Abstract

The paper investigates the characterisation of vague concepts within the framework of modal logic. This work builds on the supervaluation approach of Fine and exploits the idea of a precisification space. A simple language is presented with two modalities: a necessity operator and an operator `it is unequivocal that' which is used to articulate the logic of vagueness. Both these operators obey the schemas of the logic S5. I show how this language can be used to represent logical properties of vague predicates which have a variety of possible precise interpretations. I consider the use within KR systems of number of different entailment relations that can be specified for this language. Certain vague predicates (such as `tall') may be indefinite even when there is no ambiguity in meaning. These can be accounted for by means of a three-valued logic, incorporating a definiteness operator. I also show the relationship between observable quantities (such as height) and vague predicates (su...

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