We need some standard that will determine how likely a belief is to be true given just that it is stored in one of us, including strangers that one can ask for directions, and with whom one might collaborate.

In arriving at the relevant theory about the specifics of our faculty of vision we will presumably use our eyes to gather relevant data. Based on such data we come to know about the optic nerve, the structure of our eyes, the rods and cones, etc., so as to explain how it is that vision gives us reliable access to the shapes and colors of objects around us. In reliably arriving at that theory we thus exercise the very faculty whose reliability is explained by the theory. There is no vice in this sort of circularity.

I am mainly concerned with unqualified knowledge, by contrast with the varieties of expert knowledge: scientific knowledge of various sorts, legal knowledge, medically expert knowledge, and so on.

We can pursue the Cartesian project without restricting ourselves to theology and a priori faculties. A better, broader perspective is properly sought if we pursue the project with reliance on science broadly and on our full span of epistemic competences, including the empirical as well as the a priori.

A successful account enables us to understand human knowledge in general.

When we speak of ordinary unqualified knowledge, my thought is that we are implicitly relativizing to the standards imposed by our evolution-derived humanity. These are standards that determine when we consider it appropriate to store beliefs just as a human being, rather than in one's capacity as an expert of one or another sort. Such stored beliefs are to be available for later use in one's own thought or in testimony to others.

Descartes's epistemology is a special case of Aristotle's virtue ethics.