Well, I suppose that, up until the last couple of centuries, most educated Europeans likely would know what he was talking about. The old liberal arts education probably included exposure to the Stoics and the Epicureans.
My education was technical. I may not be all that rude a mechanical, but I'm still a mechanical. What I know of this stuff I learned in my spare time.
Later:
http://en.wikipedia.org/wiki/Epicureanism
http://en.wikipedia.org/wiki/Stoicism
http://en.wikipedia.org/wiki/Logos
The challenge to the Epicureans is obvious, but I'm increasingly puzzled because the more I read about the Stoics the more he sounds like one. Is there something about the Stoic use of the Logos that really doesn't fit Christian theology? Does it suggest pantheism or something? I don't have enough background in this to be sure of what these brief descriptions imply.