A pertinent excerpt:
"How has the Church received the thought of Casel? The reception has been mixed. The first acknowledgment of Casel’s theory was in Pope Pius XII’s groundbreaking 1947 encyclical on the liturgy, Mediator Dei. The encyclical endorses the same type of “mystical realism” that Casel proposed:51 “While the sacred liturgy calls to mind the mysteries of Jesus Christ, it strives to make all believers take their part in them so that the divine Head of the mystical Body may live in all the members with the fullness of His holiness.”52 But at the same time, there seems to be some veiled criticism of the details of Odo Casel’s approach. “These mysteries are ever present and active not in a vague and uncertain way as some modern writers hold [effutire, to blabber or prattle], but in the way that Catholic doctrine teaches us.”53 The monks of Maria Laach interpreted the encyclical as a vindication of Casel, while his detractors interpreted it as a condemnation. To make matters more confusing, both sides have some support. The then-secretary of the Holy Office, Cardinal Marchetti Selvaggiani, in a letter dated December 11, 1948, said that Mediator Dei rejected mystery theology, especially its theory of the festal mystery.54 On the other hand, Antonio Bernareggi, a bishop-theologian close to Pius XII, said that the encyclical did not reject Casel’s approach, but rather sought a more careful elucidation of the relationship between the historical and liturgical aspects of the mystery.55"