%Nr: DS-2001-01 %Author: Maria Aloni %Title: Quantification under Conceptual Covers Someone has killed Spiderman. After a careful investigation you discover that John Smith is the culprit and now you want to arrest him. He is attending a masked ball. You go there, but you do not know what he looks like. Is the sentence `You know who killed Spiderman' true or false in such a situation? On the one hand, the sentence is true, you know that John Smith did it. On the other hand, the sentence is false. Since you do not know what he looks like, you cannot point him out. As far as you know, this person here might be the culprit, or that person there. The evaluation of this sentence seems to be dependent on the way in which the relevant individuals are specified. These can be identified by a number of methods like naming (John Smith, Bill White, and so on) or ostension (this man here, that person there, and so on). If identification by name is assumed, the sentence is true. If identification by ostension is assumed, the sentence is false. This example illustrates the central idea I defend and investigate in this book. Different methods of identification are operative in different conversational circumstances and the evaluation of fragments of discourse can vary relative to these methods. Classical semantic theory abstracts from the ways in which individuals are identified and therefore has difficulties in accounting for this dependence. The analysis I propose represents different methods of identification and is able to account for their impact on interpretation. Questions, propositional attitude reports, and quantified sentences containing epistemic modals are examples of linguistic constructions whose interpretation depends on the ways in which objects are given to us. In this thesis I will study these three constructions using the partition theory for questions; modal predicate logic for propositional attitudes; and an intensional dynamic semantics for epistemic modals, respectively. These three theories make crucial use of the notion of a _possible world_. Possible worlds are evaluation points where expressions of the language receive a denotation. In the present context, worlds receive an information-oriented interpretation. A world is meant as representing an epistemic or doxastic possibility, that is, a possible description of what is the case which is compatible with someone's information or belief. The interpretation of questions, propositional attitudes, and epistemic modals crucially involves a shift from one world of evaluation to another. Notions which behave in such a way are usually called _intensional_ notions. The context sensitive constructions that I will consider are classically represented by logical formulae which contain some variable occurring free in the scope of such an intensional operator. In ordinary logical systems, variables are taken to range over bare individuals, and for this reason these systems do not account for the dependence of such constructions on the way in which these individuals are identified. The analysis I propose maintains the classical representation of this type of sentences, but accounts for their meaning by proposing a non-standard interpretation of variables in intensional contexts. One part of my proposal consists in letting variables range over functions from worlds to objects, rather than over the objects themselves. These functions are traditionally called intensional objects or _individual_ concepts}, as they formalize (different) ways of identifying objects. The other part consists in making quantifiers range over sets of concepts which (a) are contextually determined and (b) satisfy the following natural constraint: in each world, each individual is identified by one and only one concept in the relevant set. I will call sets of concepts which satisfy this constraint _conceptual covers_. A conceptual cover represents a method of identification. Different conceptual covers represent different ways of looking at one domain. By adopting quantification under conceptual covers in the three previously mentioned theories, the interpretation of questions, propositional attitudes, and epistemic modals are made dependent on the conceptualizations of the universe of discourse which are pragmatically operative. I will show that such a relativization enable us to solve a number of traditional difficulties, and new ones, which emerge in connection with these notions; at the same time we avoid the specific problems which normally arise when we quantify over concepts rather than objects.