The reforms ultimately adopted by the papal commission were guided by five principles illustrated by the papal bull Quo Primum:
“First, a single rite for mass and office is to be used throughout the church. Second, the antiquity, quality, and probity of the missal’s contents are to be guaranteed by the work of scholars. Third, the commission’s primary goal is to restore the mass to the “pristine norm of the ancient Fathers.” Fourth, this patristic norm will be strictly interpreted by papal authority. Fifth, nothing may be added or subtracted either from the rites and rubrics found in the missal or from the bull, except by direction of the pope.”(30)
It is the last item that many people cite to condemn liturgical changes enacted by the Second Vatican Council. When interpreted absolutely, it leaves no room for any modifications whatsoever to the Roman Missal of Pius V. History, however, shows the Church interpreting the bull differently. First of all, Quo Primum itself had a provision allowing rites to continue in existence if already established for at least 200 years, so that from the beginning the Roman Rite was not the only rite in existence. A plurality of practice, albeit limited, was envisioned from the beginning of the reform of the Roman Rite. Secondly, another thing we can point out to show that the clause to have nothing added or subtracted was not to be absolute, is the number of subsequent updates made to the rite by later popes: It was modified by Gregory XIII, Sixtus V (immediate successors of Pius V), later by Clement VIII, Urban VIII, Benedict XIV, Leo XIII. Closer to our times, Pius X introduced many modifications, as did Pius XII, and before the Second Vatican Council in 1962, John XXIII also modified it with the addition of St. Joseph to the Roman Canon.(31)
30. Geoffrey Wainwright, The Oxford History of Christian Worship, p. 337.
31. Denis Crouan, The Liturgy after Vatican II: Collapsing or Resurgent?, p. 21