One of the splits today pits Catholic proponents of "unity in diversity" against their co-religionists arguing for one single, uniform Mass. The former group, from a historical standpoint, can point to the medieval Catholic Church, which supported the coexistence of multiple forms of worship (aka "rites"). Some examples include now-defunct rites such as the English Sarum Rite and the Iberian Mozarabic Rite, used by Arabic-speaking Christians living under Muslim rule. In Northern Italy, the Ambrosian Rite, based in Milan (pictured above) still exists today. These rites all bear close similarity to the Latin Rite but have their own unique features, differing in order of Mass, readings, and varying degrees of Greek influence.
As Fr. Marijan Steiner of the Philosophy Institute of the Society of Jesus in Zagreb notes, there was no single, uniform Catholic Mass in Medieval Europe, which may surprise at first, but makes sense from a Catholic perspective. EWTN notes that the Catholic Church is not "Roman," but universal. In fact, according to Catholic Answers, the term "Roman Catholic" started as a Protestant slur. Thus, nothing precluded liturgical diversity in medieval Catholicism, as long as the rites followed the traditions outlined inherited from early Christianity and rejected heretical innovations. It was the Protestant Reformation that led the papacy to codify one liturgy from Rome that all Catholics would follow, and therein lies the origin of today's Catholic Mass controversy.
