Student: SOME CANONISTS, as you say, think that it pertains principally to them to discriminate between a catholic and an heretical assertion, yet since they would seem to me to be putting their scythe into someone else's harvest [cf. Deuteronomy 23:25] if they presumed to attempt this without theology, in that without theology they would be unable to understand the chapters inserted in the decretals which speak about heresies. Tell me, I pray, departing a little from our original plan, what the learned think about the meaning of the materials found in the decretals---to whom, that is, does it more chiefly and profoundly pertain to know their meaning?
Master: Opposing opinions are found about your question. For canonists seem to think that they not only have a greater memory of those things that are inserted in the books of canon law but also that they understand them more clearly and deeply, and that it pertains chiefly to them to judge, at least by way of teaching, what their meaning is. It seems possible that they are moved by the following argument for this opinion. According to the maxim of the wise man, "Everyone judges well those things which he knows, and of these he is a good judge." [Aristotle, Nicomachean Ethics I.4, 1094b 33] But canonists know better than others the contents of their books. It pertains chiefly to them, therefore, to judge their meaning.
Again, another argument can be brought forward for that opinion. Knowledge of any matters pertains to no one more than to the experts on the science that considers them. Knowledge of what is handed on in the canon law pertains to no one, therefore, more than to experts on canon law, such as the canonists. It chiefly pertains to them, therefore, to determine their meaning.
WILLIAM OF OCKHAM, DIALOGUS
part 1, prologue and book 1
Text and translation by John Kilcullen and John Scott
as at december, 2003