Chapter 2.

Mental pertinacity

Is it possible to be a heretic knowingly?

Disciple I do not want to discuss that difficulty with you at the moment, but I want to ask you about the main subject, namely, how someone can be convicted of pertinacity.

Master Two kinds of pertinacity can be found in connection with matters of faith. One is mental, namely when someone pertinaciously clings in his heart to heretical wickedness or pertinaciously doubts catholic truth. The other is exterior pertinacity which consists in an outward deed or a word.We can not convict anyone of the first form of pertinacity except by a probable or a violent presumption, because in such cases what is on the outside does not necessarily correspond to what is within; indeed, often one thing is held within and another thing counterfeited on the outside.

Disciple Although my intention was to question you only about exterior pertinacity, yet as an exercise [causa exercitii] would you say something about interior and mental pertinacity; who, that is to say, errs pertinaciously in his mind?

Master Some people say that there are three ways someone can err pertinaciously in his mind. The first is if, for example, notwithstanding the miracles that he has heard have been done to confirm the faith, someone thinks that the faith is false or uncertain. The second is if in general he believes that the whole faith is true yet he adheres so strongly to some particular error, which he does not know pertains explicitly to the faith, that no matter how clearly it were shown to him that the said error does pertain to the faith he would in no way put it aside but would sooner think that the faith is false. It is just as if, when the faithful in the Old Testament were not bound to believe explicitly in a trinity of persons together with a unity of divinity, someone believing that the whole teaching of Moses and the faithful is true had thought in particular that three persons are not one God and had clung so strongly to his error that he would have believed the teaching of Moses and the prophets to be false before he would have held that three persons are one God. Although he would have believed in general that the whole faith of Moses and the prophets is true, he would have been pertinacious.Thirdly, someone can be mentally pertinacious in error if he clings to some error and neglects when and how he ought to seek the truth, because such a person is not ready to be corrected but persists in an error which he ought to put aside from necessity of salvation.

Disciple A difference is found between negligence and pertinacity; but that last-mentioned person is negligent; therefore he is not pertinacious.

Master It is replied that although negligence and pertinacity are distinguished, someone negligent is nevertheless also pertinacious and it is not inappropriate that some negligence should be considered to be pertinacity.

Disciple Can someone pertinaciously doubt the faith?

Master It is said that someone can doubt the faith pertinaciously in as many ways as he can err pertinaciously against the faith.

Disciple Can a distinction concerning the pertinacious person be made in another way, on account of interior pertinacity?

Master A distinction is made concerning the pertinacious person in another way, at least as far as it concerns words, because just as, according to blessed Augustine, one person is knowingly a heretic and another person is unknowingly a heretic, so one person is knowingly pertinacious - namely he who thinks that the christian faith is in some part false - and another is unknowingly pertinacious - namely he who believes in general that the whole christian faith is true but clings pertinaciously to some particular error against the faith.

[See Significant Variants, para. 15.] Disciple How can someone be knowingly pertinacious? This seems to contain a contradiction, for if he is knowingly pertinacious, he knows that he is pertinacious; but this contains a contradiction, because he who errs thinks that to be true about which he is in error, in that to err is to regard the false as true. No one therefore knows that he errs; and thus no one is knowingly pertinacious because no one knows that he is pertinacious in error.

Master That phrase "knowingly pertinacious" should not be related to the pertinacity of the person erring - in the sense that someone knows himself to err pertinaciously - but should be related to the opposition between his pertinacity or error and the christian faith - in the sense that he is said to be knowingly pertinacious because he knows that the assertion about which he is in error is opposed to christian faith. In the same way someone is said to be knowingly a heretic not because he may know he is a heretic but because he knows that his assertion is opposed to the christian faith. Just as he is called knowingly a heretic, therefore, who knows that his assertion, which in truth of fact is a heresy, is contrary to christian faith and he is called ignorantly or unknowingly a heretic who does not know that his assertion is opposed to christian faith but thinks that it is consistent with christian faith, so he is called knowingly pertinacious in heretical error who knows that an assertion which he thinks is true is opposed to christian faith. But he is called ignorantly or unknowingly pertinacious in heretical error who does not know that his assertion is opposed to christian faith.

William of Ockham, Dialogus,
part 1, book 4, chapters 1-5

Text and translation by John Scott.
Copyright © 1999, The British Academy.


  1. Pertinacity as defined by Canon Law is nothing other than knowing that one's opinions are contrary to what the Catholic Church teaches and holding them anyway.


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