was at fault in ignoring the possibility that ¬I. Moreover, Thelma and Louise both know, in the evening, that Louise-in-the-morning was in a lowstakes situation, and so they both believe, in the evening, that Louise-in-the-morning was entirely reasonable and by no means irresponsible when ignoring the possibility that ¬I. Thus, neither Thelma nor Louise presupposes, in the evening, that Louise-in-the-morning ought not to have ignored the mentioned possibility. As a consequence, the Rule of Presumed Interests does not mark out the possibility that ¬I as not being properly ignored in the evening and therefore cannot help in accounting for the datum that Louise, in Thelma 11 and Louise*, speaks truly when uttering 'You were right, I didn't know either that he had been in all day'.26 A different approach is needed. To see what I have in mind, note firstly that both examples are cases in which certain possibilities are not properly ignored in a context C, even though they are incompatible with the pragmatic presuppositions at C. In fact, both examples are cases in which the possibilities at issue are incompatible not only with what is mutually pragmatically presupposed at the respective context, but also with what is mutually known: the possibilities at issue are, at their respective contexts, epistemically impossible. Of course, this is due to the rather obvious fact that propositions are sometimes pragmatically presupposed at a context because they are mutually known or eliminated by the speakers' evidence. It is this connection between the speakers' evidential states at a context and their pragmatic presuppositions, I take it, that provides the key to handling our recalcitrant examples. Consider the following principle: Rule of Evidence-Based Ignoring (REBI): If the speakers in C ignore w because w is eliminated by their evidence, then w is not properly ignored in C.27 Let us see how (REBI) handles Previously High Stakes. Firstly, note that the reason why Hannah and John on Saturday evening ignore the possibility that the bank had changed its hours recently and was therefore not open on Saturday ('¬O') is that that possibility is incompatible with their evidence: Hannah has, after all, been at the bank in the morning and it was open. If Hannah and John ignore ¬O because ¬O is incompatible with their evidence, however, then it follows, assuming (REBI), that the possibility that ¬O is not properly ignored on Saturday evening at the dinner party. Thus, we have a straightforward explanation of why Hannah can, in Previously High Stakes, truthfully utter 'I didn't know that the bank would be open on Saturday'. Next, consider Thelma and Louise*. In this case our two protagonists ignore, in the evening, the possibility that ¬I-that is, the possibility that John had not been in the office on Wednesday and had left misleading clues designed to create an alibi for himself. Moreover, the reason why they ignore that possibility is, of course, because their evidence eliminates it. Thelma herself has, after all, heard from the police by what means they eliminated John as a suspect. If Thelma and Louise ignore ¬I because ¬I is incompatible with their evidence, however, then it follows, assuming (REBI), that the possibility that ¬I is not properly ignored in their evening conversation at the local pub. Thus, we also have a straightforward explanation of why Louise can, in the evening, truthfully utter 'You were right, I didn't know either that he had been in all day'. It might be objected at this point that while (REBI) allows us to account for the mentioned cases, the principle itself is implausible and subject to counterexamples. For instance, if the speaker and the subject coincide at a context C, it seems rather odd to claim that a possibility w cannot be properly ignored in C despite the fact that her evidence eliminates w: if anything enables x to properly ignore w, is it not her evidence that rules out 26 Of course, similarly to DeRose's (2004) original example, Thelma and Louise* is also (at least prima facie) problematic for SSI. 27 A counterfactual cousin of (REBI) is the following principle: If the speakers in C ignore w, but would not do so if w were compatible with their evidence, then w is not properly ignored in C. Note also that (REBI) might have to be refined to talk about the speakers' beliefs that their evidence eliminates w rather than the fact that it does. 12 w? It is important at this point to note that the notion of 'proper ignoring' is a technical notion that is meant to pick out, for any given context C, precisely those worlds that a subject's evidence must eliminate for her to satisfy 'knows p' in C. We might also (and perhaps more intuitively) refer to these possibilities as the possibilities that are epistemically relevant in C or as the relevant alternatives in C. Of course, the possibility that ¬I is, in the everyday sense of the phrase, 'properly ignored' by Thelma and Louise in the evening. But surely that very possibility is nevertheless