1 The Blessed Apostle Paul in laying down the form for appointing a bishop and creating by his instructions an entirely new type of member of the Church, has taught us in the following words the sum total of all the virtues perfected in him:— Holding fast the word according to the doctrine of faith that he may be able to exhort to sound doctrine and to convict gainsayers. For there are many unruly men, vain talkers and deceivers. For in this way he points out that the essentials of orderliness and morals are only profitable for good service in the priesthood if at the same time the qualities needful for knowing how to teach and preserve the faith are not lacking, for a man is not straightway made a good and useful priest by a merely innocent life or by a mere knowledge of preaching.
For an innocent minister is profitable to himself alone unless he be instructed also; while he that is instructed has nothing to support his teaching unless he be innocent. For the words of the Apostle do not merely fit a man for his life in this world by precepts of honesty and uprightness, nor on the other hand do they educate in expertness of teaching a mere Scribe of the Synagogue for the expounding of the Law: but the Apostle is training a leader of the Church, perfected by the perfect accomplishment of the greatest virtues, so that his life may be adorned by his teaching, and his teaching by his life.
Accordingly he has provided Titus, the person to whom his words were addressed, with an injunction as to the perfect practice of religion to this effect:— In all things showing yourself an ensample of good works, teaching with gravity sound words that cannot be condemned, that the adversary may be ashamed, having nothing disgraceful or evil to say of us. This teacher of the Gentiles and elect doctor of the Church, from his consciousness of Christ who spoke and dwelt within him, knew well that the infection of tainted speech would spread abroad, and that the corruption of pestilent doctrine would furiously rage against the sound form of faithful words, and infusing the poison of its own evil tenets into the inmost soul, would creep on with deep-seated mischief.
For it is of these that he says, Whose word spreads like a cancer, tainting the health of the mind, invaded by it with a secret and stealthy contagion. For this reason, he wished that there should be in the bishop the teaching of sound words, a good conscience in the faith and expertness in exhortation to withstand wicked and false and wild gainsayings. For there are many who pretend to the faith, but are not subject to the faith, and rather set up a faith for themselves than receive that which is given, being puffed up with the thoughts of human vanity, knowing the things they wish to know and unwilling to know the things that are true; since it is a mark of true wisdom sometimes to know what we do not like.
However, this will-wisdom is followed by foolish preaching, for what is foolishly learned must needs be foolishly preached. Yet how great an evil to those who hear is foolish preaching, when they are misled into foolish opinions by conceit of wisdom! And for this cause the Apostle described them thus: There are many unruly, vain talkers and deceivers. Hence we must utter our voice against arrogant wickedness and boastful arrogance and seductive boastfulness—yes, we must speak against such things through the soundness of our doctrine, the truth of our faith, the sincerity of our preaching, so that we may have the purity of truth and the truth of sound doctrine.
Source: On the Trinity (New Advent)