On the epistemic entrenchment of different types of knowledge expressed as conditionals in belief revision tasks

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  • Technical report TR96-16. Some belief revision theories appeal to the notion of epistemic entrenchment as a guide to choosing among alternative ways of removing inconsistency that new information may cause with existing beliefs. While belief revision theorists may not be interested in natural language uses of conditionals per se, the appeal to epistemic entrenchment because certain kinds of knowledge (e.g., physical laws) are expressed in conditional form opens the door to a more careful consideration of whether the syntactic form itself serves as a useful cue, even in the mind of the researcher, for epistemic entrenchment principles. This study determines whether there is any empirical support for the notion that the type of knowledge expressed in a statement can serve as the basis for epistemic entrenchment principles. Four types of knowledge - promises, causal relationships, familiar definitions and unfamiliar definitions - were expressed in a common syntactic if p then q form. A belief revision task was given to people, in which these conditionals were used to define \"initial belief\" sentences, which were then followed by a \"new information\" sentence that created an inconsistency with the intial set of beliefs. The frequency with which people chose to disbelieve the conditional (or lower their degree of belief in it) as a way of resolving the inconsistency depended on the type of knowledge - causal, definitional, or promises - that the conditional expressed. The conditionals that expressed causal information were further analyzed according to the possible alternative causes and disabling factors associated with the causal relationship. These more subtle distinctions also affected how people revised the belief sets using causal scenarios. For normative belief revision models, such findings call into question the notion that conditionals ought to be more entrenched by virtue of their syntactic form. They also question whether the syntactic if-then form of conditionals can even serve as a useful cue for signaling the types of knowledge that it might be plausible to entrench, such as causal relationships. These results support higher-order epistemic entrenchment principles that distinguish among types of knowledge (regardless of the syntactic form in which they are expressed) and known necessity and sufficiency aspects of causality relationships in particular. | TRID-ID TR96-16

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    Attribution 3.0 International