2. Again, if sacred doctrine proceeded by argument, it would argue either on the ground of authority or on the ground of reason. But to argue from authority would be beneath its dignity, since “authority is the weakest kind of proof,” as Boethius says (Topica 6), and to argue by reason would be unworthy of its end, since “faith has no merit when human reason proves it by test,” as Gregory says (Hom. in Evang. 26). It follows that sacred doctrine does not proceed by argument.
I think that Thomas Aquinas would have had the same opinion about the New Atheists that I do- that when arguing online, they often accuse the Catholic of Appeal to Authority, insisting that this is a logical fallacy because it's on a list at Changingminds.org (or some other such nonsense, doesn't matter whose list it is on).