The composition of the specific group of listeners presently at hand, then, for Augustine determined not only what the preacher was to say and in what terms it was to be said, but also the very style of his delivery.
The need to communicate made Augustine sceptical about the potential impact in the context of Christian preaching of a formally eloquent rhetoric.
He certainly made selective use of various rhetorical devices - his own skills in that field were considerable - but he saw that they contributed little to the essential problem a preacher faced, that is, how to touch the hearts of people.
In this context, for Augustine the most important principle of preaching was immediacy.
He held that, if something was worth saying and the speaker identified himself with it, the way of saying it would come naturally.
The words of a preacher come alive through the very joy he takes in what his is speaking about.
It is a waste of time for the preacher to expound to others about what they should admire or do if he does not sense it himself.
Because of this immediacy which makes heart speak to heart, the sermons of Augustine sermons are still interesting to read.
According to his biographer Possidius
, those who gained most from him were those who had been able actually to see and hear him as he spoke in Church.
In an age where most of the people were illiterate, Christian doctrine was communicated mainly through sermons, not through books.
The close interaction between the preacher and his audience and the rhetorical quality of the sermon served the end of moving the listeners to a life pleasing to God.
Augustine repeatedly reminded his listeners that simply to delight in the words and images offered by the preacher was not enough.