There are, indeed, some men who have a good delivery, but cannot compose anything to deliver. Now, if such men take what has been written with wisdom and eloquence by others, and commit it to memory, and deliver it to the people, they cannot be blamed, supposing them to do it without deception. For in this way many become preachers of the truth (which is certainly desirable), and yet not many teachers; for all deliver the discourse which one real teacher has composed, and there are no divisions among them. (De Doctrina Christiana, 4:29)

Clearly the context here is somewhat different to the context in most churches today: the question of whether a good communicator can preach a message written by someone else. (I know of at least one church that does this, but I imagine it is not that common.) But it is worth highlighting the logic that underlies Augustine’s answer. If you do this, then “many become preachers”, which is a good thing, but “not many teachers” (clearly an allusion to James 3:1), because “all deliver the discourse which one real teacher has composed.” In other words, there is a distinction in Augustine’s mind between “delivering a discourse” and being the “real teacher”—that is, the composer of the message.

That, it seems to me, is fairly similar to the distinction I have been making, albeit applied into a very different context. If X prescribes the content to be preached, and Y delivers it to the congregation, then the “real teacher”—or, we could perhaps say, the Teacher with a big-T—is X, rather than Y. Interesting.