I answer that, We are speaking of heresy now as denoting a corruption of the Christian faith. Now it does not imply a corruption of the Christian faith, if a man has a false opinion in matters that are not of faith, for instance, in questions of geometry and so forth, which cannot belong to the faith by any means; but only when a person has a false opinion about things belonging to the faith.
Now a thing may be of the faith in two ways, as stated above (I, Q. 32, A. 4; I-II, Q. 1, A. 6, ad 1; I-II, Q. 2, A. 5), in one way, directly and principally, e.g. the articles of faith; in another way, indirectly and secondarily, e.g. those matters, the denial of which leads to the corruption of some article of faith; and there may be heresy in either way, even as there can be faith.
Reply Obj. 1: Just as the heresies of the Jews and Pharisees were about opinions relating to Judaism or Pharisaism, so also heresies among Christians are about matter touching the Christian faith.
Reply Obj. 2: A man is said to expound Holy Writ in another sense than that required by the Holy Ghost, when he so distorts the meaning of Holy Writ, that it is contrary to what the Holy Ghost has revealed. Hence it is written (Ezech. 13:6) about the false prophets: "They have persisted to confirm what they have said," viz. by false interpretations of Scripture. Moreover a man professes his faith by the words that he utters, since confession is an act of faith, as stated above (Q. 3, A. 1). Wherefore inordinate words about matters of faith may lead to corruption of the faith; and hence it is that Pope Leo says in a letter to Proterius, Bishop of Alexandria: "The enemies of Christ's cross lie in wait for our every deed and word, so that, if we but give them the slightest pretext, they may accuse us mendaciously of agreeing with Nestorius."
Reply Obj. 3: As Augustine says (Ep. xliii) and we find it stated in the Decretals (xxiv, qu. 3, can. Dixit Apostolus): "By no means should we accuse of heresy those who, however false and perverse their opinion may be, defend it without obstinate fervor, and seek the truth with careful anxiety, ready to mend their opinion, when they have found the truth," because, to wit, they do not make a choice in contradiction to the doctrine of the Church. Accordingly, certain doctors seem to have differed either in matters the holding of which in this or that way is of no consequence, so far as faith is concerned, or even in matters of faith, which were not as yet defined by the Church; although if anyone were obstinately to deny them after they had been defined by the authority of the universal Church, he would be deemed a heretic. This authority resides chiefly in the Sovereign Pontiff. For we read [*Decret. xxiv, qu. 1, can. Quoties]: "Whenever a question of faith is in dispute, I think, that all our brethren and fellow bishops ought to refer the matter to none other than Peter, as being the source of their name and honor, against whose authority neither Jerome nor Augustine nor any of the holy doctors defended their opinion." Hence Jerome says (Exposit. Symbol [*Among the supposititious works of St. Jerome]): "This, most blessed Pope, is the faith that we have been taught in the Catholic Church. If anything therein has been incorrectly or carelessly expressed, we beg that it may be set aright by you who hold the faith and see of Peter. If however this, our profession, be approved by the judgment of your apostleship, whoever may blame me, will prove that he himself is ignorant, or malicious, or even not a catholic but a heretic." _______________________
THIRD ARTICLE [II-II, Q. 11, Art. 3]
Whether Heretics Ought to Be Tolerated?
Objection 1: It seems that heretics ought to be tolerated. For the Apostle says (2 Tim. 2:24, 25): "The servant of the Lord must not wrangle . . . with modesty admonishing them that resist the truth, if peradventure God may give them repentance to know the truth, and they may recover themselves from the snares of the devil." Now if heretics are not tolerated but put to death, they lose the opportunity of repentance. Therefore it seems contrary to the Apostle's command.
Obj. 2: Further, whatever is necessary in the Church should be tolerated. Now heresies are necessary in the Church, since the Apostle says (1 Cor. 11:19): "There must be . . . heresies, that they . . . who are reproved, may be manifest among you." Therefore it seems that heretics should be tolerated.
Obj. 3: Further, the Master commanded his servants (Matt. 13:30) to suffer the cockle "to grow until the harvest," i.e. the end of the world, as a gloss explains it. Now holy men explain that the cockle denotes heretics. Therefore heretics should be tolerated.