As indicated by its subtitle, this dissertation is intended as an examination of the relationship between ontology and epistemology in Descartes' philosophy. The author is aware that a study of the philosophical system of one philosopher cannot be expected to decide the relationship between the theory of knowledge and of reality as such. However, proceeding from "the generally accepted... thesis" of metascience "that a knowledge of reality which is without presuppositions and independent of the subject or of a theory is (...) impossible," he is convinced that the dogmatism and circularity of thinking using epistemological principles as ontological descriptions and vice versa are not merely characteristic of Cartesian thought but are necessary, essential features of every philosophical attempt "at a universally valid and unmodifiable theory of knowledge and reality". His study of Descartes' case merely confirms the view that the realization of a system "claiming incorrigible validity without dogmatic procedures or without intrinsic incoherences is impossible". The purpose of the book is to expose the metaphysical presuppositions of Cartesianism first with regard to the Cogito-argumentation and its inner-systematic role, then with regard to the function of the idea of God in the system, and finally with regard to the understanding of the relations between metaphysics and physics. A summary of the results of the study is to answer the question concerning "the ultimate theoretical conditions of the formulation of a philosophical system like Cartesianism and concerning the responsibility for the incoherences discovered". (shrink)