Summa summae S. Thomae, Tomus III

I answer. affirmative. That is, this revelation is possible whereby other men are taught divinely revealed truths through others, who received them from God immediately.

It is proved. It has been demonstrated that immediate divine revelation is possible. Yet nothing prevents a man from communicating to others the truths he has received from God: and in this consists mediate revelation. Therefore mediate revelation is possible.

If any difficulty arises, it arises not so much on the side of the thing itself as on the side of other men, who are in no way bound to extend faith to revelations handed over to them in this way. But, if the revelation has truly proceeded from God, since he made it only for the common good, he will win faith for it by extrinsic helps, and especially by miracles and prophecies; and if these motives of credibility are altogether lacking, no one is certainly bound to grant assent to anyone affirming some revelation or other.

You will object.: The supernatural order ought to be perfectly fitted to the natural order and to correspond with it. Yet God demonstrates natural truths to individual men through reason. Therefore it is more fitting that he open supernatural truths to individuals through private revelation. — I subsume. Yet it is repugnant for God to prefer less fitting means. Therefore mediate revelation is impossible.

I answer. I concede the major, thus understood, that the elevation of the whole of human nature to the supernatural order takes place through means corresponding to each of its faculties, which are not only internal but also external, as happens likewise in the natural order. — I distinguish the minor. God demonstrates natural truths to individual men through reason, not only admonished by the spectacle of his works, in which his invisible things are clearly seen, being understood from the creation of the world through the things that have been made, Rom., 1, 20; but also and necessarily through the discipline which they receive from their instructors: first, that they may perceive primary truths, then that they may make progress in them and avoid the admixture of error: in this sense I concede.

I deny, however, that God demonstrates natural truths to any private man through reason in such a way that man, alone and without any help whatsoever, could apprehend all natural truths, order them, and possess them safely. We have proved, from St. Thomas, in the treatise de Deo creatore, diss. IV, art. 1., that children in the state of innocence would not have been born perfect in knowledge, but would only easily have acquired it with the passage of time. Even then, therefore, they would have needed educators. How much more do they need the same in the state of fallen nature, in which even the external senses are now no longer intact, and the mind has suffered a notable weakening of its native perspicacity? Hence the manifold errors into which, not only private men, but almost the whole human race has lapsed, wherever divine revelation has not bedewed even natural truths with its light. Would it not have to be feared that men, who have so lamentably abused their reason, which nevertheless proceeds from God himself, would likewise abuse private revelations, if God deigned to manifest his mysteries to each individual? Besides, very many would affirm that they had received from God things that would be nothing but ravings of their own mind, and there could be as many religions as heads. God most wisely forestalled this most deadly evil, by manifesting the highest truths to others through selected men, attesting the mission of his heralds by signs truly divine. Therefore, although he could have obtained his end absolutely in another way, by acting thus he truly adapted himself to the condition of fallen man, so that satisfaction is made to the objection. — And thus the following inference is forestalled.]