You attain aptness by judging while in good shape and in a good situation (good light, good distance, etc.), through the exercise of good barn-sorting epistemic competence.
Descartes's epistemology is a special case of Aristotle's virtue ethics.
There isn't a formal definition of success.
A successful account enables us to understand human knowledge in general.
We must distinguish judging from guessing.
The correctness of much testimonially based belief is no more than minimally creditable to the believer.