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).