Context as Assumptions

Erich Rast

Context as Assumptions

MSH Lorraine Preprints 2010 of the Proceedings of the Epiconfor Workshop on Epistemology, Nancy 2009 (2010)

Abstract

In the tradition of Stalnaker (1978,2002, context can be regarded as a set of assumptions that are mutually shared by a group of epistemic agents.An obvious generalization of this view is to explicitly represent each agent’s assumptions in a given situation and update them accordingly when new information is accepted. I lay out a number of philosophical and linguistic requirements for using such a model in order to describe communication of ideally-rational agents. In particular,the following questions are addressed: 1. What is the logical status of assumptions as opposed to rational belief, how are these assumptions generated from an underlying belief base in a given interpretation situation,and how are assumptions revised/contracted? 2.What kind of ideal reasoning processes underly the interpretation of ‘incomplete’ content that may for example be obtained by an agent from an utterance by deriving some literal meaning from the lexicon and a grammar? Regarding the first set of questions, my proposal is to consider assumptions akin to rational belief, but not stronger than modal logic KD, since positive and negative introspection do not seem to hold for them.Given that, an obvious question is what the relation between beliefs and assumptions is. One possible answer is to generate an agent’s assumptions from an agent’s beliefs in a given interpretation situation by revising his beliefs with his beliefs about what the message sender believes in that situation. If such an account is based on AGM belief revision/contraction(Alchourrón 1985, Gärdenfors 1989)there is a number of well-known problems that need to be addressed, because revision of iterated belief modalities is required in this case. These problems have already been investigated in detail in recent works on DDL Leitgeb/Segerberg 2007)and DEL see e.g. Ditmarsch et. (2008) Another strategy would be to maintain and revise assumptions independently of the beliefs of an agent.I will briefly discuss the advantages and disadvantages of each of these views. In both views, assumptions constitute the subjective context in which an agent interprets an utterance and encounters the world. The result of an interpretation is in turn checked against the agent’s original beliefs, and if the checking operation succeeds the agent revises his beliefs by the result in the normal way described by the AGM paradigm. The second of the above questions needs to be addressed on the basis of concrete examples. Considering utterance like David is ready’ or ‘John is tall’that from a contextualist viewpoint express semantically incomplete content in the sense of Bach(2005, 2007, how may an agent arrive at interpretations of these utterances that are more complete? A first step is to presume that missing semantic ingredients are represented by missing argument places, which is a problematic assumption as it introduces a dependence on the semantic representation language. Given that, a default interpretation can be obtained by existentially quantifying over the missing argument and interpretation can then be regarded as an inference process. In case of the two examples mentioned,the assumptions of the agent allow him to obtain more specific readings by instantiating a value for the existentially bound variable. As I will show, this inference can be relatively straightforward in some cases like ‘John is tall’, whereas it requires complicated encyclopedic background knowledge and a number of default reasoning steps in other cases. Based on more examples of this kind, I argue that first, belief revision with iterated modalities in a multi-agent setting is needed to generate an agent’s assumptions as laid out above. Second, default reasoning is needed. Third, a qualitative or quantitative representation of uncertainty (‘degrees of belief’) is needed in order to obtain a useful model of the checking step, since fortunately not everybody believes everything that other people say. These requirements put the theory of interpretation based on assumptions in the frontline of ongoing research on the implementation of belief revision and update in dynamic logics. Such a theory might also be useful for contextualist accounts of strong knowledge, as it can be argued convincingly that when a knowledge ascription appears to be context-sensitive, this is so because the embedded proposition is context-sensitive and not because knowledge itself is context-sensitive. Hence,the context-sensitivity of embedded propositions in knowledge claims and how different agents in the same situation arrive at different assessments about them may be explained by an inferential theory of interpretation similar to the one outlined here but with another underlying concept of assumptions. Literature Alchourrón, C. E.; Gärdenfors, P. & Makinson, D. (1985), 'On the logic of theory change: partial meet contraction and revision functions', Journal of Symbolic Logic(50), 510-530. Bach, K. (2007), 'Minimalism for Dummies: Reply to Cappelen and Lepore', Technical report, University of San Fransisco, Department of Philosophy. Bach, K. (2005), Context ex Machina, in án Gendler Szabó, ed.,'Semantics versus Pragmatics', Oxford UP, Oxford, pp. 16-44. Ditmarsch, H. v.; Hoek, W. v. d. & Kooi, B. (2008), Dynamic Epistemic Logic, Kluwer. Gärdenfors, P. (1988), Knowledge in Flux, MIT Press. Leitgeb, H. & Segerberg, K. (2007), 'Dynamic doxastic logic: why, how, and where to?', Synthese155(2), 167-190. Stalnaker, R. (1978), Assertion, in . Cole, ed.,'Pragmatics', Academic Press, New York, pp. 315-332. Stalnaker, R. (2002), 'Common Ground', Linguistics and Philosophy25(5-6), 701--721.

Keywords

contextuals simple type theory indexicals deixis interpretation communicative assumptions belief revision preferences

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Context as Assumptions

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