"Perfectum imperficit perficiens imperfectum"Johannes de Muris, "Notitia Artes Musicae" II, 3, 12

Zusammenfassung

It is a fact that Johannes de Muris followed accurately the ideas advocated by ars nova and defended by Philippe de Vitry. Despite this, it is possible to find in the first chapters of Johannes de Muris' Notitia artis musicae an unexpected agreement with the notions about the perfect number supported by Franco Teutonicus, the most eminent master of ars antiqua. Leaving aside whether Johannes de Muris was or not sincere, these passages relating to perfect number allow to stablish the interpretation of a difficult passage. After their study, it will be clear that the dark 27. quae perfectum imperficit perficiens imperfectum (Notitia artis musicae, 11, 3, 12) has to be interpreted as: "27 makes imperfect the perfect number 81, making perfect the imperfect number 18".