“At Sixes and Sevens” — And Eights and Nines: The Sacred Mathematics of Sacred Orders in the Early Middle Ages

Some Medieval sevens were relatively fixed: the seven gifts of the Holy Spirit, seven petitions in the Pater noster, seven penitential psalms, seven churches of the Apocalypse, and even seven days of the week. Other sevens, like the deadly sins, the beatitudes, or the virtues, varied from time to time and place to place and were arranged from bottom to top, top to bottom, or inside out. One of these changing medieval sevens was the seven ecclesiastical grades.