WHO SHOULD BE REGARDED AS A CATHOLIC?
Disciple Concerning Catholic truths the above investigation is enough. Now, however, I will try to investigate some points concerning Catholics and heretics. And first I ask who should be regarded as a Catholic.
Master He should be considered a Catholic who observes the Catholic faith whole and inviolate.
Disciple How can a simple layman observe the whole faith, who has never thought of many things that belong to the Catholic faith? Such a layman therefore cannot be a Catholic, if every Catholic holds the whole Catholic faith.
Master Theologians answer that to observe or hold the whole faith is possible by believing faithfully and without any doubt, explicitly or implicitly, all things that pertain to the orthodox faith.
Disciple What is it to believe something implicitly?
Master It is answered that to believe implicitly is to assent firmly to some universal [statement] from which many things follow and not adhere pertinaciously to anything contrary, and therefore whoever firmly holds that everything handed down in divine scripture and the teaching of the universal church is true and sound and does not adhere pertinaciously to any assertion contrary to orthodox truth holds the Catholic faith inviolate and whole and should be considered a Catholic.
Disciple It seems that for someone to be regarded as a Catholic it would be enough to believe that all things that the universal church hands down are true, and thus it is superfluous to add that he should not adhere pertinaciously to anything contrary.
Master Some of the learned say that it is not enough to believe that all things that the universal church hands down are true, unless together with this nothing contrary is adhered to pertinaciously in particular. For many heretics have been condemned by general councils who nevertheless firmly held that all things handed down in sacred scripture are true; however, because they adhered pertinaciously to some assertion in truth contrary to an assertion of divine scripture (although they did not see this), they were judged to be not Catholics but heretics.
Disciple It seems to me not possible to know perfectly who is to be regarded as a Catholic unless one knows who is to be judged a heretic, and therefore I will turn to the inquiry concerning heretics. But say first how it is explained that someone can believe that all things that divine scripture contains, or the [doctrine of the] universal church, are true, and yet adhere pertinaciously to some assertion opposed to some truth contained in sacred scripture or in the teaching of the universal church.
Master This is explained as follows. Just as it is possible to know something in a universal [statement] and not know it in particular (according to the opinion of the wise man), which is simply to know the universal proposition and not know one of its singulars (for example, I can know that every man is rational, not knowing the singular, "This is rational", when some man is pointed out whom I see from a distance and do not know whether he is a man or a brute animal), so it is possible to know some universal and think that one of its singulars is false (for example, I can know that every man is capable of laughter, and yet, when some man is pointed out whom I see from a distance and think to be an ass or some other animal, as often happens, I can believe that he is not capable of laughter, because I think that he is not a man) -- so it is possible for someone to believe the universal statement, "All things contained in divine scripture are Catholic and true", and yet believe it to be false that "Blessed Andrew was an apostle of Christ", because he does not know that the truth "Blessed Andrew was an apostle of Christ" is contained in or can be inferred from divine scripture. Assuming that this is so, if he adheres pertinaciously, for whatever reason, to the statement that "Blessed Andrew was not an apostle of Christ", he must be judged not a Catholic but a heretic, however firmly he may hold the universal statement, "All things that divine scripture teaches are Catholic and true".
William of Ockham, Dialogus
part 1, book 3, chapters 1-5.
Text by John Kilcullen and John Scott,
Translation by John Kilcullen.