Jolley, Nicholas - The Light of the Soul: Theories of Ideas in Leibniz, Malebranche, and Descartes

There is a story about seventeenth-century philosophy which goes roughly as follows. Descartes broke with the scholastic tradition by advancing an austere new mechanistic theory of the physical world; according to this theory, bodies intrinsically possess only geometrical properties. Descartes thus stripped the world of many properties which were formerly classified as unambiguously physical. Some of the properties which were left over from the new scientific picture of the world could be safely discarded; the powers, natures, and faculties beloved of the scholastics are obvious examples. But there were many other properties, such as secondary qualities, which could not be treated in this cavalier fashion; they had to be located somewhere, and Descartes invented a new concept of mind in order to accommodate them.