48 "In doctrina. In the face of the combined efforts of incredulity and heresy to consummate the ruin of Catholic faith, it would be a real crime for the clergy to remain in a state of hesitancy and inactivity. In such an outpouring of error and conflict of opinion he must not prove faithless to his mission, which is to defend dogma assaulted, morality travestied and justice frequently outraged. It is for him to oppose himself as a barrier to the attacks of error and the deceits of heresy; to watch the tactics of the wicked who war on the faith and honor of this Catholic country; to unmask their plots and reveal their ambuscades; to warn the confiding, strengthen the timid and open the eyes of the blinded. Superficial erudition or merely common knowledge will not suffice for all this-there is need of study, solid, profound and continuous, in a word of a mass of doctrinal knowledge sufficient to cope with the subtlety and remarkable cunning of our modern opponents. . . .
Source: Depuis le Jour (Vatican.va)