with one who denies its principles, if only the opponent will make
some concession; but if he concede nothing, it can have no dispute
with him, though it can answer his objections. Hence Sacred Scripture,
since it has no science above itself, can dispute with one who denies
its principles only if the opponent admits some at least of the truths
obtained through divine revelation; thus we can argue with heretics
from texts in Holy Writ, and against those who deny one article of
faith, we can argue from another. If our opponent believes nothing of
divine revelation, there is no longer any means of proving the
articles of faith by reasoning, but only of answering his
objections--if he has any--against faith. Since faith rests upon
infallible truth, and since the contrary of a truth can never be
demonstrated, it is clear that the arguments brought against faith
cannot be demonstrations, but are difficulties that can be answered.

Reply Obj. 1: Although arguments from human reason cannot
avail to prove what must be received on faith, nevertheless, this
doctrine argues from articles of faith to other truths.

Reply Obj. 2: This doctrine is especially based upon arguments
from authority, inasmuch as its principles are obtained by revelation:
thus we ought to believe on the authority of those to whom the
revelation has been made. Nor does this take away from the dignity of
this doctrine, for although the argument from authority based on human
reason is the weakest, yet the argument from authority based on divine
revelation is the strongest. But sacred doctrine makes use even of
human reason, not, indeed, to prove faith (for thereby the merit of
faith would come to an end), but to make clear other things that are
put forward in this doctrine. Since therefore grace does not destroy
nature but perfects it, natural reason should minister to faith as the