Aquinas on the use of reason vs. authority

From the lapidary mind of Thomas Aquinas [my translation, and minor interpolation; for Latin original see here]:

Quodlibet 9, Qu. 4, Art. 3: 

Whether a teacher determining (or deciding) theological questions should make use more of reason, or of authority.

It seems that the teacher determining theological questions should make use of authorities rather than reasons.

 Argument: For in any science, its questions are best determined by the first principles of that science. But the first principles of theological science are the articles of faith, which are known to us through authorities. Therefore theological questions should be mainly determined through authorities.

Sed contra: But against this it is said in Titus I, 9: “that he might be able to encourage others in sound doctrine and refute those contradicting it.” But those who contradict are better refuted by reasons than by authorities. Therefore, it is more necessary to determine questions through reasons than through authorities.

I respond. It should be said that every act should be carried out as befits its end. Now a disputation can be ordered to a twofold end. For one kind of disputation is ordered toward removing doubt whether something is the case; and in such a theological disputation, those authorities should most of all be used, which are accepted by those with whom one is disputing. For example, if one disputes with Jews, it is necessary to introduce the authorities of the Old Testament; if with Manicheans, who reject the Old Testament, it is necessary to use only the texts of the New Testament; but if it be with schismatics who accept the Old and the New Testament, but not the teaching of our saints, as is the case with the Greeks, it is necessary to dispute with them using authorities from the Old or New Testament and from those doctors which they accept. If, however, they accept no authority, it is necessary, for the purpose of refuting them, to take recourse to natural reasons. [And – Thomas forgot to mention – if one is disputing with a woman, who accepts neither authorities nor reasons, and relies only on her emotions, it is necessary to discreetly withdraw from the disputation, lest she upbraid you and slap you in the face. (Relax, I’m kidding! – obviously that's not true of all women. Still, would that it were true of fewer!)]

But another kind of disputation is for the purpose of teaching in the schools, not for the purpose of removing error, but for instructing the hearers, that they may be led to an understanding of the truth towards which it points: and then it is necessary to rely on reasons which search out the root of truth, and which make one to know in what way (quomodo) what is said is true; otherwise, if the teacher were to determine the question on the basis of bare authorities, the hearer would be assured that the matter is thus, but he would acquire no knowledge or understanding and would depart empty.

And from what has been said, the response to the objection is clear.