As I was reading St. Augustine, I was thinking of associations I have that tie the ability to speak/write well and the Judeo-Christian tradition.
One story that comes to mind (and is mentioned in Kennedy) is that of Moses. God told him to go talk to Pharoah, and Moses begged off, saying that he couldn't speak well. The story goes that this didn't stop God from sending him anyway--he simply told him that his brother Aaron could fill in the gaps caused by his stutter (which I'm under the impression was one of the reasons why he was saying he couldn't speak well).
Augustine talks about God's power being behind rhetoric--that prayer is an essential part of the rhetorical act. Moses' way of thinking was that he had to be perfect. The point behind a lot of Biblical stories is that God uses weak people. Augustine seems to be saying that powerful rhetoric is God-inspired rhetoric. But he very often seems to indicate that the orator has the ability to improve on his (or her) own by studying well wrought oratory and imitating it.
The God influence is mentioned at the beginning and the end of this discussion, much like literary bookends, but the core seems to veer a bit a way from God's role in the oratory.
Biblical rhetoric has intrigued me since my undergrad days, when I took a course centered around the New Testament. The professor was a pretty liberal Presbyterian minister.
The NT contains four gospels. Three are considered to be synoptic gospels in that there are stories that run parallel to each other and can be found in two to three of the gospels. But the stories are told differently even when they the same story in a different gospel.
When I was growing up, my mother explained this to me by telling me that they were different because they were told by different people and that it would be more suspect if they were identical. When I got to college, I learned that they had been written at different times. There was a mysterious Q document rumored to be the writings of Jesus that predated the gospels, and Mark was the first gosel to be composed. Later gospel writers looked off of the Q document and Mark for material. The difference between the gospels lies in the fact that they were directed toward different audiences.
For example, the book of Matthew is believed to have been directed toward a Jewish audience and is sprinkled with language that points to numerology and Jewish prophecies. The book begins with a geneology that is divided into three parts of 14 generations a piece. Three is a number to point to God. In Hebrew, each letter represents a number, so each name has a number associated with it. The name that equals 14 is David, which points back to the prophecies about the messiah coming from the "house and lineage of David." There are a bunch of people left out of the geneology. It's the numbers that make the argument, and Jewish scholars would have been trained in numerology and would have been able to pick that out. The audience-centered perspective of the Biblical texts is something that fascinates me.
Augustine seems to focus on the purpose more than on the audience. There are three possible purposes that an orator can have, and these affect what type of style will be employed.
It bothered me that he gave a liberal number of examples of types of styles, but never really pointed out what made these particular examples representative samples of this particular style--at least he never sufficiently explained that. But I got to thinking that he also condemned teaching rhetoric and believed that we should learn through the study of examples and imitation, so I guess he's just being consistent.
Another thing that I find interesting is the recurrence of a struggle within Christian orators between a yearning for eloquence and a guilt associated with this yearning. I'm in a Metaphysical poetry class, and George Herbert, a 17th-century religious poet, faced this problem. He, too, was a former rhetorician.