The role of the simple natures and method in Descartes' meditations

My topic is the continuity of thought from Descartes' earliest writings to his mature thought as expressed in the Meditations. In the early work, the Rules, Descartes replaces the scholastic form-matter model of the physical world with a quantitative description of the physical as matter in a Euclidian space.;In the first two chapters I examine the early work showing its break with scholasticism and the structure of his new vision. The Rules was Descartes first major work; it was to consist of thirty six rules. It was neither completed nor published. He stopped working on it in 1628, completing only twenty one rules with commentary on the first eighteen. The first twelve are the philosophically interesting ones. In those he develops a method based on mathematical proofs and introduces a set of basic principles he calls `simple natures' which are intuitively known. This model has the simple principles (natures) analogous to the postulates and axioms of Euclidian geometry. From the principles complex problems are solved by reducing the terms to those of the simple natures and re-constructing the problem in those terms. While the Rules emphasizes material natures as the basis for physical science, he also introduces a definition of mind as thought.;In the next two chapters I argue that this basic structure of method and simple natures carries over into the Meditations. The goal is different but the tools are the same. The definitions of matter and mind that Descartes sets in Meditation II are the same as in the Rules: mind as thought and matter as extension. Doubt, which is often taken as the new method is shown to be just a part of the early stage of the original method. It is used to reduce a complex to simples by eliminating any uncertainties until an indubitable simple nature is reached: the cogito..;In the final chapter I examine the problem of apparent contrasting explanations of true and immutable natures in Meditation V and the First Reply. I argue that they are compatible if we understand natures in terms of the principles of the Rules..