Abstract

The goal of the dissertation is the application of a formal method to the philosophical study of ontology. In order to study the ontological structure of a system or theory T we construct a model of the structure of T. This sort of model we call an "ontological model" . The technique itself we call "ontological modelling". A given theory T is taken as an ordered quadruple $\langle$T$\sp{\rm g }$,T$\sp{\rm c}$,T$\sp{\rm s}$,T$\sp{\rm m}\rangle$, where T$\sp{\rm g}$ is the grammar for T, T$\sp{\rm c}$ is the calculus for T, T$\sp{\rm s}$ is the semantics for T, and T$\sp{\rm m}$ is the metalanguage for T. This model is intended to represent the language in which the theory is expressed, reasoning methods within the theory, the interpretation of the language of the theory, and metatheory for the theory. Roughly, the entities that appear in recursive definitions for these four systems are argued to constitute the ontological domain for T. Such entities make up the basis for the ontology of a given theory T, that is, the set of things that exist from the point of view of T. ;The problem of ontology is set up in Chapter 0, and in Chapter 1 we begin to study the ontological problem in connection with the work of several authors working in philosophy and philosophical logic. A philosophical critique of the various accounts is given in Chapter 2, which is intended to motivate a basic notion of what we require in a theory of ontology. Kit Fine's approach to the study of ontology is examined in Chapter 3. Finally, in Chapter 4, it is argued that ontological modelling represents an explanatory gain over other theories in that it provides for the reductive analysis of ontological notions such as ontological acceptance, ontological requirement and ontological commitment. Roughly, an object is accepted by a theory's ontology if and only if that object exists from the point of view of the theory. An object in an ontology requires another object in that ontology if and only if the former is existentially dependent, and an ontology is committed to an object if and only if it affirms the object's existence. It is argued that the notions of ontological acceptance, commitment, and requirement may be analyzed in terms of ontological modelling