PROOF THAT PERTINACITY IS REQUIRED
Student You have discussed copiously enough the words of blessed Augustine set out above to prove that no one erring against the faith is a heretic unless he clings pertinaciously to his error. Would you now adduce other proofs for the same conclusion, if you have thought of others?
Master This same conclusion is proved by a text of Augustine against the Manichees which is recorded in 24, q. 3, c. Qui in ecclesia Christi [col.998]. For he says, "Those in the church of Christ who think something unwholesome and perverse and contumaciously resist if they are corrected that they might think something wholesome and sound and refuse to correct their pestiferous and deadly teachings but persist in defending them are heretics." We are given to understand by these words that not all those in the church of Christ who are inspired by something unwholesome and perverse should immediately be judged heretical, but, according to what Augustine implies in the above words, they should be convicted of pertinacity first.
[See Significant Variants, para. 12.] Student Augustine seems to imply in the above words that not all those in the church of Christ who err pertinaciously should be held to be heretics, since he seems to imply that three things are required for those in the church of Christ who are inspired by something unwholesome and perverse to be heretics. The first is that they resist contumaciously when corrected that they might be inspired by what is wholesome and sound. The second is that they refuse to correct their errors. The third is that they persist in defending those same errors. If those three are required, however, for someone to be a heretic, as Augustine seems to imply, and many people cling to their errors pertinaciously who nevertheless do not defend them - indeed sometimes they deny them - it follows that not all those pertinaciously clinging to their errors should be added to the number of the heretics.
Master They say that you understand Augustine wrongly. For he does not mean that those three things are required for someone to be a heretic; rather he means that any one of them makes an errant heretical. However, the three are distinguished in this way. The first is as it were common and the [other] two are as it were less common and spell out the first to some extent. For it can happen in two ways that those who are corrected that they might be inspired by what is right and sound resist contumaciously, either because they refuse to change, that is to revoke [their error], or because they persist in defending it. And so any one of those three renders someone erring heretical, and also pertinacious, because everyone who is pertinacious should be considered a heretic.