Scepticism, Wittgenstein s Hinge Propositions, and Common Ground 1 Introduction The sceptical paradox (1) a. K(S, p) K(S, p sh ) K(S, sh) b. K(S, sh) c. K(S, p) Responses Sceptics advocate (1a) and (1b) and reject (1c). Mooreans advocate (1a) and (1c) and reject (1b). Contextualists and subject-sensitive invariantists suggest that all sentences can be true, although not at the same time. Dealing with the intuitions If we want to maintain epistemic closure (1a) and respect the intuitiveness of both K(S, p) and K(S, SH) the last response seems to be the most promising one. Contextualists and subject-sensitive invariantists focused on the knowledge ascriber or the putative knower. As Michael Williams (2003, 2007) pointed out, Wittgenstein s notion of hinge proposition provides the basis for a slightly different answer. Aim of this talk Show how the apparent context-sensitivity of knowledge claims might be linked to discourse rather than to indexicals or circumstances of evaluation. Thesis Which of the premises we reject depends (at least in part) on the question which other propositions we (tacitly) accept in a given context. 2 Hinge Propositions On Certainty 337 If I make an experiment I do not doubt the existence of the apparatus before my eyes. I have plenty of doubts, but not that. On Certainty 334 That is to say: only in such-and-such circumstances does a reasonable person doubt that. On Certainty 341 That is to say, the questions that we raise and our doubts depend on the fact that some propositions are exempt from doubt, are as it were like hinges on which those turn. 1
Scepticism, Wittgenstein s Hinge Propositions, and Common Ground On Certainty 343 But it isn t that the situation is like this: We just can t investigate everything, and for that reason we are forced to rest content with assumption. If I want the door to turn, the hinges must stay put. Hinge propositions and the sceptical paradox A discourse relies on certain propositions that we take for granted the hinge propositions. These hinge propositions (HP) in turn depend on the inquiry we are interested in. In an epistemology classroom we have different conversational goals than in an ordinary situation. Thesis reformulation The acceptability of a given knowledge claim might vary, depending on which HP are taken for granted in a conversational context. 3 Sceptical Presuppositions (Pragmatic) presupposition Q is presupposed by an assertion that P just in case under normal conditions one can reasonably infer that a speaker believes that Q from either his assertion or his denial that P. (Stalnaker Pragmatic Presuppositions 1999: 47) Scepticism without presuppositions? A cartesian bias Scepticism operates in some kind of neutral context. It does not rely on any axioms or assumptions. If this were true then the sceptic would indeed be in a privileged position. Some presuppositions of the sceptic (Some of) our perceptions are independent of how the world really is. The meanings we assign to words and propositions are in our heads only. If we cannot give a general account of knowledge we do not possess any knowledge at all. Encapsulating the sceptic S: Consider that (1b) can be derived from a set of HP operative in a given context. We could then conclude that S does not know any ordinary proposition p. M: Consider that, in another context, different HP are taken for granted. These might be consistent with K(S, p) but not with some of the sceptic s presuppositions outlined above. Then, this would allow us to infer by means of (1a) and (1c) that S knows the denial of the sceptical hypothesis. 2
Disclaimer: Of course, this is not a direct argument against the sceptic. But it is enough to restrict the devastating impact on our ordinary knowledge claims to contexts in which sceptical HP hold. In order to avoid overgeneration one needs some externalist conception of justification, e.g., a reliabilist account that incorporates the methods by which we form our beliefs about certain propositions. HP could then be justified by a link to reliable methods. This would yield an account that supports both the sceptic s and the Moorean s intuitions, is nonetheless able to set limits to scepticism. 