epistemically relevant in the sense that the subject's evidence-that is, Louise-in-the-morning's evidence-must eliminate it for her to satisfy 'knows' in the evening. Thus, in the technical sense relevant here, the possibility that ¬I is not properly ignored in the evening-despite the fact that it is eliminated by Thelma and Louise's evidence. It might be further objected to (REBI) that it just cannot be correct that w is not properly ignored in C in every case in which the ascribers in C have evidence that eliminates w, for this has the unwelcome consequence that any subject x must have evidence that eliminates w in order to satisfy 'knows p' in C. But this is surely exceedingly implausible, for it has as a consequence that ascribers with a lot of evidence can ascribe less 'knowledge' than ascribers with very little evidence. In other words, according to (REBI), the objection goes, increasing the attributer's evidence reduces what the attributee 'knows'. This objection, however, misconstrues (REBI), for the principle does not state that a possibility w is not properly ignored in C if it is eliminated by the ascribers' evidence in C. Rather, it demands that there be a causal connection between the speakers' ignoring w and her evidence eliminating it. According to (REBI), if a speaker ignores a possibility w because it is eliminated by her evidence, then that possibility is relevant or 'not properly ignored' in the relevant technical sense. Thus, contrary to the objection at issue, (REBI) does not have as a consequence that all possibilities that are eliminated by one's evidence are relevant at one's context. Rather, the possibilities that (REBI) marks out as relevant are merely those that one ignores because they are eliminated by one's evidence. In fact, the guiding idea underlying (REBI) can be illustrated further in counterfactual rather than causal terms. Consider the following counterfactual principle: Rule of Evidence-Based Ignoring* (REBI*): If the speakers in C ignore w, but would not do so if w were compatible with their evidence, then w is not properly ignored in C. I shall not discuss the relationship between (REBI) and (REBI*) further here, and simply assume that the notion of causation appealed to in (REBI) and the counterfactual conditional of (REBI*) are sufficiently clear and well understood to serve our purposes in this context. The goal of the discussion here is, after all, not to offer an analysis or a noncircular, reductive definition of the satisfaction of 'knows p' in a context C, but rather merely to show that the semantic content of 'knows' at a context C is partly (and no doubt intricately) determined by the pragmatic presuppositions at C. Another objection worth addressing here is that it is unclear how (REBI) or (REBI*) would deal with a variant of the Thelma and Louise case in which Thelma and Louise discuss Thelma-in-the-morning's epistemic state before they acquire evidence that will rule out the possibility that John merely created convincing evidence of his presence at work but was in fact absent. Surely, in such a case, Thelma and Louise are right to claim that Louise 'did not know' earlier in the day that John was in the office (on the basis of 13 the colleague's testimony and his hat being in the hall). But how can PEC account for this datum? This objection is, of course, taken care of by PEC's Rule of Presupposition. In the envisaged example, Thelma and Louise do not presuppose that John did not create convincing but misleading clues of his presence at work but was in fact absent. Thus, worlds in which he did create such convincing but misleading clues are epistemically relevant or not properly ignored at their context. And since Louise's evidence in the morning did not eliminate the possibility at issue, she does not-at the context envisaged-satisfy 'knows'. It is important, in other words, to note that, on the current proposal, the Rule of Presupposition remains intact and is merely complemented-but not replaced-by the Rule of Evidence-Based Ignoring. Summing up, PEC together with (REBI) draw a picture on which, amongst the worlds that are incompatible with the presuppositions in C (the worlds that are not 'live options' in C), there are some that cannot be properly ignored-despite the fact that they are not 'live options' in C. Worlds that may, for instance, be incompatible with the presuppositions in C but that can nonetheless never be properly ignored are the subject's actuality (Rule of Actuality) and also those worlds that resemble the subject's actuality (Rule of Resemblance). (REBI) adds another group of worlds to the set of worlds that are epistemically relevant while (potentially) being incompatible with the presuppositions in C- namely, precisely those worlds that are ignored because they are eliminated by the speakers' evidence or, in counterfactual terms, those worlds that would not otherwise be ignored, if the speakers' evidence did not eliminate them. 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