When discussing the dogma of papal infallibility as defined by the First Vatican Council in 1870, I always ask people Since the definition of that dogma, how many infallible declarations have there been? Well, the answer is one: Munificentissimus Deus, promulgated by Pope Pius XII on 1 November 1950, defining the Blessed Virgin's bodily Assumption into heaven, something that certainly meets St. Vincent Lérins' three-fold criteria of being believed always, everywhere, and by all, as the Apostolic Constitution goes to great pains to show:
"Since the universal Church, within which dwells the Spirit of Truth who infallibly directs it toward an ever more perfect knowledge of the revealed truths, has expressed its own belief many times over the course of the centuries, and since the bishops of the entire world are almost unanimously petitioning that the truth of the bodily Assumption of the Blessed Virgin Mary into heaven should be defined as a dogma of divine and Catholic faith--this truth which is based on the Sacred Writings, which is thoroughly rooted in the minds of the faithful, which has been approved in ecclesiastical worship from the most remote times, which is completely in harmony with the other revealed truths, and which has been expounded and explained magnificently in the work, the science, and the wisdom of the theologians - we believe that the moment appointed in the plan of divine providence for the solemn proclamation of this outstanding privilege of the Virgin Mary has already arrived...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" (par. 41 and 45).Remember, O most blessed Virgin Mary, that never was it known that anyone who fled to thy protection, implored thy help, or sought thy intercession was left unaided. Inspired by this confidence, I fly unto thee, O Virgin of virgins, my mother; to thee do I come, before thee I stand, sinful and sorrowful. O Mother of the Word Incarnate, despise not my petitions, but in thy mercy hear and answer me.
Veni Sancte Spiritus, veni per Mariam.
you gave a humble virgin
the privilege of being mother of your Son,
and crowned her with the glory of heaven.
May the prayers of the Virgin Mary
bring us to the salvation of Christ
and raise us up to eternal life.
We ask this through our Lord Jesus Christ, your Son,
who lives an reigns with you and Holy Spirit,
one God for ever and ever. Amen.