“The sin of the sophist is that he denies the necessity of subject matter and believes that forma alone is desirable. An opposite vice, one to which historians of rhetoric have never given a name, depends upon the belief that the man possessed of truth will ipso facto be able to communicate the truth to others. It is a dependence upon materia alone. Its chief proponent in ancient times was the young Plato, and it would seem fair to label it the “Platonic rhetorical heresy” just as we apply the term “sophistry” to its opposite theory. This is not to say that the ecclesiastical writers of the fourth century looked to the Gorgias and Protagoras for a theory of communication, but rather that their reactions to the pagan culture of Rome led many of them to take up a somewhat similar attitude toward the rhetoric which was a part of that culture. Augustine apparently recognized a danger in this aspect of the cultural debate of his times, and used the De Doctrina [Christiana’s fourth book] to urge a union of both matter and form in Christian preaching.
Only if one views the book as part of the great debate of the fourth century, therefore, does its historical importance emerge clearly. The reader is struck by the author’s insistence upon the folly of abandoning a useful tool to the enemy.”
—James J. Murphy, “The Debate about a Christian Rhetoric,” in The Rhetoric of St. Augustine of Hippo, eds. Enos, Thompson, et al. (2008)