4 Conversational Mechanisms Stalnaker s definition of common ground It is common ground that φ in a group if all members accept (for the purpose of the conversation) that φ, and all believe that all accept that φ, and all believe that all believe that all accept that φ, etc. (Stalnaker 2002: 716) Stalnaker s definition of acceptance Acceptance is a propositional attitude as well as a methodological stance toward a proposition. To accept some proposition φ is to treat it as true and to ignore, at least temporarily, and perhaps in a limited context, the possibility that it is false. (Stalnaker 2002: 716) Consider two examples, in which Alice and Bob discuss the question who is going to the meeting next Friday and Alice utters (2). Context-change (2) I can t come to the meeting I have to pick up my sister at the airport. Assume: i) Alice is a competent speaker of English and ii) a basic pragmatic apparatus (e.g., Grice s CP and maxims). The mechanism of context-change (cf. Stalnaker 2002: 709) Bob can infer from (2) that Alice believes that it is common belief that she has a sister. Bob believes that Alice believes that it is common belief that Alice has a sister. Bob believes that it is common belief that Alice has a sister. It is common ground that Alice has a sister in the context at issue. Alice introduced a proposition compatible with the common ground at the state of the conversation. By decreasing the set of possible worlds compatible with the common ground, the participants advance toward a certain goal of the conversation. 3
Scepticism, Wittgenstein s Hinge Propositions, and Common Ground Context-shift (3) a. [Alice]: I can t come to the meeting I have to pick up my sister at the airport. b. [Bob]: You can t pick up your sister at the airport. In fact there is no airport, there is no sister, and I m not here either. You are a brain in a vat with all your impressions stimulated by a mad scientist. Here, it does not seem as if Bob introduced new information. Rather, his answer (3b) reveals a defective context. Nondefective vs. defective context While in a nondefective context the participants beliefs about the common ground are all correct (Stalnaker 2002: 717), this is not the case in a defective context. While uttering (3a) Alice believes that a proposition like that the external world exists is part of the common ground. Bob s utterance of (3b), however, makes it manifest that it was not and thus, that the context was defective. Propositions in context Context-change Introducing a proposition that is consistent with the common ground. Decreasing the set of possible worlds. Context-shift Introducing a proposition that is inconsistent with the common ground. Starting all over again. The peculiarity of context-shifts A context-shift is always a bit awkward as something inconsistent with a subjects presuppositions is uttered. Consider Bob s utterance of (3b) or a scenario in which Alice proves the existence of the external world in a sceptical context by saying I know that I have hands. However, context-shifts are a standard conversational phenomenon. They reveal defective contexts. Options in case of a defective context a) accommodating the proposition inconsistent with what is presupposed by revising what one believes to be common ground, i.e., fix the context by accepting the other s HP. b) refusing to accommodate the proposition inconsistent with what is presupposed, i.e., sticking to one s presuppositions. Accepting the context-shift Consider that Alice revises what she believed to be common ground before Bob s utterance, i.e., she adopts Bob s HP. Then, intuitively, she no longer knows most of the ordinary proposition p she knew before (e.g., that she has a sister). 4
However, the topic of the conversation changed. Bob and Alice are now doing epistemology. Rejecting the context-shift Insisting on discussing the question who is going to the meeting on Friday, Alice might as reject the sceptical HP Bob is relying on. She refuses to change the topic. In this case one would be inclined to concede that Alice knows p. Whose HP are the correct ones? Here, the recourse to the inquiry at issue comes into play, again. There might be some deliberation on the correct method for this inquiry, but this again can be linked to the externalist account of justification. 5 Conclusion Summing up Wittgenstein s notion of hinge propositions links the acceptability of knowledge claims to discourse. In a discourse the sceptic, just like Moorean, needs to presuppose certain hinge propositions. Stalnaker s common ground can be used to systematize this thought. Claims and Conjectures If this account works, some problems of indexical contextualism (e.g., single severity scale, retraction of knowledge claims) might be avoided. The framework is compatible with both a semantic as well as a pragmatic explanation of the context-sensitivity of knowledge. References Stalnaker, Robert 1999 Pragmatics, in: Context and Content, Oxford: Oxford University Press, 31-46. Stalnaker, Robert 1999 Pragmatic Presuppositions, in: Context and Content, Oxford: Oxford University Press, 47-62. Stalnaker, Robert 2002 Common Ground, Linguistics and Philosophy 25, 701-721. Williams, Michael 2003 Skeptizismus und der Kontext der Philosophie, Deutsche Zeitschrift für Philosophie 51, 973-991. Williams, Michael 2007 Why (Wittgensteinian) Contextualism is not Relativism, Episteme 4, 93-114. Williamson, Timothy 2000 Knowledge and its Limits, Oxford: Oxford University Press. Wittgenstein, Ludwig 1984 Über Gewissheit, Werkausgabe, Band 8, Frankfurt am Main: Suhrkamp. 5