Tuesday is the Solemnity of the Assumption of the Blessed Virgin Mary into heaven—a Holy Day of Obligation for all Catholics.
This solemnity is significant for a variety of reasons. For example, it is one of only two instances of the use of papal infallibility in the history of the Church. This belief in papal infallibility, though present throughout the history of the Church, was only formally defined in the First Vatican Council (1869-1870). It was exercised once prior to this definition–for the promulgation of the dogma of the Immaculate Conception in 1854. It was nearly one hundred years later when Pius XII exercised this special charism for the second time in the proclamation of Our Lady’s Assumption in 1950. When the pope exercises this charism, he is said to speak “ex cathedra,” i.e. “from the chair.” The chair is an image of authority—the authority received from Christ by St. Peter and exercised by all of his subsequent successors in the papal office.
It is important to note that this belief in Our Lady’s Assumption into heaven did not begin with Pope Pius XII in 1950. Though written evidence of this Christian belief only dates back to the 4th century, the belief in this truth began with the apostles, especially St. John, to whom Our Lady was entrusted by Christ immediately before his death on the cross. He and any other apostles present were witnesses to the events surrounding her Assumption and passed their experience down to the Christians in their community. Though not part of the canon of scripture, some of these accounts are recorded in early Christian writings and in the accounts of mystics to whom God made this event known. Though the accounts differ in various ways, one thing is consistent—the union of our Lady’s body and soul in heaven as singular grace. As the years went on, the Church reflected upon, prayed over, and entered into this sacred mystery. Gradually, Christ’s faithful began to understand more fully the meaning of Our Lady’s Assumption. They began to see its connection to their lives, their relationship to Christ, and their hope for heaven. This growth in faith finally found its culmination in the ex cathedra declaration of Pius XII:
“After we have poured forth prayers of supplication again and again to God, and have invoked the light of the Spirit of Truth, for the glory of Almighty God who has lavished his special affection upon the Virgin Mary, for the honor of her Son, the immortal King of the Ages and the Victor over sin and death, for the increase of the glory of that same august Mother, and for the joy and exultation of the entire Church; 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.“
Lest anyone mistakenly think that this is a mere theological opinion of the pope, he adds the following: “Hence if anyone, which God forbid, should dare willfully to deny or to call into doubt that which we have defined, let him know that he has fallen away completely from the divine and Catholic Faith.”
These words come only at the end of Pope Pius’ exposition on the topic. If you have not yet had the opportunity, I warmly encourage you to read his reflections in Munificentissimus Deus. It is relatively short and available online.