Next in our reading of Pope Pius XII are the two documents on the Assumption of Mary into heaven. First is a short letter titled Deiparae Virginis Mariae sent in 1946 to all the bishops of the world. In it, Pius XII explains that large numbers of Catholics over the last 100 years have asked the Church to solemnly declare the Assumption of Mary as a dogma of the faith, which means it would be something Catholics are required to believe and that it cannot be changed. His letter then invites all the bishops of the world to respond with their input and recalls how Pius IX did something similar in the previous century when he collected the opinions of bishops on the Immaculate Conception of Mary. Pius IX then declared that a dogma.
The reason for this worldwide consultation is that the Magisterium of the Church includes all the bishops of the Church. While the pope has the highest authority, he is not alone in that power and is charged with preserving and handing on the faith of the whole church. By consulting in this way, he is making room for the Holy Spirit to guide the Church as a whole and making sure that he is not acting solely on his own impulses.
Since the support was overwhelmingly positive, in 1950, Pope Pius XII issued the highest level of papal document – called an Apostolic Constitution – to solemnly declare that all Catholics are required to believe that Mary was assumed bodily into heaven. Titled Munificentissimus Deus (“The Most Bountiful God”), it explains why he is now making this a dogma. There have always been Catholics who believed and taught this, but time and development enabled it to be understood more fully and so explicitly declared a dogma.
Pius XII explains that, by his death, Christ overcame sin and it’s effects. That includes death and decay. Nonetheless, the fullness of this victory will only be seen at the end of time in the resurrection of the dead when all souls will be reunited with their body. As a general rule, we will have to wait for this moment to become complete in heaven. Mary is exempted from this general rule because, unlike everyone other than her son, she was never affected by Original Sin. Just as her son ascended bodily into heaven, so it follows that her body too would enter into heaven, spared of the effects of Original Sin.
The pope also highlights the way in which this belief has been long held by the Church. He points to the many churches named after Mary’s assumption as well as the liturgical feasts and prayers. The law of “lex orandi, lex credendi” (“the law of prayer is the law of belief”) means that official prayers of the Church show us what our beliefs are. The Feast of the Assumption was gradually raised up to a place of greater and greater importance by popes throughout history and became a solemnity around 850 AD. Further, a number of great theologians and doctors of the Church taught this from very early on. Pius XII cites St. John Damascene (675-749) in particular “It was fitting that she, who had kept her virginity intact in childbirth, should keep her own body free from all corruption even after death.” He mentions St. Albert the Great, St. Thomas Aquinas, St. Bernardine of Siena, St. Francis de Sales, and St. Alphonsus among others. When only one or two saints or doctors teach something, it is worthy of notice. When almost every doctor teaches the same thing, it starts to stand out as a significant part of the Catholic faith.
So, having established the tradition, Pope Pius XII explicitly invokes his papal authority saying “by the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory.” So, we believe it and praise God for it.