Lat. ad fidem argument, fides, “faith”.
Revealed truth can be used either as arguments, or disputed as claims.
1. Revealed truths as arguments
Revealed truths can be used as arguments justifying some conduct; we follow the Law because our God has given it to us; because He will reward His Followers, the Good, and punish the Wicked. Appeals to religious beliefs may be dismissed as appeals to superstition, S. Threat.
2. Revealed truths as claims
Faith and religious mysteries can be opposed to reason and argument. Thomas Aquinas discusses “whether sacred doctrine is a matter of argument?” and quotes St. Ambrose’s categorically negative response: “Put arguments aside where faith is sought” (ST, Part 1, Quest.1, Art. 8)[1].
For a believer, revealed truths have precedence over all other forms of truth; trying to demonstrate a revealed truth would degrade it. It should be emphasized that, for a believer, renouncing to argue does not imply submitting to the argument from authority, since he or she considers that authority has a human origin, while faith has a divine origin. Whether religious tradition is of human or divine origin is a controversial issue among theologians.
But the precedence of faith does not invalidate the necessity of argument. Thomas Aquinas distinguishes three kinds of situations, depending on whether one addresses Christians, heretics or unbelievers.
— Where a speaker is addressing a Christian audience, argumentation will have two significant uses. The first use is to connect two articles of faith, to show that one can be logically deduced from the other. For example, if somebody believes in the resurrection of Christ, then he or she must believe in the resurrection of the dead. In addition, arguments may be used to extend the domain of faith to deeper truths, derived from the elementary ones.
— When arguing with heretics who agree on some point of the dogma, an argument will be built upon this point to show that they must also accept the validity of other connected points. The technique is basically the same as in the previous case.
In both cases, argumentation about matters of faith is based on arguments postulated as true because they are taken from the corpus of revealed truths.
— Where confronting unbelievers, the argument will essentially be ad hominem, showing that their beliefs are contradictory (after Trottman 1999, p. 148-151).
As can be seen, the Angelic Doctor does not exclude situations of deep disagreement from the field of argumentation, S. Disagreement.
3. Superstition
[1] Quoted after Thomas Aquinas, The Summa Theologica. Benziger Bros, 1947. Translated by Fathers of the English Dominican Province. http://dhspriory.org/thomas/summa/FP/FP001.html#FPQ1OUTP1 (11-08-2017)