Unbelievers, however, cannot come to know the Trinity through these vestiges which rational creatures reflect as in a glass, because without a heart purified by faith they cannot know even that it is a glass; and hence they cannot come to know through it the things which are visible there. Thus Augustine says, in Book XV, On the Trinity: "Those who know their own mind, in whatever way it can be seen, and in it this Trinity, and yet do not believe nor understand that it is the image of God, do indeed see the glass, but so far do not see through it him who is to be seen there. Thus they do not know that what they see is a glass, that is, an image. If they knew this, perhaps they would realize that he whose glass this is should be sought through it, and somehow provisionally be seen, their hearts being purified by unfeigned faith so that he who is now seen through a glass may be seen face to face."
Matthew of Aquasparta, Disputed Questions on Faith, q. 5; A Scholastic Miscellany: From Anselm to Ockham, Fairweather, ed. Westminster Press (Philadelphia: 1961) 415-416.
I am looking for a good set of resources on Matthew of Aquasparta (one of the major Bonaventurans of the thirteenth century), but haven't been able to find any. Does anyone know of some?