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.

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

It is possible to produce something that is grammatical either by chance or under the supervision of another. To be proficient in grammar, then, one must both produce what is grammatical and produce it grammatically, that is, in accord with knowledge of grammar in oneself.

Success is better than failure; an attempt is a better attempt, it is better as an attempt, if competent than if incompetent; and it is better to succeed through competence - aptly - than through sheer luck.

It is also certain that when we assent to some piece of reasoning when our perception of it is lacking, then either we go wrong, or, if we do stumble on the truth, it is by accident, so that we cannot be sure that we are not in error.

If a shot aimed at aptness succeeds aptly, it is then fully apt, since it is not only apt but also aptly apt. But the full aptness of such an attempt is entirely compatible with its being a horrible murder, if the "hunter" is an assassin and the prey his victim. That hunter's shot may still be outstandingly, fully apt, if it manifests the agent's competence in both archery dexterity and shot selection.

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.