Prokopton : One who has become aware that he is ignorant and of his need to pursue virtue is making progress
In the philosophy of Stoicism, a Prokopton is one who is "making progress:(prokope), especially in being a Stoic.
In order to make progress as a Stoic one has to understand that they need to learn i.e. that they are, to one extent or another, ignorant. In Stoicism, especially the kind promoted by Epictetus, the goal or end (telos) is virtue, that should be pursued for it's own sake and not for the sake of any other thing. Therefore, to be a person "making progress" (Prokopton) one must also seek virtue.
Prokopton, then, is a person who seeks the truth understanding his own ignorance and seeks virtue as the highest goal.
If I had to give a condensed version of Stoicism it would be that happiness (eudaimonia) can be attained by living a life of reason. A life of reason for a Stoic means living virtuously and living according to nature. Living according to nature can be described as pursuing a course responding to ones own needs as well as performing ones duties as a social human being while always accepting ones own fate and putting no importance in things outside of one's own control.
Epictetuts is prominent as a Stoic Philosopher largely because many of his writings still exist. However, his philosophy takes much from earlier Stoic philosophers going back to Zeno (of the famous Zeno's paradox) 400 years before Epictetus.
All of that being said, I am not an expert on Stoicism or Philosophy. I like the way Stoicism dovetails with Christianity and believe much of it's tenets are wise. Prokopton, though, is just a screen name.