A topic in epistemology which has long interested me is testimony, the question of whether – and how – we can know things by having been told them by another. Aurelius Augustinus – St. Augustine to you and me – has an opinion.

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. I thought that the Church was entirely honest in this and far less pretentious than [others], who laughed at people who took things on faith…. [F]or I began to realize that I believed countless things which I had never seen of which had taken place when I was not there to see – so many events in the history of the world, so many facts about places and towns which I had never seen, and so much that I believed on the word of friends or doctors or various other people. Unless we took these things on trust, we should accomplish absolutely nothing in this life. Most of all it came home to me how firm and unshakeable was the faith which told me who my parents were, because I could never have known this unless I believed what I was told. (Confessions, Book VI, 5).

Sure. We can know things by testimony, which involves faith. But only if the witnesses is trustworthy. But how can we know that?

Note that one thing that concerns Augustine is the fact that an insistence on proof would make Christianity a religion unaccessible to the unintelligent, those who could not understand the proof: children, the uneducated, the developmentally disabled and so forth.