Pius XII, 1939-

and so possesses the authority of an even higher order, because the magisterium of the Church has carefully weighed its principles and chief assertions, which were gradually made clear and defined by men of great genius, by the test of divine "revelation" itself. Indeed, this philosophy, recognized and accepted within the Church, protects the true and sincere value of human understanding, and constant metaphysical principles —namely, of sufficient reason, causality, and finality—and, finally, the acquisition of certain and immutable truth.

2321. To be sure in this philosophy many things are treated with which matters of faith and morals are neither directly nor indirectly concerned, and which, therefore, the Church entrusts to free discussion of learned men; but in regard to other matters, especially the principles and chief assertions which we mentioned above, the same freedom is not granted. In such essential questions, one may indeed clothe philosophy with a more fitting and richer dress, fortify it with more efficacious words, rid it of certain supports of scholars which are not fitting, and also cautiously enrich it with certain sound elements of progressive human study; but it is never right to subvert it, or to contaminate it with false principles, or to consider it a great but obsolete monument. For truth and its philosophic declaration cannot be changed from day to day, especially when it is a question of principles known to the human mind per se, or of those opinions which rest both on the wisdom of the ages, and on the consent and support of divine revelation. Whatever truth the human mind in its honest search will be able to discover, surely cannot be opposed to truth already acquired, since God, the highest Truth, created and directs the human intellect not that it may daily oppose new truths to those rightly acquired, but that by the removal of errors, which perchance have crept in, it can build truth upon truth in the same order and structure by which the very nature of things, from which truth is drawn, is perceived to have been constituted. Therefore, the Christian, whether philosopher or theologian, does not hastily and easily adopt every new thing thought up from day to day, but with the greatest care places it in the scale of justice, and weighs it, lest he lose or corrupt the truth already acquired, indeed with grave danger and harm to faith itself.

2322. If these matters are thoroughly examined, it will be evident why the Church demands that future priests be instructed in the philosophic disciplines "according to the manner, doctrine, and principles of the Angelic Doctor," ¹ since it knows well from the experience of many ages that the method and system of Aquinas, whether in training beginners or investigating hidden truth, stand out with special prominence; moreover, that his doctrine is in harmony, as in a kind of symphony, with divine "revelation," and is most efficacious in laying safe foundations of