Hans Kamp

Vagueness is an ultimate challenge. An enormous diversity of literature on the topic has accumulated over the years, with no hint of a consensus emerging. In this light, Section 1 presents the main aspects of the challenge vagueness poses, focusing on the category of adjectives, and then gives some brief illustrations of the pervasive manifestations of vagueness in grammar.Section 2 deals with theSorites paradox, which for many philosophers is the hallmark of vagueness: By assigning avague predicate step by apparently inescapable step to more and more objects one is eventually led to assign it to entities of which it plainly isn’t true.It is hard to resist the force of the paradox once one has been exposed to it. The result of this has been that many see the philosophical problem presented by vagueness as nothing other than the problem of solving the Sorites.The efforts to solve the Sorites paradox have uncovered a range of important connections between vagueness and other aspects of language and thought. But most of these seem to lead further and further away from what some consider the core issues that vagueness raises.Given the challenge posed by the Sorites, it is rather remarkable to discover that there is a lot more to vagueness beyond the paradox. In fact, linguists traditionally leave it to the philosophers to deal with the Sorites and put their own efforts into dealing with other manifestations of vagueness in natural language and their consequences for grammar. Page 2 2Section 3 reviews some of these additional phenomena, centering around three issues: (i) the controversial connections between vagueness and morphological gradability, (ii) the similarity and differences between the phenomena of vagueness and imprecision, and (iii) the ways in which vagueness infiltrates various grammatical constructions we find in language, with consequences for the architecture of grammar.The aim of this section is to highlight the main questions which any theory of vagueness will ultimately have to address.

This paper presents a sound and complete proof system for the first order fragment of Discourse Representation Theory. Since the inferences that human language users draw from the verbal input they receive for the most transcend the capacities of such a system, it can be no more than a basis on which more powerful systems, which are capable of producing those inferences, may then be built. Nevertheless, even within the general setting of first order logic the structure of the formulas of DRS-languages, i.e. of the Discourse Representation Structures suggest for the components of such a system inference rules that differ somewhat from those usually found in proof systems for the first order predicate calculus and which are, we believe, more in keeping with inference patterns that are actually employed in common sense reasoning.This is why we have decided to publish the present exercise, in spite of the fact that it is not one for which a great deal of originality could be claimed. In fact, it could be argued that the problem addressed in this paper was solved when Gödel first established the completeness of the system of Principia Mathematica for first order logic. For the DRS-languages we consider here are straightforwardly intertranslatable with standard formulations of the predicate calculus; in fact the translations are so straightforward that any sound and complete proof system for first order logic can be used as a sound and complete proof system for DRSs: simply translate the DRSs into formulas of predicate logic and then proceed as usual. As a matter of fact, this is how one has chosen to proceed in some implementations of DRT, which involve inferencing as well as semantic representation; an example is the Lex system developed jointly by IBM and the University of Tübingen )