From this, however, being led to prefer the Catholic doctrine, I felt that it was with more moderation and honesty that it commanded things to be believed that were not demonstrated (whether it was that they could be demonstrated, but not to any one, or could not be demonstrated at all) [Confessions VI.5]
The sense of this passage is more easily grasped, I think, in R.S. Pine-Coffin’s rendering:
The Church demanded that certain things should be believed even though they could not be proved, for if they could be proved, not all men could understand the proof, and some could not be proved at all [p. 116]
In any case, two things are certain. St. Augustine did not believe that a dogma of faith must be demonstrable by reason: some dogmas are not demonstrable by reason at all, and in other cases they exceed the measure of some men (though not necessarily all men) to grasp by reason. In either case, the important thing is that we are obliged to receive the dogmas by virtue of the authority of the Church, just as St. Augustine says.
Secondly, it is obvious that St. Augustine’s words here rule out any sense of the Protestant novelty of “sola scriptura;” he unambiguously assents to the authority of the Church to define dogmas that must be believed.
It occurs to me that perhaps these considerations might be of use to David Waltz, who continues to wrestle with certain dogmas. I think it bears mentioning that history as an enterprise is unquestionably an enterprise of reason, and that the “conclusions” of history are unquestionably conclusions of reason, and that consequently St. Augustine’s observations about Church authority and the limits of reason surely apply not merely to syllogisms we work out in our heads but also to our conclusions from history. This is not to say that the Church’s dogmas are ahistorical or contrary to history at all—indeed, quite the reverse is true. But it is to say that individual men may err concerning the “facts” of history, and also that history does not contradict the dogmas of the Church.