Here they describe what is on page 99 of their new book, Descartes's Changing Mind, and relate it to wider issues discussed throughout the text:
Critical to Descartes's development is his reflection in the Meditations on First Philosophy (1640-1641) on the nature of God and God's relation to human knowledge. He feels a tension at that time, and works to resolve it over the next few years--succeeding for the most part by the time he publishes the Principles of Philosophy (1644). The resolution comes by noting the limited perspective of human knowledge in relation to the exemplary Divine ideas. The term "archetype" appears in Mediation III and is also used in the Principles [I.18], in the section entitled Principles of Human Knowledge. But in the former work archetype seems to describe the formal containment in God’s divine ideas of the things created in the world. In this way humans could come to know how things are in the world, really and ontologically. In the later work, things in the world seem to be contained in God's ideas only eminently, which reflects our finite and limited understanding of God and his creation. What this means is that we humans are able to know only very limited aspects of the world. We call this Descartes's epistemic stance.Read an excerpt from Descartes's Changing Mind, and learn more about the book at the Princeton University Press website.