4 First, direct your efforts to inculcating the discipline of good morals and a lively zeal for acquiring knowledge in the seminarians. This will ensure that the studies which now decline and languish among the youths growing up as the hope of the Church will attain that splendor which We justly desire and which the religious times require. For you know that the plan of divine providence was this: at first to use the valiant martyrs to break the manifest opposition and ferocity of tyrants, so that their blood would be the seed of Christianity; then according to the same plan to destine men of outstanding wisdom in every age to defend, not only by sacred authority but by the aid of human reason, the treasures of truth which Christ brought to the Church. Now, however, the contagion of perverse opinions contaminates and corrupts all things, and, under the pretext of the development of doctrine, the wisdom given by God is opposed and rejected. So it is easy to understand that there is a need for defenders who have put on the armor of knowledge and are always prepared(2) as the Apostle warns, to satisfy everyone seeking a reason for the hope which is in us, and to give instruction in sound doctrine and also to confute those who contradict.(3) In regulating the course of studies in your seminaries, We desire that you consider what We have prescribed in encyclical letters concerning this matter. Certainly in the teaching of philosophy the Angelic Doctor Thomas Aquinas is to be greatly honored. The wisdom which always flows richly from his writings and which is considered worthy of lasting praise by Roman Pontiffs is to be imparted to the students in great and generous measure. Then the physical sciences are not to be neglected. For besides the fact that at present they are so highly esteemed, it is from them that those who hate Catholic dogmas draw their arguments to assail the truths of religion. For this reason care must be taken that enough clergy are knowledgeable in such warfare to answer the detractors and refute their errors with their own arguments. Finally observe religiously what We have recently decreed concerning the cultivation of Biblical studies. If you will do these things, the honor of the clergy will flourish and the reputation of the Church will endure. She always was considered to be the advocate and mother of sound learning and truly should be so considered. Besides you will have at hand suitable men, called to share your ministry and most useful in teaching the faithful and promoting piety.
Source: Inter Graves (Vatican.va)